On July 3, 2019, the FDA granted accelerated approval to selinexor (Xpovio; Karyopharm Therapeutics), a nuclear export inhibitor, in combination with dexamethasone for the treatment of patients with relapsed or refractory multiple myeloma (MM) who had received ≥4 previous therapies and whose disease is resistant to several other forms of treatment, including ≥2 proteasome inhibitors, ≥2 immunomodulatory agents, and an anti-CD38 monoclonal antibody.
This approval was based on results from the phase 2b STROM clinical trial of 122 patients with relapsed or refractory MM who had previously received ≥3 treatment regimens, including an alkylating agent, glucocorticoids, bortezomib (Velcade; Takeda), carfilzomib (Kyprolis; Amgen), lenalidomide (Revlimid; Celgene), pomalidomide (Pomalyst; Celgene), and an anti-CD38 monoclonal antibody; and whose MM was documented to be refractory to glucocorticoids, a proteasome inhibitor, an immunomodulatory agent, an anti-CD38 monoclonal antibody, and to the last line of therapy. Patients were treated with selinexor plus dexamethasone on days 1 and 3 of every week. Treatment continued until disease progression, death, or unacceptable toxicity.
In a prespecified subgroup analysis of 83 patients, treatment with the selinexor plus dexamethasone regimen resulted in an overall response rate of 25.3%, which included 1 stringent complete response, no complete responses, 4 very good partial responses, and 16 partial responses. The median time to first response was 4 weeks and the median duration of response was 3.8 months.
The most common adverse reactions (≥20%) were thrombocytopenia, fatigue, nausea, anemia, decreased appetite, decreased weight, diarrhea, vomiting, hyponatremia, neutropenia, leukopenia, constipation, dyspnea, and upper respiratory tract infections.