Science1 publisher3 min readPublished
Ariadne Bio aims a non-hallucinogenic 5-HT2A agonist at Parkinson's apathy
Palomar Labs' first spinout is built on a molecule whose parent compound was tested in the 1970s and documented not to be hallucinogenic. Apathy affects about 40% of people with Parkinson's, and no drug is approved for it.
The Scientist · Science desk
What happened
- Palomar Labs, a venture studio formerly called Negev Labs that builds companies around candidates with prior human validation, has spun out its first portfolio company, Ariadne Bio.
- Ariadne's lead program, AB-300, is a clinical-stage molecule described as a non-hallucinogenic serotonin 2A receptor agonist, in development for apathy in people with Parkinson's disease.
- No therapy is approved for apathy in any indication, and GEN reports AB-300 could be among the first if it clears trials and regulators.
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Why it matters
- constraint With nothing approved for apathy anywhere, Ariadne has no active comparator and no earlier approval to show what evidence a regulator found sufficient, so it has to argue its own measure of motivation.
- capability Activating 5-HT2A without hallucinations would put the receptor within reach of older patients who cannot take a psilocybin-scale dose; Raz makes that argument for the third generation of these compounds.
- precedent Palomar's selection rule now rides on one program, so its thesis about candidates with prior human use will be judged on whether AB-300 works in a single indication.
Prior human exposure retires one risk and leaves the other standing. Raz said the studio's "mission is to find promising drug candidates with some history of human use" that target "conditions associated with late life" [4], and Palomar's stated plan is to take candidates with documented safety and efficacy evidence through the clinic to proof-of-concept [5]. That covers how people tolerated the drug. Whether AB-300 changes goal-directed behavior in people with Parkinson's is a separate question, and answering it takes a controlled trial [6][10].
What is on the record for the parent compound is an observation from testing in the 1970s, when it was documented to lack hallucinogenic effects, Jeffries told GEN, and several groups have since worked on why that molecule does not cause hallucinations [22]. GEN's account does not include trial results for AB-300, a phase designation beyond "clinical-stage," or Ariadne's financing [23].
Apathy in Parkinson's is defined clinically as a persistent reduction in goal-directed behavior [10], and roughly 40% of patients are estimated to develop it at some point in the illness, with higher rates in the mid and late stages [11]. It overlaps with depression without being the same condition. SSRIs remain the appropriate treatment for Parkinson's-associated depression, while some evidence links SSRI use to emotional blunting and worsening apathy [13]. A trial enrolling apathetic patients who are already on an SSRI is measuring its drug against a background that may be moving the outcome the other way.
"We built Ariadne Bio around a single question: whether motivation can be restored pharmacologically. AB-300 is how we intend to answer it," Raz said [8]. Jeffries called apathy "among the most disabling non-motor features of Parkinson's disease" [9], and studies of caregiver burden rank neuropsychiatric symptoms like it ahead of motor symptoms as drivers of distress [12]. Nothing is approved for apathy in any indication [14]. There is no competitor to beat, and no earlier approval showing what evidence a regulator accepted for this kind of endpoint [25].
Serotonergic psychiatry, in Raz's telling, arrives in generations. "Coming out of the psychedelic space, the way I view it is that the first generation of that drug class were these very potent classical psychedelics like psilocybin and LSD," he said [20]. The second changed formulation to alter pharmacodynamics; the third hits the same receptors without the hallucinations, which Raz argues makes them suited to older adults [21]. He moved to Palomar after a stint at Beckley Psytech, he said, because of the opportunity in drugs with demonstrated therapeutic potential that never became FDA-approved therapies [19].
He has run this play once. Raz founded Eleusis [15], Beckley Psytech acquired it in 2022 [16], Beckley combined with Atai Life Sciences to form AtaiBeckley in 2025 [17], and in July 2026 Eli Lilly entered a definitive agreement to acquire AtaiBeckley [18]. Three transactions in about four years [24]. Ariadne is the second neuropsychiatry company Raz has launched [26].
What to watch
- Whether Ariadne registers a trial that separates apathy from depression at screening, and what measure of goal-directed behavior it names as primary.
- Whether the 1970s human data on AB-300's parent compound is published or filed with the FDA in support of the program.
- Whether Eli Lilly's definitive agreement to acquire AtaiBeckley completes.