FDA delays Karyopharm PDUFA to review extra information

The FDA has pushed back the PDUFA date for Karyopharm Therapeutics’ oncology drug selinexor by three months. Officials took the action after Karyopharm complied with the FDA’s request for more information.

Briefing documents released by the FDA last month savaged Karyopharm’s filing for approval of XPO1 inhibitor selinexor, highlighting the “significant toxicity” and “limited efficacy” seen in studies of the drug in multiple myeloma. Days later, an advisory committee of outside experts convened by the FDA voted in favor of keeping selinexor off the market until data from a phase 3 trial are available.

In the wake of those events, which crushed Karyopharm’s stock price, the FDA asked the company to share additional, existing information on selinexor. Karyopharm filed the information as an amendment to its NDA, leading FDA to move the PDUFA date back by three months to July 6.

Karyopharm is yet to detail the contents of the amendment. The biotech described the information as “existing,” a term analysts think could encompass follow-up data from the phase 2b that formed the backbone of the NDA. And real-time data from the ongoing phase 3 trial, to which Karyopharm is blinded.

Investors viewed the development favorably, sending shares in Karyopharm up more than 20% on the back of the news. Brian Abrahams, an analyst at RBC Capital Markets, outlined the upbeat reading of the news.

“The fact that the FDA requested additional data suggests that they are interested in better understanding seli's benefit/risk profile, and whether, despite their reviewers' initial unfavorable views expressed in the briefing docs, it could still be beneficial to make it available for refractory MM pts,” Abrahams wrote in a note to investors.

Even after the recent rise, the stock remains well down on the highs it hit in the run up to the release of the FDA briefing documents. The PDUFA delay moves the big catalyst that will change Karyopharm’s position, for better or worse, back from early April to the first week of July.

Massachusetts-based Karyopharm reached this point by pursuing a belief that inhibiting the nuclear export protein XPO1 will cause tumor suppressor proteins to accumulate in the cell nucleus. The accumulation could lead to the death of cancer cells without harming healthy tissues.

Karyopharm tested that idea in a phase 2b trial in multiple myeloma patients who had already been treated with the five most widely-used treatments for the disease.