To studyJUV-161 Administered to Healthy Volunteers Undergoing Unilateral Lower Limb Immobilization (ULLI)

JUV-161 is being developed for the treatment of muscle atrophy or sarcopenia and myotonic dystrophy. This study is investigating the safety and efficacy of JUV-161 administered in healthy participants who are undergoing unilateral lower limb immobilization (ULLI). Muscle atrophy is a general term to describe loss of muscle mass, whereas sarcopenia is a more specific term used to describe age-related loss of muscle. Muscle atrophy can be associated with a multitude of causes ranging from poor nutrition to neurological diseases, myopathies or disuse.

JUV-161 is an agonist designed to activate key signaling pathways in skeletal muscle, promoting muscle growth, maintenance, and strength, and may help prevent muscle atrophy during periods of immobilization. ULLI or unilateral lower limb suspension (ULLS) is often the consequence of common injuries such as falls, fractures or joint injuries. Because it isolates a specific group of muscles, it is also a frequently used model to study muscle disuse atrophy. In fact, ULLI/S using a brace or cast is the most frequent model used to study disuse atrophy.

This is a double-blind, placebo-controlled, randomized multicenter study of 96 days total duration. The purpose is to assess the effect of JUV-161 on muscle disuse atrophy. The study will include up to 40 healthy volunteers aged between 40 and 65 years of age (inclusive). Following the screening period, subjects will be randomized 1:1 to receive either weekly subcutaneous (SC) injections ofJUV-161 or a matching placebo for a period of approximately 6 weeks (total of 7 doses).

The study will be conducted in three phases:

* Immobilization to induce disuse muscle atrophy. Subjects will have one leg immobilized using a brace and boot to prevent weight bearing. (Crutches will be provided). The leg will be immobilized for 14 days, then the brace/boot will be removed. * Recovery (mobilization) After the brace/boot is removed, subjects will undergo a 4-week period of mobilization to help restore muscle mass and strength lost in the immobilized leg * Resistance exercise training (RET) After 4 weeks of mobilization, subjects will undergo a further 3 weeks of personalized (RET) to fully restore muscle mass and strength in the immobilized leg. Participants and researchers will be blinded to the study allocation. Every person in the study will have their dominant leg fitted with a brace, which they will wear for 15 days. They will then receive 5mg/kg of the JUV-161 (or matching placebo) once a week for 6 weeks (7 doses total). This will be given as a subcutaneous (SC) injection in the abdomen or thigh. The study design includes an option for a single escalation of the JUV-161 dose based on SRC review of blinded aggregate safety data after 18 participants in the initial dose group have completed the first 14 days of treatment with study drug.