ARC-12: Phase 1/1b Study to Evaluate Safety and Tolerability of AB308 + Zimberelimab (AB122) in Advanced Malignancies

Background: PD-(L)1 pathway inhibitors have demonstrated durable clinical benefit in both solid tumors and hematologic malignancies; however, as less than 1/3 of patients respond to anti-PD-(L)1 monotherapy, combination therapies may be needed for improved response rates and survival. T cell Immunoglobulin and ITIM domain (TIGIT) is expressed on activated T cell and natural killer (NK) cell subsets; TIGIT-CD155 binding suppresses T and NK cell function and inhibits the antitumor immune response. AB308, an Fc-enabled anti-TIGIT humanized IgG1 monoclonal antibody (mAb), has reversed TIGIT-CD155-mediated T cell inhibition in preclinical models. ARC-12 will assess whether TIGIT pathway blockade by AB308 can augment zimberelimab (zim; anti-PD-1 mAb) activity in patients with solid and hematologic malignancies.

Study Design and Methods: ARC-12 is a phase 1/1b, first-in-human, open-label, dose-escalation study of AB308 + zim in patients with advanced solid tumors or hematologic malignancies. Dose expansion cohorts include relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) and multiple myeloma (MM). For the dose-escalation, eligible adults have solid tumors for which no standard-of-care therapy exists or have pathologically-confirmed R/R non-Hodgkin lymphoma (NHL) and have not received or are ineligible for allogeneic stem cell transplant or adoptive cell transfer; ≤5 lines of prior systemic therapy; ≥1 measurable lesion per RECIST (solid tumors) or Lugano Classification (NHL) criteria; and ECOG performance score of 0-1. As shown in the figure, patients will receive AB308 + zim intravenously (IV) once every 3 weeks (Q3W; Part A) or once every 4 weeks (Q4W; Part B). In Part A, the first 6 patients of Cohort 1 will follow 3+3+6 rules, allowing for AB308 dose adjustment if dose-limiting toxicities (DLTs) warrant; all other dose-escalation cohorts will use 3+3 rules. After the Cohort 2 DLT period has been cleared, Part B enrollment will begin in parallel with Part A to determine the recommended dose for expansion (RDE) for AB308 + zim for both the Q3W (Part A) and Q4W (Part B) schedules. Each part can independently proceed to dose-expansion once the RDE is determined for that dose schedule. In the dose-expansion, patients will be enrolled into disease-specific cohorts for non-small cell lung cancer (NSCLC), melanoma, gastrointestinal cancer, cervical cancer, and hematologic malignancies (DLBCL or MM). AB308 + zim may be dosed on either a Q3W or Q4W schedule; all patients in each expansion cohort will receive the same dose schedule. For both the dose-escalation and dose-expansion, the primary endpoints assess safety and tolerability of AB308 + zim; secondary endpoints include pharmacokinetics (PK), immunogenicity, and objective response rate for AB308 + zim. Additional secondary endpoints in the dose-expansion are disease control rate and duration of response. Safety and efficacy data will be analyzed using summary statistics and Kaplan Meier estimates as appropriate; PK parameters will be estimated using noncompartmental methods. ARC-12 is actively recruiting at sites in the United States (NCT04772989).

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