An oral medication already approved for thrombocytopenia in patients with liver disease significantly improved platelet recovery and helped patients with gastrointestinal cancers maintain platelet counts needed to continue chemotherapy as scheduled, according to results from a phase 2 clinical trial led by researchers at Sylvester Comprehensive Cancer Center, part of the University of Miami Miller School of Medicine, and Mass General Hospital. The findings showed 65% of patients receiving avatrombopag met key treatment goals, compared with 17% of patients receiving placebo treatment.
These results point to a potential new treatment for a common chemotherapy side effect: chemotherapy-induced thrombocytopenia (CIT), or low blood platelet counts. Platelets are a type of blood cell that helps form clots after injuries; patients with low platelets are at risk of excessive, life-threatening bleeding after even minor injuries.
The oral medication avatrombopag, a type of thrombopoietin receptor agonist, is FDA-approved to treat thrombocytopenia in patients with liver disease, but its effectiveness for CIT remained unclear until now.
Gerald A. Soff, M.D., chief of classical hematology at Sylvester, led the phase 2 clinical trial of avatrombopag with a goal to treat 40 patients with gastrointestinal cancers who were experiencing ongoing CIT. The drug proved so effective, however, that Soff and his colleagues were able to stop the trial at their interim analysis of 23 patients. He will present the results in a poster session at the 2026 American Society of Clinical Oncology (ASCO) annual meeting.
The trial enrolled patients with gastrointestinal cancers who had persistent CIT, those who were unlikely to recover from low platelets on their own in the time between chemotherapy cycles. Most patients will have a dip in platelet numbers following chemotherapy, but many of them will bounce back without needing treatment or to delay the next cycle. Those with persistent CIT often can't receive the next chemotherapy dose as scheduled; it would need to be either delayed or reduced in amount. And patients who have delayed or reduced chemotherapy treatment are known to have worse outcomes than those who receive their treatment as originally scheduled.
These are the patients, based on our experience, who have the greatest need and will benefit the most from use of a thrombopoietin receptor agonist."
Gerald A. Soff, M.D., chief of classical hematology at Sylvester
To date, no thrombopoietin receptor agonist has been approved for CIT, but several have shown promise in clinical trials. Soff also recently led a phase 3 clinical trial of a different thrombopoietin receptor agonist, romiplostim, for patients with gastrointestinal cancers and persistent CIT. Romiplostim also proved very effective to treat CIT, but it needs to be given as an injection. As an oral medication, avatrombopag has the advantage that patients wouldn't need to travel to an infusion center to receive it, Soff said. For those who have to travel long distances for their chemotherapy cycles, reducing trips to the clinic can be a big bonus.
"You can imagine if someone is dealing with metastatic cancer and they're not feeling great, and they're trying to maintain a life, having to go in every single week for a shot is not ideal," Soff said. "If there's a good oral option, that would be very appealing for many people."
In the clinical trial of avatrombopag, Soff and his colleagues were looking for two positive effects of the study drug:
- Patients needed to recover from low platelet counts within two weeks, and
- That platelet count needed to stay high through the next chemotherapy cycle.
Of the 23 patients who received avatrombopag, 65% hit both these metrics, as compared to only 17% of those who received placebo treatment. That's a very significant difference, Soff said. Many of the patients in the trial have continued receiving the drug for the long term, and he and his colleagues are now following them to understand whether the medication has a continued long-term benefit.
They also want to study whether avatrombopag could benefit patients with other types of tumors. There's no reason to think it wouldn't, Soff said. They focused on gastrointestinal cancers to minimize treatment differences among their patients, but patients with many other types of cancers also have to contend with CIT and treatment delays.
"There is pretty clear evidence that dose reduction or delay has an impact on cancer outcomes, and CIT is a common reason that doses would be delayed or reduced," Soff said. "Our goal here is to avoid compromising the cancer treatment."
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