SESEN BIO SHAREHOLDERS: October 18, 2021 Filing Deadline in Class Action – Contact Lieff Cabraser

The law firm of Lieff Cabraser Heimann & Bernstein, LLP announces that class action litigation has been filed on behalf of investors who purchased or otherwise acquired the securities of Sesen Bio, Inc. (“Sesen Bio” or the “Company”) (NASDAQ: SESN) between December 21, 2020 and August 17, 2021, inclusive (the “Class Period”).

If you purchased or otherwise acquired Sesen Bio securities during the Class Period, you may move the Court for appointment as lead plaintiff by no later than October 18, 2021. A lead plaintiff is a representative party who acts on behalf of other class members in directing the litigation. Your share of any recovery in the actions will not be affected by your decision of whether to seek appointment as lead plaintiff. You may retain Lieff Cabraser, or other attorneys, as your counsel in the action.

Sesen Bio investors who wish to learn more about the litigation and how to seek appointment as lead plaintiff should click here, or email investorinfo@lchb.com, or call Sharon M. Lee of Lieff Cabraser at 1-800-541-7358.

Background on the Sesen Bio Securities Class Litigation

Sesen Bio, headquartered in Cambridge, Massachusetts, is a late-stage clinical company that purports to develop targeted fusion protein therapeutics for cancer treatments. The Company’s lead product is the drug Vicineum, a treatment for bacillus Calmette-Gurin (“BCG”)-unresponsive non-muscle invasive bladder cancer (“NMIBC”). In August 2019, Sesen Bio reported preliminary efficacy data from its ongoing Phase 3 clinical trial for Vicineum. In December 2020, the Company submitted its Biologics License Application (“BLA”) to the U.S. Food and Drug Administration (“FDA”) for Vicineum.

The actions allege that throughout the Class Period, defendants failed to disclose to investors: (1) more than 2,000 violations of trial protocol in Sesen Bio's clinical trial for Vicineum, 215 of which were classified as “major”; (2) three clinical investigators were found guilty of “serious noncompliance,” including “back-dating data”; (3) Sesen Bio’s submission of tainted data related to the BLA for Vicineum; and (4) incidents of Vicineum leaking into patients’ bodies in the Company’s clinical trials, leading to side effects including liver failure and liver toxicity, and increasing the risks for fatal, drug-induced liver injury. Furthermore, defendants failed to reveal that, as a result of the foregoing, the Company’s BLA for Vicineum was not likely to be approved and that there was a reasonable likelihood that Sesen Bio would be required to conduct additional trials to show the efficacy and safety of Vicineum.

On August 13, 2021, Sesen Bio revealed that the FDA declined to approve its BLA for Vicineum. In its complete response letter (“CRL”), the FDA outlined “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 stock price fell $2.80 per share, or 57%, from its closing price of $4.91 on August 12, 2021, to close at $2.11 per share on August 13, 2021, on unusually heavy trading volume.

Then, on August 16, 2021, Sesen Bio announced it needed “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 stock price fell $0.89 per share, or 42%, from its closing price of $2.11 on August 12, 2021, to close at $1.22 per share on August 16, 2021, on unusually heavy trading volume.

Finally, on August 18, 2021, before the market opened, the health and medicine news site STAT published an article revealing “thousands of violations of study rules, damning investigator conduct, and worrying signs of toxicity the company [Sesen] did not publicly disclose” regarding its clinical trial for Vicineum. The STAT article was reportedly based on cited “hundreds of pages of internal documents” and “three people familiar with the matter.” On this news, the Company’s stock price fell $0.20 per share, or 13%, from its closing price of $1.51 on August 17, 2021, to close at $1.31 per share on August 18, 2021, on unusually heavy trading volume.

About Lieff Cabraser

Lieff Cabraser Heimann & Bernstein, LLP, with offices in San Francisco, New York, and Nashville, is a nationally recognized law firm committed to advancing the rights of investors and promoting corporate responsibility.

The National Law Journal has recognized Lieff Cabraser as one of the nation’s top plaintiffs’ law firms for fourteen years. In compiling the list, the National Law Journal examines recent verdicts and settlements and looked for firms “representing the best qualities of the plaintiffs’ bar and that demonstrated unusual dedication and creativity.” Law360 has selected Lieff Cabraser as one of the Top 50 law firms nationwide for litigation, highlighting our firm’s “laser focus” and noting that our firm routinely finds itself “facing off against some of the largest and strongest defense law firms in the world.” Benchmark Litigation has named Lieff Cabraser one of the “Top 10 Plaintiffs’ Firms in America.”

For more information about Lieff Cabraser and the firm’s representation of investors, please visit https://www.lieffcabraser.com/.

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