Shares of Acceleron Pharma (NASDAQ: XLRN) fell 12% in September, according to data provided by S&P Global Market Intelligence, after the biotech reported disappointing results for its drug candidate ACE-083 in patients who have facioscapulohumeral muscular dystrophy (FSHD).
Interestingly, the drug increased total muscle volume in the FSHD patients, but that didn't translate into improvements in functional tests. In other words, the patients gained muscle, but weren't any stronger.
FSHD is characterized by muscle weakness, so gaining strength, rather than just muscle, is obviously important.