* Prostate cancer drug shown to improve overall survival
* Independent committee: placebo patients should take drug
* Drug could surpass Zytiga, Provenge -analysts
* Redemption for Medivation after Alzheimer's setback
* Medivation shares soar 110 percent
Nov 3 (Reuters) - A prostate cancer drug from Medivation Inc helped patients live longer in a late-stage study, sending the company's shares soaring on hopes that it will become a strong contender in an estimated $9 billion market.
Medivation said on Thursday that an independent monitoring committee even recommended stopping the clinical trial of the experimental drug, MDV3100, after seeing interim results, arguing that they showed enough benefit to warrant giving the experimental drug to patients who were taking placebo.
Shares of Medivation more than doubled to $34.79 in heavy trading, giving the company a market value of about $1.2 billion. It is developing MDV3100 with Japanese partner Astellas Pharma Inc .
If approved, the Medivation pill could become the favored treatment in a new generation of prostate cancer medicines, surpassing Johnson & Johnson's Zytiga, also taken orally, and Dendreon's infusion Provenge, analysts said.
Prostate cancer kills about 250,000 men a year globally and is the second-most common cause of cancer death in men in the United States, after lung cancer.
Better understanding of the molecular abnormalities underlying prostate cancer has led to new approaches to treating patients. Decision Resources, a healthcare advisory firm, expects global sales of prostate cancer drugs to more than double to $8.9 billion in 2019 from nearly $4 billion in 2009.
Medivation's prostate cancer success would also represent a comeback for the company and its chief executive officer, David Hung. MDV3100 is their main product after a closely watched experimental drug for Alzheimer's failed in a late-stage study in March 2010, slashing the company's share price from $40.
Hung, who owns 3.5 percent of the company according to recent data, will also benefit from the 110 percent share surge. Medivation's largest shareholders are investment funds QVT Financial LP and Lansdowne Partners.
MEASURING UP TO RIVALS
The company's interim analysis found that MDV3100 improved median overall survival by 4.8 months compared with a placebo. The estimated median survival for men treated with the drug was 18.4 months, while those treated with placebo had a survival of 13.6 months.
Wall Street was expecting a benefit of about three months, according to JPMorgan analyst Geoff Meacham.
Medivation's data comes as Dendreon late on Wednesday forecast only modest sales growth for its Provenge prostate cancer vaccine for the next several quarters. Dendreon shares were down 35 percent at $6.77.
The Phase III trial, named Affirm, tested MDV3100 against placebo in 1,199 men with advanced prostate cancer who were previously treated with chemotherapy based on the generic docetaxel.
Medivation and Astellas plan to meet with the U.S. Food and Drug Administration early next year and will provide an update on when they might seek approval for the drug. Analysts expect approval at the beginning of 2013.
While both MDV3100 and Zytiga work by targeting the male hormone testosterone that fuels prostate cancer cell growth, their mechanisms differ.
Zytiga works inside cancer cells to block testosterone production, while MDV3100 aims to interfere with the ability of testosterone to bind to prostate cells.
Zytiga improved median overall survival by 3.9 months, so "MDV3100 does look better than Zytiga from an efficacy perspective," JPMorgan's Meacham said in a research note.
While Medivation did not give any details on MDV3100's safety profile, the drug's main advantage over Zytiga is that it does not need to be taken with a steroid.
The J&J drug can cause hypertension and liver damage and so has to be taken in combination with the steroid prednisone. Prednisone, in turn, has several side-effects ranging from weight gain and pain to depression and weakness.
"Prednisone degrades the quality of life, which is very important to this patient population," Wedbush Securities analyst David Nierengarten said.
"When (MDV3100) is on the market it will displace Zytiga. It is a once-a-day pill without prednisone, and beats Zytiga which is twice-a-day with prednisone, very easily."
Shares of J&J were up 1 percent at $64.25.
Dendreon's Provenge also extended life by about four months on average in clinical trials. But the infused product is expensive at $93,000 for a course of therapy, and is a more complicated approach that has been slow to gain physician acceptance.
Provenge works by spurring a patient's immune system to attack cancer cells, and so each therapy is individually tailored to a patient.
One mitigating factor for Provenge could be that it is approved for use prior to chemotherapy, while Zytiga and MDV3100 have been tested for patients who have already taken chemotherapy, so they may not be direct rivals.
However, analysts noted, Zytiga and MDV3100 are being tested in a pre-chemo setting.
Provenge and MDV3100 "are two very different treatments and target different populations, but that said, this news does not bode well for Dendreon," Global Hunter Securities analyst Brian Lian said.