Keenan, Bridget P.

TPS2675 Background: Checkpoint inhibitor therapy is the standard first-line treatment for advanced/recurrent HCC, but there is a significant unmet therapeutic need for patients (pts) who progress after first-line treatment. Adoptive cellular immunotherapy may provide a novel treatment option. Glypican-3 (GPC3), a heparan sulfate proteoglycan, is overexpressed by tumor cells in HCC and virtually absent in healthy tissues, making it an ideal target for CAR-T therapy. AZD5851 is an autologous CAR-T product that expresses a CAR specific for GPC3 and a dominant negative (dn)TGFβRII as an armoring strategy. Expression of dnTGFβRII can block TGFβ signaling, protecting CAR T-cells from the immunosuppressive effects of this cytokine. Early clinical data with C-CAR031, a CAR-T product with the same GPC3-specific CAR and dnTGFβRII-armoring transgene as AZD5851, showed promising tolerability and antitumor activity in pts with HCC [1]. ATHENA (NCT06084884) is a first-in-human, single-arm, open-label, multicenter phase 1/2 study to evaluate the safety, tolerability, and antitumor activity of AZD5851 in pts with GPC3+ advanced/recurrent HCC, for whom ≥1 prior line of standard therapy failed or was not tolerable. Methods: Eligible pts are aged ≥18 years with histologically confirmed advanced/recurrent or metastatic and/or unresectable HCC, GPC3+ tumor sample as determined by immunohistochemistry, ≥1 prior line of standard systemic therapy, ≥1 measurable lesion per RECIST 1.1, Child-Pugh A, ECOG PS 0/1, and adequate organ and bone marrow function. Approximately 24 pts will be enrolled in Part A (Phase I, dose escalation) and 50 in Part B (Phase II dose expansion). Pts will undergo apheresis to collect peripheral blood mononuclear cells for AZD5851 production, after which they may receive approved bridging therapy for disease control. Upon successful generation of AZD5851 product, pts will undergo lymphodepletion before receiving a single dose of IV AZD5851. Subsequent follow-up is divided into 3 stages: Stage 1, active follow-up of all pts through 6 months post AZD5851 infusion; Stage 2, further evaluation of pts who have not progressed or started a new anticancer regimen during Stage 1; Stage 3, long-term follow-up for all pts who have received AZD5851. The primary endpoints are to assess the safety/tolerability of AZD5851 (both study parts), and to determine the recommended dose(s) of AZD5851 for expansion and phase 2 trials (Part A). Secondary endpoints include efficacy (objective response rate, best overall response, duration of response, disease control rate, durable response rate, time to response, progression-free survival, and overall survival) and pharmacokinetics. Exploratory endpoints include pharmacodynamic biomarkers and immunogenicity. Enrollment began Nov 2023. 1. Zhang et al. AACR 2023. Abstract CT097. Clinical trial information: NCT06084884 .

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.