Background Immune checkpoint blockers (ICBs) have been a breakthrough for cancer treatment. However, ICBs benefit only a subset of patients and can cause immune-related adverse events (irAEs).¹ In particular, recent studies have identified correlation between dysregulated gut microbiomes and poor clinical outcomes with ICBs, as well as increased risks of immunotherapy-induced colitis.² Toward the goals of gut microbiome modulation and potentiating ICB treatment, we have developed an oral gel formulation based on inulin – a dietary fiber classified as a generally recognized as safe (GRAS) ingredient by the FDA.

Methods We optimized the formulation of the inulin gel and scaled up the production. In mice, the inulin gel was dosed orally starting on day 7 post-tumor inoculation, and ICBs were administered intraperitoneally from day 10. Tumor-infiltrating lymphocytes were analyzed using flow cytometry. Inulin gel was tested in an ICB-associated colitis model, where 3% dextran sulphate sodium (DSS) was supplied in drinking water. In the human trial, healthy volunteers were randomized into two cohorts, consuming either 20 grams of inulin powder or inulin gel daily for ten days. Stool samples were collected and analyzed for short-chain fatty acid (SCFA) levels.

Results Following oral gavage in mice, the inulin gel demonstrated prolonged retention in the colon, leading to increased fermentation and enrichment of ‘beneficial’ commensal microbes prevalent in ICB-responsive patients. Inulin gel supplement boosted the antitumor efficacy of ICBs in multiple tumor models, including CT26, B16F10, and DSS-accelerated colon tumor model. Moreover, inulin gel treatment ameliorated DSS-induced, ICBs-exacerbated colitis, suggesting improved safety profiles. Metabolomics analysis showed that inulin gel elevated SCFA levels in mice, leading to the differentiation of stem-like Tcf1⁺PD-1⁺CD8⁺ T cells for long-lasting anti-tumor immunity.³ For clinical translation, we further optimized the formulation and produced inulin gel at a 10.5-kilogram scale, which exhibited long-term shelf stability without significant physicochemical changes or microbial contamination. In the human trial with healthy participants, 20 grams inulin gel for 10 days oral dose was well tolerated without causing major gastrointestinal discomfort and resulted in increased SCFA levels in stool samples.

Conclusions Oral inulin gel effectively regulates the gut microbiome, enhances anti-tumor efficacy of ICB, and reduces ICB-associated colitis in animal models. The human study demonstrates the safety of inulin gel as well as the SCFA promotion capacity. Our study underscores the efficacy of inulin gel in modulating the gut microbiome and its potential to improve both the efficacy and safety of ICBs.

Acknowledgements This work was supported by NIH (R01AI127070, R01CA210273, U01CA210152, R01DK108901, R01DE026728, R01DE030691, R01DE031951) and the University of Michigan Rogel Cancer Center Support Grant (P30CA46592).

References

1. Watson Alexander S, et al. ‘Association of immune-related adverse events, hospitalization, and therapy resumption with survival among patients with metastatic melanoma receiving single-agent or combination immunotherapy.’ JAMA Network Open 2022;5(12):e2245596-e2245596.

2. Oey Oliver, et al. ‘Gut microbiota diversity and composition in predicting immunotherapy response and immunotherapy-related colitis in melanoma patients: a systematic review.’ World Journal of Clinical Oncology 2022;13(11):929.

3. Han Kai, et al. ‘Generation of systemic antitumour immunity via the in situ modulation of the gut microbiome by an orally administered inulin gel.’ Nature Biomedical Engineering 2021;5(11):1377–1388.

Ethics Approval The human subject study (HUM00207275) was reviewed and approved by the University of Michigan Institutional Review Board (IRB).’