Investigation of Sesen Bio, Inc.

Sesen Bio, Inc. (SESN) Hid Information Relating to the Failure of its Clinical Trials for Vicineum

On December 21, 2020, Sesen Bio announced it had submitted its Biologics License Application (“BLA”) to the FDA for Vicineum for the treatment of BCG-unresponsive NMIBC.

Between December 21, 2020 and August 17, 2021, defendants expressed Vicineum’s “significant commercial progress” and ramped up operations in anticipation that the drug would be granted FDA approval.   However, defendants failed to disclose to investors that: (1) Sesen Bio’s clinical trial for Vicineum had more than 2,000 violations of trial protocol; (2) three of Sesen Bio’s clinical investigators were found guilty of “serious noncompliance,” including “back-dating data”; (3) Sesen Bio had submitted the tainted data in connection with the BLA for Vicineum; (4) 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) as a result of the foregoing, the Company’s BLA for Vicineum was not likely to be approved; and (6) consequently, there was a reasonable likelihood that Sesen Bio would be required to conduct additional trials to support the efficacy and safety of Vicineum.

On August 13, 2021, the Company announced that the FDA declined to approve its BLA for Vicineum in its current form.  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 August 16, 2021, the Company 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 stock fell $0.89, or 42%, to close at $1.22 per share on August 16, 2021.

Then, on August 18, 2021, the health and medicine news site STAT published an article detailing 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 another 13%, to close at $1.31 per share on August 18, 2021. The stock continues to decline and now trades below $1.00.


If you purchased shares of Sesen Bio, Inc. (SESN) securities between December 21, 2020 and August 17, 2021, you have until October 18, 2021, to ask the court to appoint you lead plaintiff for the class.

All representation is on a contingency fee basis. Shareholders pay no fees or expenses.

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