Patients Treated With AskBio’s Limb-Girdle Muscular Dystrophy Gene Therapy AB-1003 Free of Serious Adverse Events at Up to 52 Weeks

Interim safety results from the randomized, placebo-controlled phase 1/2 LION-CS101 clinical trial (NCT05230459) evaluating Asklepios BioPharmaceutical (AskBio)’s AB-1003 (LION-101), an investigational adeno-associated virus (AAV) vector-based gene therapy intended to treat limb-girdle muscular dystrophy type 2I/R9 (LGMD2I/R9), have shown that patients remained free of serious adverse events (SAEs) at up to 52 weeks posttreatment.¹ The data were presented at the 30th Annual International Congress of the World Muscle Society, held October 7 to 11, 2025, in Vienna, Austria.

The data comes from LION-CS101's first cohort, which is one of 2 sequential dose-level cohorts and enrolled 5 patients. AskBio noted that all 5 patients are continuing to participate in the trial and are expected to remain on-study through completion. The 5 patients received either AB-1003 or a placebo and underwent adverse event monitoring, laboratory testing, physical exams, vital signs, electrocardiograms, and echocardiograms.

As of up to 52 weeks after receiving the gene therapy, no patients experienced any SAEs or dose-limiting toxicities. Headaches, falls, and nausea constituted the common treatment-emergent AEs, occurring in 2 or more patients each, and were deemed mild-to-moderate in terms of severity. Asymptomatic transient transaminase elevations without changes in bilirubin levels occurred in 3 patients, but following corticosteroid adjustments they were brought back to baseline levels.

“These initial safety data are encouraging and suggest an acceptable safety profile for AB-1003,” Canwen Jiang, MD, PhD, the chief development officer and chief medical officer at AskBio, said in a statement.¹ “We believe AAV-mediated gene therapy has the potential to restore FKRP function and stabilize disease progression, and we are excited to continue our clinical research efforts with the goal of developing an effective treatment for LGMD.”

The double-blind, dose escalation LION-CS101 trial, which was launched in 2023, is open to adults aged 18 to 65 years who have genetically-confirmed LGMD2I/R9. The trial’s second cohort is actively enrolling patients and the study is expected to include up to 14 patients in total, who will participate at 6 sites across the United States.

AB-1003, which is delivered as a single dose via intravenous infusion, is intended to provide a functional copy of FKRP, the disease-targeted gene. In March 2023, AB-1003 received orphan drug designation from the European Commission through AskBio’s Europe-based subsidiary, BrainVectis and prior to that, the gene therapy had been granted fast track designation by the FDA in June 2021.^2,3

“While the inherited nature of LGMD means those with the FKRP gene mutation can’t produce a normal FKRP protein for physiological muscle function, AB-1003 is designed to introduce the normal FKRP gene into the muscle and express a normal protein, and it has shown promise in restoring normal FKRP protein function in muscle in preclinical studies performed in mouse models of LGMD,” Nicholas Johnson, MD, the principal investigator and vice chair of research in the Department of Neurology at Virginia Commonwealth University School of Medicine, said in a statement made when the dosing of the first patient in LION-CS101 was announced in August 2023.⁴ “This trial is the first step toward evaluating the safety of AB-1003 and assessing the potential that AB-1003 has to improve the lives of patients with this serious, inherited ultra rare condition.”

AskBio is one of several companies currently developing gene therapies for the treatment of forms of LGMD. Others include Atamyo Therapeutics, which is developing ATA-100 (previously referred to as GNT0006), an investigational AAV vector-based gene therapy intended to treat LGMD2I/R9, and Sarepta Therapeutics, which is developing SRP-9003 (bidridistrogene xeboparvovec), an investigational AAV vector-based gene therapy intended to treat LGMD Type 2E (LGMD2E/R4, also known as beta sarcoglycanopathy).^5,6 Atamyo is additionally developing ATA-200, an investigational AAV vector-based gene therapy for the treatment of γ-sarcoglycan-related LGMD Type 2C/R5 (LGMD2C/R5).⁷

REFERENCES
1. AskBio presents interim safety results from phase 1/phase 2 LION-CS101 clinical trial of AB-1003 in participants with limb-girdle muscular dystrophy 2I/R9. News release. AskBio Inc. October 10, 2025. Accessed October 17, 2025. https://www.askbio.com/interim-safety-results-from-lion-cs101-clinical-trial-of-ab-1003-limb-girdle-muscular-dystrophy-2i-r9/
2. AskBio receives European Commission orphan drug designation through its EU-based subsidiary BrainVectis for AB-1003, a novel investigational AAV gene therapy for the treatment of limb-girdle muscular dystrophy (LGMD). News release. Asklepios BioPharmaceutical, Inc. February 16, 2023. Accessed October 17, 2025. https://www.askbio.com/askbio-receives-european-commission-orphan-drug-designation-through-its-eu-based-subsidiary-brainvectis-for-ab-1003-a-novel-investigational-aav-gene-therapy-for-the-treatment-of-limb-girdle-muscular/
3. AskBio receives FDA fast track designation for LION-101, a novel investigational AAV gene therapy for the treatment of limb-girdle muscular dystrophy type 2I/R9 (LGMD2I/R9). News release. Asklepios BioPharmaceutical, Inc. June 28, 2021. Accessed October 17, 2025. https://www.askbio.com/askbio-receives-fda-fast-track-designation-for-lion-101-a-novel-investigational-aav-gene-therapy-for-the-treatment-of-limb-girdle-muscular-dystrophy-type-2i-r9-lgmd2i-r9/
4. AskBio announces first patient dosed in phase 1 / phase 2 trial of AB-1003 gene therapy for limb-girdle muscular dystrophy type 2I/R9 (LGMD2I/R9). News release. Asklepios BioPharmaceutical, Inc. August 3, 2023. Accessed October 17, 2025. https://www.askbio.com/askbio-announces-first-patient-dosed-in-phase-1-phase-2-lgmd2i-r9/
5. ATA-200, AtamyoTherapeutics’ gene therapy to treat limb-girdle muscular dystrophy type 2C/R5, reaches key milestones with the filing of a clinical trial application in Europe and a non-dilutive financing from France 2030 program. News release. Atamyo Therapeutics. September 19, 2023. Accessed October 17, 2025. https://atamyo.com/press-releases/https-atamyo-com-wp-content-uploads-pr-sept-19-2023-ata-200-reaches-key-milestones-with-cta-in-europe-and-france2030-financing-pdf/
6. Sarepta Therapeutics initiates screening in EMERGENE, a phase 3 clinical study of SRP-9003 for the treatment of limb-girdle muscular dystrophy type 2E/R4. News release. Sarepta Therapeutics, Inc. January 16, 2024. Accessed October 17, 2025. https://investorrelations.sarepta.com/news-releases/news-release-details/sarepta-therapeutics-initiates-screening-emergene-phase-3?_ga=2.7071793.2083102767.1706027313-1116878115.1706027313
7. ATA-200, AtamyoTherapeutics’ gene therapy to treat limb-girdle muscular dystrophy type 2C/R5, reaches key milestones with the filing of a clinical trial application in Europe and a non-dilutive financing from France 2030 program. News release. Atamyo Therapeutics. September 19, 2023. Accessed October 17, 2025. https://atamyo.com/press-releases/https-atamyo-com-wp-content-uploads-pr-sept-19-2023-ata-200-reaches-key-milestones-with-cta-in-europe-and-france2030-financing-pdf/