158P XCR1+ dendritic cell (DC) role in antitumoral response to anti PD-L1 antibody: Data from the phase Ib/II trial of DC vaccination in small cell lung cancer patients

Background: Up to 70% of OPC are HPV-mediated with most caused by HPV16.Oncoproteins E6/E7 are constitutively expressed in HPV-infected malignant cells and ideal immunotherapeutic target antigens (Ag).We tested a new Ag delivery using CD40HVac, a sub-unit vaccine composed of a humanized IgG4 monoclonal antibody fused to HPV16 E6/E7 proteins, targeting CD40 receptor of DCs.Methods: HPV.DCVax phase I/IIa dose-escalation trial (NCT06007092), planned to recruit OPC HPV16+ patients (pts), in complete remission after curative treatment.Twelve pts were included per dose group (1 (completed), or 3 mg (ongoing) CD40HVac subcutaneously-adjuvanted with Hiltonol1mg), and randomized 5:1 to receive vaccine or placebo at Week (W) 0, 4 and 24 starting 16 e 22 W after end of curative treatment.Dose limiting toxicity (DLT) was evaluated from W0-W6 and immunogenicity at W6, 26 and 48.We report blinded safety and immunogenicity results at W6 from the 1 st cohort.Blood E6/E7 specific T-cells responses were evaluated after in vitro expansion (8d) and ex vivo stimulation (24h) with E6/E7 peptide pools and assessed by cytokine expression or activation induced markers (AIM), respectively.