A Study Comparing the Safety, Efficacy, and Diffusion of Letibotulinum Toxin A Versus Other Botulinum Toxin Products in Adults With Moderate-to-Severe Forehead Wrinkles

The goal of this clinical trial is to learn if letibotulinum toxin A is effective and safe for treating moderate-to-severe horizontal forehead wrinkles in adults. It will also compare its diffusion characteristics with two other botulinum toxin A products. The main questions it aims to answer are: 1. Does letibotulinum toxin A reduce forehead wrinkles as effectively as other botulinum toxin A products? 2. Does letibotulinum toxin A show more localized (smaller) diffusion after injection? Researchers will compare letibotulinum toxin A with prabotulinum toxin A and onabotulinum toxin A (Botox®) to evaluate their diffusion profiles and wrinkle-reduction effects. Participants will: 1. Receive botulinum toxin A injections on each side of the forehead (split-face design) 2. Undergo wrinkle assessments and sweat gland function testing using 3D imaging and iodine-starch tests 3. Return to the clinic 2 weeks after treatment for follow-up evaluation