** Shares of drug developer Aardvark Therapeutics AARD.O fall 26.5% to $4.95, snapping a four-day gaining streak

** Co said late on Thursday the U.S. FDA has placed a full clinical hold on its experimental drug, ARD-101, to treat extreme hunger linked to the rare genetic disorder, Prader-Willi syndrome

** Co had previously paused enrollment and dosing in February after heart-related side effects were seen in healthy volunteers given higher-than-planned doses of the drug

** AARD says it is in active talks with the FDA to resolve the issue and plans to review trial data to assess safety, efficacy and next steps

** BTIG says "a lack of concrete timelines makes it hard to lean into AARD at this juncture, and until we get more clarity on several of these points, we are stepping to the sidelines"

** Stifel says "it remains hard for us to get comfortable here with what was always a high-risk trial to begin with"

** Including session's move, AARD down 62% YTD