Abstract CT068: Interim results of the ongoing phase 1-2 clinical trial of KVA12123, an engineered IgG1 targeting VISTA, as monotherapy and in combination with pembrolizumab in patients with advanced solid tumors

Abstract V-domain Ig Suppressor of T-cell Activation (VISTA), a promising immuno-oncology target, is primarily expressed by immunosuppressive myeloid cells that infiltrate solid tumors. VISTA may contribute to resistance to anti-PD-(L)1 and anti-CTLA-4 therapies and correlates with a poor prognosis. KVA12123 is a human IgG1 monoclonal antibody that specifically binds to VISTA at neutral and acidic pHs. It was designed to improve pharmacokinetic (PK) characteristics as well as reduce the risk of cytokine release syndrome (CRS). KVA12123 exhibited strong anti-tumor activity alone and in combination with anti-PD1 in preclinical studies. It demonstrated an excellent safety profile in non-human primates. The VISTA-101 clinical trial is a first-in-human, Phase 1/2, multicenter, open-label, safety, PK and pharmacodynamic (PD) evaluation of KVA12123, both as monotherapy and in combination with pembrolizumab, in adult patients with advanced solid tumors (NCT05708950). METHODS: The phase 1 of VISTA-101 is an accelerated Bayesian Optimal Interval Design consisting of two arms: Part A) KVA12123 monotherapy dose escalation from 3 mg to 1000 mg including 6 cohorts and Part B) KVA12123 dose escalation from 30 mg to 1000 mg in combination with 400 mg fixed dosing of pembrolizumab including 4 cohorts. The primary objectives are safety, tolerability and to define a recommended phase 2 dose. Safety, PK and receptor occupancy data were considered during dose escalation. VISTA-101 is also assessing PD and predictive biomarkers of response. Patient tumor response is evaluated by iRECIST. RESULTS: Forty-two patients have been enrolled in the dose escalation monotherapy arm of the study. KVA12123 was administered at doses ranging from 3 to 1000 mg every 2 weeks over a 6-week cycle. KVA12123 was well tolerated at all dose levels and no DLTs were observed. The most frequently observed adverse events were grade 1 or 2 transient infusion-related reactions. No evidence of CRS-associated cytokines were detected. PK analysis demonstrated greater than dose-proportional exposure consistent with target-mediated metabolism. A VISTA receptor occupancy assay demonstrated full target engagement at doses of 30 mg and above. PD analysis indicated a dose-dependent induction of pro-inflammatory myeloid derived cytokines and chemokines involved in immune cell activation and recruitment to the tumor microenvironment including CCL2, CCL3, CCL4 and CXCL10. Increases in nonclassical monocytes, NK cells, CD4+ and CD8+ T cells were also demonstrated, consistent with observations made in preclinical models and indicative of VISTA target engagement. Patient tumor response evaluations in the monotherapy arm will be reported. The study continues to evaluate KVA12123 both as a monotherapy and in combination with pembrolizumab to define the recommended phase 2 dose. Citation Format: Evan Y. Yu, Jason Henry, Manish R. Patel, Paul Swiecicki, Ida Micaily, Benjamin Garmezy, Kalyan Banda, Vinny Hayreh, Kurt Lustig, Yulia Ovechkina, Shawn P. Iadonato, Thierry Guillaudeux, Lee Rosen. Interim results of the ongoing phase 1-2 clinical trial of KVA12123, an engineered IgG1 targeting VISTA, as monotherapy and in combination with pembrolizumab in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT068.