Clinical Trials Portfolio and Regulatory History of Idelalisib in Indolent Non-Hodgkin Lymphoma: A Systematic Review and Meta-analysis

IMPORTANCE: Idelalisib is a first-in-class phosphatidylinositol 3-kinase inhibitor that received US Food and Drug Administration accelerated approval in July 2014 as a single-agent treatment for relapsed follicular lymphoma (FL) and small lymphocytic lymphoma (SLL). Serious adverse effects were reported in 2016 leading to termination of postmarketing registry trials. However, idelalisib remained on the market until 2022 when Gilead voluntarily withdrew the drug for the accelerated approval indication. OBJECTIVE: Evaluate the regulatory oversight of the accelerated approval pathway and evidence generation for idelalisib during premarketing (2008-2014), postmarketing (2014-2016), and premarketing withdrawal periods (2016-2022). DATA SOURCES: ClinicalTrials.gov, FDA.gov, PubMed database. STUDY SELECTION: Clinical trials investigating the safety and effectiveness of idelalisib. DATA EXTRACTION AND SYNTHESIS: Study characteristics and relative risk (RR) of safety outcomes were abstracted. Data were pooled using random effects meta-analysis. The analysis was performed in October of 2022. MAIN OUTCOMES AND MEASURES: Trial status, recruitment status, publication status, serious adverse events (SAEs), fatal adverse events (FAEs), and all-cause mortality. RESULTS: Overall, 31 idelalisib trials met selection criteria. In total, 20 of 30 (65%) included SLL and/or FL; 13 (42%) trials were completed, 13 (42%) had published results, and 7 (23%) were randomized clinical trials (RCTs). Overall, 6 RCTs of idelalisib had publicly available data on safety outcomes. By the initial postmarketing period (2016), the cumulative RR for SAEs was 1.86 (95% CI, 1.63-2.11), for FAEs was 3.30 (95% CI, 1.56-7.00), and for death was 1.35 (95% CI, 0.85-2.12). In the premarketing withdrawal period, only a single phase 3 trial was enrolling patients for FL and was terminated. However, idelalisib was not withdrawn from the market until 2022. Gilead reported cumulative sales revenue of $842 million during market authorization (2014-2022) and annual sales had a steady decline from $168 million to $62 million during the premarketing withdrawal period (2016-2021). CONCLUSIONS AND RELEVANCE: Findings of this systematic review and meta-analysis show that serious risks of SAE, FAE, and death with idelalisib treatment were evident by 2016. However, idelalisib remained on the market for another 6 years, with minimal evidence generation. It was voluntarily withdrawn for FL and SLL accelerated approval indications coinciding with decreasing revenue generation. Closer attention for safety and effectiveness of drugs reaching market by accelerated approval is needed.