A Study to Assess the Efficacy and Safety of GIA632 Across a Range of Doses in Participants With Moderate to Severe Cutaneous Lichen Planus

Key Inclusion Criteria: * Male or female (as assigned at birth) participants ≥ 18 years of age at the time of screening. * Individuals with a diagnosis of cLP, confirmed * histologically by a skin biopsy (either historically within 1 year prior to screening or at screening if historical one not available), and * by physical examination by the investigator at screening. * Moderate to severe cLP * Two or more body regions affected (any two or more of the following: head and neck, trunk, upper extremities including hands, lower extremities including feet). * Diagnosis of cLP inadequately controlled by at least one topical treatment for at least 3 months (either via continuous use or burst and taper regimen), or such treatment being considered not advisable, as per investigator judgement, assessed at screening. Topical treatment includes, but is not limited to, topical corticosteroids, topical calcineurin inhibitors, topical cholecalciferol analogues, topical PDE4 inhibitors, topical JAK inhibitors, and topical aryl hydrocarbon receptor agonists. Key Exclusion Criteria: * Individuals unable or unwilling to follow the study procedures, handle the electronic diary (eDiary), and/or to complete the study-related questionnaires. * Diagnosis of drug-induced lichen planus (lichenoid drug eruption) or lichen planus pigmentosus. * Presence of skin conditions that may interfere with study assessments, including histologic findings in the biopsy, as assessed at screening and baseline. * Previous exposure to biologic drugs directly targeting IL-15 or any subunit of the IL-15 receptor. * Use of prohibited medication and treatments. Other protocol-defined inclusion/exclusion criteria may apply.