This thesis investigates the impact of drug regulatory changes on pharmaceutical business strategy through comprehensive mixed-methods analysis spanning 2010-2025. The research examined 147 major regulatory changes across key pharmaceutical markets and analyzed strategic responses of 156 companies through quantitative analysis and eight detailed case studies. Findings reveal that regulatory changes substantially influenced R&D investment patterns, with rare disease R&D increasing 409.9% correlating with orphan drug incentives, and oncology R&D growing 147% aligned with expedited approval pathways.