A New Treatment for Resistant Multiple Myeloma Receives FDA Approval

For adult patients with relapsed or treatment-resistant multiple myeloma, the drug selinexor (Xpovio) received accelerated approval on July 3, 2019, from the United States Food and Drug Administration (FDA).

To be eligible for selinexor, a patient with multiple myeloma must previously have received:

• At least 4 lines of treatment,
• At least 2 proteasome inhibitors, and
• At least 2 immunomodulatory agents and an anti-CD38 monoclonal antibody.

What Is Selinexor’s Mechanism of Action?

Xpovio is a first-in-class oral selective inhibitor of nuclear export. By blocking the nuclear export of tumor-suppressor, growth-regulating, and anti-inflammatory proteins, it causes these proteins to accumulate in the nucleus and enhances their anticancer activity within the cell.

The Clinical Study That Led to FDA Approval of Selinexor

Approval was based on data in patients with relapsed (recurrent) or refractory (treatment-resistant) multiple myeloma from the phase 2b, single-arm, open-label, multicenter STORM study involving 83 patients. The primary efficacy measure was overall response rate. Patients received selinexor together with dexamethasone (cortisone).

The Study Found That:

• The overall response rate to treatment was 25.3%,
• Median time to first response was 4 weeks (range: 1-10 weeks),
• Median duration of response was 3.8 months.

“Full” approval of selinexor for multiple myeloma may be granted based on efficacy results from the ongoing phase 3 BOSTON study, which evaluates selinexor in combination with bortezomib (Velcade) and low-dose dexamethasone.

Although there is no complete cure for multiple myeloma, FDA-approved treatments target the cancer and slow its spread. Unfortunately, patients may often exhaust all available treatments and still see their disease progress. This accelerated approval provides patients with multiple myeloma with a previously unavailable option from a new drug class.

The most common side effects of selinexor treatment were thrombocytopenia (low blood platelet count, PLT), fatigue, nausea, anemia, decreased appetite, weight loss, diarrhea, vomiting, hyponatremia (low blood sodium / Na), neutropenia, leukopenia, constipation, dyspnea and upper respiratory tract infection.