The Phase 2a study EXIST (EXIdavnemab Synucleinopathy Trial), is a randomized, double-blinded, placebo-controlled study in Parkinson's disease patients to evaluate the safety and tolerability of exidavnemab, an alpha-synuclein antibody. The obtained regulatory approval of the substantial protocol modification enables inclusion of an additional cohort of Multiple System Atrophy (MSA) patients in the ongoing EXIST trial.  

The study is conducted in Spain and Poland. In addition to the 24 participants with mild to moderate Parkinson's Disease, an additional 12 participants with MSA will be recruited. In addition to the primary endpoints of safety and tolerability, a broad range of biomarkers will be evaluated, in plasma, cerebrospinal fluid (CSF) and using digital measurements.

MSA is a rapidly progressive and fatal rare disease affecting the central and autonomic nervous systems. MSA is characterized by pathological alpha-synuclein aggregation, that causes gradual damage to nerve cells in the brain. This affects balance, movement and the autonomic nervous system, which controls several basic functions, such as breathing, digestion and bladder control. Currently there is no cure and no available treatment to slow its progression.

Exidavnemab is being developed as a novel disease-modifying treatment for neuronal synuclein diseases such as MSA and Parkinson's disease. Exidavnemab is a monoclonal antibody (mAb) that selectively targets alpha-synuclein aggregates, such as oligomers or protofibrils. By promoting the clearance of aggregated alpha-synuclein, exidavnemab may reduce the spreading and the negative effects of alpha-synuclein. Thereby cellular function and survival may be preserved, and disease progression ultimately slowed down.

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This release discusses investigational uses of an agent in development and is not intended to convey conclusions about efficacy or safety. There is no guarantee that such investigational agents will successfully complete clinical development or gain health authority approval.

The information was released for public disclosure, through the agency of the contact person below, on May 8, 2025, at 13:30.

For further information, please contact:

Charlotte af Klercker, Senior Director Sustainability and Communications
Phone: +46 73 515 09 70
E-mail: charlotte.afklercker@bioarctic.com

Anders Martin-Löf, CFO 
Phone: +46 70 683 79 77
E-mail:  anders.martin-lof@bioarctic.com

About MSA
Multiple System Atrophy (MSA) is a rapidly progressive and fatal rare disease affecting the central and autonomic nervous systems. MSA is a synucleinopathy, a group of neurodegenerative diseases characterized by an abnormal alpha-synuclein aggregation, that causes gradual damage to nerve cells in the brain. This affects balance, movement and the autonomic nervous system, which controls several basic functions, such as breathing, digestion and bladder control. Currently there is no cure and no available treatment to slow its progression.

MSA is a condition with very high unmet medical need and poor prognosis. Currently, no cure or treatment is available to slow the progression of the disease. Patients typically live about 6 to 10 years after MSA symptoms first appear, with few patients surviving more than 15 years[1]^,[2]. MSA is significantly debilitating and classified as a rare disease, affecting less than 42,000 persons in the U.S.

About Exidavnemab
Exidavnemab is a monoclonal antibody drug candidate that is designed to selectively bind and eliminate aggregated forms of alpha-synuclein such as oligomers and protofibrils, as well as fibrillar forms, which participates in neurodegenerative disorders including Parkinson's disease and Multiple System Atrophy (MSA). The goal is to develop a disease modifying treatment that stops or slow down the progression of alpha-synucleinopathies e.g. Parkinson's disease and MSA. BioArctic's phase 2a study EXIST with exidavnemab is ongoing since 2024. EXIST is an important step towards a proof-of-concept study focusing on the efficacy of the drug candidate.

In March 2025, the US FDA Office of Orphan Products Development (OOPD) granted orphan drug designation (ODD) to exidavnemab for the treatment of MSA. 

About BioArctic AB
BioArctic AB (publ) is a Swedish research-based biopharma company focusing on innovative treatments that can delay or stop the progression of neurodegenerative diseases. The company is the originator of Leqembi® (lecanemab) - the world's first drug proven to slow the progression of the disease and reduce cognitive impairment in early Alzheimer's disease. Leqembi has been developed together with Eisai. BioArctic has a broad research portfolio within Alzheimer's disease, Parkinson's disease, ALS and enzyme deficiency diseases. Several of the projects utilize the company's proprietary BrainTransporter™ technology, which improves the transport of drugs into the brain. BioArctic's B share (BIOA B) is listed on Nasdaq Stockholm Large Cap. For more information, please visit www.bioarctic.com.