Geron permanently discontinues imetelstat trial after survival benefit deemed unlikely
Key Facts
Geron on October 28 announced it was stopping the Phase 3 IMpactMF trial of imetelstat after an independent data monitoring committee recommended that the study was unlikely to meet its primary endpoint of overall survival. The decision ends the trial, which tested the drug in patients with intermediate-2 or high-risk myelofibrosis who had relapsed after or failed to respond to JAK inhibitors. The company said the committee concluded that "the trial is unlikely to meet the primary endpoint of overall survival." Geron's announcement did not include a numerical efficacy comparison between the study arms or details explaining the basis for the committee's recommendation. It also said it would conduct a detailed data analysis and share the results with the scientific community at a later date that it did not specify.
The study included 327 patients, randomly assigned in a 2 to 1 ratio between the treatment arms in an open-label, controlled trial. The patients had intermediate-2 or high-risk myelofibrosis after their disease relapsed following treatment with JAK inhibitors or failed to respond to them. The trial tested imetelstat against best available therapy, focusing on patients who had not achieved a sustained response to prior treatment. Participants in the imetelstat arm received a dose of 9.4 mg per kilogram intravenously every three weeks. Overall survival was the primary measure the study was designed to assess.
Geron distinguished the decision to stop the trial from safety concerns, saying the study had not shown new safety signals that changed the drug's known profile or warranted additional monitoring. The stated reason for stopping was therefore linked to the likelihood of not meeting the survival goal, rather than to a new safety signal reported by the company. Geron did not publish detailed analysis results or an estimate of the difference between imetelstat and the comparator in its announcement. In a corporate presentation issued in February 2026, the company had expected to conduct an interim survival analysis in the second half of 2026. The presentation also projected a final analysis in the second half of 2028, under the base-case scenario and assumptions about the death rate that the company said could change.
The decision to stop the trial brings an end to those earlier estimated timelines, which were linked to the timing of deaths, while Geron said a detailed data analysis would be conducted and results shared later. The company did not set a date to publish the IMpactMF results or present them to the scientific community. Its next announced date is November 4, 2026, when it plans to report third-quarter results before the market opens. It said an investor call would be held the same day at 8:00 a.m. Eastern Time. That financial update is a set date for the company after the trial-stoppage announcement, while the timing of the clinical study results remains unannounced.
On the commercial front, Geron said it would continue to focus on growing demand for Rytelo in the United States and expanding access to the treatment outside the country for eligible patients with lower-risk myelodysplastic syndromes. Rytelo, which contains imetelstat, is approved in the United States and the European Union for certain groups of patients with these syndromes. Its net revenue was $57.5 million in the second quarter of 2026, up 11% from the first quarter, according to company results issued in August. In guidance published at the time, Geron projected annual Rytelo revenue of $220 million to $240 million and total operating expenses of $230 million to $240 million. Cash, restricted cash and marketable securities stood at $326.9 million on June 30, compared with $341.0 million on March 31.
Geron said in August that its net revenue in the first half of 2026 rose 24% from the same period a year earlier, while total operating expenses fell 4%. The company then estimated the potential U.S. second-line Rytelo patient population at about 8,000. This commercial path comes as the company faces the end of a clinical trial targeting myelofibrosis patients whose treatment with JAK inhibitors had failed. The latest available stock close before the announcement was $1.15 on October 26, compared with $1.12 on October 23. These prices did not include a closing price after the stoppage decision announced on October 28.