Oncology Leads Clinical Trials as Phase II Attrition Hits Four-Year Low
A recent global analysis shows oncology dominates clinical trial activity in 2025, while Phase II attrition rates dropped to 26%—the lowest in four years. The US remains the leader in investigator sites, but China is the fastest-growing market. Obesity research is poised to break into the top five most-studied diseases.
Oncology remains the dominant area of clinical trial activity in 2025, supported by deeper understanding of cancer biomarkers and sustained investment, according to a recent global analysis. The analysis also revealed that Phase II trial attrition dropped to 26%, the lowest level in four years, though early trial stoppages continue to pressure Phase III throughput and return on investment.
The report, conducted by clinical data analytics company Phesi, found that breast cancer is once again the most studied disease. Cancer indications account for a significant share of trial activity due to advances in cancer biomarker research, though unmet needs persist in subtypes like triple-negative breast cancer.
The 26% attrition rate marks an improvement from 31% in 2024 and 29% in 2023. The company’s CEO noted that the industry is gradually recovering from COVID-related disruptions. However, a quarter of Phase II trials ending early is still unacceptably high, with knock-on effects on later-stage trials and financial returns.
The United States continues to lead globally in recruiting investigator sites, hosting the largest number across all five most-studied diseases. However, site saturation is a challenge, with well-known centers becoming overburdened while other capable sites go underutilized. Phesi’s CEO emphasized the role of clinical data science in identifying high-performing but less-recognized sites to ease bottlenecks.
China is the fastest-growing market for clinical trials. Between 2023 and 2025, the number of investigator sites in China grew by 51%, compared to 42% in the US. China now ranks second in site numbers for all top diseases except prostate cancer, where Canada holds second place. This growth has been supported by the return of US-trained researchers who bring expertise to local infrastructure.
Obesity research is closely watched, ranking sixth among most-studied diseases and likely to enter the top five within one to two years. Over 100 diseases are now being studied in connection with GLP-1 use. The rise of GLP-1 therapies may reshape clinical development by altering study parameters and shifting focus toward prevention and treating clusters of related diseases.