Abstract LB205: Feasibility and immunogenicity of adjuvant TG4050, a patient tailored cancer vaccine in head and neck and ovarian cancer

Abstract

Abstract Background: Head and Neck (HNSCC) and Ovarian cancer (OC) are two indications for which immunotherapy had limited impact so far. Current treatments achieve high rates of initial success through surgery and adjuvant chemo/radiotherapy, but patients (pts) remain at high risk of relapse in both indications. Immune stimulation using a vaccine is a promising strategy to a clinically meaningful improvement. Herein we report phase I data of TG4050, a vaccine engineered to carry a pt tailored antigen payload, in pts with HNSCC (NCT04183166) or OC (NCT03839524). Methods: Tumor specific variants are identified using next generation sequencing of tumor and normal samples whereby immune relevant mutations are predicted using a machine learning algorithm factoring in parameters known to affect immunogenicity including MHC binding, level of expression, prevalence across clones, and antigen processing. DNA sequences of the mutations of interest, typically 30 per pt, are cloned in a viral vector (Modified Vaccinia Virus Ankara). Following curative intent treatment, HNSCC pts in complete remission were randomized to an immediate vaccination arm to receive weekly doses of TG4050 for 6 weeks followed by a maintenance period of one dose every 3 weeks for up to 20 doses or to a delayed vaccination arm where the same vaccination regimen is initiated at relapse. OC pts received the vaccine upon onset of signs of relapse. PBMC were collected at Baseline and after 6 doses of vaccine. Primary endpoint was vaccine safety and secondary endpoints included feasibility, immunogenicity. Results: 18 pts received TG4050 (5 OC and 13 HNSCC) treatment with no related grade ≥ 3 adverse events. Tumor mutational burden (TMB) was on average 3.00±0.98 and 2.43±0.69 mutations per megabase for HNSCC and OC respectively. Despite this low TMB, all pts had sufficient cancer specific neoantigens to design a vaccine. Ex-vivo ELISPOT was completed for 7 pts at the time of submission. A mean of 44% of selected mutations were associated with a reactive T cell responses either spontaneously or after TG4050 stimulation ranging from 6 to 22 mutations per pt. Vaccination induced a stimulation of T cell response in all tested pts on an average of 10 targeted mutations, induction of de novo responses was seen in all 7 tested pts and amplification of pre-existing response in 6/7 pts. None of the evaluable HNSCC pts receiving TG4050 immediately after first line treatment had relapse after a median follow-up of 7 months while 2 pts had relapse in the delayed vaccination arm. Furthermore, in OC pts treated at early relapse, TG4050 has normalized disease markers (ctDNA and/or CA-125) for 2/4 pts with stable disease for 9 and 11 months. Conclusion: TG4050 treatment is feasible and immunogenic in pts with low to moderate TMB. It is effective in inducing T cell responses and first signs of antitumor activity are encouraging for the continuation of development. Citation Format: Ana Lalanne, Camille Jamet, Christian H. Ottensmeier, Jean-Pierre Delord, Christophe Le Tourneau, Matthew S. Block, Gerardo Colon-Otero, Keith L. Knutson, Annette Tavernaro, Gisele Lacoste, Benoit Grellier, Xavier Noiriel, Thierry Huss, Bernard Burtin, Yoshiko Yamashita, Kousuke Onoue, Kazuhide Onoguchi, Brandon Malone, Olivier Lantz, Oliver Baker, Naoko Yamagata, Yuki Tanaka, Eric Quemeneur, Maud Brandely, Kaidre Bendjama. Feasibility and immunogenicity of adjuvant TG4050, a patient tailored cancer vaccine in head and neck and ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB205.