The Exelixis (EXEL - Get Report) drug Cometriq prolonged survival in advanced kidney cancer patients, according to an updated analysis of a previously presented phase III clinical trial.

Exelixis did not provide any specifics Monday about the duration of the survival benefit demonstrated by Cometriq in the kidney cancer study, so it's not known if these new data will help the company compete any better against Bristol-Myers Squibb (BMY - Get Report) .

In November, Bristol's drug Opdivo secured an expanded approval in kidney cancer based on a study in which the immunotherapy reduced the risk of death by 27% compared to Afinitor, an older drug sold by Novartis (NVS - Get Report) . At the median, kidney cancer patients treated with Opdivo lived 25 months compared to 19.6 months for Afinitor -- a five-month difference.

The Food and Drug Administration is still reviewing the Cometriq kidney cancer data with an approval decision expected on June 22. The drug is also under review by European regulators.

Exelixis is staying mum on details of the Cometriq survival benefit despite the widely held belief that the company faces a significant challenge luring kidney cancer patients away from Bristol and Opdivo. The only likely way Exelixis convinces doctors to use Cometriq before Opdivo is with a superior survival advantage, particularly since Cometriq causes more adverse side effects than Opdivo.

Investors, too, would probably be more excited about Cometriq's commercial potential in kidney cancer if they had specifics about the survival benefit to compare against Bristol's Opdivo.

But Exelixis says it is withholding the pertinent survival data until it can be presented at a future medical meeting, even though prior results from this phase III study were already presented publicly and published in the New England Journal of Medicine. An editorial in the NEJM published at the same time gave the treatment edge in kidney cancer to Opdivo over Cometriq.

Exelixis' stock closed Friday at $4.62, or just over 20% lower than its level in September when the results from the Cometriq and Opdivo kidney cancer studies were announced.

Exelixis enrolled previously-treated, or second-line, kidney cancer patients into its phase III study dubbed METEOR and randomized them to treatment with a daily dose of oral Cometriq or a daily oral dose of Afinitor. As announced last September, Cometriq demonstrated a 42% reduction in the risk of disease progression or death compared to Afinitor. At the median, progression-free survival was 7.4 months for Cometriq against 3.8 months for Afinitor. The response rate attributable to Cometriq was 21% compared to 5% for Afinitor. while the incidence rate of serious adverse events was higher with Cometriq (68%) versus Afinitor (58%.)

A survival benefit trended in favor of Cometriq but was not statistically significant at the September analysis. A new look at the trial now shows Cometriq demonstrating a survival advantage over Afinitor reaching statistical significance, Exelixis said Monday.

Renal cell carcinoma is the most common form of kidney cancer, with more than 330,00 cases diagnosed and more than 140,000 deaths worldwide each year. Pfizer's Sutent is the most commonly used therapy for newly diagnosed kidney cancer patients. Opdivo is approved for patients who no longer respond to Sutent or some other targeted therapy. This is the same indication Exelixis is seeking for Cometriq.

Cometriq is already approved for a rare form of thyroid cancer. Opdivo is approved to treat skin cancer, lung cancer and kidney cancer.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.