Independent experts cast doubt on OncoMed's cancer drug

By Amrutha Penumudi (Reuters) - OncoMed Pharmaceuticals Inc lost nearly half its market value after independent investigators informed the company that its pancreatic cancer drug was unlikely to meet the main goal in a mid-stage study. The investigators told OncoMed that while the drug, tarextumab, had a clean safety profile, they had observed worsening response rates in patients taking the treatment. There is a low probability of the drug achieving a clear benefit in overall survival rates of the patients, according to the independent assessors. The setback sent the company's shares down by as much 46 percent to a record-low of $9.45 on Monday. Independent safety monitors oversee blinded trials so that they can be halted or unblinded early in case they determine that the drug is doomed to fail. A trial can also be halted if the benefit becomes so clear that the medicine can be offered to placebo patients. OncoMed said it was planning to unblind the trial to further analyze and verify data. Typically, in a clinical trial patients are randomly allocated one or other of the different treatments under study. When unblinding a trial, a company voluntarily breaks this code and becomes aware of the treatment each patient is taking. Tarextumab is an anti-cancer stem cell therapy that is tested in combination with the chemotherapy agent Abraxane. The company's other lead drug, Demcizumab, is also a stem cell therapy, aimed at treating lung cancer. OncoMed said it was difficult to conclude that its mid-stage trial on Demcizumab could go down the same path. Leerink Partners analysts slashed their price target on the stock to $11 from $27, saying they were now less confident about results from other trials in OncoMed's pipeline. The independent assessment also puts a question mark on OncoMed's partnership with GlaxoSmithKline Plc for Tarextumab. The British drugmaker has the option to obtain rights to the drug through the completion of the mid-stage studies. "This was OMED’s first Phase II trial that we expected data from, which may cause a re-assessment of OMED's pipeline, Mizuho analysts wrote in note. (Reporting by Amrutha Penumudi in Bengaluru; Editing by Shounak Dasgupta and Saumyadeb Chakrabarty)