Update: FDA ODAC delays approval of selinexor until more data are available

The U.S. Food and Drug Administration (FDA) oncologic drugs advisory committee (ODAC) yesterday voted 8 to 5 in favor of delaying the accelerated approval of selinexor until more data are available from the phase III BOSTON trial (NCT03110562).¹

The draft voting question for the committee centered around whether approval of selinexor should be postponed until the randomized phase III trial results are available. Those voting in favor of the delay questioned whether the data supported the risk-benefit profile of the drug. 

Considerations that arose during the ODAC meeting included:

• The STORM study, which the application was based on, was a combination trial
• The previous phase I study did not demonstrate that selinexor exhibited strong single-agent activity meaning the benefit of selinexor is difficult to ascertain
• Significant toxicity was reported during the study that resulted in patient mortality

The FDA will now await the results of the BOSTON trial which is an open-label, phase III study in patients with relapsed/refractory multiple myeloma, evaluating whether the addition of selinexor to bortezomib and dexamethasone therapy is superior to bortezomib and dexamethasone alone.

Background²

Selinexor is an XPO1 inhibitor indicated in the treatment of penta-refractory multiple myeloma (MM). The application is based on part 2 of the STORM study (KCP-330-012) which was a multicentre, open-label, single arm, phase IIb trial investigating the efficacy and safety of treatment with selinexor (80mg orally, twice weekly) and dexamethasone (20mg orally twice weekly) in 123 enrolled patients.

• Efficacy (N = 122)
• Overall response rate: 25.4% (95% CI, 18.0–34.1)
• Median duration of response in responders (N = 31): 4.4 months (0.8–9.0)
• Safety (N = 123)
• Mortality within 30 days of treatment: N = 23
• Causes of mortality: disease progression (N = 13), fatal treatment-emergent adverse events (TEAE; N = 10)
• TEAE any grade: 100%
• TEAE grade ≥3: 93.5%
• TEAE was the cause of study discontinuation in 28.5% of patients