Aptevo announces ALG.APV-527 meets trial endpoints in Phase 1 study

Aptevo Therapeutics (APVO) and Alligator Bioscience announced preliminary data from the companies’ Phase 1 trial evaluating the first-in-class bispecific antibody, ALG.APV-527, as monotherapy for the treatment of multiple solid tumor types likely to express tumor antigen 5T4. These data indicate that trial endpoints of adequate exposure, safety, tolerability and biological activity were met. Outcomes were presented at a poster session on Friday November 8, 2024, at the Society for Immunotherapy of Cancer Conference in Houston, Texas. “The interim results from Phase 1 trials of ALG.APV-527 are showing encouraging outcomes, particularly in terms of safety and disease stability in the trial patients who were refractory to multiple previous therapies. Among evaluable patients, 56% (9/16) achieved stable disease in this monotherapy trial. A colon cancer patient remained on study with stable disease for more than six months as well as a breast cancer patient who remained stable for over 11 months. Importantly, there were no instances of serious liver toxicity, a notable outcome given the relatively high incidence of this side effect associated with other treatments targeting 4-1BB. By leveraging a novel bispecific approach, ALG.APV-527 aims to enhance anti-tumor immunity while avoiding the systemic toxicities that previously have hampered the 4-1BB immune receptor pathway. These findings underscore the drug’s potential as a viable option for patients with solid tumors,” noted Dr. Thomas Marron, MD, PhD, Professor of Immunology & Immunotherapy and Hematology/Oncology at the Icahn School of Medicine at Mount Sinai, and a leading investigator in the trial. Clinical Highlights: Safety and Tolerability: ALG.APV-527 demonstrated positive safety and tolerability across all cohorts; No serious liver toxicity, a common side effect of other 4-1BB targeting treatments that can cause patients to discontinue dosing, was observed; A maximum tolerated dose has not been identified, highlighting the tolerability of the drug at high dose levels. Clinical Activity/Efficacy: Nine of 16 efficacy evaluable patients achieved stable disease; One colon cancer patient achieved SD for more than six months; The longest SD duration was in a breast cancer patient who entered the study with progressive disease, achieved stable disease and remained on study for greater than11 months. This patient successfully transitioned to a higher dose level twice. Evidence of biological activity of ALG.APV-527: ALG.APV-527 could be measured in all patients. Serum concentrations of ALG.APV-527 were proportional to the administered dose; Analysis of biomarkers in the serum of treated patients including soluble 4-1BB confirm biological activity of ALG.APV-527; Analysis of biomarkers in biopsies. This observation consistent with ALG.APV-527 expected MOA.