BOSTON ( TheStreet) -- Sanofi-Aventis' ( SNY) success with its new prostate cancer drug could present challenges for competing late-stage drugs from Medivation ( MDVN) and Johnson & Johnson ( JNJ).

Dendreon's ( DNDN) prostate cancer vaccine Provenge should not be affected, however.

Sanofi's cabazitaxel, an experimental drug, extended significantly the survival of men who failed previous chemotherapy treatment for advanced prostate cancer, according to results from a phase III study disclosed Wednesday.

Sanofi plans to seek approval for cabazitaxel later this year, and if approved, the drug is likely to become the standard of care for so-called second-line prostate cancer treatment and the first such drug to demonstrate a meaningful survival benefit.

Johnson & Johnson is developing its own prostate cancer drug abiraterone in the same second-line patient population. A phase III study is fully enrolled and data, including overall survival results, are expected before the middle of the year.

Cabazitaxel won't be approved in time to force Johnson & Johnson to make any changes to the design of the abiraterone study, but the cabazitaxel results do set an efficacy benchmark of sorts that abiraterone may need to surpass if the drug is to gain commercial traction.

Prostate cancer patients treated with cabazitaxel reported a median overall survival of 15.1 months compared to a median overall survival of 12.7 months for patients treated with another chemotherapy mitoxantrone, according to the phase III results.

Medivation faces a similar challenge with its prostate cancer drug MDV3100. A phase III study in second-line prostate cancer is still enrolling patients, with data not expected until 2011. By that time, cabazitaxel could be approved and on the market.

The last thing Medivation needs now is more uncertainty about its drug pipeline following Wednesday's failure of the company's Alzheimer's drug Dimebon in a closely watched phase III study.

Both Medivation and Johnson & Johnson are studying their respective drugs in other stages of prostate cancer treatment that, if approved, may not directly compete with cabazitaxel. However, these studies are not as far along.

Abiraterone and MDV3100 work by interfering with the way prostate cancer cells feed from testosterone produced in the body. That's different from cabazitaxel, which interferes with cancer cell division.

"I would predict FDA would look favorably on cabazitaxel, so if approved, the drug will set a new standard for prostate cancer therapy," said Dr. Oliver Sartor of Tulane University's School of Medicine and the co-principal investigator of the cabazitaxel study.

"There may be multiple, new standards of care in prostate cancer therapy, but that will depend on the outcomes of these other trials," he added, referring to abiraterone and MDV3100.

Dendreon's Provenge is currently under review by the FDA with an expected approval decision date of May 1. If approved, Provenge will be administered to prostate cancer patients before they're treated with any chemotherapy at all, which means the vaccine will be used much earlier than cabazitaxel in the treatment cycle.

Provenge is not without potential competition. AstraZeneca ( AZN) is running multiple phase III studies of a drug called zibotentan, one of which is enrolling the same type of prostate cancer patients that Dendreon included in its successful Provenge study. Data from this zibotentan study is expected in the second half of the year.

Other companies with phase III prostate cancer drugs include Bristol-Myers Squibb ( BMY), Roche/Genentech and Pfizer ( PFE).

-- Reported by Adam Feuerstein in Boston.

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