Abstract CT265: Phase 1 dose-escalation study of SGN-TGT monotherapy in patients with advanced malignancies

Abstract Background: T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain (TIGIT) is an inhibitory immune checkpoint receptor expressed on subsets of T-cells and natural killer (NK) cells. TIGIT inhibits T and NK cell function by binding to CD155 and CD112. SEA-TGT is an investigational human, nonfucosylated monoclonal antibody directed against TIGIT, blocking TIGIT's interaction with CD155 and CD112. SGNTGT-001 (NCT04254107) is a phase 1, open-label, multicenter study of SEA-TGT in patients (pts) with advanced malignancies (solid tumors and lymphomas). In this abstract, we present data from the dose-escalation phase (Part A). Methods: Pts received SEA-TGT ranging from 0.01 to 6.0 mg/kg of body weight intravenously every 3 weeks (Q3W). The primary objectives were to evaluate the safety and tolerability of SEA-TGT and identify the maximum tolerated dose (MTD) or the recommended dose and schedule of SEA-TGT. The optimal biological dose was defined using the Clinical Utility Index. Secondary objectives included the evaluation of antitumor activity, pharmacokinetics (PK) and immunogenicity. Antitumor activity was based on Response Evaluation Criteria in Solid Tumors version 1.1 or the Lugano classification criteria with Lymphoma Response to Immunomodulatory Therapy Criteria. Results: From June 12, 2020, to October 5, 2022, 41 pts were enrolled (2, 4, 5, 11, 12, and 7 pts in the 0.01, 0.1, 0.3, 1, 3, and 6 mg/kg cohorts, respectively). Among the 39 pts who were treated 23 pts had solid tumors and 16 had lymphomas. The median number of prior therapies across all cohorts was 5. Treatment emergent adverse events of any grade were reported in 100% of pts, and treatment-related adverse events (TRAEs) of any grade were reported in 69.2%. TRAEs seen in ≥10% of the pts were infusion-related reaction (38.5%), chills (25.6%), pyrexia (17.9%), fatigue (12.8%), maculopapular rash (12.8%), and rash (10.3%). Seven pts (17.9%) reported TRAEs grade ≥3, and rash (5.1%) was the most frequently reported. No grade 4 or 5 TRAEs were reported. One dose-limiting toxicity, pruritic rash, was observed in 1 pt in the 6 mg/kg cohort, and MTD was not exceeded. Based on the PK and pharmacodynamic data, 1 mg/kg Q3W was selected as the optimal biological dose for the expansion cohorts. One partial response was observed in a pt with gastric cancer, and 2 partial metabolic responses were seen in a pt with Hodgkin’s lymphoma and a pt with diffuse large B-cell lymphoma. Conclusions: Overall, clinical data for SEA-TGT from the SGNTGT-001 trial suggest a manageable and tolerable safety profile. Preliminary antitumor activity warrants further clinical evaluation of SEA-TGT. SGNTGT-001 is ongoing and evaluating monotherapy and combination therapies. Citation Format: Elena Garralda Cabanas, Elisa Fontana, Honey Kumar Oberoi, Nataliya V. Uboha, Ecaterina E. Dumbrava, Emiliano Calvo, Giuseppe Curigliano, Diwakar Davar, Bridget K. Keenan, Vincent K. Lam, Sudhir Manda, Amitkuma Mehta, Anna Minchom, Alison Moskowitz, Ravi Paluri, Vincent Ribrag, Donald Richards, Lillian Siu, Paul Swiecicki, Trisha Wise-Draper, Jasmine Zain, Andres Forero-Torres, Ping Xu, Stephen Ansell. Phase 1 dose-escalation study of SGN-TGT monotherapy in patients with advanced malignancies [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 CT265.