[PART I - FINANCIAL INFORMATION](index=4&type=section&id=PART%20I%20-%20FINANCIAL%20INFORMATION) [Financial Statements](index=4&type=section&id=Item%201.%20Financial%20Statements) Financial statements reflect significant impacts from the FDA's CRL, including asset impairment, contingent consideration revaluation, and restructuring charges [Condensed Consolidated Balance Sheets](index=4&type=section&id=Condensed%20Consolidated%20Balance%20Sheets) The balance sheet strengthened with increased cash and positive stockholders' equity, driven by financing and a reduced contingent consideration liability Condensed Consolidated Balance Sheet Highlights (in thousands) | Account | Sep 30, 2021 | Dec 31, 2020 | Change | | :--- | :--- | :--- | :--- | | **Assets** | | | | | Cash and cash equivalents | $175,236 | $52,389 | +$122,847 | | Intangible assets | $14,700 | $46,400 | -$31,700 | | Total Assets | $235,671 | $122,823 | +$112,848 | | **Liabilities & Equity** | | | | | Contingent consideration (Total) | $56,600 | $108,840 | -$52,240 | | Total Liabilities | $74,663 | $132,050 | -$57,387 | | Total Stockholders' Equity (Deficit) | $161,008 | $(9,227) | +$170,235 | [Condensed Consolidated Statements of Income (Operations) and Comprehensive Income (Loss)](index=5&type=section&id=Condensed%20Consolidated%20Statements%20of%20Income%20(Operations)%20and%20Comprehensive%20Income%20(Loss)) A significant non-cash gain on contingent consideration drove Q3 2021 net income to $71.7 million, offsetting impairment and restructuring charges Statement of Operations Highlights (in thousands, except per share data) | Metric | Q3 2021 | Q3 2020 | 9 Months 2021 | 9 Months 2020 | | :--- | :--- | :--- | :--- | :--- | | License and related revenue | $0 | $11,236 | $6,544 | $11,236 | | Intangibles impairment charge | $31,700 | $0 | $31,700 | $0 | | Change in fair value of contingent consideration | $(114,000) | $18,400 | $(52,240) | $(16,820) | | Restructuring charge | $5,522 | $0 | $5,522 | $0 | | **Net Income (Loss)** | **$71,674** | **$(22,608)** | **$(9,280)** | **$(7,388)** | | Net income (loss) per share - diluted | $0.36 | $(0.19) | $(0.05) | $(0.07) | [Condensed Consolidated Statements of Cash Flows](index=8&type=section&id=Condensed%20Consolidated%20Statements%20of%20Cash%20Flows) Cash flow reflects increased use in operations, offset by $176.1 million in financing from an ATM offering, resulting in a net cash increase Cash Flow Summary for the Nine Months Ended Sep 30 (in thousands) | Cash Flow Activity | 2021 | 2020 | | :--- | :--- | :--- | | Net cash used in operating activities | $(56,278) | $(22,328) | | Net cash used in investing activities | $(4) | $(8) | | Net cash provided by financing activities | $176,129 | $16,184 | | **Net increase (decrease) in cash** | **$119,847** | **$(6,152)** | [Notes to Condensed Consolidated Financial Statements](index=9&type=section&id=Notes%20to%20Condensed%20Consolidated%20Financial%20Statements) Notes detail the accounting impacts of the FDA's CRL, including impairment of Vicineum's U.S. rights, revaluation of liabilities, and new legal proceedings - On August 13, 2021, the company received a Complete Response Letter (CRL) from the FDA, which stated it could not approve the Biologics License Application (BLA) for Vicineum in its present form[30](index=30&type=chunk)[116](index=116&type=chunk) - The fair value of contingent consideration decreased by **$52.2 million** during the first nine months of 2021, driven by the CRL which led to reassessed assumptions including delays in commercialization and lower probabilities of clinical and regulatory success (now estimated at **45% to 55% globally**)[48](index=48&type=chunk) - The company recorded a **$31.7 million impairment charge**, fully writing off the value of Vicineum's United States rights intangible asset due to the CRL, while the European Union rights were not impaired[51](index=51&type=chunk) - Following the CRL, the company initiated a restructuring plan on August 30, 2021, resulting in a **$5.5 million charge** in Q3 2021, comprising **$2.8 million** in severance and benefits and **$2.7 million** in contract termination costs[110](index=110&type=chunk)[111](index=111&type=chunk) - The company is facing **three securities class action lawsuits and two derivative lawsuits**, all filed after the announcement of the CRL, alleging violations of securities laws and breach of fiduciary duties[114](index=114&type=chunk)[238](index=238&type=chunk)[239](index=239&type=chunk) [Management's Discussion and Analysis of Financial Condition and Results of Operations](index=28&type=section&id=Item%202.%20Management's%20Discussion%20and%20Analysis%20of%20Financial%20Condition%20and%20Results%20of%20Operations.) Management analyzes the CRL's impact on Vicineum's regulatory path, financial condition, restructuring efforts, and capital resources [Overview](index=31&type=section&id=Overview) The company's focus is on addressing the FDA's CRL for its lead candidate Vicineum, which includes pursuing further regulatory meetings and a potential new trial - The FDA issued a CRL for Vicineum's BLA on August 13, 2021, stating it could not be approved in its present form due to needs for additional clinical/statistical data and CMC issues[129](index=129&type=chunk) - The company participated in a CMC-focused Type A meeting with the FDA on October 29, 2021, and is preparing for a separate clinical-focused Type A meeting to determine the path forward[129](index=129&type=chunk)[145](index=145&type=chunk) - On August 20, 2021, the company withdrew its Marketing Authorization Application (MAA) from the EMA for Vysyneum (Vicineum) to pause European regulatory efforts until there is more clarity from the FDA[129](index=129&type=chunk)[145](index=145&type=chunk) - The company has established OUS partnerships for Vicineum, including with Qilu in Greater China, Hikma in the MENA region, and EIP in Turkey[150](index=150&type=chunk)[154](index=154&type=chunk)[155](index=155&type=chunk) [Results of Operations](index=40&type=section&id=Results%20of%20Operations) Q3 2021 results were dominated by non-cash items from the CRL, including a $114.0 million gain on contingent consideration and a $31.7 million impairment charge Comparison of Operating Expenses for the Three Months Ended Sep 30 (in thousands) | Expense Category | Q3 2021 | Q3 2020 | Change ($) | Change (%) | | :--- | :--- | :--- | :--- | :--- | | Research and development | $4,967 | $10,196 | $(5,229) | (51)% | | General and administrative | $8,699 | $4,115 | $4,584 | 111% | | Restructuring charge | $5,522 | $0 | $5,522 | N/A | | Intangibles impairment charge | $31,700 | $0 | $31,700 | N/A | | Change in fair value of contingent consideration | $(114,000) | $18,400 | $(132,400) | (720)% | - The decrease in R&D expense in Q3 2021 was primarily due to lower costs for technology transfer and manufacturing (**$6.3 million**), partially offset by increased license and regulatory fees[177](index=177&type=chunk) - The increase in G&A expense in Q3 2021 was driven by pre-commercial launch planning for Vicineum (**$2.4 million**), higher employee compensation (**$1.3 million**), and increased legal fees related to lawsuits and an internal review (**$0.9 million**)[178](index=178&type=chunk) [Liquidity and Capital Resources](index=43&type=section&id=Liquidity%20and%20Capital%20Resources) The company holds $175.2 million in cash, primarily from a recent ATM offering, which is expected to fund operations and a new clinical trial through 2023 - The company had cash and cash equivalents of **$175.2 million** as of September 30, 2021[201](index=201&type=chunk) - The company raised **$175.0 million in net proceeds** from its ATM offering during the nine months ended September 30, 2021[201](index=201&type=chunk) - Management believes current cash is sufficient to fund operations **through 2023**, which accounts for the costs of an additional clinical trial for Vicineum[201](index=201&type=chunk) [Critical Accounting Policies and Use of Estimates](index=46&type=section&id=Critical%20Accounting%20Policies%20and%20Use%20of%20Estimates) The CRL triggered a reassessment of critical accounting estimates, leading to the impairment of an intangible asset and revaluation of contingent consideration - The receipt of the CRL was an impairment indicator, triggering a quantitative analysis of intangible assets and goodwill[217](index=217&type=chunk)[218](index=218&type=chunk) - The analysis concluded that the Vicineum United States rights intangible asset was fully impaired, resulting in a **$31.7 million charge**[217](index=217&type=chunk) - The fair value of contingent consideration is based on significant unobservable inputs (Level 3), including financial forecasts, probabilities of success, and timing of milestones, all of which were revised downward following the CRL[219](index=219&type=chunk) [Quantitative and Qualitative Disclosures About Market Risk](index=49&type=section&id=Item%203.%20Quantitative%20and%20Qualitative%20Disclosures%20About%20Market%20Risk.) The company is a smaller reporting company and is not required to provide the information under this item - As a smaller reporting company, Sesen Bio is not required to provide disclosures about market risk[231](index=231&type=chunk) [Controls and Procedures](index=49&type=section&id=Item%204.%20Controls%20and%20Procedures.) Management concluded that the company's disclosure controls and procedures were effective as of September 30, 2021 - The Chief Executive Officer and Chief Financial Officer concluded that the company's disclosure controls and procedures were **effective** as of September 30, 2021[232](index=232&type=chunk) - There were **no changes in internal control over financial reporting** during the third quarter of 2021 that materially affected, or are reasonably likely to materially affect, internal controls[234](index=234&type=chunk) [PART II - OTHER INFORMATION](index=50&type=section&id=PART%20II%20-%20OTHER%20INFORMATION) [Legal Proceedings](index=50&type=section&id=Item%201.%20Legal%20Proceedings.) The company is defending against multiple securities and derivative lawsuits filed in response to the CRL announcement - **Three securities class action lawsuits** were filed against the company and certain officers in the Southern District of New York, alleging violations of the Exchange Act related to statements about the Vicineum BLA[238](index=238&type=chunk) - **Two derivative lawsuits** were filed against the company's board and certain officers in the District of Massachusetts, alleging breach of fiduciary duties, waste of corporate assets, and other claims[239](index=239&type=chunk) - The company believes the lawsuits are **without merit** and intends to defend itself vigorously; the outcome and potential financial impact are currently uncertain[240](index=240&type=chunk) [Risk Factors](index=50&type=section&id=Item%201A.%20Risk%20Factors.) Primary risks involve the regulatory and commercial future of Vicineum, the success of a potential new trial, and the impact of ongoing litigation - The company is **highly dependent on Vicineum**, and its business could be materially harmed if it cannot resolve the issues in the FDA's CRL and EMA's report to obtain marketing approval[241](index=241&type=chunk) - The company expects it will need to conduct **one or more additional clinical trials** to address regulatory concerns, which will incur substantial costs, delay potential commercialization, and has an uncertain outcome[244](index=244&type=chunk) - The company's recent restructuring plan and headcount reduction may not yield anticipated savings and could **disrupt business operations** or employee retention[248](index=248&type=chunk) - Pending securities class action and shareholder derivative lawsuits could result in **substantial damages** and divert management's attention[248](index=248&type=chunk) [Unregistered Sales of Equity Securities and Use of Proceeds](index=53&type=section&id=Item%202.%20Unregistered%20Sales%20of%20Equity%20Securities%20and%20Use%20of%20Proceeds.) The company did not issue any unregistered equity securities during the nine months ended September 30, 2021 - No unregistered equity securities were issued during the nine months ended September 30, 2021[251](index=251&type=chunk) [Defaults Upon Senior Securities](index=53&type=section&id=Item%203.%20Defaults%20Upon%20Senior%20Securities.) Not applicable [Mine Safety Disclosures](index=53&type=section&id=Item%204.%20Mine%20Safety%20Disclosures.) Not applicable [Other Information](index=53&type=section&id=Item%205.%20Other%20Information.) None [Exhibits](index=54&type=section&id=Item%206.%20Exhibits.) This section provides an index of the exhibits filed with the Quarterly Report on Form 10-Q

Table of Contents Title of each class Trading Symbol(s) Name of each exchange on which registered Common Stock, $0.001 par value SESN The Nasdaq Stock Market UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from t ...

Financial Data and Key Metrics Changes - The company ended Q1 2021 with approximately $110 million in cash and cash equivalents, significantly strengthening its cash position [29] - There was a strong increase in stock price and market capitalization compared to the end of 2020 [29] Business Line Data and Key Metrics Changes - The company is focused on the commercial readiness of Vicineum, with plans to begin promotion to physicians and patients upon potential approval in August 2021 [10][15] - The anticipated global peak sales for Vicineum are projected to be between $1 billion and $3 billion [15] Market Data and Key Metrics Changes - In the U.S., the company is preparing for a late cycle meeting with the FDA in July, with a target PDUFA date of August 18, 2021 [10][12] - In Europe, the company received conditional acceptance of the proprietary brand name Vicineum, with potential approval expected in early 2022 [11] - The IND for Vicineum was approved in China, allowing for clinical trials to assess efficacy and safety [12] Company Strategy and Development Direction - The company aims to launch a best-in-class therapeutic that improves patient outcomes while reducing overall healthcare costs [15] - A customer engagement strategy has been developed, targeting approximately 300 key opinion leaders and 2,000 high-prescribing physicians [16][18] - The company plans to utilize a contract sales organization to support its sales efforts, with 35 representatives across four geographic regions [18] Management's Comments on Operating Environment and Future Outlook - Management believes there is a clear regulatory path forward for Vicineum, with significant unmet needs in bladder cancer [6][33] - The company anticipates early commercial success by mid-2022, driven by the differentiated clinical profile of Vicineum [10][15] - Management highlighted the importance of urologists in the treatment decision-making process and the potential for strong advocacy from patients, payers, and physicians [41][47] Other Important Information - The manufacturing process for Vicineum is designed to be reliable and robust, utilizing world-class manufacturing partners [22][24] - The company is strategically managing its balance sheet through stage-gated investments focused on high-priority initiatives [30] Q&A Session Summary Question: Can you comment on the design of the Phase 3 studies for Vicineum? - Management indicated that the FDA's guidance suggests eligibility for either full or accelerated approval, with a confirmatory trial planned if required [36][39] Question: What will change in terms of views on the company once Vicineum hits the market? - Management believes that the market will come to understand the powerful role of urologists and the advocacy from patients, payers, and physicians, which could significantly enhance the company's value [41][46] Question: What should we expect regarding the confirmatory study before the approval decision? - Management confirmed readiness to launch a confirmatory trial in the less than adequate BCG population, regardless of whether the FDA requires it [54] Question: What is the expected ramp-up in SG&A costs with the contract sales organization? - Management expects annual costs of approximately $10 million to $15 million for the contract sales organization, with sufficient cash to fund operations through Q4 2021 [58][59]

seser b i o 1Q 2021 Business Update May 10, 2021 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 management, are forw ...

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 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 (State or ot ...

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) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from _____ to _____ Commiss ...

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2020 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 (State o ...

Financial Data and Key Metrics Changes - The company reported a cash balance of $42 million at the end of Q3 2020, an increase from $38 million at the end of Q2 2020, indicating effective capital management [34][37] - Cash used in operations for the quarter was $14 million, primarily for activities related to the BLA submission and regulatory support [35] Business Line Data and Key Metrics Changes - The company is on track to complete the BLA submission by the end of 2020, with potential FDA approval projected for mid-2021 [13][14] - The market opportunity for Vicinium is estimated to be substantial, with potential peak sales ranging from $1 billion to $3 billion [15][31] Market Data and Key Metrics Changes - The company conducted market research indicating that over 80% of high prescribers of bladder cancer would choose Vicinium over Keytruda, highlighting a favorable perception of Vicinium in the market [17][18] - The company is focusing on key markets including the U.S., Europe, China, and MENA, with ongoing negotiations for partnerships in these regions [33] Company Strategy and Development Direction - The company aims to establish a 50-50 value share partnership for marketing authorization in Europe, indicating a strategic approach to market entry [41] - The company emphasizes a robust supply chain with partnerships with world-class manufacturers to ensure reliable production of Vicinium [20] Management's Comments on Operating Environment and Future Outlook - Management expressed confidence in the regulatory path forward in both the U.S. and Europe, with a clear understanding of the requirements for approval [5][9] - The company highlighted the significant unmet need in bladder cancer and the differentiated clinical profile of Vicinium as key drivers for future growth [5][38] Other Important Information - The company received $10 million in net proceeds from Qilu Pharmaceutical, which is crucial for funding operations without dilution [34] - The ATM facility has generated approximately $16 million year-to-date, providing an efficient source of capital for ongoing projects [36] Q&A Session Summary Question: What are the final steps needed with Module 3 before the BLA submission? - Management confirmed that all testing is completed, and the final step involves finalizing the statistical analysis and documentation for Module 3 [40][42] Question: What are the long-term plans in Europe regarding partnerships? - Management indicated plans to seek a partner for the European market, aiming for a 50-50 value share arrangement [41]

seser i b O 3Q 2020 Business Update November 9, 2020 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 management, are forwardlooking ...

Table of Contents Title of each class Trading Symbol(s) Name of each exchange on which registered Common Stock, $0.001 par value SESN The Nasdaq Stock Market UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from t ...