** Shares of drug developer Avidity Biosciences RNA.O rise 2% to $47.57

** Avidity's experimental drug, Del-zota, for form of Duchenne muscular dystrophy showed that patients improved on key movement tests in early-mid stage trial

** These included getting up from floor, climbing four stairs, 10-meter walk/run and upper arm function, compared with usual decline seen over time

** Treatment boosted missing muscle protein (dystrophin) to about one-quarter of normal on average, with some patients reaching over half of normal

** Safety looked generally good; most side effects were mild to moderate and one person stopped due to allergic-type reaction

** Company plans to ask U.S. FDA for early approval by end of 2025 and is preparing follow-up study to confirm results

** "We think RNA has an approvable drug that can soon offer floor valuation to the stock (we model ~$350m in 2032)," RBC Capital Markets analysts say

** Including session's move, RNA stock up ~65% YTD

(Reporting by Padmanabhan Ananthan)

((Padmanabhan.Ananthan@thomsonreuters.com))