Myostatin normally keeps muscles from growing. Scientist are trying to inhibit myostatin as a therapeutic approach for kids with muscular dystrophy; this strategy has just entered clinical trials using an antibody that sops up the myostatin.
Working with Wyeth (say that ten times fast), these researchers have now developed a new drug that is much better than the antibody and allows muscles to grow even more than 60% increase in muscle size with twice weekly injections.
Obviously, you would want to be sure this is very safe before thinking about using it in PWS, but it might have potential to help build muscle mass to help with the general weakness associated with PWS (now alleviated to some extent with growth hormone). Also, since muscle is actually very important in regulating metabolism, helping to build muscle may improve overall body composition. This new agent will need to undergo toxicity testing in animals, then probably will undergo clinical trials in muscular dystrophy so it will be a while before this can even be considered for PWS. (there will also be a great potential for abuse by athletes, but that's another story).
Regulation of muscle growth by multiple ligands signaling through activin type II receptors . Lee SJ, Reed LA, Davies MV, Girgenrath S, Goad ME, Tomkinson KN, Wright JF, Barker C, Ehrmantraut G, Holmstrom J, Trowell B, Gertz B, Jiang MS, Sebald SM, Matzuk M, Li E, Liang LF, Quattlebaum E, Stotish RL, Wolfman NM. Proc Natl Acad Sci U S A. 2005 102(50):18117-22, 2005
Myostatin is a secreted protein that normally functions as a negative regulator of muscle growth. Agents capable of blocking the myostatin signaling pathway could have important applications for treating human muscle degenerative diseases as well as for enhancing livestock production. Here we describe a potent myostatin inhibitor, a soluble form of the activin type IIB receptor (ACVR2B), which can cause dramatic increases in muscle mass (up to 60% in 2 weeks) when injected into wild-type mice. Furthermore, we show that the effect of the soluble receptor is attenuated but not eliminated in Mstn(-/-) mice, suggesting that at least one other ligand in addition to myostatin normally functions to limit muscle growth. Finally, we provide genetic evidence that these ligands signal through both activin type II receptors, ACVR2 and ACVR2B, to regulate muscle growth in vivo.