T cell population expansion in response to allogeneic cancer vaccine alone (DPV-001) or with granulocyte-macrophage colony-stimulating factor (GM-CSF) or imiquimod (I) for definitively-treated stage III NSCLC patients (pts).
e14639 Background: The DPV-001 DRibble is a dendritic cell-targeted microvesicle (proteasome blocked autophagosome) vaccine derived from an adenocarcinoma and a mixed histology cell line. It contains multiple TLR agonists and > 130 potential NSCLC antigens, many as prospective altered-peptide ligands. In preclinical studies, DRibble immunotherapy provided significant anti-cancer effects in a dozen models. We hypothesize that DRibble’ vaccination efficacy can be attributed to their capacity to present tumor-derived short-lived proteins (SLiPs) and defective ribosomal products (DRiPs) that are typically not processed and presented by professional antigen presenting cells and against which the host may be less tolerant. Methods: Pts received induction cyclophosphamide, 7 vaccines every 3-weeks, then every 6 weeks x 4 more doses. Pts were randomized to receive DRibble alone (A), or with I (B) or GM-CSF (C). PBMCs /serum were collected at baseline and at each vaccination to assess changes in antibodies (Ab) (ProtoArray and microsphere affinity proteomics), peripheral lymphocyte populations (flow cytometry) and T cell receptor (TCR) repertoires (Adaptive immunoSEQ). Results: 13 pts were enrolled (Arm A: 5; B: 4; C: 4). We previously reported that vaccination induced or increased IgG Ab responses against targets over-expressed by NSCLC. Patients receiving DPV-001 had a significant (p < 0.04) increase in total (CD4 + CD8) TCRs that increased 10 fold over baseline compared to normal controls (independent from trial, n = 3) and the increase in CD4 clones was similar to that seen following ipilimumab (melanoma pts, independent from trial, n = 9). Analysis of a resected metastasis (progressing on treatment), identified brisk infiltration of T cells and tumor that was strongly PD-L1+. Conclusions: Vaccination with DPV-001 expanded populations of T cells over that observed in controls and the increase in CD4 T cells was similar to that observed in patients receiving ipilimumab and may represent vaccine-reactive T cells. Clinical Trial Identifier: NCT01909752, Support: R44 CA121612 Clinical trial information: NCT01909752.