Study of Intramuscular Injections of ABBV-950 to Assess Adverse Events and Change in Disease Activity in Adult Participants With Upper Limb Spasticity

Spasticity is often observed as muscle tightness and stiffness in the upper and/or lower limbs. Upper limb spasticity can interfere with joint movement and its severity can range from mild to severe. Common causes of spasticity include cerebral palsy, traumatic brain injury, multiple sclerosis, spinal cord injury, and stroke. This study will assess how safe and effective ABBV-950 is in treating upper limb spasticity in adult post-stroke participants. Adverse events and change in symptoms will be assessed. ABBV-950 in an investigational drug being developed for treating spasticity. This study is conducted in 2 parts. In Part 1, participants are assigned to receive different doses of ABBV-950 or placebo. There is 1 in 4 chance that participants will be assigned to receive placebo. In Part 2, participants will be randomly assigned to receive BOTOX, ABBV-950, or placebo. There is 1 in 5 chance for participants to receive placebo. Approximately 297 adult post-stroke participants with upper limb spasticity will be enrolled at approximately 50 sites in the United States. In Part 1, participants will receive intramuscular (IM) injections of ABBV-950 or placebo on Day 1. In Part 2, participants will receive IM injections of BOTOX, ABBV-950, or placebo on Day 1. All participants will be followed for 24 weeks. There may be higher treatment burden for participants in this trial compared to the standard of care. Participants will attend regular clinic visits during the study. The effect of the treatment will be checked by medical assessments, checking for side effects and completing questionnaires.