March 03, 2020
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Selinexor regimen extends PFS in pretreated multiple myeloma

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The addition of selinexor to bortezomib and dexamethasone significantly extended PFS among patients with multiple myeloma who received one to three prior lines of therapy, according to randomized phase 3 study results released by the agent’s manufacturer.

Selinexor (Xpovio, Karyopharm Therapeutics) is a first-in-class, oral selective inhibitor of nuclear export compound. The drug binds with and inhibits the nuclear export protein XPO1, leading to the accumulation of tumor suppressor proteins in the cell nucleus.

Selinexor is approved in the United States for treatment of adults with relapsed or refractory multiple myeloma who received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, at least two immunomodulatory agents and an anti-CD38 monoclonal antibody.

The open-label, multicenter BOSTON study included 402 patients with relapsed or refractory multiple myeloma who received one to three prior lines of therapy.

Results showed longer median PFS in the selinexor group (P = .0066).

Researchers assigned patients to one of two regimens.

In the experimental group, patients received once-weekly oral selinexor dosed at 100 mg, once-weekly bortezomib (Velcade, Takeda) administered subcutaneously at a dose of 1.3 mg/m2, and low-dose dexamethasone (40 mg weekly).

In the control group, patients received a standard regimen of twice-weekly bortezomib plus low-dose dexamethasone.

Study protocol allowed for patients in the control group to cross over to the experimental group after disease progression.

PFS served as the primary endpoint. Overall response rate served as a key secondary endpoint.

Results showed longer median PFS in the selinexor group (13.93 months vs. 9.46 months; HR = 0.7; P = .0066).

No new safety signals emerged in the experimental treatment group.

“We are thrilled to report these highly significant top-line results from the BOSTON study, the first randomized phase 3 trial to demonstrate clinically and statistically significant activity of once-weekly Xpovio in combination with a current standard-of-care treatment in patients with myeloma after one to three prior therapies,” Sharon Shacham, PhD, MBA, president and chief scientific officer of Karyopharm, said in a company-issued press release. “In the study, patients on the [selinexor-bortezomib-dexamethasone] regimen lived 47% longer without their disease worsening, which we believe represents an important improvement in the treatment of patients with relapsed or refractory multiple myeloma.”

More results of the study will be submitted for presentation at a medical meeting.

Karyopharm officials plan a regulatory submission in the second quarter of this year.