FDA Approves Selinexor for Refractory Multiple Myeloma

Nick Mulcahy

July 03, 2019

The US Food and Drug Administration (FDA) has granted accelerated approval to the oral therapy selinexor (Xpovio, Karyopharm Therapeutics) in combination with the corticosteroid dexamethasone for the treatment of adults with relapsed/refractory multiple myeloma (RRMM) who are out of treatment options.

More specifically, the drug is indicated for patients who have received at least four prior therapies and have disease that is resistant to other forms of treatment, including at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti-CD38 monoclonal antibody.

"Today we approved a treatment under our accelerated approval program that provides a treatment option for patients with multiple myeloma with no available therapy," said Richard Pazdur, MD, director of the FDA's Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research.

Pazdur explained that there is no cure for multiple myeloma, but existing treatments can target the cancer and slow disease spread. However, patients may exhaust available treatments and still have disease progression.

Selinexor was approved on the basis of safety and efficacy data from 83 patients with RRMM who were treated with the drug in combination with dexamethasone. The overall response rate was 25%. The median time to first response was 4 weeks (range, 1 to 10 weeks). The median duration of response was 3.8 months.

These data come from a subgroup of 83 patients from the open-label phase 2b STORM (Selinexor Treatment of Refractory Myeloma) trial, notes the company.

"The 25.3% response rate seen...is clinically meaningful and a validated surrogate marker for clinical benefit in our patients with advanced refractory disease," said Sundar Jagannath, MD, director of the multiple myeloma program, professor of medicine (hematology and medical oncology) at the Tisch Cancer Institute, and principal investigator of the STORM study, said in a company press release.

The FDA notes that the efficacy evaluation was supported by additional information from an ongoing, randomized trial among patients with multiple myeloma and that further clinical trials are required to verify and describe selinexor's clinical benefit.

In fact, a phase 3 trial called BOSTON is ongoing. At an FDA Oncological Drugs Advisory Committee meeting earlier this year, the committee voted against recommending approval for the drug and recommended waiting until the results of BOSTON became available.

In a rare instance of the FDA going against the advice of its advisory committee, the agency went ahead and granted accelerated approval for the drug. As FDA's Pazdur explained in the agency's press release, the drug offers an option for patients who have exhausted all other therapies.  

In a company press release, Paul Richardson, MD, clinical program leader and director of clinical research, Jerome Lipper Multiple Myeloma Center at the Dana-Farber Cancer Institute, Boston, Massachusetts, commented: "Despite recent advances in the treatment of multiple myeloma, almost all our patients will develop disease that is resistant to the five most commonly used antimyeloma drugs we currently have available, and the prognosis for this patient population is particularly poor."

"The accelerated approval of oral Xpovio marks an important advance in the treatment paradigm for patients with relapsed refractory multiple myeloma, and in my view, is an important addition to our therapeutic armamentarium," he said.

The FDA notes that the efficacy evaluation was supported by additional information from an ongoing, randomized trial among patients with multiple myeloma. Further clinical trials are required to verify and describe selinexor's clinical benefit.

Common side effects of patients receiving selinexor include leukopenia, neutropenia, thrombocytopenia, and anemia. Patients also reported vomiting, nausea, fatigue, diarrhea, fever, decreased appetite and weight, constipation, upper respiratory tract infections, and hyponatremia.

The FDA advises healthcare professionals to monitor patients on selinexor for low blood count, platelets, and sodium levels. Patients on the drug should avoid other medications that may cause dizziness or confusion and avoid situations that may cause dizziness. To avoid dizziness or confusion, optimizing a patient's hydration status and blood count is also advised.

Selinexor must be dispensed with a patient medication guide about the drug's uses and risks.

Females of reproductive age and males with a female partner of reproductive potential should use contraception during treatment, says the FDA. Women who are pregnant or breastfeeding should not take the drug.

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