Avidity shares fall 23% after announcing partial clinical hold for myotonic dystrophy trial

Shares of Avidity Biosciences Inc. RNA, -17.20% tumbled 23.7% in premarket trading on Tuesday after the company said the Food and Drug Administration placed a partial clinical hold on new enrollment in a Phase 1/2 clinical trial trial evaluating a new treatment for myotonic dystrophy type 1, a progressive neuromuscular disease. Avidity said the partial hold is the result of a serious adverse event reported in one patient. The adverse event “driving the partial hold is currently undisclosed, but we think it is promising that the FDA is allowing enrolled patients who already initiated dosing to continue receiving drug or placebo and roll into the open-label extension study,” SVB Securities analyst Joseph Schwartz wrote in a note to investors on Tuesday. Avidity’s stock is down 21.1% so far this year, while the S&P 500 SPX, +1.01% has declined 23.3%. T