P015 Interleukin-17 inhibitors rescue therapy in checkpoint inhibitor-associated adverse events: the state of play in 2025

Background/Aims Since ipilimumab’s FDA approval for refractory melanoma, there are now 11 FDA-approved checkpoint inhibitors (CPIs) available for use amongst 13 different organ systems. Of these, 9 are approved for use in the UK by the MHRA. The potential role of IL17 inhibitors in the treatment of immune-related adverse events (irAEs) was briefly touched upon in the EULAR 2021 guidance on the management of rheumatic irAEs from CPIs, which concluded that were was insufficient evidence to support their use. The guideline is currently under revision, and our objective was to re-evaluate the evidence base for the use of IL17 inhibitors in the treatment of irAEs. Methods We performed a Pubmed, EMBASE and MEDLINE search from inception till 10 August 2025 for reports of IL17 inhibitors used in the treatment of irAEs caused by CPIs. The four EMA-licenced IL17 inhibitors were included (bimekizumab, brodalumab, secukinumab and ixekizumab) alongside PD1 inhibitors (ipilimumab, tremelimumab, nivolumab, pembrolizumab, atezolizumab, avelumab, durvalumab, cemiplimab and dostarlimab). Baseline data for age, gender, irAE, and outcomes of irAE were collected. Results Seven case reports of IL17 inhibitor rescue therapy for PD1-associated irAEs were identified. The average age of treated patients was 65 years, with 6/7 patients being male. Of the 7 patients, 5 were given secukinumab with 1 patient receiving ixekizumab and 1 patient receiving bimekizumab. 4 patients had metastatic melanoma, 1 patient had metastatic renal cell cancer, and 2 had metastatic lung cancer. Pembrolizumab was used in 6 patients, with ipilimumab/nivolumab combination in 1 patient. The indication for IL17i was psoriasis and/or psoriatic arthritis in 4 patients with 3 patients having an undifferentiated inflammatory arthritis. 3/7 patients had received a TNF inhibitor prior to cancer diagnosis, which was stopped at the time of immunotherapy. Resolution of the irAE was achieved in all 7 patients and no adverse events from IL17i were reported. The checkpoint inhibitors were suspended in all cases. Conclusion While still limited in number, the number of reports of IL17i use in the treatment of CPI-induced irAEs is increasing. The available data suggest that IL17i are effective treatments for CPI-induced irAEs. Further studies are required to strengthen the evidence base for national and international guidelines. Disclosure S. Goh: None. M. Jayasinghe: None. R. Hassan: None. M. Baghaffar: None. D. Nagra: None. A. Khan: None. M. Russell: None. S. Banerjee: None. C. Rosa: None. J. Galloway: None.