Experimental Drug Extends Overall Survival in Men With Advanced Prostate Cancer
Early research studies show that patients with advanced prostate cancer given AstraZeneca's experimental pill ZD4054 lived around seven months longer than did those on placebo, but additional clinical trial data are needed

By Michael Kahn and Ben Hirschler

TUESDAY, September 25 (Reuters) - Patients with advanced prostate cancer given AstraZeneca's experimental pill ZD4054 live around seven months longer than those on placebo, according to results of a clinical trial presented on Tuesday.

But the drug - which some analysts think could be a blockbuster - failed to show an improvement in progression-free survival, a measure of how long patients survive before their condition worsens.

AstraZeneca said in July that ZD4054 demonstrated overall survival benefits and was being moved into final phase III studies. The scale of the improvement was revealed at the European Cancer Conference in Barcelona.

The Anglo-Swedish firm hopes the new medicine, which could be filed for approval in 2009, will revive its fortunes in the fast-growing cancer treatment market.

Men with advanced prostate cancer are normally given hormonal therapies, which can be highly effective. But in most cases resistance develops - leaving Sanofi-Aventis's chemotherapy drug Taxotere, which improves survival by around 2.4 months, as the only option.

Nick James, professor of clinical oncology at the Institute for Cancer Studies in Birmingham, England, said the phase II trial results with the new once-daily pill were "promising".

In the study of 312 pain-free or mildly symptomatic patients with metastatic hormone-resistant prostate cancer (HRPC), the median survival time for those on 10 milligrams of ZD4054 was 24.5 months, against 17.3 months for placebo.

Those given a 15 mg dose of the drug lived 23.5 months.

However, the study failed to show a statistically significant difference in progression-free survival (PFS), which had been its primary endpoint.

"It is usual to use PFS as an endpoint in phase II studies; however, it can be difficult to measure accurately in patients with metastatic HRPC. Overall survival is an unambiguous endpoint and clearly an important outcome for patients," James said.

Deutsche Bank analyst Mark Purcell, who rates the stock a "buy", said the seven-month survival benefit compared very favourably with Taxotere. He raised his forecast for sales of the drug by 2012 to $460 million from $182 million previously.

"Assuming a $2,000 per month treatment cost and a 25 percent patient penetration rate, ZD4054 carries more than $1 billion sales potential," he said in a note.

Other industry analysts said ZD4054 still needed to prove itself decisively in phase III tests.

The field is littered with prostate cancer drugs that have not won approval, including a similar product called Xinlay from Abbott Laboratories, which was rejected by U.S. regulators in 2005 after it failed to delay disease progression.

ZD4054 works by blocking the action of a cell protein called endothelin A, which is believed to play a key role in prostate tumour growth.

AstraZeneca shares were 0.3 percent higher in a sharply lower London market by 1310 GMT.

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