No silver lining in failed Bristol cancer drug trial

Bristol-Myers Squibb disappointed investors as researchers detailed data for its Opdivo cancer immunotherapy, which was already known to have failed to do better than older chemotherapies in a closely watched clinical trial.

Some analysts had speculated the study would at least show Opdivo worked in a subset of lung cancer patients with a biomarker that should make them more receptive to immunotherapy, but there was no sign of this.

Bristol first announced the trial failure in August, since when its shares have fallen by around a quarter, but experts have been waiting eagerly to learn exactly what went wrong and see if something might be salvaged from the setback.

In the event, data showed patients actually did worse on Opdivo, surviving only 4.2 months before their disease worsened against 5.9 months for those on chemotherapy, although the difference was not statistically significant.

What is more, researchers told the European Society for Medical Oncology congress that they were unable to point to any group of patients who did better in the trial, possibly due to imbalances between patients in different subsets.

Bristol took a big gamble by accepting a wide range of previously untreated lung cancer patients into its trial, in contrast to Merck which succeeded in a similar study by only taking people with high levels of a protein called PD-L1.

Immunotherapies like Opdivo and Merck's Keytruda work by taking the brakes off the immune system and are known to be most effective when tumor cells express lots of PD-L1.

Some investors had hoped Bristol would be able to point to a clear benefit in patients whose tumors had at least 50 percent of cells producing PD-L1. However, even in this group the trial did not show a benefit.

Commenting on the results, Naiyer Rizvi of Columbia University Medical Center, who was not involved in the study, said the failure to see a benefit was unexpected and hard to resolve with other clinical trials.

Bristol's bad news day contrasted sharply with that of Merck, which was able to point to a double success in clinical trials using Keytruda.