Gritstone bio, Inc. announced that a paper detailing the development of its ?off-the-shelf? neoantigen platform, SLATE, recently published in Nature Medicine. The paper, ?A shared neoantigen vaccine combined with immune checkpoint blockade for advanced metastatic solid tumors: phase 1 trial interim results,?

describes a novel immunodominance hierarchy of tumor neoantigens (including KRAS) that Gritstone discovered in Phase 1 translational studies and leveraged to develop SLATE-KRAS, a ?pure? KRAS-directed candidate that demonstrated superior immunogenicity to the initial version in a subsequent Phase 2 study and is currently being evaluated in a novel cell therapy-vaccine combination study run by Steven A. Rosenberg of the National Cancer Institute (NCT06253520). Results from the SLATE 1/2 Study: The data published in Nature Medicine report the interim safety, tolerability and immunogenicity results from the Phase 1 portion of the Phase 1/2 clinical trial (NCT03953235) assessing the off-the-shelf vaccine SLATEv1 in patients with advanced/metastatic solid tumors.

SLATEv1 utilizes a heterologous ChAd68 followed by samRNA-based vaccine regimen encoding 20 shared neoantigens targeting multiple recurrent mutations in several oncogenes, including KRAS, TP53, BRAF and CTNNB1. Neoantigens were identified using Gritstone bio?s proprietary neoantigen prediction platform, EDGETM, and selected based on shared mutation and matched HLA frequencies in patient populations with solid tumors. Biased T cell responses toward HLA-matched TP53 neoantigens encoded in the vaccine relative to KRAS neoantigens expressed by the patients?

tumors, indicated a previously unknown hierarchy of neoantigen immunodominance that may impact the therapeutic efficacy of multi-epitope shared neoantigen vaccines. These data led to the development of SLATE-KRAS, a vaccine focused on KRAS-derived neoantigens that subsequently was evaluated in the Phase 2 portion of the clinical study. Initial Phase 2 data suggesting an increased vaccine induced T cell response were presented in September 2022.