SUZHOU, China, May 20, 2020 – Transcenta Holding Limited (“Transcenta”), a global biotherapeutics company with fully-integrated capabilities in discovery, development and manufacturing of antibody-based therapeutics, announced that the updated Phase I clinical study (NCT04272944) data on the safety and efficacy of MSB2311, a pH-dependent PD-L1 antibody, in Chinese patients with advanced solid tumors and hematological malignancies have been presented as an abstract online publication at the 2021 Annual Meeting of the American Society of Clinical Oncology (ASCO) (Abstract #e14547, 5:00 PM, U.S. East Time, Wednesday, May 19, 2021).

The study, presented at the 2021 ASCO annual meeting by abstract, was led by Professor Lin Shen from Beijing Cancer Hospital, and was a Phase I study of MSB2311 with a unique pH-dependent antigen binding property in Chinese patients with advanced solid tumors and lymphoma. Its primary objectives were to evaluate the safety and tolerability and to identify the maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D). The secondary objectives included the assessment of pharmacokinetic parameter, immunogenicity, and preliminary anti-cancer activity per RECIST version 1.1.

The study included a dose escalation Phase and a dose expansion Phase. In the dose escalation Phase, MSB2311 was given at dose levels of 3, 10, and 20mg/kg intravenously every 3 weeks. At the dose expansion Phase, patients with 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.

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 and weight loss. 13 patients (39.4%) experienced grade 3 AEs, and 6 patients (18.2%) experienced serious adverse events (SAEs). No treatment related grade 4 or 5 AEs was reported.

Of the 17 efficacy evaluable solid tumor patients with biomarker expression, 6 achieved confirmed partial response with an ORR of 35%: 2/8 (25%) at 10mg/kg Q2W and 4/9 (44%) at 20mg/kg Q3W. Additionally, one patient achieved sustained iPR per 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.

“In recent years, tumor immunotherapy has gradually become a research hotspot in the field of tumor treatment. It has played a great role in the treatment of tumors, and we have been making efforts in this area,” said Professor Lin Shen, the leading investigator from Beijing Cancer Hospital. “Patients with metastatic solid tumors or selected lymphoma progressed on or after standard treatments were enrolled in this Phase I study. This Phase I study showed promising preliminary efficacy and tolerability of MSB2311 in patients with advanced solid tumors and hematological malignancies.”

“MSB2311 demonstrated a manageable safety profile and promising antitumor activity in patients with advanced solid tumors and lymphomas.” said Dr. Michael Shi, EVP, Head of Global R&D and CMO of Transcenta. “We are excited to see how our in-house developed medicines can help to benefit the patients. We will continue to forge ahead with our commitment to differentiated and affordable biologics for patients around the world.”

About MSB2311

MSB2311 is an investigational humanized PD-L1 with pH dependent binding property. PD-L1 is involved in inhibiting the immune system's response to fight cancer. MSB2311 blocks the interaction between PD-L1 and PD-1, which reactivates the suppressed or exhausted anti-tumor effector T cell function in the tumor microenvironment. MSB2311 employs engineered IgG1 which lacks FcR binding. In addition, the binding of MSB2311 to PD-L1 results in internalization of MSB2311 and MSB2311 can dissociate from bound PD-L1 in endosome with pH level lower than 5.5. This allows MSB2311 to be recycled to plasma membrane and be reused to bind with PD-L1 on another tumor cell or immune cell. Results from preclinical studies demonstrate that MSB2311 can inhibit tumor growth of PD-L1 expressing tumor cells in syngeneic mouse-model. Two Phase 1 studies of MSB2311 have been completed in the US and China. MSB2311 is currently to be tested in Phase 2 trial in patients with solid tumors expressing selected biomarker in China.