Pharmaceutical Drug Lifecycle: A Comprehensive Scientific Review of Research and Development Phases, Attrition Rates, and Global Disparities

Background: Drug development is one of the most complex, costly, and prolonged processes in biomedical sciences, yet comprehensive reviews integrating quantitative attrition data across all phases with global equity perspectives remain scarce. Objective: To provide a comprehensive scientific review of the pharmaceutical drug lifecycle during the Research and Development (R&D) phase, from initial discovery through Phase III clinical trials, analyzing success rates, timelines, costs, and disparities between developed and developing countries. Methods: A narrative review was conducted synthesizing evidence from peer-reviewed literature, regulatory agency reports, and published systematic reviews. Sources were identified through PubMed, Scopus, and Web of Science databases, with selection criteria emphasizing quantitative data on attrition rates, development timelines, costs, and geographic disparities in pharmaceutical R&D. Results: The complete drug development process typically requires 10–15 years, with costs ranging from $897 million to $1.9 billion per approved drug. Only 9.6–21.5% of compounds entering clinical trials achieve regulatory approval. Preclinical attrition reaches 95%, with Phase I-to-II progression at 50%, Phase II-to-III at 34%, and Phase III-to-approval at 52%. Lack of efficacy accounts for 56% of Phase II/III failures, followed by safety concerns (28%). Therapeutic area variability is substantial: Alzheimer's disease shows a 0.4% success rate versus 21.5% overall. Critical disparities exist between developed and developing countries in R&D capacity, regulatory infrastructure, and disease priorities, with clinical trials in emerging markets costing up to 60% less but raising ethical and quality standards challenges. Conclusions: Drug development efficiency remains a critical challenge for global health. Improving preclinical predictability, adopting biomarker-driven patient selection, implementing adaptive trial designs, and addressing global R&D inequities through innovative financing mechanisms represent key strategies to improve development efficiency and health equity. Future research should focus on generating systematic data from low- and middle-income countries to better characterize and address global pharmaceutical R&D disparities.