The hunt is on for alternatives to anabolic steroids, which build muscle by mimicking the effects of the hormone testosterone but whose reputation has been tarnished by athletic doping scandals and side effects like liver damage.
A federally financed study showed that testosterone increased strength in the elderly. But the study was ended abruptly last year because those getting the hormone suffered far more cardiac problems than those getting a placebo.
Human growth hormone is also controversial because of side effects and questions about whether it can increase strength.
Companies like GTx and Ligand Pharmaceuticals are trying to develop drugs that possess the muscle-building ability of testosterone without its side effects, like the development of facial hair and other masculine features in women. These drugs are called selective androgen receptor modulators, or Sarms.
Pfizer, Amgen and Acceleron Pharma are separately pursuing drugs that block myostatin, a protein made by the body that acts as a brake on muscle formation.
Belgian Blue cattle, which do not make myostatin, have huge, rippling muscles and yet are otherwise apparently healthy. Several years ago, scientists reported that a German boy who lacked myostatin because of genetic mutations had abnormal strength and muscle mass.
Cytokinetics is testing a drug for Lou Gehrig’s disease that improves the ability of muscles to contract by, in effect, making them more sensitive to nerve signals.
Most of the drugs have been tested in only early-stage clinical trials so far, and there have been many setbacks.
Wyeth, now part of Pfizer, dropped a myostatin inhibitor that did not work well in a muscular dystrophy clinical trial. Amgen last month called off a trial to test its myostatin blocker for age-related muscle decline. Merck withdrew from a partnership to develop GTx’s drug.
But those companies all say they are not giving up on the quest.
