Abstract CT178: GQ1001: A next generation HER2-targeting ADC that exhibits promising early clinical efficacy with excellent tolerance in a multi-center, Phase Ia study

Abstract

Abstract Background: GQ1001 is a novel HER2-targeted antibody-drug conjugate (ADC) that was developed using innovative conjugation technologies coined intelligent Ligase-Dependent Conjugation (iLDC), that can significantly improves homogeneity and biostability of ADC. In preclinical studies, GQ1001 showed a robust anti-tumor response in multiple HER2+ models alone or in combination with HER2 TKIs and chemotherapeutics, and excellent pharmacokinetics and safety profiles in rats and monkeys due to low level of payload release. Herein we report the initial results of the ongoing phase Ia study, which aims to investigate the safety, tolerability, pharmacokinetics and antitumor activity of GQ1001 in subjects with HER2+ advanced solid tumors. Methods: In phase Ia dose escalation, a modified 3+3 model was adopted to assess the safety, dose-limiting toxicity (DLT) and maximal tolerable dose (MTD) or dose recommended for dose expansion (DRDE) of GQ1001. GQ1001 was administered intravenously as a monotherapy on Day 1 of 21-day cycles. The starting dose was 1.2 mg/kg, followed by 2.4, 3.6, 4.8, 6.0, 7.2 and 8.4 mg/kg. Results: As of Dec. 28th, 2022, 32 subjects with HER2-positive advanced solid tumors, predominantly in breast (9), gastric or gastro-esophageal junction (9) and salivary gland (4), were enrolled and received GQ1001 treatment. Patients had a median 3 (range, 0-11) prior lines of therapies, and 37.5% of those previously received ≥2 lines of anti-HER2 therapies. Median exposure time of GQ1001 was 18.5 weeks. The longest treatment duration exceeded 370 days. No DLT was observed in all doses, MTD was not reached up to 8.4 mg/kg, the highest dose tested. Treatment-related adverse events (TRAEs) occurred in 24 subjects (75%). The most common TRAEs (>10.0%) were aspartate aminotransferase (AST) increased (37.5%), thrombocytopenia (28.1%), alanine aminotransferase (ALT) increased (25.0%), pyrexia (21.9%), anemia (18.8%), alkaline phosphatase increased (12.5%), vomiting (12.5%) and nausea (12.5%). Grade ≥3 TRAEs occurred in 9 subjects (28.1%), including 5 myelosuppression, 2 abnormal liver function, 1 hypertension and 1 vomiting. There were no drug-related deaths. The pharmacokinetics analysis showed the concentration of GQ1001 and TAb generally peaked rapidly and declined in a roughly biphasic manner. Among 15 evaluable subjects who received ≥ 7.2 mg/kg, 6 cases achieved confirmed partial response, and 3 had stable disease, the median progression-free survival was 4.8 months Conclusions: GQ1001 demonstrates an excellent tolerability and promising antitumor activity in heavily pretreated HER2-positive advanced solid tumors, supporting further evaluation of the safety and efficacy of GQ1001 at DRDE of 8.4 mg/kg in the following phase Ib trial. (NCT04450732; sponsored by GeneQuantum Healthcare (Suzhou) Co., Ltd.) Citation Format: Charlotte Lemech, Chenfei Zhou, Xianbao Zhan, Yan Shi, Jieqiong Liu, Sarina A Piha-Paul, Gary Richardson, Gang Qin, Paul H. Song, Lili Shi, Yajun Sun, Yi Xia. GQ1001: A next generation HER2-targeting ADC that exhibits promising early clinical efficacy with excellent tolerance in a multi-center, Phase Ia study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT178.