I-Mab Announces Encouraging Phase 1 Clinical Data of PD-L1x4-1BB Bispecific Antibody Ragistomig at ASCO 2024

• Encouraging objective responses were observed in heavily pre-treated patients, including 1 complete response (CR) and 6 partial responses (PR), mainly in patients previously treated with checkpoint inhibitors
• Phase 1 dose-escalation data demonstrated that ragistomig monotherapy can be safely administered through the highest planned doses
• Data will be presented at the 2024 Annual Meeting of the American Society of Clinical Oncology (ASCO2024) in a poster session scheduled for June 1, 2024 at 9:00 am CDT
  

ROCKVILLE, Md., May 23, 2024 (GLOBE NEWSWIRE) -- I-Mab (the “Company”) (NASDAQ: IMAB) a U.S.-based, global biotech company, exclusively focused on the development and potential commercialization of highly differentiated immunotherapies for the treatment of cancer, today announced that Gerald Falchook, MD, and the team at I-Mab’s partner for ragistomig (or “ABL503”), ABL Bio (KOSDAQ: 298380), will present a poster related to Phase 1 data for ragistomig at the 2024 American Society for Clinical Oncology Annual Meeting (“ASCO 2024”), taking place from May 31^st to June 4^th at the McCormick Place Convention Center in Chicago, IL.

Ragistomig was designed as a bispecific antibody to provide anti-PD-L1 activity and 4-1BB-driven T-cell activation in one molecule. The combination of an Fc-silent and conditional 4-1BB engagement was intended to optimize the compound for safety, including the potential for lower hepatotoxicity compared to traditional 4-1BB agonists.

The first-in-human Phase 1 study was designed to define the dose-limiting toxicity and safety profile of ragistomig monotherapy (primary endpoints) as well as to observe the objective response rate (ORR), pharmacokinetic (PK) and immunogenicity profiles (secondary endpoints). The study is being conducted in patients with advanced or relapsed/refractory solid tumors and the majority of patients (56.6%) received prior anti-PD(L)-1 immunotherapy. The main observations from the study include:

• A manageable safety profile;
• Definition of an optimal dose of 5 mg/kg, with dose proportional pharmacokinetics (PK);
• Overall response rate of 25% at 5 mg/kg, based on 3 partial responses (PR) out of 12 patients with median progression free survival (PFS) of 15.6 weeks;
• Clinical benefit rate of 75% at 5 mg/kg, based on 3 PRs and 6 stable disease (SD);
• 71.4% of responders had received prior anti-PD-(L1) inhibitors and were all relapsed or refractory to anti-PD-(L1) inhibitors; and
• A complete response (CR) was seen in one heavily pretreated patient (7 prior lines of therapy, ovarian cancer) at 3 mg/kg.

“We are pleased to present the Phase 1 data to date for ragistomig at ASCO 2024. While immune checkpoint inhibitors have made a significant contribution to the treatment of solid tumor cancers, many tumors do not respond or become refractory to these agents. Ragistomig was designed to provide a new treatment option for patients who are resistant to immune checkpoint inhibitors,” said Raj Kannan, Chief Executive Officer at I-Mab. “Topline data indicate that the study met its objectives, enabling the definition of an optimal dose, and provided several early efficacy observations in patients relapsed or refractory to prior checkpoint inhibitor treatment. These data support further development of ragistomig as both a monotherapy and in combination with other compounds. We look forward to advancing the clinical program in collaboration with our partner, ABL Bio.”