Biogen falls after US FDA declines to approve higher dose of co's genetic disorder drug

** Shares of drugmaker Biogen BIIB.O fall 1.5% to $137.25 in extended trading

** Company says the U.S. FDA has declined to approve higher dose version of its drug for a rare genetic disorder that causes progressive muscle weakness, citing the need for updated technical information in the application

** The FDA has requested revisions to the Chemistry Manufacturing and Controls module in its "complete response letter," but did not identify deficiencies in the clinical data supporting the high-dose regimen — BIIB

** Company plans to resubmit the application promptly based on readily available information

** As of last close, stock down 8.9% YTD