Onconova Therapeutics has announced that it is advancing the oral formulation of rigosertib (Estybon, ON 01910.Na), an anti-cancer agent, into a new Phase 2 study.

Rigosertib is a small molecule inhibitor of critical pathways, important in the growth and survival of cancer cells and is currently in a pivotal Phase 3 trial for refractory myelodysplastic syndromes (MDS) in the US and European Union.

The Phase 2 study follows a Phase 1 dose escalation study in MDS patients where orally-administered rigosertib showed bone marrow responses in high-risk patients who were refractory to hypomethylating agents, a reduction in need for red blood cell transfusions in transfusion-dependent patients, and a transition to transfusion independence.

Principal investigator of the study, assistant professor of medicine at Columbia University and staff physician at Herbert Irving Comprehensive Cancer Center of Columbia University Medical Center/New York-Presbyterian Hospital in New York, Siddhartha Mukherjee, said a randomised Phase 2 evaluation of oral rigosertib will be conducted in patients with low or intermediate-1 risk, transfusion-dependent myelodysplastic syndromes at Columbia University Medical Center.

"The objective of the study is to determine if oral rigosertib will reduce the need for blood transfusions in transfusion-dependent MDS patients. The need for blood transfusions and the complications from receiving transfusions are serious medical issues for these patients," Mukherjee added.

Columbia University Medical Center medicine professor Azra Raza said the reduction in RBC transfusions observed in the study was a breakthrough.

"Confirmation of these findings in the Phase 2 study will be a significant step forward, potentially leading to a safe and effective treatment for patients with low-risk MDS," Raza added.

The ongoing Phase 3 ON 01910.Na trial in myelodysplastic syndrome (ONTIME) study is a pivotal, multicentre, randomised trial, comparing rigosertib with best supportive care to best supportive care alone, in high-risk MDS patients with excess blasts, who are refractory, intolerant to, or have relapsed after azacitidine or decitabine treatment.