Karyopharm Therapeutics has announced positive top-line results from the randomised Phase III BOSTON trial on patients suffering from multiple myeloma.

The trial is assessing once-weekly XPOVIO (selinexor) along with once-weekly Velcade (bortezomib) and low-dose dexamethasone (SVd) against standard twice-weekly Velcade plus low-dose dexamethasone (Vd) in patients who have received one to three prior lines of therapy.

The trial met its primary endpoint of a statistically significant increase in progression-free survival (PFS).

The median PFS in the SVd arm was found to be 13.93 months, compared to 9.46 months in the Vd arm, accounting for a 4.47 month (47%) increase in median PFS (hazard ratio=0.70; p=0.0066).

Researchers found that there were no new safety signals in the SVd arm and no imbalance in deaths between the two arms in the study.

Full top-line data will be presented at upcoming medical meetings.

Karyopharm president and chief scientific officer Sharon Shacham said: “We are thrilled to report these highly significant top-line results from the BOSTON study, the first randomised Phase III 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.”

“In the study, patients on the SVd 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.”

The company plans to submit the data to the US Food and Drug Administration (FDA) as part of a supplemental new drug application, which seeks to expand the approved indication for XPOVIO into second line treatment for patients suffering with relapsed or refractory multiple myeloma.

If the FDA gives approval, the SVd regimen is then claimed to become the only FDA-approved combination drug regimen that includes once-weekly Velcade therapy for relapsed myeloma.

In July 2019, XPOVIO secured accelerated approval from the FDA for the treatment of adult patients with relapsed or refractory multiple myeloma who have received at least four therapies prior and whose disease is refractory to at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti-CD38 monoclonal antibody.

This indication has received accelerated approval based on the response rate.

Continued approval for this indication may depend upon the verification and description of clinical benefit in a confirmatory trial.

Karyopharm intends to submit data from the Phase III trial to act as this confirmatory study.