This study focuses on the impact of off-patent drugs on Indonesia’s pharmaceutical industry, with a particular emphasis on Acilatem, an innovative antipsychotic drug produced by PT GOMI Indonesia. The research investigates key factors influencing the performance of originator drugs during the patent expiration period. Utilizing internal and external analyses, the study evaluates regulatory landscapes, market dynamics, and competitive pressures within Indonesia's healthcare sector. The study uses frameworks such as PEST, Porter's Five Forces, Competitive analysis, VRIO Value chain analysis and TOWS to identify challenges and marketing initiative to mitigate Acilatem's market share decline after patent expiration. It also explores marketing initiatives tailored to PT GOMI's resources and organizational capabilities, focusing on customer segmentation, product positioning, and value chain improvements. The results suggest a comprehensive marketing initiative to maintain Acilatem's market presence and ensure profitability and sustainability against competition from generics and me-too products. This approach highlights the need for operational efficiencies, strategic partnerships, and ongoing education of healthcare professionals to drive adoption and maintain market leadership in Indonesia's evolving pharmaceutical landscape.