Wang et al. evaluated a combination of nivolumab, ipilimumab, and mKRAS-VAX (six 21-mer synthetic long peptides targeting common KRAS mutations) in 13 heavily pretreated patients with MMRp/MSS metastatic colorectal cancer. Treatment was well tolerated, with a 15% overall response rate and a median progression-free and overall survival of 2 and 24.9 months, respectively. Direct ex vivo peptide stimulation revealed reactive T cell responses in 75% of patients, which reached 100% following in vitro expansion (mainly CD4+ and polyfunctional). Tumor infiltration by peripheral mKRAS-reactive T cells was associated with tumor regression.

Contributed by Ute Burkhardt

ABSTRACT: Immune checkpoint inhibitors (ICIs) have limited activity in mismatch repair proficient or microsatellite stable (MMRp/MSS) colorectal cancer (CRC). KRAS mutations, present in approximately 40% of these cancers, can generate neoantigens that are targets for therapeutic vaccines. In this single-arm, phase I study (NCT04117087), we evaluated mKRAS-VAX, a pooled mutant KRAS (mKRAS) peptide vaccine targeting six KRAS mutations with nivolumab and ipilimumab in 13 patients with pretreated metastatic MMRp/MSS CRC. Both primary endpoints of safety and immunogenicity (within 17 weeks post-vaccination) were met. Secondary endpoints included treatment efficacy defined by RECIST v1.1 criteria. All adverse events attributed to mKRAS-VAX were grade 1 or 2, and the addition of mKRAS-VAX did not increase the frequency of severe immune-related adverse events beyond the expected profile of dual ICIs alone. mKRAS-VAX elicited an increase in tumor-specific mKRAS-reactive T-cells in 8/12 biomarker-evaluable patients (75%) by direct ex vivo IFN_ ELISpot and in 12 patients (100%) following in vitro expansion. Our findings support further development of mKRAS vaccines with ICIs for advanced MMRp/MSS CRC.

Author Info: (1) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University S chool of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (2) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (3) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. Department of Gastrointestinal Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. (4) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. (5) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (6) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. Department of Hematology/Oncology, Department of Internal Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. (7) Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. (8) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (9) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (10) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. (11) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. (12) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (13) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (14) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (15) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (16) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (17) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. (18) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (19) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (20) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. (21) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. (22) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. (23) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. nilo.azad@jhu.edu. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. nilo.azad@jhu.edu. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. nilo.azad@jhu.edu. (24) Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, USA. nzaidi1@jhmi.edu. Johns Hopkins Convergence Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA. nzaidi1@jhmi.edu. The Bloomberg Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University of Medicine, Baltimore, MD, USA. nzaidi1@jhmi.edu.