The aim of this study is to investigate the safety and efficacy of KB304, an investigational gene therapy to correct moderate to severe wrinkles in the décolleté region (V-shaped chest area). KB304 is an investigational gene therapy that delivers functional, full-length human collagen (COL3) and elastin (tropoelastin) to the skin through small injections using the Sponsor's genetically engineered Herpes Simplex Virus (HSV-1) vector. The study is a randomized double-blind study and participants will receive either KB304 (active group) or placebo (inactive group).