Shares of Karyopharm Therapeutics (KPTI 5.33%), a biopharmaceutical company, are sputtering today in response to lackluster clinical trial results for the company's lead drug. Investors worried about Xpovio's ability to reach a new patient population pushed the stock 21.8% lower as of 12:37 p.m ET on Tuesday.
In 2019, the Food and Drug Administration (FDA) approved Karyopharm's first drug, Xpovio, to treat multiple myeloma. Today the company reported fourth-quarter Xpovio sales that rose 29% year over year to $98.4 million.
It wasn't Xpovio's sales in the present that caused the stock to fall today. This morning, the company also posted results of the Siendo study for the drug in treating endometrial cancer, and they were a little disappointing. Receiving Xpovio as a maintenance treatment reduced patients' risk of disease progression or death by 30%. The improvement was strong enough to be considered statistically significant, but it was really close.
Even if the FDA approves Xpovio to treat endometrial cancer, selling the drug as a treatment for this population could be a challenge. Median progression-free survival among patients treated with Xpovio was just 5.7 months compared to 3.8 months among patients randomized to receive a placebo.
Karyopharm plans to submit an application to treat endometrial cancer with Xpovio in the second half of the year. The company also plans to follow up on signs of success with a genetically defined subgroup of patients who participated.
While top-line results from the Siendo trial weren't as impressive as hoped, it's way too early to assume Xpovio will never achieve significant sales as a treatment for endometrial cancer. In the Siendo trial, there were 103 endometrial cancer patients with tumors containing nonmutated p53 proteins. Progression-free survival among this subgroup was 13.7 months, compared to 3.7 months for patients given a placebo.