Dive Insight:

Selinexor, a multiple myeloma drug sold under the name Xpovio, has been slow to catch on with doctors since receiving initial approval in July 2019. The drug is Karyopharm’s first product and also the first in its class, offering a new way to target the blood cancer. But it initially received a narrow clearance, as part of a combination regimen for multiple myeloma patients who had already tried at least four other therapies.

In June 2020, the company won approval to sell Xpovio for patients with a form of lymphoma and then got another boost after a positive study in patients who had only received one to three previous treatments for myeloma led to an expanded label later that year.

Still, 2021 sales climbed to just $98 million from $76 million in 2020. Karyopharm recently forecasted revenue of $135 million to $145 million for the drug in 2022.

The company has been trying to accelerate Xpovio’s sales trajectory with an approval in endometrial cancer and a less advanced program targeting myelofibrosis. The Phase 3 SIENDO study, which evaluated the therapy as a so-called maintenance treatment, was a key part of that plan.

The trial tested selinexor against a placebo in patients with advanced or recurrent endometrial tumors who had already received chemotherapy. The goal was to have Karyopharm’s drug help in keeping endometrial cancer at bay for longer. But while the study succeeded, the statistical significance of the findings was “so borderline” that a reassessment by the FDA might have found the benefit wasn’t good enough, RBC Capital Markets analyst Brian Abrahams wrote in a note to investors. Karyopharm reported a roughly two-month benefit, over a placebo, in progression-free survival.

After meeting with FDA officials, company executives decided the best path forward is to focus on the subset of patients with p53 wild-type endometrial cancer, a group that covers close to half of all of those with the disease and who appeared to respond best to treatment. Karyopharm said it will move quickly to start the new study, but won’t have results available until the the first half of 2024.

Company executives “strongly believe” in the drug’s potential in endometrial cancer, Chief Scientific Officer Sharon Shacham said in a statement.