Long-term Safety and Efficacy Evaluation of Ulviprubart (ABC008) in Patients with Inclusion Body Myositis Following Completion of Prior Ulviprubart Trials

The primary objective of this study is to assess the long-term **safety** and tolerability of **ulviprubart** (ABC008) in subjects with **inclusion body myositis**. This objective is clinically relevant as it aims to ensure that the therapeutic use of ulviprubart does not result in adverse effects over extended periods, which is crucial for chronic conditions like inclusion body myositis where long-term treatment may be necessary.

Secondary objectives include evaluating the long-term efficacy of ulviprubart in subjects with inclusion body myositis. This is important to determine the sustained therapeutic benefits of the treatment, ensuring that it continues to provide clinical improvements or stabilization of the disease over time.

The clinical trial involves a total of **257 participants** diagnosed with **inclusion body myositis**, a progressive muscle disorder. The study population includes both male and female subjects, with an age range that encompasses adults and older adults. Participants were selected based on their prior involvement and completion of either Study ABC008-IBM-101 or Study ABC008-IBM-201, ensuring they have demonstrated adequate compliance with study procedures. The trial includes individuals who are willing and able to adhere to the protocol requirements, including travel for study-related assessments and administration of the investigational product, ulviprubart. Lifestyle considerations such as the use of highly effective contraception are mandated for women of childbearing potential and male subjects with female partners who are of childbearing potential. The trial population is characterized by a vulnerable group, reflecting the specific health challenges associated with the condition under investigation.

The clinical trial is designed to evaluate the long-term safety and efficacy of **ulviprubart** in subjects with **inclusion body myositis** who have completed a prior trial involving the same investigational product. This study is an open-label, multicenter trial, and it is not categorized as low intervention. The trial is expected to run until September 30, 2028, with recruitment starting on August 22, 2025. Participants will receive **ulviprubart** via subcutaneous injection, with a maximum daily dose of 2.0 mg/kg and a total dose not exceeding 38 mg/kg over a treatment period of up to 152 weeks.

The trial will include several key visits: an inclusion (screening) visit, regular follow-up visits, and an end-of-study visit. The inclusion visit will confirm eligibility based on criteria such as prior participation in specific studies, compliance with study procedures, and agreement to use effective contraception. Follow-up visits will monitor the incidence, type, and severity of treatment-emergent adverse events (TEAEs) and other safety parameters. The end-of-study visit will assess the overall safety and efficacy outcomes, including changes in the IBM Functional Rating Scale (IBMFRS) and Manual Muscle Testing (MMT) scores from baseline.

Participant involvement is expected to last for the duration of the treatment period, with conditions for early termination including the occurrence of serious adverse events or non-compliance with study protocols. The primary endpoint focuses on the incidence, type, and severity of TEAEs, while secondary endpoints include the incidence of serious adverse events, clinically significant changes in laboratory parameters, and efficacy measures. The study aims to provide comprehensive data on the long-term use of **ulviprubart** in this patient population.

The clinical trial involves the administration of **Ulviprubart**, an experimental medication developed by ABCURO, INC. Ulviprubart is a **solution for injection** and is classified as a humanised afucosylated IgG1 monoclonal antibody that binds to the killer cell lectin-like receptor G1 (KLRG1). The pharmaceutical form of Ulviprubart is a solution intended for **subcutaneous injection**. The dosing regimen for this trial specifies a maximum daily dose of 2.0 mg/kg, with a total maximum dose of 38 mg/kg over the course of the treatment period. The maximum treatment period is set at 152 days. The medication is not formulated for pediatric use and has been designated as an orphan drug, indicating its use in the treatment of a rare condition.

In this study, Ulviprubart is the sole investigational product being evaluated, and no non-experimental treatments such as standard-of-care therapy, placebo, or comparator treatments are included. The trial aims to assess the long-term safety and tolerability of Ulviprubart in subjects with **inclusion body myositis** who have completed a prior trial of the same medication. Participant compliance with the dosing schedule will be monitored throughout the study to ensure adherence to the prescribed regimen. The trial is open-label and multicenter, allowing for a comprehensive evaluation of the investigational product's safety profile over an extended period.

The efficacy of Ulviprubart in the treatment of **Inclusion Body Myositis** will be assessed through specific secondary endpoints. These endpoints include the mean change from Baseline (Day 1) in the Inclusion Body Myositis Functional Rating Scale (IBMFRS) and the Manual Muscle Testing 12 (MMT 12) over the duration of the study. These measures will provide quantitative data on the improvement in muscle function and strength, which are critical parameters in evaluating the efficacy of the treatment.