Vγ9Vδ2 T (γδ) lymphocytes: a promising approach for immunotherapy of solid tumors

3064 Background: The Vγ9Vd2 T (γd) blood lymphocyte subset has a strong cytotoxic potential and can be selectively activated with chemically-synthesized, structural analogues of non-conventional antigens like BrHPP (IPH1101). Their proliferation requires low dose of Interleukin-2 (IL-2). Methods: We developed several in vitro and in vivo models to assess the immunotherapeutic potential of IPH1101-activated γd cells: - Direct cytotoxicity assays on patient-derived primary tumor cell lines - Extensive pharmacodynamics in the non human primate (NHP) - Small scale in vitro amplification assays for IPH1101-sensitive patient pre-selection Then, two Phase I clinical trials were performed in solid tumor patients: - Autologous cell therapy with ex vivo IPH1101- expanded γd cells (1, 4 or 8.109 cells) - Direct administration of IPH1101 (200 to 1800 mg/m2 i.v.) and low dose IL-2 (106 U/m2 s.c.). Results: In NHP, IPH1101 and low dose IL-2 induce early pro-inflammatory cytokine release and dose-dependent γd cell amplification in peripheral blood. In vitro, mRCC tumor cells are efficiently and selectively killed by autologous γd cells. In Phase I clinical trials, both ex vivo expanded γd cells and IPH1101 were well tolerated. - Cell therapy-related AEs included mainly gastrointestinal disorders, flu-like symptoms and hypotension. Six patients showed stabilized disease. Median duration of stabilization was 25.7 weeks. 2 pts treated with 4.109 or 8.109 cells showed substantial tumor shrinkage at the 14-week evaluation (-22% and -48%, respectively). - When IPH1101 was administered with low dose of IL-2, a significant increase of blood γd T cells was observed (up to 240 times the basal values) and in terms of clinical activity assessment, among the evaluable mRCC population (n=15), 8 patients presented disease stabilization for more than 35 weeks, including 6 for more than 51 weeks. Conclusions: For the first time, a specific γd immunotherapy was fully developed and led to Phase I clinical trials. It has been found well tolerated. Encouraging signs of disease stabilisation in mRCC patients suggest that γd may have a role in the treatment of cancers resistant to conventional therapies. A phase 2 is ongoing in mRCC patients. No significant financial relationships to disclose.