Karyopharm Therapeutics, Inc.

On February 22, 2019, the U.S. Food and Drug Administration (“FDA”) released a briefing document which contradicted the Company’s assertions that its treatment selinexor was “well-tolerated” by patients. Specifically, the FDA revealed that a previous trial of the Company’s selinexor yielded “worse overall survival” and concluded that selinexor “is associated with significant toxicity” and “limited efficacy.”

On this news, shares of Karyopharm fell $3.90 per share, or over 43%, to close at $5.07 per share on February 22, 2019, thereby injuring investors.

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 data demonstrated that selinexor was associated with significant toxicity, was not well-tolerated among patients with acute myeloid leukemia (“AML”), and resulted in a higher risk of death; (2) that patients experienced serious drug-related side effects, and eighty percent of the AML patients treated in the selinexor trial experienced a serious adverse event; (3) that, as a result, nearly half of the AML patients were forced to withdraw from the trial because of drug-related toxicity; (4) that the toxicity profile of selinexor for the treatment of patients with multiple myeloma was similar to that observed in AML patients; and (5) that, as a result, selinexor was neither effective nor safe.