Bragar Eagel & Squire, P.C., a nationally recognized stockholder rights law firm, announces that a class action lawsuit has been filed against Sesen Bio, Inc. (“Sesen Bio” or the “Company”) (NASDAQ: SESN) in the United States District Court for the Southern District of New York on behalf of all persons and entities who purchased or otherwise acquired Sesen Bio securities between December 21, 2020 and August 17, 2021, both dates inclusive (the “Class Period”). Investors have until October 18, 2021 to apply to the Court to be appointed as lead plaintiff in the lawsuit.

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On December 21, 2020, the Company announced that it had submitted its Biologics License Application (“BLA”) to the U.S. Food and Drug Administration (“FDA”) for Vicineum for the treatment of BCG-unresponsive NMIBC.

On August 13, 2021, Sesen Bio announced that the FDA declined to approve its BLA for Vicineum in its current form. The FDA provided certain “recommendations specific to additional clinical/statistical data and analyses in addition to Chemistry, Manufacturing and Controls (CMC) issues pertaining to a recent pre-approval inspection and product quality.”

On this news, the Company’s share price fell $2.80, or 57%, to close at $2.11 per share on August 13, 2021, on unusually heavy trading volume.

Then, on August 16, 2021, Sesen Bio further revealed that “it appears that [the Company] will need to do a clinical trial to provide the additional efficacy and safety data necessary for the FDA to assess the benefit-risk profile, which is the basis for approval.” As a result, the Company expected that it could not resubmit its BLA until 2023.

On this news, the Company’s share price fell $0.89, or 42%, to close at $1.22 per share on August 16, 2021, on unusually heavy trading volume.

Then, on August 18, 2021, before the market opened, the health and medicine news site STAT published an article entitled “Sesen Bio trial of cancer drug marked by misconduct and worrisome side effects, documents show." Citing “hundreds of pages of internal documents” and “three people familiar with the matter,” the article detailed that the clinical trial for Vicineum was “marked by thousands of violations of study rules, damning investigator conduct, and worrying signs of toxicity the company did not publicly disclose.”

On this news, the Company’s share price fell $0.20, or 13%, to close at $1.31 per share on August 18, 2021, on unusually heavy trading volume.

The complaint filed in this class action alleges that throughout the Class Period, Defendants made materially false and/or misleading statements, as well as failed to disclose material adverse facts about the Company’s business, operations, and prospects. Specifically, Defendants failed to disclose to investors: (1) that Sesen Bio’s clinical trial for Vicineum had more than 2,000 violations of trial protocol, including 215 classified as “major”; (2) that three of Sesen Bio’s clinical investigators were found guilty of "serious noncompliance,” including “back-dating data”; (3) that Sesen Bio had submitted the tainted data in connection with the BLA for Vicineum; (4) that Sesen Bio’s clinical trials showed that Vicineum leaked out into the body, leading to side effects including liver failure and liver toxicity, and increasing the risks for fatal, drug-induced liver injury; (5) that, as a result of the foregoing, the Company’s BLA for Vicineum was not likely to be approved; (6) that, as a result of the foregoing, there was a reasonable likelihood that Sesen Bio would be required to conduct additional trials to support the efficacy and safety of Vicineum; and (7) that, as a result of the foregoing, Defendants’ positive statements about the Company’s business, operations, and prospects were materially misleading and/or lacked a reasonable basis.

If you purchased or otherwise acquired Sesen Bio shares and suffered a loss, are a long-term stockholder, have information, would like to learn more about these claims, or have any questions concerning this announcement or your rights or interests with respect to these matters, please contact Brandon Walker, Melissa Fortunato, or Marion Passmore by email at investigations@bespc.com, telephone at (212) 355-4648, or by filling out this contact form. There is no cost or obligation to you.

About Bragar Eagel & Squire, P.C.:

Bragar Eagel & Squire, P.C. is a nationally recognized law firm with offices in New York, California, and South Carolina. The firm represents individual and institutional investors in commercial, securities, derivative, and other complex litigation in state and federal courts across the country. For more information about the firm, please visit www.bespc.com. Attorney advertising. Prior results do not guarantee similar outcomes.

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