Abstract CT188: ICT01, an anti-butyrophilin 3A targeted mAb activating g9d2 T cells, induces immune remodeling of the tumor microenvironment and clinical responses in combination with pembrolizumab in patients with advanced solid tumors who failed prior checkpoint inhibitor therapy: EVICTION Trial

Background: γ9δ2 T cells are part of the innate-like immune response to malignancies and have the ability to bridge to the adaptive immune response via cytokine release (e.g., IFNγ and TNFα). Butyrophilin 3A is a novel checkpoint molecule required to activate γ9δ2 T cells highly expressed on immune and malignant cells, and the target of a monoclonal antibody ICT01. ICT01 induces activation/migration of γ9δ2 T cells from the blood to induce immune remodeling of the tumor microenvironment at doses ≥700 μg being tested in the ongoing EVICTION clinical trial (NCT04243499) (AACR 2021, CT034). In vitro studies showed that ICT01 induces upregulation of PD-1 on γ9δ2 T cells and that the combination with pembrolizumab leads to enhanced cancer cell killing, providing scientific rationale for evaluating this combination. Methods: EVICTION is an ongoing Phase 1/2a, international, open-label trial with Group C assessing ICT01 (IV Q3W) plus pembrolizumab (200mg IV Q3W) in patients with bladder cancer, HNSCC, melanoma, or NSCLC who failed ≥1 CPI. Pharmacodynamic activity was monitored by immunophenotyping and cytokine level analysis. Tumor biopsies (baseline, Day 28) were used for immunohistochemistry of BTN3A and tumor-infiltrating lymphocytes, and gene expression profiling. Efficacy evaluations by i/RECIST 1.1 were conducted every 8 weeks. Results: Five Group C patient cohorts have been enrolled and treated with ICT01 doses of 700μg, 2mg, 7mg, 20mg or 75mg (n=30) plus pembrolizumab, with the 200mg ICT01 cohort enrolling currently. To date, no DLTs have been observed with the combination. First-dose fever and chills (Grade 1/2) were the most common AEs that increased in frequency up to 75mg (100%, n=6), without any increase in severity, and rarely recur with subsequent dosing. ICT01+pembrolizumab induced trafficking of >95% of circulating γ9δ2 T cells within 30 min post ICT01 (≥700 μg), which was sustained for 21 days at 75mg. Transient, dose-dependent increases in serum cytokines at 30 min (TNFα) or 4h (IFNγ) post-dose were correlated with baseline γ9δ2 T cell counts and returned to baseline by 24 hrs post dose. Baseline γ9δ2 T cell count also correlated with increases in tumor infiltration of γδ, CD3, and CD8 T cells, confirming the ability to remodel the TME, and the potential to select/enrich patients with higher baseline γ9δ2 T cell counts. Sixteen patients (9/16 pembro-experienced, 5/16 received >1 prior CPI) were efficacy-evaluable at ≥Week 8 by RECIST1.1 at ICT01 doses up to 20 mg, with an observed disease control rate of 44% including 3 confirmed PRs beyond 6 months: bladder (2mg), melanoma (2mg), NSCLC (7mg). The Ipi/Nivo-refractory melanoma patient with PR also achieving a CR on their non-target lesion brain metastasis at 6 months. Data from the 75 and 200mg cohorts will be presented. Conclusion: The immune remodeling of the TME by ICT01-activated γ9δ2 T cells is associated with clinical benefit in CPI-experienced patients when used in combination with pembrolizumab. The selection of patients with higher baseline γ9δ2 T cells may improve the response profile to this novel therapeutic combination in CPI-failure patients, which will be tested in the Phase 2a portion of EVICTION starting in Q2 2022. Citation Format: Stephane Champiat, Martin Wermke, Johann de Bono, Aurelien Marabelle, Christiane Jungels, Cécile Vicier, Norbert Vey, Catrin List, Katrin Wetzko, Leo Ruhnke, Elena Garralda, Vladimir Galvão de Aguiar, Patricia LoRusso, Nuria Kotecki, Aude De Gassart, Emmanuel Valentin, Patrick Brune, Marina Iché, Céline Leparquier, Daniel Olive, Paul Frohna. ICT01, an anti-butyrophilin 3A targeted mAb activating g9d2 T cells, induces immune remodeling of the tumor microenvironment and clinical responses in combination with pembrolizumab in patients with advanced solid tumors who failed prior checkpoint inhibitor therapy: EVICTION Trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT188.