** Shares of drug developer Sangamo Therapeutics SGMO.O rise 6% to $0.47

** Co says U.S. FDA granted fast-track designation to its experimental treatment, ST-503, for a severe form of chronic nerve pain

** ST-503 is experimental epigenetic regulator aimed at providing non-opioid treatment options, co says

** U.S. FDA's "fast track" tag aims to speed development and review of drugs for serious conditions with unmet medical needs

** Co expects to dose first patient in its early-stage trial in coming months - SGMO

** Including session's move, stock down ~56% YTD

(Reporting by Sahil Pandey in Bengaluru)

((Sahil.Pandey@thomsonreuters.com))