Xtandi

BY MARK SCHOLZ, MD

It’s here!  Only 3 months after submitting the data from their phase III randomized trial, Medivation’s new prostate cancer super drug was approved by the FDA. Why so quick?  The FDA usually moves like molasses on a chilly morning. It can’t be simply because Xtandi (aka enzalutamide, aka MDV-3100) prolongs survival in men with life-threatening prostate cancer. We have all seen how the FDA ruminates, disseminates and procrastinates. Has the FDA suddenly grown a heart?

No, I think the quick approval of Medivation’s pill can be credited to the nature of the pill itself. It has an amazingly benign side effect profile.  The FDA is charged with two responsibilities: Confirming that a pharmaceutical company’s claims of anti-cancer effectiveness are valid and, ensuring that new products placed on the market are safe. In the latter case Xtandi made the FDA’s job simple.  The results from the study data submitted to the FDA for review showed that men taking Xtandi had fewer side effects than men treated with placebo.

What? Less side effects than placebo?  That sounds impossible. How can an active pharmaceutical agent that is potent enough to block cancer have absolutely zero side effects?  Even aspirin (stomach ulcers) Tylenol (liver damage) and Benadryl (drowsiness, slow urination) have known toxicity.

Actually Xtandi does have a significant side effect profile.  However, the side effects were completely masked because all the men being tested in the study—the men taking placebo and the men taking Xtandi—were also taking Lupron to block their testosterone. So the typical side effects of blocking testosterone (low libido, hot flashes and fatigue) already preexisted in everyone in the study. Therefore Xtandi’s side effects were “cloaked” by the Lupron.

The above explanation can account for Xtandi having the same side effect profile as a  placebo. However, in the study, Xtandi had fewer side effects than placebo. This mystery can be unraveled by considering the generally advanced stages of cancer present in the men being studied.  Uncontrolled cancer can cause “side effects” that are indistinguishable from drug-related side effects.  Xtandi works. It controls cancer and reduces “side effects.”

Medivation deserves enthusiastic commendation for developing this lifesaving new medication. The company should also be recognized for its generous community spirit because while waiting for FDA approval they have been distributing Xtandi free of charge to hundreds of patients through a compassionate-use research protocol.