Trial to Investigate Experimental Drug’s Effect on Improving Survival in Refractory Myelofibrosis

The first patient has been dosed in the phase 3 IMpactMF trial, which aims to demonstrate an overall survival benefit associated with treatment with GRN163L (imetelstat) versus the best available therapy in patients with refractory myelofibrosis, according to the experimental drug’s manufacturer, Geron Corporation.

“As the only study in refractory (myelofibrosis) with overall survival as the primary endpoint, dosing of the first patient in IMpactMF is an important step in developing (GRN163L) as a potential treatment for these patients,” said Geron’s chief medical officer Dr. Aleksandra Rizo in a news release. “With a median overall survival of only approximately 14 to 16 months for patients who fail or no longer respond to (Janus kinase [JAK]) inhibitor treatment, there is a significant unmet medical need for therapies that will improve survival.”

Previous phase 2 study results have shown that high doses of GRN163L may offer patients with high-risk myelofibrosis multiple clinical benefits, including improved overall survival compared to JAK inhibitor treatment.

Geron announced it estimates to enroll 320 patients onto the phase 3 clinical trial and that it expects to complete the trial in May 2024. Patients will be randomized to receive either study drug or investigator-selected non-JAK-inhibitor treatment. Those randomized to receive GRN163L will receive treatment intravenously every 21 days until their disease progresses, they experience unacceptable toxicities, treatment is discontinued or the study ends. The other group will receive best available therapy until any of those same endpoints are hit.

Measuring overall survival (time from treatment initiation that a patient is still alive) is the main goal of the study. Other goals of the study include assessing symptom response, spleen response, progression-free survival (time during and after treatment when a patient lives with cancer without disease progression), complete and partial responses to treatment.

The final analysis of overall survival data is planned to be conducted after more than half of the trial participants have died, according to the manufacturer. Geron noted it expects to report limited results in 2024 and final results in 2025. The company noted, however, that the study results could be available at different times than currently expected.

Patients across North and South America, as well as Europe, Australia and Asia are expected to be enrolled onto the trial.

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