Exidavnemab (EXIST)

The research record

This is the project's file for this landmark, as written and checked. Sources are listed at the end; anything not yet confirmed is marked "Not yet verified".

Who

BioArctic AB (Sweden), with Worldwide Clinical Trials as a collaborator (registry). The antibody (also called BAN0805) came from research at Uppsala University (BioArctic report).

What happened

Exidavnemab binds the neurotoxic aggregated forms of alpha-synuclein rather than the normal protein. The idea follows the spread model (landmark 8) and the first antibody tests (landmark 63).

• Design (ClinicalTrials.gov NCT06671938). Phase 2a, randomised 2:1 to drug or placebo, quadruple-masked, sequential dose cohorts, given by infusion. Cohort 1: Parkinson's. Cohort 2a: Parkinson's at a higher dose. Cohort 2b: multiple system atrophy (MSA). The registry lists 38 enrolled. Parkinson's cohorts need a dopamine-transporter scan consistent with the disease, Hoehn and Yahr stage 1 to 2.5 and a poor sense of smell.
• Dates. Started 24 October 2024; finished 10 August 2026 (registry, updated 21 August 2026). No results posted.
• Primary measure. Safety: adverse events to day 176. Biomarkers in blood, spinal fluid and digital measures are exploratory.
• Interim review, Q2 2025. The first part was completed and the safety review supported moving to the higher dose.
• BioArctic's April–June 2026 report. A safety assessment of the second part showed a favourable profile. It says "results from the EXIST study are expected in H2 2026". Two Phase 2b studies are being planned, one in MSA and one in Parkinson's dementia and dementia with Lewy bodies, due to start in the first half of 2027. Neither is in plain Parkinson's disease.
• Two Phase 1 studies found it generally well tolerated, with a half-life of about 30 days. Exidavnemab has orphan drug designation for MSA in the US and EU.

Why it moved us toward a cure

It is a second, different type of antibody test after prasinezumab (landmark 63): it targets aggregated forms, not the whole protein. The next step has moved to dementia and MSA, which tells us the company sees those groups as a better place to test the idea.

Outcome

Pending: changed from open because BioArctic expects EXIST results in the second half of 2026 (set to 2026-12). The study was not built to show benefit, and none has been reported. No Parkinson's-only efficacy study is announced.

Sources

• ClinicalTrials.gov NCT06671938 (read via API, 19 Oct 2026)
• BioArctic interim report, April–June 2026 (PDF)
• BioArctic, AD/PD 2025 exidavnemab data · BioArctic, next cohorts after safety review (June 2025)
• Not yet verified: any actual safety numbers or biomarker results; doses; whether a separate press release on EXIST topline exists; exact enrolment split by cohort; an earlier AbbVie partnership (not mentioned in the 2026 report).