The US Food and Drug Administration granted accelerated approval to selinexor on July 3, 2019. The oral drug is to be taken in combination with dexamethasone in patients with relapsed/refractory multiple myeloma (RRMM) who have received at least four prior therapies.
Selinexor was previously granted fast track designation, and orphan drug designation by the US FDA.
The patients’ disease should be refractory to at least two immunomodulatory agents, two proteasome inhibitors and an anti-CD38 monoclonal antibody, and the recommended dose is 80mg, taken orally, in combination with dexamethasone on days 1 and 3 of each week.
The multicenter, single-arm, open-label, phase IIb STORM study ( NCT02336815) analyzed 122 adult patients who had previously been treated with three or more anti-myeloma treatment regimens, including an alkylating agent, lenalidomide, pomalidomide, bortezomib, carfilzomib, daratumumab, glucocorticoids and an anti-CD38 monoclonal antibody. There was no upper limit on the number of prior therapies, providing other criteria were met.
Patients with active smoldering MM, active plasma cell leukemia, documented systemic amyloid light chain amyloidosis and active CNS MM were excluded.
During the study patients were treated with 80mg of selinexor combined with 20mg dexamethasone twice per week orally (on days 1 and 3).
In a subgroup analysis of 83 patients with disease refractory to daratumumab, bortezomib, carfilzomib, lenalidomide and pomalidomide, the overall response rate was 25.3% (95% CI; 16.4, 36). There was one stringent complete response, no complete response, four very good partial responses, and 16 partial responses.
The median time to first response was 4 weeks (range, 1–10), and the median duration of response was 3.8 months (95% CI; 2.3).
Thrombocytopenia, fatigue, nausea, anemia, decreased appetite and weight, diarrhea, vomiting, hyponatremia, neutropenia, leukopenia, constipation, dyspnea, and upper respiratory tract infection were the most common adverse events reported in at least 20% of patients.
As the FDA approval was accelerated, additional clinical trials may be required to verify the findings of this phase IIb trial.
The full prescribing information of selinexor can be found here.