Aptevo, Alligator Bioscience announce data from Phase 1 ALG.APV-527 trial

Aptevo Therapeutics and Alligator Bioscience announced interim data from the dose escalation phase of their Phase 1 trial evaluating ALG.APV-527 for the treatment of solid tumors likely to express the tumor antigen 5T4. The results, which include clinical activity, safety, tolerability outcomes, pharmacokinetics and pharmacodynamics were presented in a poster session on Saturday, September 14, 2024, at the European Society for Medical Oncology Annual Congress in Barcelona, Spain. ALG.APV-527, is a first-in-class bispecific antibody that targets 4-1BB and the tumor antigen 5T4. The compound is being evaluated in a multi-center, dose escalation trial that has 18 patients included in the safety analysis. These patients received multiple, prior rounds of therapy for the treatment of solid tumor types. The trial is approaching full enrollment and interim results include: Clinical Activity/Efficacy: Nine of 15 efficacy evaluable patients have a best overall response to date of stable disease; 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; One colon cancer patient with sustained SD remains on study for more than four months. Safety and Tolerability; ALG.APV-527 demonstrated positive safety and tolerability across all cohorts; A maximum tolerated dose has not been identified; Evidence of favorable pharmacokinetics and biological activity of ALG.APV-527; ALG.APV-527 could be measured in all patients with serum concentration of ALG.APV-527 consistent with the administered dose and preclinical predictions.; Biomarker analyses confirm biological activity of ALG.APV-527 “4-1BB has been a target of interest – though with excess toxicity – for decades, and novel bispecific approaches like this will enable us to maximize anti-tumor immunity while limiting the systemic toxicity concerns that have plagued this key immune costimulatory receptor. With this backdrop, these Phase 1 interim results are very encouraging, with ALG.APV-527 showing a positive safety profile with 60% of evaluable patients achieving stable disease, meaning not progressing for variable time frames including one breast cancer patient being treated with monotherapy on study with SD for more than 11 months. We are excited to see signs of clinical activity, underscoring the potential of the drug to benefit patients with solid tumors in the clinical setting, supported by a positive safety and tolerability profile,” stated Thomas Marron, MD, PhD, Professor in Immunology & Immunotherapy and in Medicine, Hematology and Medical Oncology at Icahn School of Medicine at Mount Sinai, participating Investigator of the trial.