Dive Brief:
- Karyopharm Therapeutics on Monday announced better-than-expected results from its Phase 2b STORM study of selinexor in penta-refractory multiple myeloma, setting the stage for Karyopharm to submit an application for U.S. approval of the drug in the second half of the year.
- Top-line results showed the oral selective inhibitor of nuclear export (SINE) compound selinexor achieved a 25.4% overall response rate in heavily pretreated patients. Karyopharm paired selinexor with low-dose dexamethasone.
- Of the 122 patients in the trial, two achieved a complete response and 29 reached partial response rates. The median duration of response was 4.4 months.
Dive Insight:
On a Tuesday morning call with analysts, Karyopharm executives and key opinion leaders emphasized that new mechanisms of action are needed to treat multiple myeloma patients who have failed multiple other treatments, and that it's important for both pieces of combination studies to be effective independently. They were happy to point out selinexor fits both these criteria.
The data reported this week for selinexor represented the second half of a mid-stage study. Results were better than previously reported at the interim analysis. Leerink analyst Jonathan Chang said in a note to clients that an overall response rate of 20% to 21% would likely be an approvable level for these patients.
The company said side effects for the drug were "manageable" and that adverse events were dealt with proactively as the study progressed. One key opinion leader on the call noted he felt this was particularly important as Karyopharm moves selinexor into the realm of combination studies.
"When it comes to combination therapies, that weekly schedule of selinexor will be an advantage," said Paul Richardson, director of clinical research, on the call. He noted that the dosing schedule will also likely allow selinexor to be used in earlier lines of treatment.
Karyopharm is testing selexinor as a combination with proteasome inhibitor Velcade (bortezomib) in the Phase 3 BOSTON study for the treatment of patients with multiple myeloma who have had one to three prior lines of therapy.
Shares of Karyopharm opened the day 20% higher on Tuesday.
"We believe selinexor could potentially achieve a $725 [million] peak US sales opportunity (not risk-adjusted) in multiple myeloma that includes $215 [million] peak US sales in penta-refractory patients assuming 35% peak market share in that setting," wrote Leerink's Chang, raising the price target for the company by $5 per share to $24 per share.