Shares of Onconova Therapeutics (ONTX) have lost nearly $6 each after the cancer drug developer said that a late-stage trial of rigosertib failed to meet its primary endpoint of improving median overall survival compared to the control in treating higher-risk myelodysplastic syndrome patients for which hypomethylating agents (HMAs) had not stopped the disease. Myelodysplastic syndrome, or MDS, is a type of cancer in which bone marrow doesn’t make enough healthy blood cells and abnormal cells are found in the bone marrow and/or blood.
Patients in the Phase III ONETIME trial enrolled 299 patients, 199 of which were in the IV rigosertib plus BSC (best supportive care) arm. Median overall survival for the group was 8.2 months, compared to the 5.8 months for the control group, which received BSC, an improvement that was short of the Newton, Pennsylvania-based biotech’s goal for the trial.
A closer look at the data did show that the treatment worked better on a subgroup of patients given rigosertib and BSC. A statistically significant increase in overall survival was seen in patients that had progressed on or failed previous treatment with HMAs. One-hundred-eighty-four (127 in treatment arm and 57 in control arm) of the 299 patients had a median survival rate of 8.5 months, versus only 4.7 months for those receiving only BSC.
Preliminary data shows that rigosertib was generally well tolerated with infrequent severe adverse events.
Despite the post-hoc analysis, it has been a brutal few months for rigosertib. In December, the drug was pulled out of the clinic in a Phase III trial in patients with pancreatic cancer. An interim analysis of the data in that trial showed that rigosertib was unlikely to outperform gemcitabine, the only single-therapy drug approved for the disease, with regards to overall survival.
Rigosertib, a small molecule inhibitor of phosphoinositide 3-kinase and polo-like kinase, both of which are frequently activated in cancer cells, is the crown jewel of Onconova and was highly touted as the company went public last July.
To that point, the company is staying focused on the subpopulation analysis and committed to developing the compound. "While we are disappointed that the ONTIME trial did not meet its primary endpoint, we are encouraged by the significant treatment benefit seen in the subset of patients who had progressed on or failed HMAs i.e., patients who had not responded to prior HMA treatment. We look forward to presenting additional information after data analysis is completed," said Ramesh Kumar, Ph.D., President and Chief Executive Officer of Onconova.
Onconova is also hanging their hat on an oral formulation of rigosertib performing better in an ongoing Phase II trial in which it is evaluating the drug candidate in low-risk MDS patients. Other than that, the company only has two other drugs in early-stage clinical trials for refractory lymphoma and acute radiation syndrome. The rest of the pipeline is still in pre-clinical stages.
Investors bailed out of the stock fast and hard on Thursday, with the stock nosediving as low as $7.75 after closing at $13.86 on Wednesday on the second highest volume in its history as a public company. Shares have pulled-up modestly as the day is winding towards a close, trading at $8.32 for a loss of 40 percent on the day.