Efficacy and safety of HLX10, a novel anti-PD-1 antibody, in patients with previously treated unresectable or metastatic microsatellite instability-high or mismatch repair-deficient solid tumors: A single-arm, multicenter, phase 2 study.
Authors: Shukui Qin, Jin Li, Haijun Zhong, Chuan Jin, Lili Chen, Xianglin Yuan, Qingxia Fan, Kehe Chen, Peiguo Cao, Jianjun Xiao, Da Jiang, Tao Zhang, Hongyu Zhang, Xicheng Wang, Wei Wang, Qingyu Wang
Journal: Journal of Clinical Oncology (2021)

2566 Background: Microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) in cells render them susceptible to immune checkpoint blockages. This study aimed to evaluate the efficacy and safety of HLX10, a fully humanized monoclonal antibody against PD-1, in patients with unresectable or metastatic MSI-H/dMMR solid tumors who have progressed on or been intolerant to standard therapies. Methods: In this single-arm, open-label, multicenter, phase 2 study (NCT03941574), patients (18≤ age ≤75 years) with histologically/cytologically confirmed unresectable or metastatic MSI-H/dMMR solid tumors were recruited to receive 3 mg/kg HLX10 every two weeks intravenously for up to 2 years until disease progression, unacceptable toxicity, or patient withdrawal. The primary endpoint was objective response rate (ORR) assessed by IRRC (evaluated every 6 weeks for the first 48 weeks and every 12 weeks thereafter) per RECIST v1.1. Secondary endpoints included ORR assessed by investigators, duration of response (DoR), progression-free survival (PFS), overall survival (OS), and safety. All eligible patients who received at least one dose of HLX10 were included in the safety analyses. Results: As of Jan 9, 2021, 108 patients were enrolled and 68 with locally or centrally confirmed MSI-H were included in the main efficacy analysis population. Among the 68 patients, the median follow-up duration was 7.7 (range: 1.1–16.4) months and the median age was 53.0 (range: 23.0–72.0) years. MSI-H tumor types included colorectal cancer (n = 54), endometrial cancer (n = 5), gastric cancer (n = 4), breast cancer (n = 2), small intestine cancer (n = 2) and fallopian tube cancer (n = 1). IRRC and investigator assessed ORR were 38.2% (95% CI: 26.7–50.8%; 2 complete response) and 35.3% (95% CI: 24.1–47.8%) respectively in the main efficacy analysis population. Median DoR, PFS and OS have not been reached. 105 (97.2%) patients experienced treatment-emergent adverse events (TEAEs), most commonly anemia (34.3%), hypoproteinemia (27.8%) and increased aspartate aminotransferase (25.0%). 53 (49.1%) patients had grade 3 or worse TEAEs, most commonly anemia (8.3%), progressive disease (6.5%), increased γ- glutamyltransferase (5.6%) and intestinal obstruction (5.6%). 52 (48.1%) patients had immune-related adverse events (irAEs) while 10 (9.3%) had grade 3 or worse irAEs. 3 (2.8%) deaths (2 PD and 1 intestinal obstruction) that might be related to the study drug were reported. Conclusions: HLX10 provides encouraging antitumor activity with a manageable safety profile in patients with MSI-H/dMMR solid tumors who have progressed on or been intolerant to standard therapies. As an effective tissue-agnostic treatment, HLX10 possesses the potential to improve patients’ clinical outcomes. Clinical trial information: NCT03941574.