Geron Ends Phase 3 Trial of Rytelo in Myelofibrosis After Review Panel Says Survival Goal Is Unlikely to Be Met

Geron said on Wednesday it will discontinue its Phase 3 IMpactMF trial of imetelstat, sold as Rytelo, in patients with myelofibrosis whose disease had relapsed or stopped responding after treatment with a JAK inhibitor. The company, based in Foster City, California, announced the decision on October 28.

The decision followed a recommendation from the trial’s independent Data Monitoring Committee, which advised that the trial was unlikely to meet its main goal of longer overall survival, Geron said. The company said no new safety signals were seen that change the known safety profile of imetelstat or require extra safety monitoring.

327 patients took part

The trial enrolled 327 patients with intermediate-2 or high-risk myelofibrosis who had relapsed or were refractory to a JAK inhibitor, according to Geron. Patients were assigned at a 2-to-1 ratio in an open-label, controlled trial comparing imetelstat with the best available therapy. Patients in the imetelstat group received 9.4 milligrams per kilogram by intravenous infusion every three weeks.

Myelofibrosis is a rare type of blood cancer in which scar tissue gradually builds up in the bone marrow, Reuters reported. A detailed analysis of the trial data will be conducted, and Geron said it will share findings with the scientific community at a later date.

Approved use is separate

The trial decision does not change Rytelo’s approved use in the United States for transfusion-dependent anemia in patients with lower-risk myelodysplastic syndromes, an approval it received in 2024, according to Reuters. Geron said it plans to keep growing demand for Rytelo in the United States and widening access for eligible patients outside the country.

Geron shares were halted in premarket trading on Wednesday, Reuters reported.

Reporting based on coverage by Reuters and Geron Corporation.