An open-label, multicenter, phase I study of ATG-022 in patients with advanced/metastatic solid tumors (CLINCH).

person Sarwan Bishnoi Cancer Research SA, Adelaide, Australia info_outline Sarwan Bishnoi, Dan Cao, Shehara Ramyalini Mendis, Jim Coward, Jun Zhao, Hui Xie, Li Zheng

Authors person Sarwan Bishnoi Cancer Research SA, Adelaide, Australia info_outline Sarwan Bishnoi, Dan Cao, Shehara Ramyalini Mendis, Jim Coward, Jun Zhao, Hui Xie, Li Zheng Organizations Cancer Research SA, Adelaide, Australia, Department of Abdominal Oncology, Cancer Center, West China Hospital, Sichuan University, Chengdu, China, Cabrini Health Limited, Malvern, Australia, ICON Cancer Centre, Brisbane, Australia, Antengene Therapeutics Ltd., Shanghai, China, Department of Clinical Research and Development, Antengene Corporation, Shanghai, China, Clinical Trial Center, National Medical Products Administration Key Laboratory for Clinical Research and Evaluation of Innovative Drugs, West China Hospital, Sichuan University, Chengdu, China Abstract Disclosures Research Funding Antengene Background: Claudin 18.2 (CLDN 18.2) is a tumor associated antigen broadly expressed in gastric, pancreatic, and other solid tumors. ATG-022 is an antibody drug conjugate (ADC), consisting of a humanized monoclonal antibody that binds to CLDN 18.2 with high affinity of sub-nM grade and a conjugated linker-payload vc-MMAE. ATG-022 has displayed promising tumor growth inhibition activity both in vitro and in vivo. Methods: CLINCH is a phase I, multi-center, open-label, dose-finding study (NCT05718895) of ATG-022 in patients with advanced solid tumours. The study design includes a dose escalation phase, enrolling subjects with advanced/metastatic solid tumors, regardless of CLDN 18.2 expression, and a dose expansion phase which will enroll select advanced/metastatic solid tumors with CLDN 18.2-positive expression at the defined maximum tolerated dose and/or recommended Phase 2 dose to further evaluate the safety, tolerability, and efficacy of ATG-022. Other endpoints include pharmacokinetics (PK) and exploratory biomarkers of drug activity. In the dose escalation phase, ATG-022 is administered intravenously every 3 weeks (Q3W) at the starting dose of 0.3 mg/kg, followed by 0.9, 1.8, 2.4, 3.0, and 3.6 mg/kg Q3W using a modified 3+3 dose-escalation design. Efficacy assessments are evaluated per RECIST1.1 criteria. Results: As of 9 Oct 2023, 10 patients (pts) with advanced solid tumors have been enrolled to receive ATG-022 at a dose from 0.3 to 2.4 mg/kg. Median age was 59 years. Baseline ECOG scores were 0 (0 pts) and 1 (10 pts); 8 pts had stage IV disease. Three pts had received more than 3 prior lines of systemic therapy. Eight pts (80%) had ≥ 1 TRAEs; 1 pt (10%) had ≥ 1 Serious TRAEs; 3 (30%) pts had grade ≥ 3 TRAEs. The most common grade ≥ 3 TRAEs included nausea (30%), vomiting (30%) and decreased appetite (30%). No DLT was reported among the current dose levels. Among 7 pts with gastric cancer, 3 pts are confirmed to be CLDN 18.2 positive. One of these pts has maintained stable disease with tumor shrinkage for more than 6 months (treatment ongoing) at a dose of 0.9 mg/kg, demonstrating tolerability of ATG-022. One PR was observed in a gastric cancer pt (CLDN 18.2 expression to be determined) at the dosage of 1.8 mg/kg. It was noteworthy that a CR was seen in a gastric cancer pt dosed at 2.4 mg/kg, with negative CLDN 18.2 expression. PK analysis of ATG-022 from 0.3 to 2.4 mg/kg revealed that the exposure of total antibody, MMAE and ADC drug is increased as dose increased. No accumulation of ATG-022 was observed. Conclusions: ATG-022 demonstrated preliminary anti-tumor activity, tolerability, safety, as well as comparable PK properties at current dose levels. The high affinity of sub-nM grade of ATG-022 in pts with low CLDN 18.2 expression needs further investigation. The dose escalation is ongoing and updated data will be presented. Clinical trial information: NCT05718895.

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