Abstract CT054: The development of a personalized autologous clonal neoantigen T cell therapy for the treatment of solid cancer using the VELOSTM manufacturing platform generates highly potent and reactive CD8+ and CD4+ T cells for clinical use

Background: Clonal neoantigens are formed early in cancer evolution and have been identified as a subset of patient specific mutations that are associated with improved clinical benefit and represent great promise as targets for the next generation of T cell therapies. Developing T cell therapies that target multiple clonal neoantigens represents a unique personalized approach to treating solid cancer, as they are present on all cancer cells, minimizing the risk of tumour escape, and absent from healthy tissue, potentially eliminating off-target toxicities. Access to sequencing data from over 600 NSCLC patients enrolled in the UK TRACERx study has enabled the development of the Achilles PELEUSTM bioinformatic platform. By opening an ethically approved tissue collection study NCT03517917, enabling access to matched tumour and blood samples from patients with selected cancers, our clonal neoantigen reactive T cell (cNeT) manufacturing process and supply chain has been validated for use in clinical trials. Methods: Matched tumor and blood samples were procured at the time of routine surgery from ten patients (eight with newly diagnosed stage I-III NSCLC and two with metastatic melanoma) for at-scale GMP runs. Briefly, TIL were isolated from tumor fragments and immature dendritic cells (DCs) generated from whole blood, prior to cryopreservation as intermediate products. Patient-specific clonal neoantigens were predicted using our proprietary PELEUSTM bioinformatic platform, enabling the manufacture of synthetic peptide masterpools to be used for the enrichment of cNeT in the VELOSTM manufacturing process. Co-culture of pre-expanded TIL and patient DCs loaded with clonal neoantigen peptides drives the selective expansion of cNeT, eliminating the requirement for high non-physiological levels of IL-2. Results: Here we present the successful scaled GMP production of cNeT from both primary and metastatic tumors using the VELOSTM manufacturing process in ten patients. All final products met QC release criteria and were composed of both CD4+ and CD8+ T cells. Extensive characterization of T cell responses showed cNeT exhibited functional responses determined by cytokine secretion following re-challenge, and specificity in response to clonal neoantigen peptides. Peptide deconvolution of masterpools identified multiple single T cell clone reactivities to clonal neoantigens in the final product. Conclusions: The VELOSTM process incorporating the PELEUSTM bioinformatic p