Abstract B029: Differential safety profiles of PD-1 inhibitors: A comparative pharmacovigilance analysis of immune-related adverse events with pembrolizumab and nivolumab in FAERS (2015–2024)

Abstract Background: Programmed death-1 (PD-1) inhibitors have transformed cancer therapy across solid and hematologic malignancies, including Hodgkin lymphoma and primary mediastinal B-cell lymphoma. Despite their efficacy, immune-related adverse events (irAEs) remain a major clinical challenge and vary between agents. While clinical trials characterize common toxicities, real-world post-marketing data can better reveal comparative safety patterns. Methods: We performed a retrospective pharmacovigilance analysis using the U.S. FDA Adverse Event Reporting System (FAERS) from 2015–2024. Reports listing pembrolizumab or nivolumab as suspect drugs were extracted (total 52,846 and 43,816 reports, respectively). Four irAEs of interest- thyroid dysfunction, immune-mediated hepatitis, colitis (including gastritis and enterocolitis), and pneumonitis- were analyzed. Two-by-two contingency tables were constructed for each event, and reporting odds ratios (RORs) with 95% confidence intervals, proportional reporting ratios (PRRs), chi-square (Yates corrected), and Fisher’s exact tests were calculated using R (v4.3). Results: Pembrolizumab demonstrated a significantly higher reporting frequency of thyroid-related AEs, whereas nivolumab showed a greater signal for pneumonitis. Reporting patterns for colitis and hepatic AEs were comparable between the two agents. Conclusions: This large real-world FAERS analysis identifies meaningful differences in immune-related toxicity patterns between pembrolizumab and nivolumab. These findings support the presence of agent-specific immune activation profiles and highlight the need for tailored surveillance strategies to optimize the safety and personalization of PD-1 inhibitor therapy. AI disclosure: Generative AI was used only for language refinement and formatting; all scientific content, data extraction, analyses, and conclusions were developed and verified by the authors. Citation Format: Zehra Rahman, Oday Elmanaseer. Differential safety profiles of PD-1 inhibitors: A comparative pharmacovigilance analysis of immune-related adverse events with pembrolizumab and nivolumab in FAERS (2015–2024) [abstract]. In: Proceedings of the AACR Immuno-Oncology Conference (AACR IO): Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2026 Feb 18-21; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2026;14(2 Suppl):Abstract nr B029.