Lin Shen, Jifang Gong, Jian Zhang, Dongmei Ji, Haijun Zhong, Ying Yuan, Lei Yang, Qingyuan Zhang, Yufeng Li, Mengde Wang, Chuan Qi, Zhenzhong Xia, Lingmin Lu, John Huang, Ling Sun, Li Xu, Michael Shi, Xichun Hu

Research Funding

Mabspace Biosciences (Suzhou) Co., Limited, Suzhou, China

Background:

MSB2311 is a novel humanized PD-L1 antibody with a unique pH-dependent antigen binding property that enables intra-tumor recycling and potentiates tumor penetration.

Methods:

Patients with metastatic solid tumors or selected lymphoma progressed on or after standard treatments were enrolled in this phase I study. In dose escalation part, MSB2311 was given at dose levels of 3, 10, and 20 mg/kg intravenously every 3 weeks. At the dose expansion part, patients with enriched biomarker expression, including EBV+, PD-L1+ (TPS≥50%), MSI-High or TMB-High (≥10muts/Mb), were dosed at 20mg/kg Q3W or 10mg/kg Q2W. Primary objectives are to evaluate the safety and tolerability and to identify MTD and RP2D. Secondary objectives include the assessment of pharmacokinetic parameter, immunogenicity, and preliminary anti-cancer activity per RECIST1.1.

Results:

As of data cutoff by Aug 31, 2020, 33 Chinese patients had been treated, including 27 heavily pre-treated solid tumor patients and 6 lymphoma patients. No dose limiting toxicity was reported and MTD has not been reached. The most common AEs (>20%) included: anemia, hypothyroidism, aspartate aminotransferase elevated, proteinuria, weight loss. 13 patients (39.4%) experienced grade 3 AEs, and 6 patients (18.2%) experienced SAEs. No treatment related grade 4 or 5 event was reported. Of the 17 efficacy evaluable solid tumor patients with biomarker selection, 6 achieved confirmed partial response with 35% ORR: 2/8 (25%) at 10 mg/kg Q2W and 4/9 (44%) at 20 mg/kg Q3W. Additionally, one patient achieved sustained iPR via iRECIST. 4 out of 7 responding patients (including one iPR) achieved tumor shrinkage of more than 50%, 3 of them got durable response (≥24 weeks).1 out of 6 lymphoma patients achieved PR.

Conclusions:

MSB2311 demonstrated a manageable safety profile and promising preliminary antitumor activity in patients with advanced solid tumors and selected lymphomas. Clinical trial information: NCT04272944