Study Identifies Potential RAS Inhibitor-Immunotherapy Strategy for Pancreatic Cancer

RESEARCH SUMMARY

Title: CD4 T cells convert transient responses to KRAS inhibition to durable remissions in pancreatic cancer
Publication: Cell; September 23, 2026
Dana-Farber Cancer Institute co-senior authors: Stephanie K. Dougan, PhD, and Michael Dougan, MD, PhD

Summary: Pancreatic cancer does not respond to most immunotherapies, but RAS inhibitors could alter tumors to make them more sensitive to a novel immunotherapeutic approach. In pancreatic tumors with RAS mutations, RAS inhibitors cause massive cell death and reduce immunosuppression. These changes tend to be temporary because tumors develop resistance to the therapy. In this study, mouse models of pancreatic cancer were treated with a RAS inhibitor plus an agent called 21h10, an AI-designed mimic of an immune-related cytokine called interleukin (IL)-21. The combination initiated an immune response that turned the transient effects of RAS inhibition into a durable response. The team found that 21h10 – which was designed by David Baker’s lab at the University of Washington to be more stable and have better drug-like qualities than naturally occurring IL-21 – primes and activates CD4 T cells in the cancer. These T cells produce a signal called interferon-γ (IFN-γ), which induces innate immune cells called macrophages to destroy tumor cells. Previous studies by this team of 21h10 in melanoma and colorectal cancer models also showed efficacy, though in those cases, CD8 T cells acted against the tumors. The findings could be relevant in humans, based on findings from this study showing that CD4 T cells from humans with pancreatic cancer produce IFN-γ in response to 21h10, though more research is needed to understand the efficacy and safety of the approach.

Significance: This study suggests that long-lasting durable remissions for patients with pancreatic cancer might be possible with a novel combination of immunotherapy and RAS-targeted therapy. Immunotherapies typically focus on the activation of cytotoxic CD8 T cells, but this study suggests that tumor-specific CD4 T cells could control pancreatic cancer by coordinating innate immune cells against the disease when stimulated through IL-21 signaling alongside treatment with a KRAS inhibitor.

Funding: Dana-Farber Cancer Institute Hale Family Center for Pancreatic Cancer Research, the Ludwig Center at Harvard, Break Through Cancer, the National Institutes of Health, the Parker Institute for Cancer Immunotherapy, the Claudia Adams Barr Foundation, the National Cancer Institute, the Washington Research Foundation, the Kuni Foundation, the Open Philanthropy Project Improving Protein Design Fund, the Audacious Project at the Institute for Protein Design, the Howard Hughes Medical Institute, and the Peter and Ann Lambertus Family Foundation.