# Exploratory Clinical Study to Evaluate the Efficacy and Safety of Sulfasalazine for Immune Checkpoint Inhibitor (ICI)‐Induced Colitis

## TL;DR

This study explores sulfasalazine as a treatment for colitis caused by cancer immunotherapy, finding it effective but noting potential hypersensitivity risks.

## Contribution

The study provides new evidence on sulfasalazine's efficacy and safety for ICI-induced colitis as a steroid-sparing agent.

## Key findings

- 80% of patients achieved a clinical response with sulfasalazine treatment.
- Defecation urgency resolved in all patients after treatment.
- Three patients discontinued sulfasalazine due to hypersensitivity-related adverse events.

## Abstract

The first‐choice treatment for immune checkpoint inhibitor (ICI)‐induced colitis is steroids; however, side effects may occur and survival may be reduced. Sulfasalazine (SSZ) is primarily used for inflammatory bowel disease but studies on ICI‐induced colitis are scarce. This study examined the efficacy and safety of SSZ for ICI‐induced colitis while testing SSZ as a steroid‐sparing agent.

This study (iRECSA) was a single‐arm, multicenter exploratory study from November 2021 to December 2024 that evaluated the efficacy and safety of SSZ for mild‐to‐moderate ICI‐induced colitis. SSZ was given at 4 g/day orally for 2 weeks. The primary outcome was clinical response (a ≥ 1‐point reduction from baseline partial Mayo score or partial Mayo score < 1). Secondary endpoints included clinical responses in the Simple Clinical Colitis Activity Index (SCCAI), Lichtiger Index, and Common Terminology Criteria for Adverse Events (CTCAE) grade, plus SSZ‐related adverse event incidence.

Ten patients were enrolled. The median partial Mayo score decreased from 4 (range 3–5) to 2 (range 0–4), with 80% of patients achieving a clinical response. Similar response rates were observed with the Lichtiger Index and CTCAE grade. Defecation urgency was present in 70% of patients at baseline but resolved in all after treatment. Nine adverse events occurred in six patients; three patients discontinued SSZ because of hypersensitivity‐related adverse events. Three patients required systemic steroids after the study treatment.

This exploratory study suggests that SSZ may be a useful option for mild‐to‐moderate ICI‐induced colitis, but caution is warranted against SSZ‐related hypersensitivity.