Aardvark Therapeutics is down 54% since Friday after the biotech said it detected “reversible cardiac observations” in a healthy volunteer study of its drug to treat extreme hunger in patients with the rare genetic disease.
Aardvark Therapeutics has voluntarily suspended dosing and enrollment in a late-stage study of its investigational taste receptor activator for hyperphagia—an extreme, insatiable hunger—in patients with a rare genetic disease called Prader-Willi syndrome.
The decision to pause the Phase 3 HERO study was driven by what the biotech said were “reversible cardiac observations” in a healthy volunteer study, according to a news release on Friday. Detected during a routine safety check, these signals occurred above therapeutic doses of the drug, called ARD-101. The pause also applies to HERO’s open-label extension. It is unclear what exact cardiac events Aardvark detected.
Aardvark was trading at $5.76 per share as the markets opened on Monday, down some 54% versus its closing price of $12.50 on Friday.
In a note to investors, Stifel analysts said the cardiovascular signal came as a “surprise” given that “this hasn’t been seen in prior preclinical/clinical studies—and regular safety monitoring of HERO has had no issues.” The group spoke with Aardvark’s management, which they said planned to meet with the FDA to figure out a way forward and was “optimistic” about ARD-101’s prospects.
Stifel, however, doesn’t seem to share the enthusiasm. “It’s hard for us to have any confidence here,” the analysts wrote, noting that because cardiac tissue expresses the specific taste receptors that ARD-101 targets, the safety signal “seems plausibly drug-related.”
“Moreover, with runway into 2027 and unclear timelines, the balance sheet is another important question,” Stifel continued. As of Sept. 30, 2025, Aardvark had $126.4 million in cash, equivalents and short-term investments, as per its quarterly report at the time.
William Blair echoed Stifel’s concerns, noting that the pause “increases the clinical risk” of ARD-101. “Due to severe disruption of the study pause, we do not believe the ongoing Phase III HERO trial will be fully completed,” the analysts said.
Aardvark has not announced when it expects to reopen HERO, though the biotech did say on Friday that given the pause, it will most likely not meet its third-quarter target for a topline readout.
ARD-101 is a small-molecule drug designed to target and activate select taste receptors—particularly those that mediate bitterness—that are expressed in the intestine. This mechanism of action allows the drug to stimulate the secretion of several gut hormones, including GLP-1, to modulate hunger. Phase 2 data in June 2023 demonstrated that 11 of 12 patients with Prader-Willi syndrome experienced a reduction in hyperphagia at 28 days after treatment, while also showing “beneficial” changes to their behavior.
Prader-Willi syndrome is a rare genetic disorder that most commonly manifests as hyperphagia: an urge to keep on eating because patients never feel full or satisfied. Those with the condition suffer from obesity and related comorbidities, as well as other physical, behavioral and cognitive problems.
Outside of ARD-101, Aardvark also has ARD-201 for weight loss and weight maintenance, though both programs are still in early development.
