Options for treating prostate cancer are expanding with the advent of novel, and more expensive, medicines, with key data expected soon for what could be one of the biggest new drugs.

After surgery or radiation, prostate cancer patients are typically treated with drugs, like Lupron, that trick the testicles into ceasing production of testosterone, the male hormone that fuels prostate cancer cell growth.

Better understanding of the molecular abnormalities underlying the disease has led to new approaches, including Johnson & Johnson's Zytiga, which works inside cancer cells to block testosterone production, and Dendreon Corp's Provenge, a therapeutic vaccine designed to spur the body's immune system to attack malignant cells.

Decision Resources, a healthcare advisory firm, expects global sales of prostate cancer drugs to more than double from nearly $4 billion in 2009 to $8.9 billion in 2019.

We now have more effective agents targeting the androgen (testosterone) receptor, said Dr. Elizabeth Plimack, an oncologist at Philadelphia's Fox Chase Cancer Center. At some point all patients will probably be completely resistant to these drugs ... ultimately we need a new approach.

Medivation Inc is developing a drug, known as MDV3100, designed to interfere with the ability of testosterone to bind to prostate cells.

KEY MEDIVATION DATA AWAITED

Full results from a pivotal trial of MDV3100 are due next year, but there is widespread debate over whether an interim analysis -- expected before the end of this year -- might prove that MDV3100 is effective and the trial could be stopped early.

If that happens, shares of Medivation -- which closed at $18.94 on Monday -- would jump to $30 or $35, according to Citigroup analyst Lucy Lu. If, however, the interim analysis is negative, she expects the stock to fall below $10.

MDV3100 is certainly promising ... but we haven't seen the data yet, said Dr. Plimack.

Optimism about the Medivation trial centers on the fact that J&J's pivotal trial of Zytiga, which had shown similar efficacy in earlier studies, was stopped as soon as it became clear that the drug improved survival.

Investor interest in Medivation has waned since March 2010, when the company announced the failure of a Phase 3 trial for its experimental Alzheimer's drug.

Wall Street analysts, on average, expect the company's sales of MDV3100 to reach $297 million by 2015, with sales by development partner Astellas Pharma forecast at $89 million, according to Thomson Reuters data.

J&J's Zytiga sales, which have exceeded expectations since the drug's approval in April, are forecast to reach $815 million by 2015.

PROVENGE SALES UNCERTAIN

The sales trajectory for Provenge remains uncertain. Analysts expect 2015 sales of nearly $1.3 billion, but that is down sharply from a nearly $2 billion average estimate before Dendreon stunned investors in August by withdrawing its own sales forecast because it was taking longer than expected for doctors to become comfortable with reimbursement issues.

Provenge is very exciting because it is the first immunotherapy for prostate cancer, but it is fraught with logistical issues, Dr. Plimack said. Centers are nervous to take on the cost in case reimbursement doesn't come through.

A course of treatment with Provenge costs $93,000, while Zytiga costs $5,000 a month, usually for eight cycles.

New York area oncologists and urologists polled in a recent focus group conducted by Sanford Bernstein said Zytiga and others drugs in the same class will be used in as many as 40 percent of patients by 2015, hormonal therapies will still be used in up to 90 percent of patients, and anti-androgens like MDV3100 would be used in 70 percent to 80 percent of men with prostate cancer.

Bernstein said both groups of doctors expect Provenge to be used in up to 12 percent of patients.

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.

Over the longer-term, drugmakers aim to move new therapies into earlier lines of treatment, possibly helping patients avoid side effects, like medical castration, that are common with current hormone-altering drugs or to reduce the need for harsh chemotherapy treatments.

In addition to MDV3100, prostate cancer medicines under development include custirsen from OncoGenex Pharmaceuticals Inc and Exelixis Inc's cabozatinib.

For supportive care, Amgen Inc's Xgeva prevents fractures and other bone problems in cancer patients and the company is seeking to expand its use to reduce the risk of bone metastases in certain prostate cancer patients.

Bayer AG has filed for use of Alpharadin in men whose prostate cancer has started spreading to bones.

(Reporting by Deena Beasley in Los Angeles; Editing by Richard Chang)

Cancer