Karyopharm's decade-old selinexor myeloma trial re-opens enrollment for a new arm
STOMP resumed recruiting to test selinexor plus the CELMoD mezigdomide, its 12th combination arm, after a completion date that has slipped nearly seven years since 2020.
Executive Summary
- A long-running selinexor combination trial in multiple myeloma returned to active recruitment, opening enrollment for a newly added arm pairing the approved XPO1 inhibitor with a next-generation CELMoD agent.
- The trial has already generated pooled data supporting one of its combinations, so the new arm's job is to show whether adding a newer partner drug extends that benefit rather than to establish selinexor's activity from scratch.
- The trial's primary completion date has been pushed out repeatedly since it first targeted 2020, and enrollment has been revised downward, reflecting how long this platform trial has run rather than a new setback.
- Selinexor remains the only XPO1 inhibitor tested in multiple myeloma trials on record, leaving this combination platform to compete less against rival mechanisms and more against the pace of its own execution.
The status change
STOMP (NCT02343042), a Phase 1/2 study evaluating selinexor combined with ten different backbone myeloma regimens, moved back to Recruiting after a stretch as Active, not recruiting that began May 4, 2026. The registry now anticipates 300 patients, with the newest arm, selinexor plus dexamethasone plus mezigdomide (Arm 12), open for enrollment while the trial's other eleven arms have completed their enrollment. Karyopharm sponsors the study across 25 sites in the United States and Canada, and Bristol-Myers Squibb, mezigdomide's developer, is listed as a collaborator. NCT02343042Selinexor and Backbone Treatments of Multiple Myeloma PatientsNCT02343042
What the trial has already shown
STOMP is not a trial without a track record. Pooled data from the selinexor-pomalidomide-dexamethasone arm across STOMP and a related Karyopharm trial, NCT04414475, reported a median progression-free survival of 18.4 months with a safety profile the company described as consistent with prior selinexor experience, published in Frontiers in Oncology in May 2024. Earlier presentations at ASH and the European Hematology Association reported response rates of 78% for the carfilzomib-containing arm and 67% and 58% for other combinations in patients refractory to an anti-CD38 antibody, though those were descriptive subgroup findings rather than the trial's registered primary endpoints.
Timeline and enrollment
The trial's primary completion date has moved three times since the study first targeted May 2020, most recently landing at April 1, 2027, a cumulative shift of nearly seven years from the original estimate. Anticipated enrollment was also cut from 518 to 300 patients in March 2024, the second adjustment to the target, as the trial's design consolidated around fewer expansion cohorts once most of its original arms finished enrolling. Selinexor itself is FDA-approved as XPOVIO for multiple myeloma, so the newest arm is testing whether adding mezigdomide extends the durability the drug has already shown in combination, rather than establishing selinexor's activity from a standing start. NCT02343042Selinexor and Backbone Treatments of Multiple Myeloma PatientsNCT02343042
Where it sits competitively
Selinexor is the only XPO1 inhibitor with active multiple myeloma trials on record, and the broader field around it is dominated by different mechanisms: BCMA-targeted bispecifics and antibody-drug conjugates such as Regeneron's linvoseltamab and GlaxoSmithKline's belantamab mafodotin, CD38 antibodies such as Sanofi's isatuximab, and CAR-T therapies including Janssen's ciltacabtagene autoleucel. None of those shares selinexor's nuclear-export mechanism, so STOMP's mezigdomide arm is less a race against a rival XPO1 program and more a test of whether combining an approved oral inhibitor with a newer CELMoD can match or extend the response durability already reported for selinexor's other backbone combinations.
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