Sesen Bio, Inc. (SESN)

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”), today announced that its stockholders have voted to approve all proposals, including the pending merger with Carisma Therapeutics Inc. (“Carisma”), at the Company's Special Meeting of Stockholders (the “Special Meeting”) held earlier today. Dr.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”), today announced that its stockholders have voted to approve all proposals, including the pending merger with Carisma Therapeutics Inc. (“Carisma”), at the Company’s Special Meeting of Stockholders (the “Special Meeting”) held earlier today. Dr. Thomas Cannell, President and Chief Executive Officer of Sesen Bio, said, “We are pleased with the outcome of today’s Special Meeting and thank our stockholders for their support of the merger with Carisma. The fact that over 88% of stockholders voted in favor of the merger provides further confidence that our thorough strategic process maximizes value for stockholders. Throughout the process, we have been actively conserving capital and we are closing the merger with approximately $150 million in cash and cash equivalents, of which roughly half will go directly to Sesen Bio stockholders in the form of a $75 million special dividend we announced today, with the remainder going toward funding the combined company.” “Looking ahead, our stockholders are positioned to benefit from the upside potential of ownership in the combined company, as well as the CVR, which provides additional potential cash upside from any sale of Sesen Bio’s legacy assets, including Vicineum, and from the potential $30 million milestone payment under the Roche Asset Purchase Agreement. We look forward to completing the merger and realizing our bright future with Carisma.” Based on a preliminary count of the voting results from today’s meeting of stockholders, more than 88% of the votes cast were voted in favor of Proposal No. 1 to approve the issuance of Sesen Bio common stock to Carisma stockholders in the merger and approximately 86% of votes were cast in favor of Proposal No. 2, representing more than 57% of outstanding shares of Sesen Bio common stock, to approve the amendment to Sesen Bio’s certificate of incorporation to effect a reverse stock split of outstanding shares of Sesen Bio common stock at a ratio of 1-for-20. The approval of Proposal Nos. 1 and 2 was needed to complete the merger. Sesen Bio currently anticipates that the reverse stock split will become effective after trading hours on March 7, 2023, such that trading of post-split Carisma (“CARM”) common stock will commence on March 8, 2023. The merger is expected to close on March 7, 2023, subject to customary closing conditions. The final voting results for the company’s special meeting will be disclosed in a Form 8-K filed with the Securities and Exchange Commission (the “SEC”) and will also be available at https://ir.sesenbio.com/, after certification by the company’s inspector of elections. In connection with the transaction, the Sesen Bio Board of Directors has declared a one-time, special cash dividend of $75 million. Based on the current number of shares outstanding, the special cash dividend is expected to result in $0.361 per share to all common stockholders of record as of the close of business on March 7, 2023, payable no later than March 10, 2023. Sesen Bio stockholders of record will also be issued one Contingent Value Right (CVR) for each outstanding share of Sesen Bio common stock, representing the right to receive any potential proceeds from the sale of Vicineum and Sesen Bio’s preclinical assets prior to March 31, 2027 and any proceeds from the potential milestone payment under the Roche Asset Purchase Agreement. The issuance of the special cash dividend and CVR remain contingent on the closing of the approved transaction. Additional information about the reverse stock split can be found in the Company’s definitive proxy statement filed with the SEC on January 19, 2023, which is available at the SEC’s website, www.sec.gov, and at the company’s website, www.sesenbio.com. SVB Securities is acting as exclusive financial advisor to Sesen Bio for the transaction and Hogan Lovells US LLP is serving as its legal counsel. About Sesen Bio Sesen Bio, Inc. is a late-stage clinical company that previously focused on advancing targeted fusion protein therapeutics for the treatment of patients with cancer. Sesen Bio’s most advanced product candidate, Vicineum™, also known as VB4-845, is a locally administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive bladder cancer. On July 15, 2022, Sesen Bio made the strategic decision to voluntarily pause further development of Vicineum in the United States. The decision was based on a thorough reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional Phase 3 clinical trial, following Sesen Bio’s discussions with the United States Food and Drug Administration. Sesen Bio has turned its primary focus to consummating a strategic transaction with the goal of maximizing stockholder value. Additionally, Sesen Bio is seeking a partner for the further development of Vicineum. For more information, please visit the Company’s website at www.sesenbio.com. Cautionary Note on Forward-Looking Statements Any statements in this press release about future expectations, plans and prospects for Sesen Bio, Inc. (Sesen Bio), CARISMA Therapeutics Inc. (Carisma) or the combined company, Sesen Bio’s, Carisma’s or the combined company’s strategy or future operations, and other statements containing the words “anticipate,” “believe,” “contemplate,” “expect,” “intend,” “may,” “plan,” “predict,” “target,” “potential,” “possible,” “will,” “would,” “could,” “should,” “continue,” and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. For example, statements concerning the proposed transaction, the concurrent financing, the contingent value rights and other matters, including without limitation: statements relating to the satisfaction of the conditions to and consummation of the proposed transaction, the expected timing of the consummation of the proposed transaction, the expected ownership percentages of the combined company, Sesen Bio’s and Carisma’s respective businesses, the strategy of the combined company, future operations, advancement of the combined company’s product candidates and product pipeline, clinical development of the combined company’s product candidates, including expectations regarding timing of initiation and results of clinical trials of the combined company, the ability of Sesen Bio to remain listed on the Nasdaq Stock Market, the completion of the concurrent financing, the receipt of any payments under the contingent value rights, and the amount and timing of distributions to be made to Sesen Bio stockholders, if any, in connection with any potential dissolution or liquidation scenario are forward-looking statements. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain stockholder approval of matters related to the proposed transaction in a timely manner or at all; (ii) uncertainties as to the timing of the consummation of the proposed transaction and the ability of each of Sesen Bio and Carisma to consummate the proposed transaction, including completing the concurrent financing; (iii) risks related to Sesen Bio’s ability to correctly estimate its expected net cash at closing and Sesen Bio’s and Carisma’s ability to correctly estimate and manage their respective operating expenses and expenses associated with the proposed transaction; (iv) risks related to Sesen Bio’s continued listing on the Nasdaq Stock Market until closing of the proposed transaction; (v) the risk that as a result of adjustments to the exchange ratio, Sesen Bio stockholders or Carisma stockholders could own less of the combined company than is currently anticipated; (vi) the risk that the conditions to payment under the contingent value rights will not be met and that the contingent value rights may otherwise never deliver any value to Sesen Bio stockholders; (vii) risks associated with the possible failure to realize certain anticipated benefits of the proposed transaction, including with respect to future financial and operating results; (viii) uncertainties regarding the impact any delay in the closing would have on the anticipated cash resources of the combined company upon closing and other events and unanticipated spending and costs that could reduce the combined company’s cash resources; (ix) the effect of uncertainties related to the actions of activist stockholders, which could make it more difficult to obtain the approval of Sesen Bio stockholders with respect to the transaction related proposals and result in Sesen Bio incurring significant fees and other expenses, including for third-party advisors; (x) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the merger agreement, as amended; (xi) the effect of the announcement, pendency or completion of the merger on Sesen Bio’s or Carisma’s business relationships, operating results and business generally; (xii) costs related to the merger; (xiii) the outcome of any legal proceedings instituted against Sesen Bio, Carisma or any of their respective directors or officers related to the merger agreement or the transactions contemplated thereby; (xiv) the ability of Sesen Bio or Carisma to protect their respective intellectual property rights; (xv) competitive responses to the proposed transaction and changes in expected or existing competition; (xvi) the success and timing of regulatory submissions and pre-clinical and clinical trials; (xvii) regulatory requirements or developments; (xviii) changes to clinical trial designs and regulatory pathways; (xix) changes in capital resource requirements; (xx) risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates and its preclinical programs; (xxi) legislative, regulatory, political and economic developments; and (xxii) other factors discussed in the “Risk Factors” section of Sesen Bio’s Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other reports filed with the Securities Exchange Commission (SEC). In addition, the forward-looking statements included in this press release represent Sesen Bio’s and Carisma’s views as of the date hereof. Sesen Bio and Carisma anticipate that subsequent events and developments will cause the respective company’s views to change. However, while Sesen Bio may elect to update these forward-looking statements at some point in the future, Sesen Bio specifically disclaims any obligation to do so, except as required under applicable law. These forward-looking statements should not be relied upon as representing Sesen Bio’s views as of any date subsequent to the date hereof. Important Additional Information In connection with the proposed transaction between Carisma and Sesen Bio, Sesen Bio first mailed to Sesen Bio stockholders a definitive proxy statement/prospectus on or about January 24, 2023 and a supplement to the proxy statement/prospectus on or about February 17, 2023. Sesen Bio may also file other relevant documents regarding the proposed transaction with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THESE MATERIALS, INCLUDING THE REGISTRATION STATEMENT, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, THE SUPPLEMENT AND ALL OTHER RELEVANT DOCUMENTS THAT ARE OR WILL BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE MATERIALS, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders are able to obtain the definitive proxy statement/prospectus and other documents that are filed or will be filed by Sesen Bio with the SEC free of charge from the SEC’s website at www.sec.gov or from Sesen Bio at the SEC Filings section of www.sesenbio.com. No Offer or Solicitation This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, a public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone or internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction. Participants in the Solicitation Sesen Bio and Carisma and their respective directors, executive officers and other members of management may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Sesen Bio’s directors and executive officers is available in Sesen Bio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, its definitive proxy statement dated April 28, 2022 for its 2022 Annual Meeting of Stockholders and its Current Report on Form 8-K filed with the SEC on August 31, 2022. Other information regarding the participants in the proxy solicitation and a description of their interests in the proposed transaction, by security holdings or otherwise, is included in the definitive proxy statement/prospectus and other relevant materials that are or will be filed with the SEC regarding the proposed transaction. Investors should read the definitive proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Sesen Bio or the SEC’s website as indicated above. _________________________ 1 Based on basic outstanding shares including unvested restricted stock units

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio (Nasdaq: SESN) today reported operating results for the fourth quarter and full year ended December 31, 2022, and provided a business update. Business Update On February 13, 2023, following extensive engagement with Sesen Bio stockholders, Sesen Bio and Carisma Therapeutics, Inc. (“Carisma”) further amended the previously amended merger agreement announced on December 29, 2022.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio (Nasdaq: SESN) today reported operating results for the fourth quarter and full year ended December 31, 2022, and provided a business update. Business Update On February 13, 2023, following extensive engagement with Sesen Bio stockholders, Sesen Bio and Carisma Therapeutics, Inc. (“Carisma”) further amended the previously amended merger agreement announced on December 29, 2022. The terms of the amended merger agreement include: An increase of the one-time special cash dividend expected to be paid to Sesen Bio stockholders to $75.0 million, or approximately $0.36 per share1. This represents an increase from the expected special cash dividend of approximately $70.0 million, or approximately $0.34 per share1, under the first amendment to the merger agreement, and an increase from the up to $25.0 million special cash dividend under the terms of the original merger agreement dated September 20, 2022. An extension of the period of time for payments under the Contingent Value Rights related to any potential proceeds from the sale of Vicineum and Sesen Bio’s other legacy assets to March 31, 2027, from December 31, 2023 under the previous terms. This is in addition to any potential proceeds from the milestone payment under the Roche Asset Purchase Agreement. Michael Torok, one of Sesen Bio’s largest stockholders, will join the Carisma Board of Directors upon closing of the merger as the sole Sesen Bio representative. An increase of the one-time special cash dividend expected to be paid to Sesen Bio stockholders to $75.0 million, or approximately $0.36 per share1. This represents an increase from the expected special cash dividend of approximately $70.0 million, or approximately $0.34 per share1, under the first amendment to the merger agreement, and an increase from the up to $25.0 million special cash dividend under the terms of the original merger agreement dated September 20, 2022. An extension of the period of time for payments under the Contingent Value Rights related to any potential proceeds from the sale of Vicineum and Sesen Bio’s other legacy assets to March 31, 2027, from December 31, 2023 under the previous terms. This is in addition to any potential proceeds from the milestone payment under the Roche Asset Purchase Agreement. Michael Torok, one of Sesen Bio’s largest stockholders, will join the Carisma Board of Directors upon closing of the merger as the sole Sesen Bio representative. The go-forward company will focus on the development of Carisma’s chimeric antigen receptor macrophage (CAR-M) therapies, which are believed to be the only therapies of their kind with demonstrated proof of mechanism and safety data in clinical trials. The combined company is expected to operate under the name “Carisma Therapeutics, Inc.” and trade on Nasdaq under the ticker symbol “CARM”. On February 16, 2023 and February 17, 2023, leading independent proxy advisors Institutional Shareholder Services (“ISS”) and Glass, Lewis & Co. (“Glass Lewis”), respectively, recommended Sesen Bio stockholders vote “FOR” all proposals at the March 2, 2023 Special Meeting of Stockholders. The positive recommendations from ISS and Glass Lewis build on the support received from several of Sesen Bio’s largest stockholders for the merger with Carisma, including Bradley L. Radoff, Michael Torok and their affiliates, as well as BML Investment Partners, L.P., who together beneficially own approximately 12.8% of Sesen Bio’s outstanding common stock. On January 31, 2023, the United States District Court for the Southern District of New York issued an order granting final approval of the settlement of the consolidated shareholder class action captioned In re Sesen Bio, Inc. Securities Litigation, Master File No. 1:21-cv-07025-AKH (the “Securities Litigation”). This follows the November 8, 2022 grant of final approval by the United States District Court for the District of Massachusetts of the settlement of the previously disclosed consolidated derivative lawsuits captioned In re Sesen Bio, Inc. Derivative Litigation, Lead Case No. 1:21-cv-11538, the derivative lawsuit captioned Tang v. Sesen Bio, Inc., et al., Case No. 2281-cv-00135 and other potential related derivative claims (collectively, the “Derivative Litigation”). On February 24, 2023, Sesen Bio received a determination from Nasdaq’s Office of General Counsel that the Nasdaq Hearings Panel (the “Panel”) had granted the Company an exception from the Company’s non-compliance with the $1.00 bid price requirement to complete the proposed merger with Carisma by March 10, 2023. Pursuant to Nasdaq Listing Rule 5110(a), the Company must demonstrate compliance with all initial listing requirements of Nasdaq upon closing of the proposed merger with Carisma. Sesen Bio was scheduled for a hearing with the Panel on March 16, 2023, following receipt of notice from Nasdaq’s Listing Qualifications Department on January 25, 2023 that the Company’s common stock is subject to delisting based upon non-compliance with the $1.00 bid price requirement. In the event the Company fails to establish compliance with the initial listing standards by March 10, 2023, its common stock will be delisted from Nasdaq, unless granted an additional exception by the Panel. 1: Based on basic outstanding shares including unvested restricted stock units Fourth Quarter 2022 Financial Results Cash Position: Cash, cash equivalents and marketable securities were $166.9 million as of December 31, 2022, compared to cash and cash equivalents of $162.6 million as of December 31, 2021. R&D Expenses: Research and development expenses were $1.0 million for the three months ended December 31, 2022, compared to $7.0 million for the three months ended December 31, 2021. Research and development expenses were $38.6 million for the year ended December 31, 2022, compared to $25.3 million for the year ended December 31, 2021. The increase of $13.3 million was primarily driven by the expense of prepaid balances related to consumables and manufacturing reservations, as the balances were deemed to have no future value due to the strategic decision to voluntarily pause further development of Vicineum in the United States ($25.2 million). Additionally, employee-related compensation increased, primarily due to the retention programs implemented in the fourth quarter of 2021 and third quarter of 2022 ($1.0 million). The increase was partially offset by decreased costs associated with manufacturing ($8.9 million), clinical and manufacturing related consulting fees ($2.3 million) and other individually immaterial research and development costs ($0.2 million), driven by the strategic decision to voluntarily pause further development of Vicineum in the United States in the third quarter of 2022. Additionally, one-time regulatory milestone payments ($1.5 million) related to the filing of the biologics license application (BLA) to the United States Food and Drug Administration (the “FDA”) for Vicineum and a marketing authorization application (MAA) to the European Medicines Agency (EMA) for Vysyneum were made in 2021. G&A Expenses: General and administrative expenses were $7.1 million for the three months ended December 31, 2022, compared to $8.6 million for the three months ended December 31, 2021. General and administrative expenses were $39.8 million for the year ended December 31, 2022, compared to $29.4 million for the year ended December 31, 2021. The increase of $10.4 million was primarily due to an increase in legal expense ($13.1 million) driven by the settlements of the Securities Litigation and Derivative Litigation net of expected insurance recovery ($8.2 million) and the Company’s assessment of strategic alternatives ($3.8 million). Additionally, there were increases in legal fees for the Securities Litigation and Derivative Litigation counseling ($0.6 million), general business counseling ($0.3 million), and other legal expenses ($0.2 million). The Company also incurred $1.2 million in connection with the fairness opinions related to the proposed merger with Carisma and increases in other individually immaterial expenses ($0.2 million). This was partially offset by decreases in marketing and commercial expenses ($4.1 million), driven by preparation for the commercial launch of Vicineum prior to the receipt of the complete response letter (the “CRL”) from the FDA in August 2021. Restructuring Charges: Restructuring charges were $0.8 million for the three months ended December 31, 2022, compared to a de minimis amount for the three months ended December 31, 2021. Restructuring expenses were $11.8 million for the year ended December 31, 2022, compared to $5.5 million for the year ended December 31, 2021. The expenses for the year ended December 31, 2022 consisted of severance and other employee-related costs ($7.0 million) and termination of certain contracts and other associated costs ($4.8 million) following the decision to pause further development of Vicineum in the United States. The expenses for the year ended December 31, 2021, consisted of severance and other employee-related costs ($2.8 million) and termination of certain contracts ($2.7 million) following the receipt of the CRL in August 2021. Non-Cash Related Expenses: The intangibles impairment charge for the year ended December 31, 2022 was $27.8 million. Due to the strategic decision to voluntarily pause further development of Vicineum in the United States during the second quarter of 2022, the Company completed its impairment testing and concluded that the carrying value of its intangible asset of Vicineum European Union rights of $14.7 million and Goodwill of $13.1 million were fully impaired and written off during the second quarter of 2022. The intangible impairment charge for the year ended December 31, 2021 was $31.7 million. In light of the CRL, the Company performed an interim impairment test, which concluded that the carrying value of its intangible asset of Vicineum United States rights of $31.7 million was fully impaired during the third quarter of 2021. The non-cash change in fair value of contingent consideration of $52.0 million for the year ended December 31, 2022 was driven by the Company’s strategic decision to voluntarily pause further development of Vicineum in the United States and the Company’s conclusion that it no longer expects to owe any related future earnout and milestone payments. The decision was based on a thorough reassessment of Vicineum following discussions with the FDA, which had implications for the size, timeline and costs for an additional Phase 3 clinical trial of Vicineum for the treatment of non-muscle invasive bladder cancer. The change in fair value of contingent consideration was $56.8 million for the year ended December 31, 2021. This was primarily due to management's assessment of a lower probability of regulatory approval following the receipt of a CRL in August 2021, in which the FDA determined that it could not approve the BLA for Vicineum in its present form. The intangibles impairment charge for the year ended December 31, 2022 was $27.8 million. Due to the strategic decision to voluntarily pause further development of Vicineum in the United States during the second quarter of 2022, the Company completed its impairment testing and concluded that the carrying value of its intangible asset of Vicineum European Union rights of $14.7 million and Goodwill of $13.1 million were fully impaired and written off during the second quarter of 2022. The intangible impairment charge for the year ended December 31, 2021 was $31.7 million. In light of the CRL, the Company performed an interim impairment test, which concluded that the carrying value of its intangible asset of Vicineum United States rights of $31.7 million was fully impaired during the third quarter of 2021. The non-cash change in fair value of contingent consideration of $52.0 million for the year ended December 31, 2022 was driven by the Company’s strategic decision to voluntarily pause further development of Vicineum in the United States and the Company’s conclusion that it no longer expects to owe any related future earnout and milestone payments. The decision was based on a thorough reassessment of Vicineum following discussions with the FDA, which had implications for the size, timeline and costs for an additional Phase 3 clinical trial of Vicineum for the treatment of non-muscle invasive bladder cancer. The change in fair value of contingent consideration was $56.8 million for the year ended December 31, 2021. This was primarily due to management's assessment of a lower probability of regulatory approval following the receipt of a CRL in August 2021, in which the FDA determined that it could not approve the BLA for Vicineum in its present form. Income Tax Benefit: For the year ended December 31, 2022, the Company recorded a benefit from income taxes of $3.9 million. In the second quarter of 2022, the Company determined that the fair value of the Vicineum European Union in-process research and development asset was zero, which resulted in an impairment charge of $14.7 million. In connection with this impairment charge, in the second quarter of 2022, the Company wrote-down the associated deferred tax liability by $3.9 million as a benefit. For the year ended December 31, 2021, the Company recorded a benefit from income taxes of $8.3 million. In the third quarter of 2021, the Company determined that the fair value of the Vicineum United States in-process research and development asset was zero, which resulted in an impairment charge of $31.7 million. In connection with this impairment charge, in the third quarter of 2021, the Company wrote-down the associated deferred tax liability by $8.6 million as a benefit. This was partially offset by $0.3 million in taxes paid related to the Qilu License Agreement. Net (Loss) Income: Net loss was $7.6 million, or $0.04 per basic and diluted share, for the fourth quarter of 2022, compared to net income of $8.9 million, or $0.04 per basic and diluted share, for the same period in 2021. Net loss was $19.9 million, or $0.10 per basic and diluted share, for the year ended December 31, 2022, compared to $0.3 million, or $0.00 per basic and per diluted share, for the year ended December 31, 2021. The increase in net loss was primarily due to an increase in operating expense ($30.8 million) and a decrease in income tax benefit ($4.4 million), which were offset by an increase in license and related revenue ($13.5 million). The revenue increase was primarily driven by the execution of the asset purchase agreement with F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (collectively, “Roche”) for EBI-031 and all other IL-6 antagonist monoclonal antibody technology in 2022 ($40.0 million), partially offset by the milestones achieved by Roche ($20.0 million), Qilu Pharmaceutical Co., Ltd., the Company’s former partner in the Greater China region ($5.0 million), and Hikma Pharmaceuticals LLC, the Company’s former partner in the Middle East and North Africa region ($1.5 million) in 2021. Additionally, interest income increased ($1.8 million) primarily due to higher yield earned on the Company’s investment account during 2022. About Sesen Bio Sesen Bio, Inc. is a late-stage clinical company that previously focused on advancing targeted fusion protein therapeutics for the treatment of patients with cancer. Sesen Bio’s most advanced product candidate, Vicineum™, also known as VB4-845, is a locally administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive bladder cancer. On July 15, 2022, Sesen Bio made the strategic decision to voluntarily pause further development of Vicineum in the United States. The decision was based on a thorough reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional Phase 3 clinical trial, following Sesen Bio’s discussions with the United States Food and Drug Administration. Sesen Bio has turned its primary focus to consummating a strategic transaction with the goal of maximizing stockholder value. Additionally, Sesen Bio is seeking a partner for the further development of Vicineum. For more information, please visit the Company’s website at www.sesenbio.com. Cautionary Note on Forward-Looking Statements Any statements in this press release about future expectations, plans and prospects for Sesen Bio, Inc. (Sesen Bio), CARISMA Therapeutics Inc. (Carisma) or the combined company, Sesen Bio’s, Carisma’s or the combined company’s strategy or future operations, and other statements containing the words “anticipate,” “believe,” “contemplate,” “expect,” “intend,” “may,” “plan,” “predict,” “target,” “potential,” “possible,” “will,” “would,” “could,” “should,” “continue,” and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. For example, statements concerning Sesen Bio’s ability to find a partner for the further development of Vicineum, the proposed transaction, the concurrent financing, the contingent value rights and other matters, including without limitation: statements relating to the satisfaction of the conditions to and consummation of the proposed transaction, the expected timing of the consummation of the proposed transaction, the expected ownership percentages of the combined company, Sesen Bio’s and Carisma’s respective businesses, the strategy of the combined company, future operations, advancement of the combined company’s product candidates and product pipeline, clinical development of the combined company’s product candidates, including expectations regarding timing of initiation and results of clinical trials of the combined company, the ability of Sesen Bio to remain listed on the Nasdaq Stock Market, the completion of the concurrent financing, the receipt of any payments under the contingent value rights, and the amount and timing of distributions to be made to Sesen Bio stockholders, if any, in connection with any potential dissolution or liquidation scenario are forward-looking statements. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain stockholder approval of matters related to the proposed transaction in a timely manner or at all; (ii) uncertainties as to the timing of the consummation of the proposed transaction and the ability of each of Sesen Bio and Carisma to consummate the proposed transaction, including completing the concurrent financing; (iii) risks related to Sesen Bio’s ability to correctly estimate its expected net cash at closing and Sesen Bio’s and Carisma’s ability to correctly estimate and manage their respective operating expenses and expenses associated with the proposed transaction; (iv) risks related to Sesen Bio’s continued listing on the Nasdaq Stock Market until closing of the proposed transaction; (v) the risk that as a result of adjustments to the exchange ratio, Sesen Bio stockholders or Carisma stockholders could own less of the combined company than is currently anticipated; (vi) the risk that the conditions to payment under the contingent value rights will not be met and that the contingent value rights may otherwise never deliver any value to Sesen Bio stockholders; (vii) risks associated with the possible failure to realize certain anticipated benefits of the proposed transaction, including with respect to future financial and operating results; (viii) uncertainties regarding the impact any delay in the closing would have on the anticipated cash resources of the combined company upon closing and other events and unanticipated spending and costs that could reduce the combined company’s cash resources; (ix) the effect of uncertainties related to the actions of activist stockholders, which could make it more difficult to obtain the approval of Sesen Bio stockholders with respect to the transaction related proposals and result in Sesen Bio incurring significant fees and other expenses, including for third-party advisors; (x) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the merger agreement, as amended; (xi) the effect of the announcement, pendency or completion of the merger on Sesen Bio’s or Carisma’s business relationships, operating results and business generally; (xii) costs related to the merger; (xiii) the outcome of any legal proceedings instituted against Sesen Bio, Carisma or any of their respective directors or officers related to the merger agreement or the transactions contemplated thereby; (xiv) the ability of Sesen Bio or Carisma to protect their respective intellectual property rights; (xv) competitive responses to the proposed transaction and changes in expected or existing competition; (xvi) the success and timing of regulatory submissions and pre-clinical and clinical trials; (xvii) regulatory requirements or developments; (xviii) changes to clinical trial designs and regulatory pathways; (xix) changes in capital resource requirements; (xx) risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates and its preclinical programs; (xxi) legislative, regulatory, political and economic developments; and (xxii) other factors discussed in the “Risk Factors” section of Sesen Bio’s Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other reports filed with the Securities and Exchange Commission (SEC). In addition, the forward-looking statements included in this press release represent Sesen Bio’s and Carisma’s views as of the date hereof. Sesen Bio and Carisma anticipate that subsequent events and developments will cause the respective company’s views to change. However, while Sesen Bio may elect to update these forward-looking statements at some point in the future, Sesen Bio specifically disclaims any obligation to do so, except as required under applicable law. These forward-looking statements should not be relied upon as representing Sesen Bio’s views as of any date subsequent to the date hereof. Important Additional Information In connection with the proposed transaction between Carisma and Sesen Bio, Sesen Bio filed with the SEC a registration statement on Form S-4 (as amended, the registration statement) that includes a proxy statement of Sesen Bio and also constitutes a prospectus of Sesen Bio with respect to shares of Sesen Bio common stock to be issued in the proposed transaction (proxy statement/prospectus), as amended by the supplement Sesen Bio filed with the SEC on February 16, 2023 (supplement). The definitive proxy statement/prospectus was first mailed to Sesen Bio stockholders on or about January 24, 2023, and the supplement was first mailed to Sesen Bio stockholders on or about February 17, 2023. Sesen Bio may also file other relevant documents regarding the proposed transaction with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THESE MATERIALS, INCLUDING THE REGISTRATION STATEMENT, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, THE SUPPLEMENT AND ALL OTHER RELEVANT DOCUMENTS THAT ARE OR WILL BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE MATERIALS, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders are able to obtain the definitive proxy statement/prospectus and other documents that are filed or will be filed by Sesen Bio with the SEC free of charge from the SEC’s website at www.sec.gov or from Sesen Bio at the SEC Filings section of www.sesenbio.com. No Offer or Solicitation This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, a public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone or internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction. Participants in the Solicitation Sesen Bio and Carisma and their respective directors, executive officers and other members of management may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Sesen Bio’s directors and executive officers is available in Sesen Bio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, its definitive proxy statement dated April 28, 2022 for its 2022 Annual Meeting of Stockholders and its Current Report on Form 8-K filed with the SEC on August 31, 2022. Other information regarding the participants in the proxy solicitation and a description of their interests in the proposed transaction, by security holdings or otherwise, is included in the definitive proxy statement/prospectus and other relevant materials that are or will be filed with the SEC regarding the proposed transaction. Investors should read the definitive proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Sesen Bio or the SEC’s website as indicated above. $ 112,553 $ 162,636 54,366 - 21,000 - - 21,011 825 3,482 400 18,476 189,144 205,605 30 20 - 43 - 14,700 - 13,064 - 7,192 - 123 30 35,142 $ 189,174 $ 240,747 $ 1,233 $ 2,853 29,636 8,255 115 460 30,984 11,568 - 52,000 - 3,969 - 1,500 - 57,469 30,984 69,037 - - 202 199 494,675 487,768 (546 ) - (336,141 ) (316,257 ) 158,190 171,710 $ 189,174 $ 240,747 2022 2021 2022 2021 $ - $ 20,000 $ 40,000 $ 26,544 $ - $ 20,000 $ 40,000 $ 26,544 $ 958 $ 7,039 $ 38,594 $ 25,312 7,082 8,597 39,787 29,393 817 6 11,764 5,528 - - 27,764 31,700 - (4,600 ) (52,000 ) (56,840 ) $ 8,857 $ 11,042 $ 65,909 $ 35,093 $ (8,857 ) $ 8,958 $ (25,909 ) $ (8,549 ) 1,384 3 1,854 17 (100 ) (18 ) 296 (77 ) $ (7,573 ) $ 8,944 $ (23,759 ) $ (8,609 ) - - 3,875 8,273 $ (7,573 ) $ 8,944 $ (19,884 ) $ (336 ) $ - $ - $ - $ - $ (7,573 ) $ 8,944 $ (19,884 ) $ (336 ) $ (0.04 ) $ 0.04 $ (0.10 ) $ (0.00 ) 202,758 199,464 200,546 182,323 2022 2021 2022 2021 $ (7,573 ) $ 8,944 $ (19,884 ) $ (336 ) 311 - 546 - $ (7,884 ) $ 8,944 $ (20,430 ) $ (336 )

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”), today announced that leading independent proxy advisory firm Glass, Lewis & Co. (“Glass Lewis”) recommends that stockholders vote “FOR” all proposals, including the pending merger with Carisma Therapeutics Inc. (“Carisma”), in advance of the Company's upcoming Special Meeting of Stockholders (the “Special Meeting”) scheduled for March 2, 2023.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”), today announced that leading independent proxy advisory firm Glass, Lewis & Co. (“Glass Lewis”) recommends that stockholders vote “FOR” all proposals, including the pending merger with Carisma Therapeutics Inc. (“Carisma”), in advance of the Company’s upcoming Special Meeting of Stockholders (the “Special Meeting”) scheduled for March 2, 2023. In reaching its conclusion that stockholders should support ALL proposals, including the merger and the proposed reverse stock split, Glass Lewis noted in its February 17, 2023, report1: "...we believe it is reasonable to conclude that the board has likely secured from Carisma the best terms reasonably available to the Company at this time." "Shareholders should understand that with the Company having halted development of Vicineum, and with the completion of the transaction contemplated under the Roche Asset Purchase Agreement, the Company is now effectively a publicly-traded cash shell. As a result, the primary components of the Company’s value are now its public listing and its available cash.” “We understand that for the purposes of the proposed merger, the Company is effectively being valued at a premium of $15 million (or approximately 21.4%) to its net cash contribution, which we believe is reasonable." “The proposed merger will allow shareholders to continue participating in the potential future upside of a combined company that will be focused on developing Carisma’s proprietary cell therapy platform. Shareholders will also obtain some immediate liquidity via the special cash dividend, along with additional potential upside from the CVRs.” “We agree with the board that it is in the best interest of the Company to reduce the number of shares of common stock outstanding and thereby attempt to proportionally raise the per share price of the Company's common stock. A higher stock price may help to increase investor interest, attract and retain employees and improve the Company's ability to raise additional capital through equity offerings.” The positive recommendation from Glass Lewis follows the February 16, 2023, report from Institutional Shareholder Services (“ISS”), another leading independent proxy advisory firm, recommending that stockholders vote “FOR” all proposals. In addition to the positive recommendations of the two leading proxy advisory firms, several of Sesen Bio’s largest stockholders that together beneficially own approximately 12.8% of Sesen Bio’s outstanding common stock have committed to vote their shares for the merger with Carisma. The Sesen Bio Board of Directors unanimously recommends that stockholders vote “FOR” each of the proposals listed on the WHITE proxy card enclosed with the previously mailed definitive proxy statement / prospectus. Stockholders are urged to vote their shares TODAY in advance of the Special Meeting. Stockholders can switch their vote at any time to vote “FOR” the merger. Only the latest-dated proxy counts. Sesen Bio’s definitive proxy statement / prospectus and supplement thereto, as well as other materials regarding the pending merger can be found at www.SesenBioandCarisma.com. The merger is expected to occur in the first quarter of 2023, subject to approval by Sesen Bio stockholders and other customary closing conditions. Sesen Bio stockholders who need assistance voting or have questions regarding the Sesen Bio Special Meeting may contact Sesen Bio’s proxy solicitor, MacKenzie Partners, toll-free at 1-800-322-2885 or email at proxy@mackenziepartners.com. SVB Securities is acting as exclusive financial advisor to Sesen Bio for the transaction and Hogan Lovells US LLP is serving as its legal counsel. About Sesen Bio Sesen Bio, Inc. is a late-stage clinical company focused on targeted fusion protein therapeutics for the treatment of patients with cancer. Sesen Bio’s most advanced product candidate, Vicineum™, also known as VB4-845, is a locally-administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive bladder cancer. On July 15, 2022, Sesen Bio made the strategic decision to voluntarily pause further development of Vicineum in the US. The decision was based on a thorough reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional Phase 3 clinical trial, following Sesen Bio’s discussions with the United States Food and Drug Administration. Sesen Bio has turned its primary focus to assessing potential strategic alternatives with the goal of maximizing shareholder value. Additionally, Sesen Bio intends to seek a partner for the further development of Vicineum. For more information, please visit the Company’s website at www.sesenbio.com. Cautionary Note on Forward-Looking Statements Any statements in this press release about future expectations, plans and prospects for Sesen Bio, Inc. (Sesen Bio), CARISMA Therapeutics Inc. (Carisma) or the combined company, Sesen Bio’s, Carisma’s or the combined company’s strategy or future operations, and other statements containing the words “anticipate,” “believe,” “contemplate,” “expect,” “intend,” “may,” “plan,” “predict,” “target,” “potential,” “possible,” “will,” “would,” “could,” “should,” “continue,” and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. For example, statements concerning the proposed transaction, the concurrent financing, the contingent value rights and other matters, including without limitation: statements relating to the satisfaction of the conditions to and consummation of the proposed transaction, the expected timing of the consummation of the proposed transaction, the expected ownership percentages of the combined company, Sesen Bio’s and Carisma’s respective businesses, the strategy of the combined company, future operations, advancement of the combined company’s product candidates and product pipeline, clinical development of the combined company’s product candidates, including expectations regarding timing of initiation and results of clinical trials of the combined company, the ability of Sesen Bio to remain listed on the Nasdaq Stock Market, the completion of the concurrent financing, the receipt of any payments under the contingent value rights, and the amount and timing of distributions to be made to Sesen Bio stockholders, if any, in connection with any potential dissolution or liquidation scenario are forward-looking statements. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain stockholder approval of matters related to the proposed transaction in a timely manner or at all; (ii) uncertainties as to the timing of the consummation of the proposed transaction and the ability of each of Sesen Bio and Carisma to consummate the proposed transaction, including completing the concurrent financing; (iii) risks related to Sesen Bio’s ability to correctly estimate its expected net cash at closing and Sesen Bio’s and Carisma’s ability to correctly estimate and manage their respective operating expenses and expenses associated with the proposed transaction; (iv) risks related to Sesen Bio’s continued listing on the Nasdaq Stock Market until closing of the proposed transaction; (v) the risk that as a result of adjustments to the exchange ratio, Sesen Bio stockholders or Carisma stockholders could own less of the combined company than is currently anticipated; (vi) the risk that the conditions to payment under the contingent value rights will not be met and that the contingent value rights may otherwise never deliver any value to Sesen Bio stockholders; (vii) risks associated with the possible failure to realize certain anticipated benefits of the proposed transaction, including with respect to future financial and operating results; (viii) uncertainties regarding the impact any delay in the closing would have on the anticipated cash resources of the combined company upon closing and other events and unanticipated spending and costs that could reduce the combined company’s cash resources; (ix) the effect of uncertainties related to the actions of activist stockholders, which could make it more difficult to obtain the approval of Sesen Bio stockholders with respect to the transaction related proposals and result in Sesen Bio incurring significant fees and other expenses, including for third-party advisors; (x) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the merger agreement, as amended; (xi) the effect of the announcement, pendency or completion of the merger on Sesen Bio’s or Carisma’s business relationships, operating results and business generally; (xii) costs related to the merger; (xiii) the outcome of any legal proceedings instituted against Sesen Bio, Carisma or any of their respective directors or officers related to the merger agreement or the transactions contemplated thereby; (xiv) the ability of Sesen Bio or Carisma to protect their respective intellectual property rights; (xv) competitive responses to the proposed transaction and changes in expected or existing competition; (xvi) the success and timing of regulatory submissions and pre-clinical and clinical trials; (xvii) regulatory requirements or developments; (xviii) changes to clinical trial designs and regulatory pathways; (xix) changes in capital resource requirements; (xx) risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates and its preclinical programs; (xxi) legislative, regulatory, political and economic developments; and (xxii) other factors discussed in the “Risk Factors” section of Sesen Bio’s Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other reports filed with the Securities Exchange Commission (SEC). In addition, the forward-looking statements included in this press release represent Sesen Bio’s and Carisma’s views as of the date hereof. Sesen Bio and Carisma anticipate that subsequent events and developments will cause the respective company’s views to change. However, while Sesen Bio may elect to update these forward-looking statements at some point in the future, Sesen Bio specifically disclaims any obligation to do so, except as required under applicable law. These forward-looking statements should not be relied upon as representing Sesen Bio’s views as of any date subsequent to the date hereof. Important Additional Information In connection with the proposed transaction between Carisma and Sesen Bio, Sesen Bio first mailed to Sesen Bio stockholders a definitive proxy statement/prospectus on or about January 24, 2023, and a supplement to the proxy statement/prospectus on or about January 17, 2023. Sesen Bio may also file other relevant documents regarding the proposed transaction with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THESE MATERIALS, INCLUDING THE REGISTRATION STATEMENT, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, THE SUPPLEMENT AND ALL OTHER RELEVANT DOCUMENTS THAT ARE OR WILL BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE MATERIALS, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders are able to obtain the definitive proxy statement/prospectus and other documents that are filed or will be filed by Sesen Bio with the SEC free of charge from the SEC’s website at www.sec.gov or from Sesen Bio at the SEC Filings section of www.sesenbio.com. No Offer or Solicitation This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, a public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone or internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction. Participants in the Solicitation Sesen Bio and Carisma and their respective directors, executive officers and other members of management may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Sesen Bio’s directors and executive officers is available in Sesen Bio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, its definitive proxy statement dated April 28, 2022 for its 2022 Annual Meeting of Stockholders and its Current Report on Form 8-K filed with the SEC on August 31, 2022. Other information regarding the participants in the proxy solicitation and a description of their interests in the proposed transaction, by security holdings or otherwise, is included in the definitive proxy statement/prospectus and other relevant materials that are or will be filed with the SEC regarding the proposed transaction. Investors should read the definitive proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Sesen Bio or the SEC’s website as indicated above. ______________________________________ 1 Permission to use quotes neither sought nor obtained. Emphasis added.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”), today announced that Institutional Shareholder Services (“ISS”) recommends that stockholders vote “FOR” all proposals, including the pending merger with Carisma Therapeutics Inc. (“Carisma”), at the Company's upcoming Special Meeting of Stockholders (the “Special Meeting”) scheduled for March 2, 2023.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”), today announced that Institutional Shareholder Services (“ISS”) recommends that stockholders vote “FOR” all proposals, including the pending merger with Carisma Therapeutics Inc. (“Carisma”), at the Company’s upcoming Special Meeting of Stockholders (the “Special Meeting”) scheduled for March 2, 2023. ISS is widely recognized as a leading independent proxy advisory firm, providing impartial analyses and reports to help investors make informed investment decisions. In reaching its conclusion to support ALL proposals, including the merger and the proposed reverse stock split, ISS noted in its February 16, 2023, report1: “[Sesen Bio] appears to have conducted a thorough overview of alternatives and is proposing to merge with a well-funded company that has attracted strategic interest from leading biotech companies.” “Carisma is expected to reach several milestones over the next 18 months, including multiple clinical data readouts, the first of which is expected in mid-2023.” “[Sesen Bio] has been able to negotiate an increase in the special dividend to be paid to its shareholders from $25 million to $75 million and an increase in the potential value of the CVR through the addition of assets and extension of the payment period.” “The reverse split is necessary to maintain the listing of the company's stock. As such, support for this proposal is warranted.” “In light of the compelling strategic rationale, estimated potential value to shareholders of $0.88 per share, as well as the apparent downside risk of non-approval given SESN's significant outperformance vs. the index since the unaffected date, support for the merger is warranted.” In accordance with the ISS recommendation, the Sesen Bio Board of Directors unanimously recommends that stockholders vote “FOR” each of the proposals listed on the WHITE proxy card enclosed with the previously mailed definitive proxy statement / prospectus. Stockholders are urged to vote their shares TODAY, in advance of the Special Meeting. Shareholders can switch their vote at any time to vote “FOR” the merger. Only the latest-dated proxy card counts. Dr. Jay Duker, Chair of the Sesen Bio Board of Directors, said “We are pleased that ISS shares our belief that the merger with Carisma maximizes value for stockholders with substantial and immediate cash value, as well as significant long-term upside through ownership in the combined company. Following the support from our largest investors, we encourage all stockholders to vote “FOR” all proposals at the March 2 Special Meeting.” In its report, ISS noted the voting and support agreement (the “Support Agreement”) between Sesen Bio and Bradley L. Radoff and Michael Torok (together with their respective affiliates, the “Investor Group”) dated February 13, 2023. The Investor Group beneficially owns approximately 8.7% of Sesen Bio’s common stock and has committed to vote its shares in support of the pending merger. As disclosed on February 14, 2023, Sesen Bio and Carisma further amended the previously amended merger agreement announced on December 29, 2022, which has been unanimously approved by the Boards of Directors of both companies to include: One-time special cash dividend expected to be paid to Sesen Bio stockholders has been increased to $75 million, $0.36 per share2; The period of time for payments under the Contingent Value Right (“CVR”) related to any potential proceeds from the sale of Vicineum and Sesen Bio’s other legacy assets has been extended to March 31, 2027, from December 31, 2023, under the previous terms. Under the CVR, Sesen Bio stockholders remain entitled to any proceeds from the potential milestone payment under the Roche Asset Purchase Agreement; and Michael Torok will join the Carisma Board of Directors upon closing of the merger as the only Sesen Bio representative. The positive recommendation from ISS builds on the support received from several of Sesen Bio’s largest stockholders for the merger with Carisma, including the Investor Group and BML Investment Partners, who together beneficially own approximately 12.8% of Sesen Bio’s outstanding common stock. Sesen Bio’s definitive proxy statement / prospectus and other materials regarding the pending merger can be found at www.SesenBioandCarisma.com. The merger is expected to occur in the first quarter of 2023, subject to approval by Sesen Bio stockholders and other customary closing conditions. Sesen Bio stockholders who need assistance voting or have questions regarding the Sesen Bio Special Meeting may contact Sesen Bio’s proxy solicitor, MacKenzie Partners, toll-free at 1-800-322-2885 or email at proxy@mackenziepartners.com. SVB Securities is acting as exclusive financial advisor to Sesen Bio for the transaction and Hogan Lovells US LLP is serving as its legal counsel. About Sesen Bio Sesen Bio, Inc. is a late-stage clinical company focused on targeted fusion protein therapeutics for the treatment of patients with cancer. Sesen Bio’s most advanced product candidate, Vicineum™, also known as VB4-845, is a locally-administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive bladder cancer. On July 15, 2022, Sesen Bio made the strategic decision to voluntarily pause further development of Vicineum in the US. The decision was based on a thorough reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional Phase 3 clinical trial, following Sesen Bio’s discussions with the United States Food and Drug Administration. Sesen Bio has turned its primary focus to assessing potential strategic alternatives with the goal of maximizing shareholder value. Additionally, Sesen Bio intends to seek a partner for the further development of Vicineum. For more information, please visit the Company’s website at www.sesenbio.com. Cautionary Note on Forward-Looking Statements Any statements in this press release about future expectations, plans and prospects for Sesen Bio, Inc. (Sesen Bio), CARISMA Therapeutics Inc. (Carisma) or the combined company, Sesen Bio’s, Carisma’s or the combined company’s strategy or future operations, and other statements containing the words “anticipate,” “believe,” “contemplate,” “expect,” “intend,” “may,” “plan,” “predict,” “target,” “potential,” “possible,” “will,” “would,” “could,” “should,” “continue,” and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. For example, statements concerning the proposed transaction, the concurrent financing, the contingent value rights and other matters, including without limitation: statements relating to the satisfaction of the conditions to and consummation of the proposed transaction, the expected timing of the consummation of the proposed transaction, the expected ownership percentages of the combined company, Sesen Bio’s and Carisma’s respective businesses, the strategy of the combined company, future operations, advancement of the combined company’s product candidates and product pipeline, clinical development of the combined company’s product candidates, including expectations regarding timing of initiation and results of clinical trials of the combined company, the ability of Sesen Bio to remain listed on the Nasdaq Stock Market, the completion of the concurrent financing, the receipt of any payments under the contingent value rights, and the amount and timing of distributions to be made to Sesen Bio stockholders, if any, in connection with any potential dissolution or liquidation scenario are forward-looking statements. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain stockholder approval of matters related to the proposed transaction in a timely manner or at all; (ii) uncertainties as to the timing of the consummation of the proposed transaction and the ability of each of Sesen Bio and Carisma to consummate the proposed transaction, including completing the concurrent financing; (iii) risks related to Sesen Bio’s ability to correctly estimate its expected net cash at closing and Sesen Bio’s and Carisma’s ability to correctly estimate and manage their respective operating expenses and expenses associated with the proposed transaction; (iv) risks related to Sesen Bio’s continued listing on the Nasdaq Stock Market until closing of the proposed transaction; (v) the risk that as a result of adjustments to the exchange ratio, Sesen Bio stockholders or Carisma stockholders could own less of the combined company than is currently anticipated; (vi) the risk that the conditions to payment under the contingent value rights will not be met and that the contingent value rights may otherwise never deliver any value to Sesen Bio stockholders; (vii) risks associated with the possible failure to realize certain anticipated benefits of the proposed transaction, including with respect to future financial and operating results; (viii) uncertainties regarding the impact any delay in the closing would have on the anticipated cash resources of the combined company upon closing and other events and unanticipated spending and costs that could reduce the combined company’s cash resources; (ix) the effect of uncertainties related to the actions of activist stockholders, which could make it more difficult to obtain the approval of Sesen Bio stockholders with respect to the transaction related proposals and result in Sesen Bio incurring significant fees and other expenses, including for third-party advisors; (x) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the merger agreement, as amended; (xi) the effect of the announcement, pendency or completion of the merger on Sesen Bio’s or Carisma’s business relationships, operating results and business generally; (xii) costs related to the merger; (xiii) the outcome of any legal proceedings instituted against Sesen Bio, Carisma or any of their respective directors or officers related to the merger agreement or the transactions contemplated thereby; (xiv) the ability of Sesen Bio or Carisma to protect their respective intellectual property rights; (xv) competitive responses to the proposed transaction and changes in expected or existing competition; (xvi) the success and timing of regulatory submissions and pre-clinical and clinical trials; (xvii) regulatory requirements or developments; (xviii) changes to clinical trial designs and regulatory pathways; (xix) changes in capital resource requirements; (xx) risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates and its preclinical programs; (xxi) legislative, regulatory, political and economic developments; and (xxii) other factors discussed in the “Risk Factors” section of Sesen Bio’s Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other reports filed with the Securities Exchange Commission (SEC). In addition, the forward-looking statements included in this press release represent Sesen Bio’s and Carisma’s views as of the date hereof. Sesen Bio and Carisma anticipate that subsequent events and developments will cause the respective company’s views to change. However, while Sesen Bio may elect to update these forward-looking statements at some point in the future, Sesen Bio specifically disclaims any obligation to do so, except as required under applicable law. These forward-looking statements should not be relied upon as representing Sesen Bio’s views as of any date subsequent to the date hereof. Important Additional Information In connection with the proposed transaction between Carisma and Sesen Bio, Sesen Bio filed with the SEC a registration statement on Form S-4 (as amended, the registration statement) that includes a proxy statement of Sesen Bio and also constitutes a prospectus of Sesen Bio with respect to shares of Sesen Bio common stock to be issued in the proposed transaction (proxy statement/prospectus). The definitive proxy statement/prospectus was first mailed to Sesen Bio stockholders on or about January 24, 2023. Sesen Bio may also file other relevant documents regarding the proposed transaction with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THESE MATERIALS, INCLUDING THE REGISTRATION STATEMENT, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, AND ALL OTHER RELEVANT DOCUMENTS THAT ARE OR WILL BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE MATERIALS, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders are able to obtain the definitive proxy statement/prospectus and other documents that are filed or will be filed by Sesen Bio with the SEC free of charge from the SEC’s website at www.sec.gov or from Sesen Bio at the SEC Filings section of www.sesenbio.com. No Offer or Solicitation This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, a public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone or internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction. Participants in the Solicitation Sesen Bio and Carisma and their respective directors, executive officers and other members of management may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Sesen Bio’s directors and executive officers is available in Sesen Bio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, its definitive proxy statement dated April 28, 2022 for its 2022 Annual Meeting of Stockholders and its Current Report on Form 8-K filed with the SEC on August 31, 2022. Other information regarding the participants in the proxy solicitation and a description of their interests in the proposed transaction, by security holdings or otherwise, is included in the definitive proxy statement/prospectus and other relevant materials that are or will be filed with the SEC regarding the proposed transaction. Investors should read the definitive proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Sesen Bio or the SEC’s website as indicated above. 1 Permission to use quotes neither sought nor obtained. Emphasis added. 2 Based on basic outstanding shares including unvested RSUs.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) today announced that members of its management team will host a fireside chat with members of the Carisma Therapeutics Inc. (“Carisma”) management team on Tuesday, February 21, 2023, at 8:00 am ET. The discussion will cover Sesen Bio’s pending merger with Carisma, as well as Carisma’s corporate strategy and clinical programs. Sesen Bio stockholders can submit questions in advance to ir@sesenbio.com. The webcast, which can be accessed on the Events and Presentations link on the Sesen Bio website, will be broadcast live and a replay will be available following the conclusion of the event. As previously announced, Sesen Bio will hold the Special Meeting of Stockholders via live webcast on March 2, 2023, at 10:00 a.m. Eastern Time. Sesen Bio stockholders of record as of January 17, 2023, will be entitled to vote at the meeting. About Sesen Bio Sesen Bio, Inc. is a late-stage clinical company focused on targeted fusion protein therapeutics for the treatment of patients with cancer. Sesen Bio’s most advanced product candidate, Vicineum™, also known as VB4-845, is a locally-administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive bladder cancer. On July 15, 2022, Sesen Bio made the strategic decision to voluntarily pause further development of Vicineum in the US. The decision was based on a thorough reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional Phase 3 clinical trial, following Sesen Bio’s discussions with the United States Food and Drug Administration. Sesen Bio has turned its primary focus to assessing potential strategic alternatives with the goal of maximizing shareholder value. Additionally, Sesen Bio intends to seek a partner for the further development of Vicineum. For more information, please visit the Company’s website at www.sesenbio.com. Cautionary Note on Forward-Looking Statements Any statements in this press release about future expectations, plans and prospects for Sesen Bio, Inc. (Sesen Bio), CARISMA Therapeutics Inc. (Carisma) or the combined company, Sesen Bio’s, Carisma’s or the combined company’s strategy or future operations, and other statements containing the words “anticipate,” “believe,” “contemplate,” “expect,” “intend,” “may,” “plan,” “predict,” “target,” “potential,” “possible,” “will,” “would,” “could,” “should,” “continue,” and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. For example, statements concerning the proposed transaction, the concurrent financing, the contingent value rights and other matters, including without limitation: statements relating to the satisfaction of the conditions to and consummation of the proposed transaction, the expected timing of the consummation of the proposed transaction, the expected ownership percentages of the combined company, Sesen Bio’s and Carisma’s respective businesses, the strategy of the combined company, future operations, advancement of the combined company’s product candidates and product pipeline, clinical development of the combined company’s product candidates, including expectations regarding timing of initiation and results of clinical trials of the combined company, the ability of Sesen Bio to remain listed on the Nasdaq Stock Market, the completion of the concurrent financing, the receipt of any payments under the contingent value rights, and the amount and timing of distributions to be made to Sesen Bio stockholders, if any, in connection with any potential dissolution or liquidation scenario are forward-looking statements. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain stockholder approval of matters related to the proposed transaction in a timely manner or at all; (ii) uncertainties as to the timing of the consummation of the proposed transaction and the ability of each of Sesen Bio and Carisma to consummate the proposed transaction, including completing the concurrent financing; (iii) risks related to Sesen Bio’s ability to correctly estimate its expected net cash at closing and Sesen Bio’s and Carisma’s ability to correctly estimate and manage their respective operating expenses and expenses associated with the proposed transaction; (iv) risks related to Sesen Bio’s continued listing on the Nasdaq Stock Market until closing of the proposed transaction; (v) the risk that as a result of adjustments to the exchange ratio, Sesen Bio stockholders or Carisma stockholders could own less of the combined company than is currently anticipated; (vi) the risk that the conditions to payment under the contingent value rights will not be met and that the contingent value rights may otherwise never deliver any value to Sesen Bio stockholders; (vii) risks associated with the possible failure to realize certain anticipated benefits of the proposed transaction, including with respect to future financial and operating results; (viii) uncertainties regarding the impact any delay in the closing would have on the anticipated cash resources of the combined company upon closing and other events and unanticipated spending and costs that could reduce the combined company’s cash resources; (ix) the effect of uncertainties related to the actions of activist stockholders, which could make it more difficult to obtain the approval of Sesen Bio stockholders with respect to the transaction related proposals and result in Sesen Bio incurring significant fees and other expenses, including for third-party advisors; (x) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the merger agreement, as amended; (xi) the effect of the announcement, pendency or completion of the merger on Sesen Bio’s or Carisma’s business relationships, operating results and business generally; (xii) costs related to the merger; (xiii) the outcome of any legal proceedings instituted against Sesen Bio, Carisma or any of their respective directors or officers related to the merger agreement or the transactions contemplated thereby; (xiv) the ability of Sesen Bio or Carisma to protect their respective intellectual property rights; (xv) competitive responses to the proposed transaction and changes in expected or existing competition; (xvi) the success and timing of regulatory submissions and pre-clinical and clinical trials; (xvii) regulatory requirements or developments; (xviii) changes to clinical trial designs and regulatory pathways; (xix) changes in capital resource requirements; (xx) risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates and its preclinical programs; (xxi) legislative, regulatory, political and economic developments; and (xxii) other factors discussed in the “Risk Factors” section of Sesen Bio’s Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other reports filed with the Securities Exchange Commission (SEC). In addition, the forward-looking statements included in this press release represent Sesen Bio’s and Carisma’s views as of the date hereof. Sesen Bio and Carisma anticipate that subsequent events and developments will cause the respective company’s views to change. However, while Sesen Bio may elect to update these forward-looking statements at some point in the future, Sesen Bio specifically disclaims any obligation to do so, except as required under applicable law. These forward-looking statements should not be relied upon as representing Sesen Bio’s views as of any date subsequent to the date hereof. Important Additional Information In connection with the proposed transaction between Carisma and Sesen Bio, Sesen Bio filed with the SEC a registration statement on Form S-4 (as amended, the registration statement) that includes a proxy statement of Sesen Bio and also constitutes a prospectus of Sesen Bio with respect to shares of Sesen Bio common stock to be issued in the proposed transaction (proxy statement/prospectus). The definitive proxy statement/prospectus was first mailed to Sesen Bio stockholders on or about January 24, 2023. Sesen Bio may also file other relevant documents regarding the proposed transaction with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THESE MATERIALS, INCLUDING THE REGISTRATION STATEMENT, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, AND ALL OTHER RELEVANT DOCUMENTS THAT ARE OR WILL BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE MATERIALS, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders are able to obtain the definitive proxy statement/prospectus and other documents that are filed or will be filed by Sesen Bio with the SEC free of charge from the SEC’s website at www.sec.gov or from Sesen Bio at the SEC Filings section of www.sesenbio.com. No Offer or Solicitation This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, a public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone or internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction. Participants in the Solicitation Sesen Bio and Carisma and their respective directors, executive officers and other members of management may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Sesen Bio’s directors and executive officers is available in Sesen Bio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, its definitive proxy statement dated April 28, 2022 for its 2022 Annual Meeting of Stockholders and its Current Report on Form 8-K filed with the SEC on August 31, 2022. Other information regarding the participants in the proxy solicitation and a description of their interests in the proposed transaction, by security holdings or otherwise, is included in the definitive proxy statement/prospectus and other relevant materials that are or will be filed with the SEC regarding the proposed transaction. Investors should read the definitive proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Sesen Bio or the SEC’s website as indicated above.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”), today announced that BML Investment Partners, L.P. (“BML”), one of Sesen Bio's top stockholders, intends to vote all of its shares in support of the Company's pending merger with Carisma Therapeutics Inc. (“Carisma”). BML owned approximately 4.1% of the Company's outstanding common stock as of the close of business on January 17, 2023, the record date for the Special Meeting of Stockholders.

CAMBRIDGE, Mass. & PHILADELPHIA--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) and Carisma Therapeutics Inc. (Carisma), a privately-held, clinical stage biopharmaceutical company focused on discovering and developing innovative immunotherapies, today announced that the companies have reached a voting and support agreement (the “Support Agreement”) with Bradley L. Radoff and Michael Torok (together with their respective affiliates, the “Investor Group”).

CAMBRIDGE, Mass. & PHILADELPHIA--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) and Carisma Therapeutics Inc. (Carisma), a privately-held, clinical stage biopharmaceutical company focused on discovering and developing innovative immunotherapies, today announced that the companies have reached a voting and support agreement (the “Support Agreement”) with Bradley L. Radoff and Michael Torok (together with their respective affiliates, the “Investor Group”). The Investor Group, which beneficially owns approximately 8.7% of Sesen Bio’s outstanding common stock, has committed to vote its shares in support of the pending merger. In connection with the Support Agreement, Sesen Bio and Carisma have further amended the previously amended merger agreement announced on December 29, 2022, which has been unanimously approved by the Boards of Directors of both companies: Increased the one-time special cash dividend expected to be paid to Sesen Bio stockholders to $75 million, $0.36 per share1. This represents an increase from the expected special cash dividend of approximately $70 million, approximately $0.34 per share, under the first amendment to the merger agreement, and an increase from the up to $25 million special cash dividend under the terms of the original merger agreement; Extended the period of time for payments under the Contingent Value Right (“CVR”) related to any potential proceeds from the sale of Vicineum and Sesen Bio’s other legacy assets to March 31, 2027, from December 31, 2023, under the previous terms. Under the CVR, Sesen Bio stockholders remain entitled to any proceeds from the potential milestone payment under the Roche Asset Purchase Agreement; and Michael Torok will join the Carisma Board of Directors upon closing of the merger as the only Sesen Bio representative. Dr. Jay Duker, Chair of the Sesen Bio Board of Directors, said, “We appreciate Mr. Radoff’s and Mr. Torok’s constructive engagement. Our discussions with our stockholders over the last several weeks have enabled valuable changes to the merger agreement that benefit all stockholders, including the significantly increased expected special cash dividend of $75 million and an enhanced CVR. We are confident that the merger with Carisma maximizes value for all Sesen Bio stockholders, and we are pleased Mr. Radoff and Mr. Torok will support the pending transaction. We look forward to expeditiously closing the merger by the end of the quarter.” Steven Kelly, President and Chief Executive Officer of Carisma, added, “We are excited to reach this agreement with Sesen Bio and Messrs. Radoff and Torok. The merger provides significant funding for Carisma's R&D pipeline to advance our revolutionary proprietary cell therapy platform. We are confident the combined company will be well positioned to create significant value for stockholders.” Mr. Torok, on behalf of the Investor Group, said, “We are pleased that our extensive engagement with Sesen Bio and its representatives has helped unlock additional value for Sesen Bio’s stockholders. We believe the amended merger terms represent the most value maximizing path for stockholders. We are excited about the long-term value potential of the Carisma platform, and I look forward to joining the Carisma Board.” Carisma’s previously announced approximately $30 million financing remains committed and is expected to close concurrently with the pending merger. The issuance of the special cash dividend and CVR remain contingent on the closing of the pending transaction, which is expected to occur in the first quarter of 2023, subject to approval by Sesen Bio stockholders and other customary closing conditions. Following completion of the incremental financing from Carisma’s key investors and subsequent completion of the merger, Sesen Bio stockholders are expected to own 24.2% of the pro forma company consistent with the exchange ratio formula set forth in the original merger agreement, dated September 20, 2022. The Sesen Bio Board unanimously recommends that stockholders vote “FOR” each of the proposals listed on the WHITE proxy card enclosed with the previously mailed definitive proxy statement / prospectus. As previously disclosed, the special meeting of stockholders will be held exclusively via live webcast on March 2, 2023, at 10:00 a.m. Eastern Time. Sesen Bio stockholders of record as of January 17, 2023, will be entitled to vote at the meeting. The complete Support Agreement, which includes other customary provisions, will be filed as an exhibit to a Form 8-K to be filed by the Company with the U.S. Securities and Exchange Commission. SVB Securities is acting as exclusive financial advisor to Sesen Bio for the transaction and Hogan Lovells US LLP is serving as its legal counsel. Evercore is serving as lead financial advisor to Carisma for the transaction and BofA Securities, Inc. is also serving as financial advisor to Carisma for the transaction. Wilmer Cutler Pickering Hale and Dorr LLP is serving as legal counsel to Carisma. BofA Securities, Inc. and Evercore are serving as co-placement agents for Carisma’s concurrent financing and Shearman & Sterling LLP is serving as the placement agents’ legal counsel. Olshan Frome Wolosky LLP is serving as legal counsel to the Investor Group. About Sesen Bio Sesen Bio, Inc. is a late-stage clinical company focused on targeted fusion protein therapeutics for the treatment of patients with cancer. Sesen Bio’s most advanced product candidate, Vicineum™, also known as VB4-845, is a locally-administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive bladder cancer. On July 15, 2022, Sesen Bio made the strategic decision to voluntarily pause further development of Vicineum in the US. The decision was based on a thorough reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional Phase 3 clinical trial, following Sesen Bio’s discussions with the United States Food and Drug Administration. Sesen Bio has turned its primary focus to assessing potential strategic alternatives with the goal of maximizing stockholder value. Additionally, Sesen Bio is seeking a partner for the further development of Vicineum. For more information, please visit the Company’s website at www.sesenbio.com. About Carisma Therapeutics Carisma Therapeutics Inc. is a biopharmaceutical company dedicated to developing a differentiated and proprietary cell therapy platform focused on engineered macrophages, cells that play a crucial role in both the innate and adaptive immune response. The first applications of the platform, developed in collaboration with the University of Pennsylvania*, are autologous chimeric antigen receptor (CAR)-macrophages for the treatment of solid tumors. Carisma is headquartered in Philadelphia, PA. For more information, please visit www.carismatx.com. *Carisma has licensed certain Penn-owned intellectual property from the University of Pennsylvania, and Penn's Perelman School of Medicine receives sponsored research and clinical trial funding from Carisma. Penn and certain of its faculty members, including Dr. Gill, are current equity holders in Carisma and have received and may be entitled to receive future financial consideration from Carisma from the development and commercialization of products based on licensed Penn intellectual property. Cautionary Note on Forward-Looking Statements Any statements in this press release about future expectations, plans and prospects for Sesen Bio, Inc. (Sesen Bio), CARISMA Therapeutics Inc. (Carisma) or the combined company, Sesen Bio’s, Carisma’s or the combined company’s strategy or future operations, and other statements containing the words “anticipate,” “believe,” “contemplate,” “expect,” “intend,” “may,” “plan,” “predict,” “target,” “potential,” “possible,” “will,” “would,” “could,” “should,” “continue,” and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. For example, statements concerning the proposed transaction, the concurrent financing, the contingent value rights and other matters, including without limitation: statements relating to the satisfaction of the conditions to and consummation of the proposed transaction, the expected timing of the consummation of the proposed transaction and the expected ownership percentages of the combined company, Sesen Bio’s and Carisma’s respective businesses, the strategy of the combined company, future operations, advancement of the combined company’s product candidates and product pipeline, clinical development of the combined company’s product candidates, including expectations regarding timing of initiation and results of clinical trials of the combined company, the ability of Sesen Bio to remain listed on the Nasdaq Stock Market, the completion of the concurrent financing and the receipt of any payments under the contingent value rights, are forward-looking statements. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain stockholder approval of matters related to the proposed transaction in a timely manner or at all; (ii) uncertainties as to the timing of the consummation of the proposed transaction and the ability of each of Sesen Bio and Carisma to consummate the proposed transaction, including completing the concurrent financing; (iii) risks related to Sesen Bio’s ability to correctly estimate its expected net cash at closing and Sesen Bio’s and Carisma’s ability to correctly estimate and manage their respective operating expenses and expenses associated with the proposed transaction; (iv) risks related to Sesen Bio’s continued listing on the Nasdaq Stock Market until closing of the proposed transaction; (v) the risk that as a result of adjustments to the exchange ratio, Sesen Bio stockholders or Carisma stockholders could own less of the combined company than is currently anticipated; (vi) the risk that the conditions to payment under the contingent value rights will not be met and that the contingent value rights may otherwise never deliver any value to Sesen Bio stockholders; (vii) risks associated with the possible failure to realize certain anticipated benefits of the proposed transaction, including with respect to future financial and operating results; (viii) uncertainties regarding the impact any delay in the closing would have on the anticipated cash resources of the combined company upon closing and other events and unanticipated spending and costs that could reduce the combined company’s cash resources; (ix) the effect of uncertainties related to the actions of activist stockholders, which could make it more difficult to obtain the approval of Sesen Bio stockholders with respect to the transaction related proposals and result in Sesen Bio incurring significant fees and other expenses, including for third-party advisors; (x) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the merger agreement, as amended; (xi) the effect of the announcement, pendency or completion of the merger on Sesen Bio’s or Carisma’s business relationships, operating results and business generally; (xii) costs related to the merger; (xiii) the outcome of any legal proceedings instituted against Sesen Bio, Carisma or any of their respective directors or officers related to the merger agreement or the transactions contemplated thereby; (xiv) the ability of Sesen Bio or Carisma to protect their respective intellectual property rights; (xv) competitive responses to the proposed transaction and changes in expected or existing competition; (xvi) the success and timing of regulatory submissions and pre-clinical and clinical trials; (xvii) regulatory requirements or developments; (xviii) changes to clinical trial designs and regulatory pathways; (xix) changes in capital resource requirements; (xx) risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates and its preclinical programs; (xxi) legislative, regulatory, political and economic developments; and (xxii) other factors discussed in the “Risk Factors” section of Sesen Bio’s Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other reports filed with the Securities Exchange Commission (SEC). In addition, the forward-looking statements included in this press release represent Sesen Bio’s and Carisma’s views as of the date hereof. Sesen Bio and Carisma anticipate that subsequent events and developments will cause the respective company’s views to change. However, while Sesen Bio may elect to update these forward-looking statements at some point in the future, Sesen Bio specifically disclaims any obligation to do so, except as required under applicable law. These forward-looking statements should not be relied upon as representing Sesen Bio’s views as of any date subsequent to the date hereof. Important Additional Information In connection with the proposed transaction between Carisma and Sesen Bio, Sesen Bio filed with the SEC a registration statement on Form S-4 (as amended, the registration statement) that includes a proxy statement of Sesen Bio and also constitutes a prospectus of Sesen Bio with respect to shares of Sesen Bio common stock to be issued in the proposed transaction (proxy statement/prospectus). The definitive proxy statement/prospectus was first mailed to Sesen Bio stockholders on or about January 24, 2023. Sesen Bio may also file other relevant documents regarding the proposed transaction with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THESE MATERIALS, INCLUDING THE REGISTRATION STATEMENT, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, AND ALL OTHER RELEVANT DOCUMENTS THAT ARE OR WILL BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE MATERIALS, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders are able to obtain the definitive proxy statement/prospectus and other documents that are filed or will be filed by Sesen Bio with the SEC free of charge from the SEC’s website at www.sec.gov or from Sesen Bio at the SEC Filings section of www.sesenbio.com. No Offer or Solicitation This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, a public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone or internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction. Participants in the Solicitation Sesen Bio and Carisma and their respective directors, executive officers and other members of management may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Sesen Bio’s directors and executive officers is available in Sesen Bio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, its definitive proxy statement dated April 28, 2022 for its 2022 Annual Meeting of Stockholders and its Current Report on Form 8-K filed with the SEC on August 31, 2022. Other information regarding the participants in the proxy solicitation and a description of their interests in the proposed transaction, by security holdings or otherwise, is included in the definitive proxy statement/prospectus and other relevant materials that are or will be filed with the SEC regarding the proposed transaction. Investors should read the definitive proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Sesen Bio or the SEC’s website as indicated above. 1 Based on basic outstanding shares including unvested RSUs.

CAMBRIDGE, Mass.--( BUSINESS WIRE )--Sesen Bio, Inc. (NASDAQ: SESN) today filed an investor presentation highlighting its value maximizing merger with Carisma Therapeutics Inc. (“Carisma”). The presentation can be found at www.SesenBioandCarisma.com.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (NASDAQ: SESN) today filed an investor presentation highlighting its value maximizing merger with Carisma Therapeutics Inc. (“Carisma”). The presentation can be found at www.SesenBioandCarisma.com. Highlights of the presentation include: The merger with Carisma delivers substantial and immediate value for Sesen Bio stockholders, which is meaningfully better than the alternative of dissolution and liquidation Expected special one-time cash dividend of approximately $70 million to be paid shortly after (and contingent upon) closing, $0.34 per share1. Additional potential cash upside via Contingent Value Right, including any potential proceeds from any sale of Sesen Bio’s legacy assets (including Vicineum) and from the potential $30 million milestone payment, $0.14 per share2, under the Roche Asset Purchase Agreement. Without the pending merger with Carisma, the most likely and feasible path for Sesen Bio would be a delisting from Nasdaq followed by a court-managed dissolution of the Company and a liquidation of assets. The Sesen Bio Board thoroughly considered dissolution and liquidation and determined there would be significant expense, delay and uncertainty. In a dissolution and liquidation scenario, only approximately 60%-90%3 of Sesen Bio’s cash balance, approximately $0.40-$0.60 per share, would be available for an initial distribution, which likely would not be available for six months or more after an additional stockholder vote. The full process could take up to three years in the Delaware court system to fully settle Sesen Bio’s potential future and unknown liabilities. Expected special one-time cash dividend of approximately $70 million to be paid shortly after (and contingent upon) closing, $0.34 per share1. Additional potential cash upside via Contingent Value Right, including any potential proceeds from any sale of Sesen Bio’s legacy assets (including Vicineum) and from the potential $30 million milestone payment, $0.14 per share2, under the Roche Asset Purchase Agreement. Without the pending merger with Carisma, the most likely and feasible path for Sesen Bio would be a delisting from Nasdaq followed by a court-managed dissolution of the Company and a liquidation of assets. The Sesen Bio Board thoroughly considered dissolution and liquidation and determined there would be significant expense, delay and uncertainty. In a dissolution and liquidation scenario, only approximately 60%-90%3 of Sesen Bio’s cash balance, approximately $0.40-$0.60 per share, would be available for an initial distribution, which likely would not be available for six months or more after an additional stockholder vote. The full process could take up to three years in the Delaware court system to fully settle Sesen Bio’s potential future and unknown liabilities. Sesen Bio conducted a robust strategic review process to maximize stockholder value The Sesen Bio Board proactively initiated a comprehensive four-month review of strategic options, including evaluating merger, sale of assets, resumption of R&D and dissolution and liquidation of assets and wind-down of Sesen Bio. Conducted outreach to over 100 parties, resulting in 42 bids. Board negotiated with Carisma extensively, including additional due diligence activities with Key Opinion Leaders with expertise in solid tumors and cell therapy to analyze and understand Carisma’s pipeline and proprietary cell therapy platform. The Sesen Bio Board proactively initiated a comprehensive four-month review of strategic options, including evaluating merger, sale of assets, resumption of R&D and dissolution and liquidation of assets and wind-down of Sesen Bio. Conducted outreach to over 100 parties, resulting in 42 bids. Board negotiated with Carisma extensively, including additional due diligence activities with Key Opinion Leaders with expertise in solid tumors and cell therapy to analyze and understand Carisma’s pipeline and proprietary cell therapy platform. Sesen Bio stockholders stand to benefit from significant potential upside through ownership in combined company Sesen Bio stockholders immediately benefit from owning 25.2% stake, $0.40 per share4, in the $357 million5 combined company with potential for significant long-term upside through Carisma’s proprietary CAR-M platform that could transform treatment for patients with cancer and other serious disorders. Combined company will be led by Carisma’s Board and management team, which has strong investor support, comprising of leaders within biotech, including AbbVie, Moderna, Wellington and TPG. Sesen Bio stockholders immediately benefit from owning 25.2% stake, $0.40 per share4, in the $357 million5 combined company with potential for significant long-term upside through Carisma’s proprietary CAR-M platform that could transform treatment for patients with cancer and other serious disorders. Combined company will be led by Carisma’s Board and management team, which has strong investor support, comprising of leaders within biotech, including AbbVie, Moderna, Wellington and TPG. Sesen Bio urges stockholders to vote today “FOR” the value maximizing transaction with Carisma using the WHITE proxy card ahead of the March 2, 2023, Special Meeting of Stockholders. Sesen Bio stockholders who need assistance voting or have questions regarding the Sesen Bio Special Meeting may contact Sesen Bio’s proxy solicitor, MacKenzie Partners, toll-free at 1-800-322-2885 or email at proxy@mackenziepartners.com. SVB Securities is acting as exclusive financial advisor to Sesen Bio for the transaction and Hogan Lovells US LLP is serving as its legal counsel. About Sesen Bio Sesen Bio, Inc. is a late-stage clinical company focused on targeted fusion protein therapeutics for the treatment of patients with cancer. Sesen Bio’s most advanced product candidate, Vicineum™, also known as VB4-845, is a locally-administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive bladder cancer. On July 15, 2022, Sesen Bio made the strategic decision to voluntarily pause further development of Vicineum in the US. The decision was based on a thorough reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional Phase 3 clinical trial, following Sesen Bio’s discussions with the United States Food and Drug Administration. Sesen Bio has turned its primary focus to assessing potential strategic alternatives with the goal of maximizing stockholder value. Additionally, Sesen Bio intends to seek a partner for the further development of Vicineum. For more information, please visit the Company’s website at www.sesenbio.com. Cautionary Note on Forward-Looking Statements Any statements in this press release about future expectations, plans and prospects for Sesen Bio, Inc. (Sesen Bio), CARISMA Therapeutics Inc. (Carisma) or the combined company, Sesen Bio’s, Carisma’s or the combined company’s strategy or future operations, and other statements containing the words “anticipate,” “believe,” “contemplate,” “expect,” “intend,” “may,” “plan,” “predict,” “target,” “potential,” “possible,” “will,” “would,” “could,” “should,” “continue,” and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. For example, statements concerning the proposed transaction, the concurrent financing, the contingent value rights and other matters, including without limitation: statements relating to the satisfaction of the conditions to and consummation of the proposed transaction, the expected timing of the consummation of the proposed transaction, the expected ownership percentages of the combined company, Sesen Bio’s and Carisma’s respective businesses, the strategy of the combined company, future operations, advancement of the combined company’s product candidates and product pipeline, clinical development of the combined company’s product candidates, including expectations regarding timing of initiation and results of clinical trials of the combined company, the ability of Sesen Bio to remain listed on the Nasdaq Stock Market, the completion of the concurrent financing, the receipt of any payments under the contingent value rights, and the amount and timing of distributions to be made to Sesen Bio stockholders, if any, in connection with any potential dissolution or liquidation scenario are forward-looking statements. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain stockholder approval of matters related to the proposed transaction in a timely manner or at all; (ii) uncertainties as to the timing of the consummation of the proposed transaction and the ability of each of Sesen Bio and Carisma to consummate the proposed transaction, including completing the concurrent financing; (iii) risks related to Sesen Bio’s ability to correctly estimate its expected net cash at closing and Sesen Bio’s and Carisma’s ability to correctly estimate and manage their respective operating expenses and expenses associated with the proposed transaction; (iv) risks related to Sesen Bio’s continued listing on the Nasdaq Stock Market until closing of the proposed transaction; (v) the risk that as a result of adjustments to the exchange ratio, Sesen Bio stockholders or Carisma stockholders could own less of the combined company than is currently anticipated; (vi) the risk that the conditions to payment under the contingent value rights will not be met and that the contingent value rights may otherwise never deliver any value to Sesen Bio stockholders; (vii) risks associated with the possible failure to realize certain anticipated benefits of the proposed transaction, including with respect to future financial and operating results; (viii) uncertainties regarding the impact any delay in the closing would have on the anticipated cash resources of the combined company upon closing and other events and unanticipated spending and costs that could reduce the combined company’s cash resources; (ix) the effect of uncertainties related to the actions of activist stockholders, which could make it more difficult to obtain the approval of Sesen Bio stockholders with respect to the transaction related proposals and result in Sesen Bio incurring significant fees and other expenses, including for third-party advisors; (x) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the merger agreement, as amended; (xi) the effect of the announcement, pendency or completion of the merger on Sesen Bio’s or Carisma’s business relationships, operating results and business generally; (xii) costs related to the merger; (xiii) the outcome of any legal proceedings instituted against Sesen Bio, Carisma or any of their respective directors or officers related to the merger agreement or the transactions contemplated thereby; (xiv) the ability of Sesen Bio or Carisma to protect their respective intellectual property rights; (xv) competitive responses to the proposed transaction and changes in expected or existing competition; (xvi) the success and timing of regulatory submissions and pre-clinical and clinical trials; (xvii) regulatory requirements or developments; (xviii) changes to clinical trial designs and regulatory pathways; (xix) changes in capital resource requirements; (xx) risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates and its preclinical programs; (xxi) legislative, regulatory, political and economic developments; and (xxii) other factors discussed in the “Risk Factors” section of Sesen Bio’s Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other reports filed with the Securities Exchange Commission (SEC). In addition, the forward-looking statements included in this press release represent Sesen Bio’s and Carisma’s views as of the date hereof. Sesen Bio and Carisma anticipate that subsequent events and developments will cause the respective company’s views to change. However, while Sesen Bio may elect to update these forward-looking statements at some point in the future, Sesen Bio specifically disclaims any obligation to do so, except as required under applicable law. These forward-looking statements should not be relied upon as representing Sesen Bio’s views as of any date subsequent to the date hereof. Important Additional Information In connection with the proposed transaction between Carisma and Sesen Bio, Sesen Bio filed with the SEC a registration statement on Form S-4 (as amended, the registration statement) that includes a proxy statement of Sesen Bio and also constitutes a prospectus of Sesen Bio with respect to shares of Sesen Bio common stock to be issued in the proposed transaction (proxy statement/prospectus). The definitive proxy statement/prospectus was first mailed to Sesen Bio stockholders on or about January 24, 2023. Sesen Bio may also file other relevant documents regarding the proposed transaction with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THESE MATERIALS, INCLUDING THE REGISTRATION STATEMENT, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, AND ALL OTHER RELEVANT DOCUMENTS THAT ARE OR WILL BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE MATERIALS, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders are able to obtain the definitive proxy statement/prospectus and other documents that are filed or will be filed by Sesen Bio with the SEC free of charge from the SEC’s website at www.sec.gov or from Sesen Bio at the SEC Filings section of www.sesenbio.com. No Offer or Solicitation This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, a public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone or internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction. Participants in the Solicitation Sesen Bio and Carisma and their respective directors, executive officers and other members of management may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Sesen Bio’s directors and executive officers is available in Sesen Bio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, its definitive proxy statement dated April 28, 2022 for its 2022 Annual Meeting of Stockholders and its Current Report on Form 8-K filed with the SEC on August 31, 2022. Other information regarding the participants in the proxy solicitation and a description of their interests in the proposed transaction, by security holdings or otherwise, is included in the definitive proxy statement/prospectus and other relevant materials that are or will be filed with the SEC regarding the proposed transaction. Investors should read the definitive proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Sesen Bio or the SEC’s website as indicated above. 1 Based on basic outstanding shares including unvested RSUs. 2 Amounts reflect potential payments in the future and have not been discounted. Does not include potential proceeds from the sale of Vicineum or the Company’s other legacy assets. 3 Based on precedent dissolution and liquidation processes and Company projections of potential liabilities and operating expenses. 4 Based on pro forma fully diluted post-close combined company shares outstanding. 5 Reflects pro forma company value including stated valuation for Sesen Bio, Carisma, and fully diluted value of the Moderna convertible note.

CAMBRIDGE, Mass.--( BUSINESS WIRE )--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”) today announced that it has received notice from the Listing Qualifications Department of The Nasdaq Stock Market LLC (“Nasdaq”) that, based upon the Company's non-compliance with the $1.00 bid price requirement for continued listing on The Nasdaq Capital Market, the Company's common stock is subject to delisting.

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Sesen Bio, Inc. (Nasdaq: SESN) (“Sesen Bio” or the “Company”) today announced that it has received notice from the Listing Qualifications Department of The Nasdaq Stock Market LLC (“Nasdaq”) that, based upon the Company’s non-compliance with the $1.00 bid price requirement for continued listing on The Nasdaq Capital Market, the Company’s common stock is subject to delisting. The Company today issued the following statement: The receipt of this notice from Nasdaq underscores our belief that, without the pending merger with Carisma Therapeutics Inc. (“Carisma”), the most likely and feasible path for Sesen Bio will be an exchange delisting of our common stock followed by the deregistration of our common stock from the SEC and a court-managed dissolution and liquidation. As noted previously, a court-managed dissolution and liquidation would be time consuming and expensive and would ultimately provide less value to Sesen Bio stockholders. Only approximately 60%-90%1 of Sesen Bio’s cash balance, or approximately $0.40-$0.60 per share2, and potentially less, would be available for an initial distribution, which may not be available for six months or more after an additional stockholder vote. The full liquidation and dissolution process could take up to three years in the Delaware court system to fully settle Sesen Bio’s potential future and unknown liabilities. We are confident that the pending merger with Carisma is a meaningfully better alternative for Sesen Bio stockholders than a court-managed dissolution and liquidation. The Sesen Bio Board of Directors continues to unanimously recommend that all stockholders vote their shares in support of the pending merger in advance of the Special Meeting. We look forward to continuing to engage with stockholders regarding the significant benefits of the merger ahead of our March 2, 2023, Special Meeting of Stockholders. As previously disclosed on January 24, 2022, the Company received written notice from the Nasdaq Listing Qualifications Department indicating that, based upon the closing bid price for the Common Stock for the previous 30 consecutive business days, the Company no longer satisfied the $1.00 bid price requirement for continued listing on The Nasdaq Capital Market, as set forth in Nasdaq Listing Rule 5550(a)(2) (the “Rule”) and, in accordance with the Nasdaq Listing Rules, was afforded an initial grace period of 180 calendar days, through July 25, 2022, and a second 180-calendar day period, through January 23, 2023, to regain compliance with the Rule. The Company did not regain compliance with the Rule by January 23, 2023, which resulted in Nasdaq’s January 25, 2023, determination. The Company plans to request a hearing before the Nasdaq Hearings Panel (the “Panel”), which will stay any delisting action by the Staff and ensure that shares of Sesen Bio remain listed and eligible for trading on Nasdaq pending a determination by the Panel. At the hearing, the Company will present its plan to evidence compliance with all applicable Nasdaq listing criteria. To that end, in connection with the proposed merger transaction with Carisma, the Company is seeking approval to implement a reverse stock split at its Special Meeting of Stockholders on March 2, 2023. There can be no assurance, however, that the Panel will grant the Company’s request for continued listing or that the Company will evidence compliance with all applicable criteria for listing within any extension period that may be granted by the Panel following the hearing. Sesen Bio’s definitive proxy statement / prospectus and other materials regarding the pending merger can be found at www.SesenBioandCarisma.com. Sesen Bio stockholders who need assistance voting or have questions regarding the Sesen Bio Special Meeting may contact Sesen Bio’s proxy solicitor, MacKenzie Partners, toll-free at 1-800-322-2885 or email at proxy@mackenziepartners.com. SVB Securities is acting as exclusive financial advisor to Sesen Bio for the transaction and Hogan Lovells US LLP is serving as its legal counsel. About Sesen Bio Sesen Bio, Inc. is a late-stage clinical company focused on targeted fusion protein therapeutics for the treatment of patients with cancer. Sesen Bio’s most advanced product candidate, Vicineum™, also known as VB4-845, is a locally-administered targeted fusion protein composed of an anti-epithelial cell adhesion molecule antibody fragment tethered to a truncated form of Pseudomonas exotoxin A for the treatment of non-muscle invasive bladder cancer. On July 15, 2022, Sesen Bio made the strategic decision to voluntarily pause further development of Vicineum in the US. The decision was based on a thorough reassessment of Vicineum, which included the incremental development timeline and associated costs for an additional Phase 3 clinical trial, following Sesen Bio’s discussions with the United States Food and Drug Administration. Sesen Bio has turned its primary focus to assessing potential strategic alternatives with the goal of maximizing shareholder value. Additionally, Sesen Bio intends to seek a partner for the further development of Vicineum. For more information, please visit the Company’s website at www.sesenbio.com. Cautionary Note on Forward-Looking Statements Any statements in this press release about future expectations, plans and prospects for Sesen Bio, Inc. (Sesen Bio), CARISMA Therapeutics Inc. (Carisma) or the combined company, Sesen Bio’s, Carisma’s or the combined company’s strategy or future operations, and other statements containing the words “anticipate,” “believe,” “contemplate,” “expect,” “intend,” “may,” “plan,” “predict,” “target,” “potential,” “possible,” “will,” “would,” “could,” “should,” “continue,” and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. For example, statements concerning the proposed transaction, the concurrent financing, the contingent value rights and other matters, including without limitation: statements relating to the satisfaction of the conditions to and consummation of the proposed transaction, the expected timing of the consummation of the proposed transaction, the expected ownership percentages of the combined company, Sesen Bio’s and Carisma’s respective businesses, the strategy of the combined company, future operations, advancement of the combined company’s product candidates and product pipeline, clinical development of the combined company’s product candidates, including expectations regarding timing of initiation and results of clinical trials of the combined company, the ability of Sesen Bio to remain listed on the Nasdaq Stock Market, the completion of the concurrent financing, the receipt of any payments under the contingent value rights, and the amount and timing of distributions to be made to Sesen Bio stockholders, if any, in connection with any potential dissolution or liquidation scenario are forward-looking statements. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain stockholder approval of matters related to the proposed transaction in a timely manner or at all; (ii) uncertainties as to the timing of the consummation of the proposed transaction and the ability of each of Sesen Bio and Carisma to consummate the proposed transaction, including completing the concurrent financing; (iii) risks related to Sesen Bio’s ability to correctly estimate its expected net cash at closing and Sesen Bio’s and Carisma’s ability to correctly estimate and manage their respective operating expenses and expenses associated with the proposed transaction; (iv) risks related to Sesen Bio’s continued listing on the Nasdaq Stock Market until closing of the proposed transaction; (v) the risk that as a result of adjustments to the exchange ratio, Sesen Bio stockholders or Carisma stockholders could own less of the combined company than is currently anticipated; (vi) the risk that the conditions to payment under the contingent value rights will not be met and that the contingent value rights may otherwise never deliver any value to Sesen Bio stockholders; (vii) risks associated with the possible failure to realize certain anticipated benefits of the proposed transaction, including with respect to future financial and operating results; (viii) uncertainties regarding the impact any delay in the closing would have on the anticipated cash resources of the combined company upon closing and other events and unanticipated spending and costs that could reduce the combined company’s cash resources; (ix) the effect of uncertainties related to the actions of activist stockholders, which could make it more difficult to obtain the approval of Sesen Bio stockholders with respect to the transaction related proposals and result in Sesen Bio incurring significant fees and other expenses, including for third-party advisors; (x) the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the merger agreement, as amended; (xi) the effect of the announcement, pendency or completion of the merger on Sesen Bio’s or Carisma’s business relationships, operating results and business generally; (xii) costs related to the merger; (xiii) the outcome of any legal proceedings instituted against Sesen Bio, Carisma or any of their respective directors or officers related to the merger agreement or the transactions contemplated thereby; (xiv) the ability of Sesen Bio or Carisma to protect their respective intellectual property rights; (xv) competitive responses to the proposed transaction and changes in expected or existing competition; (xvi) the success and timing of regulatory submissions and pre-clinical and clinical trials; (xvii) regulatory requirements or developments; (xviii) changes to clinical trial designs and regulatory pathways; (xix) changes in capital resource requirements; (xx) risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates and its preclinical programs; (xxi) legislative, regulatory, political and economic developments; and (xxii) other factors discussed in the “Risk Factors” section of Sesen Bio’s Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other reports filed with the Securities Exchange Commission (SEC). In addition, the forward-looking statements included in this press release represent Sesen Bio’s and Carisma’s views as of the date hereof. Sesen Bio and Carisma anticipate that subsequent events and developments will cause the respective company’s views to change. However, while Sesen Bio may elect to update these forward-looking statements at some point in the future, Sesen Bio specifically disclaims any obligation to do so, except as required under applicable law. These forward-looking statements should not be relied upon as representing Sesen Bio’s views as of any date subsequent to the date hereof. Important Additional Information In connection with the proposed transaction between Carisma and Sesen Bio, Sesen Bio filed with the SEC a registration statement on Form S-4 (as amended, the registration statement) that includes a proxy statement of Sesen Bio and also constitutes a prospectus of Sesen Bio with respect to shares of Sesen Bio common stock to be issued in the proposed transaction (proxy statement/prospectus). The definitive proxy statement/prospectus was first mailed to Sesen Bio stockholders on or about January 24, 2023. Sesen Bio may also file other relevant documents regarding the proposed transaction with the SEC. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THESE MATERIALS, INCLUDING THE REGISTRATION STATEMENT, THE DEFINITIVE PROXY STATEMENT/PROSPECTUS, AND ALL OTHER RELEVANT DOCUMENTS THAT ARE OR WILL BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE MATERIALS, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders are able to obtain the definitive proxy statement/prospectus and other documents that are filed or will be filed by Sesen Bio with the SEC free of charge from the SEC’s website at www.sec.gov or from Sesen Bio at the SEC Filings section of www.sesenbio.com. No Offer or Solicitation This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, a public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone or internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction. Participants in the Solicitation Sesen Bio and Carisma and their respective directors, executive officers and other members of management may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about Sesen Bio’s directors and executive officers is available in Sesen Bio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, its definitive proxy statement dated April 28, 2022 for its 2022 Annual Meeting of Stockholders and its Current Report on Form 8-K filed with the SEC on August 31, 2022. Other information regarding the participants in the proxy solicitation and a description of their interests in the proposed transaction, by security holdings or otherwise, is included in the definitive proxy statement/prospectus and other relevant materials that are or will be filed with the SEC regarding the proposed transaction. Investors should read the definitive proxy statement/prospectus carefully before making any voting or investment decisions. You may obtain free copies of these documents from Sesen Bio or the SEC’s website as indicated above. 1 Based on precedent liquidation processes and company projections of potential liabilities and operating expenses. 2 Assumes stockholder approval of liquidation in 2Q 2023 and a cash balance of approximately $140 million.