Oral Estybon Shows Activity In Myelodysplastic Syndromes (ASH 2011)
Published: Feb 14, 2012 9:13 am
An oral formulation of Estybon shows activity and is safe in patients with myelodysplastic syndromes, according to results of a Phase 1 study.
The study investigators found that the optimal dose for oral Estybon was 560 mg twice daily for two weeks of a three-week treatment cycle. The most common observed side effects were problems involving urination, such as painful urination and blood in the urine.
The findings were presented during a poster session at the 2011 American Society of Hematology (ASH) meeting in December.
Estybon (rigosertib, ON 01910.Na) is an investigational drug, not yet approved by the Food and Drug Administration for use outside of clinical trials. The biopharmaceutical company Onconova Therapeutics is developing Estybon as a potential new treatment for MDS. Estybon works by selectively killing cancer cells and immature stem cells (called blasts).
Recent Phase 1/2 trial results showed that Estybon is effective in MDS patients when administered intravenously (see related Beacon news). The intravenous formulation is being tested further as an MDS treatment in an ongoing Phase 3 trial.
In the current Phase 1 study, researchers evaluated the safety and activity of oral Estybon at different doses in 33 MDS patients. All study participants were resistant to the MDS drugs Revlimid (lenalidomide), Vidaza (azacitidine), and Dacogen (decitabine).
The patients received 70 mg to 700 mg of oral Estybon twice daily for two weeks of a three-week treatment cycle.
After treatment with Estybon, 6 percent of patients achieved a complete response and 12 percent showed improvements in red blood cell counts. The study investigators described these results as encouraging.
The researchers also said that treatment with Estybon was well tolerated. The most common side effects were urinary symptoms: painful urination, blood in urine, frequent urination, nighttime urination, and urinary bladder inflammation. The frequency of these symptoms was much higher in patients treated at the 700 mg level (83 percent), compared to those treated at the 560 mg level (29 percent).
Side effects related to urination also have been observed in trials of the intravenous formulation of Estybon.
One patient in the trial of oral Estybon experienced dose-limiting side effects at the 700 mg dose level during the first treatment cycle. Based on that finding, the researchers recommended a dose of 560 mg of Estybon for a Phase 2 trial.
For more information, please see abstract 3797 at the ASH 2011 meeting website.
- Estybon May Be Effective For MDS Patients Who Experience Vidaza And Dacogen Failure (ASH 2010)
- Phase 1/2 Trials Find Estybon Effective And Safe For MDS Patients (ASH 2011)
- Estybon May Be Effective As Salvage Therapy For Higher-Risk MDS Patients And Patients With Trisomy 8
- Phase 3 Trial To Begin For Potential New MDS Drug Estybon
- Estybon May Extend Survival In MDS Patients Who Fail Vidaza Or Dacogen (EHA 2011)