A multicenter phase Ia study of AbGn-107, a novel antibody-drug conjugate, in patients with advanced gastrointestinal cancer

AbGn-107 is an antibody-drug conjugate directed against AG-7 antigen, a Lewis A-like glycol-epitope expressed in a variety of gastrointestinal (GI) malignancies. Based on promising antitumor activity of AbGn-107 in both in vitro and in vivo preclinical studies, we performed a GI cancer-specific Phase I trial. Standard 3 + 3 dose escalation was used evaluating intravenous doses ranging from 0.1 mg/kg every 4 weeks to 1.0 mg/kg every 2 weeks. Key eligibility included chemo-refractory locally advanced, recurrent, or metastatic gastric, colorectal, pancreatic, or biliary cancer, with ECOG PS 0-1; positive AG-7 expression was not required during dose escalation phase. Patients were treated until disease progression or unacceptable toxicity, with tumor assessments every 8 weeks. Primary objectives included safety and determination of maximum tolerated dose; secondary objectives included efficacy defined by objective response rate. Thirty-nine patients were enrolled across seven dose levels during dose escalation phase. Based on safety profile and pharmacokinetic data, 1.0 mg/kg Q2W was selected as the dose schedule for cohort expansion phase, in which an additional seven patients were enrolled. Median number of lines of prior therapy was 3 (range 1-7). AbGn-107 was generally well-tolerated, with infections, cytopenias, hyponatremia, fatigue, abdominal pain, and diarrhea representing the most common grade 3 or higher treatment-emergent adverse events. One subject achieved a partial response, while 18 (46.2%) achieved a best response of stable disease. Disease control lasting > 6 months was observed in 6 subjects (13.0%), including 4 of 15 (26.7%) treated at the highest dose level. AbGn-107 showed a reasonable safety profile and modest clinical activity in this highly pretreated patient population. Further evaluation is required to assess the clinical validity of AG-7 as a suitable antigen for therapeutic targeting. Clinical Trial information: NCT02908451.