AC Immune NLRP3 inhibitor clears Phase 1 with CSF penetration
AC Immune has reported encouraging interim data from its first-in-human Phase 1 study of ACI-19764, an orally available small molecule inhibitor of the NLRP3 inflammasome, saying the candidate was safe and well tolerated across both single and multiple ascending dose cohorts in healthy volunteers with no serious adverse events and no treatment withdrawals.
The Lausanne-based company said doses up to 20mg per day were tested in the single ascending dose cohort, with a serum half-life exceeding 30 hours. Crucially, ACI-19764 showed clear evidence of brain penetration via cerebrospinal fluid exposure, a milestone that materially broadens its potential applications in neurological disease. Pharmacokinetic data indicated that daily doses at or below 10mg achieved concentrations above the IC90, and blinded analysis of whole blood assays showed dose-dependent inhibition of IL-1 beta release.
Martin Zügel, interim chief executive of AC Immune, said the results represent "an important milestone for this programme" and that the company is "now poised to deliver key clinical evidence of anti-inflammatory activity in the coming months."
Phase 1b and next milestones
Having cleared the healthy-volunteer portion of the study, AC Immune has commenced dosing of a cardiovascular risk cohort, defined by elevated high-sensitivity C-reactive protein and the presence of type 2 diabetes and/or obesity. This Phase 1b arm is designed to generate early proof-of-concept for anti-inflammatory activity, with initial hsCRP readout data expected before the end of 2026. Full Phase 1/1b results are anticipated in the first half of 2027.
The decision to evaluate cardiovascular disease risk patients in a Phase 1b cohort is a deliberate cross-disease strategy. NLRP3 inhibition has attracted considerable scientific interest across multiple inflammatory and metabolic conditions, and AC Immune appears to be positioning ACI-19764 as a broad platform asset rather than a single-indication play.
Competitive landscape
The NLRP3 inhibitor space has become increasingly competitive over the past several years. Novartis acquired Cardior Pharmaceuticals and has explored inflammasome biology, while Inflazome, acquired by Roche, developed its own NLRP3 programme before that work was eventually discontinued. Olatec Therapeutics and IFM Therapeutics have also advanced candidates targeting related inflammatory pathway nodes. What distinguishes ACI-19764 in this field, if the clinical data continue to hold, is the confirmed central nervous system penetration. Most competing programmes have been developed with peripheral inflammatory indications in mind; CNS bioavailability is significantly harder to achieve with a small molecule and, if maintained into later-stage trials, would represent a meaningful differentiator for neuroinflammatory conditions such as Alzheimer's disease and Parkinson's disease.
AC Immune's broader pipeline already includes ACI-7104, an active immunotherapy targeting alpha-synuclein in Parkinson's disease, and several Alzheimer's-focused assets partnered with major pharmaceutical companies. The company cites more than 4.5 billion dollars in potential milestone payments from those partnerships. ACI-19764 is entirely company-owned, giving AC Immune full economics on any eventual out-licensing or commercial development.
Investors will focus on the hsCRP readout expected later this year as the first genuine test of pharmacodynamic activity in a disease-relevant patient population. A clean signal there would meaningfully de-risk the programme ahead of a potential Phase 2 design discussion.