May 2020 Business Update For Investor Purposes Only May 11, 2020 NASDAQ: SESN FORWARD-LOOKING STATEMENTS This presentation contains forward-looking statements that involve substantial risks and uncertainties. All statements, other than statements of historical facts, contained in this presentation, including statements regarding our strategy, future operations, clinical development of our protein therapies, future financial position, future revenues, projected costs, prospects, plans and objectives of manag ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Title of each class Trading Symbol(s) Name of each exchange on which registered Common Stock, $0.001 par value SESN The Nasdaq Global Market FORM 10-K (Mark One) [X] ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2019 OR [ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from _____ to _____ Com ...

Financial Data and Key Metrics Changes - The company ended 2019 with approximately $48 million in cash and cash equivalents, which is deemed sufficient to fund strategic priorities into 2021 [35] - The company has no debt and ended the year with 106.8 million shares of common stock outstanding, equating to $136 million on a fully diluted basis [35] Business Line Data and Key Metrics Changes - Vicinium is positioned to address a significant unmet need in bladder cancer treatment, with a projected $6 billion burden on payers in the U.S. alone for the year [8] - In Phase III data, 76% of patients were able to avoid radical cystectomy for at least three years, showcasing a strong clinical benefit [12] Market Data and Key Metrics Changes - Approximately 80,000 patients are diagnosed with bladder cancer each year in the U.S., with urologists managing the majority of treatment journeys [8] - Market research indicates that physicians prefer Vicinium over Keytruda for high-risk non-muscle invasive bladder cancer patients about 80% of the time [17] Company Strategy and Development Direction - The company aims to complete its Biologics License Application (BLA) submission this year, with a clear regulatory path forward based on recent FDA meetings [7][31] - A focused commercial model is planned, targeting approximately 1,500 urologists who prescribe the majority of treatments in this category [23] Management's Comments on Operating Environment and Future Outlook - Management expressed confidence in the regulatory path forward and the potential for a successful launch of Vicinium, emphasizing the strong advocacy from stakeholders [36] - The company has not experienced any business disruptions due to the COVID-19 pandemic and is executing risk mitigation strategies [45] Other Important Information - The company has partnered with Fuji and Baxter for manufacturing capabilities to meet global demand for Vicinium [32] - The company plans to initiate a confirmatory trial prior to approval, projecting possible approval in the first half of 2021 [51] Q&A Session Summary Question: Differences in Keytruda data for approval in the U.S. versus outside - Management noted a significant disparity in Keytruda's overall data, with a 41% complete response rate globally compared to roughly 31% in the U.S. [39] Question: Stability data for Vicinium's manufacturing and analytical comparability - Management outlined that the FDA will look for analytical release testing, biophysical characterization, forced degradation studies, and long-term stability studies [41] Question: Modifications due to the pandemic and status of confirmatory trial - Management confirmed that there are currently no significant regulatory or manufacturing risks due to COVID-19 and that the confirmatory trial is projected to start in the first half of 2021 [50][51]

seser b i o March 2020 Business Update March 16, 2020 NASDAQ: SESN For investor purposes only FORWARD-LOOKING STATEMENTS This presentation contains forward-looking statements that involve substantial risks and uncertainties. All statements, other than statements of historical facts, contained in this presentation, including statements regarding our strategy, future operations, clinical development of our protein therapies, future financial position, future revenues, projected costs, prospects, plans and obj ...

seser i b O Regulatory Update December 16, 2019 FORWARD-LOOKING STATEMENTS We may not actually achieve the plans, intentions or expectations disclosed in our forwardlooking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make as a result of various important factors, including: our projected financial position and estimated cash bu ...

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) [X] QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2019 OR [ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-36296 Sesen Bio, Inc. (Exact name of registrant as specified in its charter) Delaware 26-2025616 (Sta ...

seser i b O 3Q 2019 Business Update November 12, 2019 FORWARD-LOOKING STATEMENTS This presentation contains forward-looking statements that involve substantial risks and uncertainties. All statements, other than statements of historical facts, contained in this presentation, including statements regarding our strategy, future operations, clinical development of our protein therapies, timing or probability of regulatory approval, future financial position, future revenues, projected costs, prospects, plans a ...

Sesen Bio, Inc. (SESN) Q3 2019 Earnings Conference Call November 12, 2019 8:00 AM ET Company Participants Chad Myskiw - Senior Director, Strategic Planning Thomas Cannell - President & CEO Monica Forbes - CFO Conference Call Participants John Newman - Canaccord Roger Song - Jefferies Operator Ladies and gentlemen, thank you for standing by, and welcome to the Sesen Bio 3Q 2019 Business Update Conference. At this time, all participants are in a listen-only mode. After the speaker presentation, there will be ...

| --- | --- | --- | --- | --- | |-------------------------------------------------------------|-------|-------|-------|-------------| | | | | | | | | | | | | | | | | | | | H.C. Wainwright 21st Annual Global Investment Conference | | | | | | Thomas Cannell DVM, President and CEO September 10, 2019 | | | | NASDAQ SESN | FORWARD-LOOKING STATEMENTS This presentation contains forward-looking statements that involve substantial risks and uncertainties. All statements, other than statements of historical facts, co ...

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2019 OR o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to | --- | --- | |----------------------------------------------------------------------------|------------------------------------------| | ...