(CBS) — It’s estimated some 28,000 American men will die of prostate cancer this year.

But there is new hope in the form of an experimental pill that is showing real promise in patients with an advanced form of the disease.

When Rick Pflaum's prostate cancer moved to his bones the slightest movement caused incredible pain.

Then he started taking an experimental drug called Abiraterone.

"Within about three months the reversal was incredibly dramatic in that I was able to return to normal activities,” Pflaum said.

The daily pill blocks hormones that fuel prostate cancer.

In a small study researchers gave the drug to men with an aggressive and advanced form of the disease.

In most tumor size shrunk significantly and a key indicator of cancer, the PSA level, dropped as well.

"It targets one of the Achilles heels of the tumor that really contributes to its growth and progression," said Dr. Howard Scher.

The drug is being developed in Los Angeles by Cougar Bio-Technology.

The first study only used 21 patients. Now researchers are awaiting results from a much larger trial involving 1,200 men.

Dr. Howard Scher is one of the principal investigators.

"This is an international trial which will look at whether or not the drug prolongs life and is safe," explained Dr. Scher.

While Abiraterone isn't a cure, it is improving the lives of patients who did not respond to other treatments.

"Swimming and bicycling and just generally living a normal life," said Pflaum.

If future study results are equally promising the drug could be widely available by 2011.