** Shares of drug developer Dyne Therapeutics down about 4% at $31.2 premarket

** J.P. Morgan downgrades stock to "Neutral" rating from "Overweight", cuts PT to $35 from $43

** Brokerage skeptical if additional results from an early-to-mid stage trial testing DYNE-101 for a genetic muscular disorder would "fundamentally move the likelihood of success materially higher" or add near-term value

** Adds recent safety concerns over another early-to-mid stage trial testing DYNE-251 for a rare muscular degeneration disorder could keep DYN stock range bound over mid-term

** Nine of 10 brokerages rate the stock "buy" or higher while one rates "hold"; their median PT is $52.5 - LSEG data

** As of last close, stock more than doubled YTD vs 7.65% gain in Nasdaq Biotechnology Index

(Reporting by Sruthi Narasimha Chari in Bengaluru)

((Sruthinarasimha.chari@thomsonreuters.com))