Phase 1 first-in-human dose-escalation study of ANV419 in patients with relapsed/refractory advanced solid tumors

Background: ANV419 is a stable antibody-cytokine fusion protein consisting of interleukin-2 (IL-2) fused to an anti-IL-2 monoclonal antibody that sterically hinders binding of IL-2 to the α subunit of its receptor but has selective affinity for the receptor βγ subunits. Thus, ANV419 preferentially stimulates CD8⁺ effector T cells and natural killer cells which are associated with tumor killing, while minimizing the activation of immunosuppressive regulatory T cells.

Methods: ANV419-001 is an open-label, multicenter, phase 1 study to evaluate the safety, tolerability, maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of ANV419. Secondary objectives were to characterize the pharmacokinetics, pharmacodynamics and tumor response. Adult patients with advanced solid tumors and disease progression after ≥1 previous line of systemic therapy were enrolled. ANV419 was administered by intravenous infusion once every 2 weeks, with a planned treatment duration of 12 months. The dose escalation part of the study explored doses 3, 6 and 12 µg/kg as single patient cohorts followed by 24-364 µg/kg in a 3+3 design. Interim results are reported here (data cut-off: March 22, 2023).

Results: Forty patients were enrolled and received at least one dose of ANV419. The MTD and RP2D were determined to be 243 µg/kg. The most common ANV419-related treatment-emergent adverse events were Grade 1 and 2 fever (31 (77.5%)), chills (23 (57.5%), vomiting (14 (35.0%)), cytokine release syndrome and nausea (12 (30.0%) each). Transient and self-limiting lymphopenia due to lymphocyte redistribution was observed in all patients. In the RP2D cohort, Grade ≥3 thrombocytopenia and fever were reported by one patient (12.5%) each. All events were manageable with standard supportive care. At doses of 243 µg/kg (RP2D/MTD), the estimated T_1/2 was approximately 12 hours. At ANV419 doses ≥108 µg/kg, 64% of patients had a best response of at least SD (15 SD and 1 confirmed PR).

Conclusions: ANV419 at doses up to 243 µg/kg (the RP2D) was well tolerated and showed signs of antitumor activity in a heavily pretreated patient population with advanced solid tumors.

Trial registration number: NCT04855929.