Background IBI188 is a humanized IgG4 monoclonal antibody targeting CD47, an antiphagocytic (‘don’t eat me’) signal present on cancer cells. Blockage of this myeloid checkpoint, IBI188 enhances tumor cell phagocytosis and cross priming of T-cells. We conducted a first-in-human phase 1a trial to evaluate the tolerability, safety and PK/PD characteristics of IBI188. (NCT03763149).
Methods Patients with advanced/refractory solid tumors or lymphoma were enrolled in this two-part dose-escalation study: Part A for testing optimal priming doses at 0.1, 0.3, and 1 mg/kg and Part B for optimal maintenance doses at 3, 10, 20, 30 mg/kg weekly. An accelerated titration followed by traditional 3+3 design was used in this study with a 28-day dose-limiting toxicity (DLT) observation period. Primary endpoint was safety profile; secondary endpoints included PK parameters and PD markers, i.e. CD47 receptor occupancy.
Results As of June 18, 2020, 20 patients have been enrolled, 6 in Part A and 14 in Part B. There was no DLT reported at any dose level. The median treatment duration was 1.8 months (0.2–5.5) months. The most common treatment-related adverse events (TRAEs) were nausea (n=7), back pain (n=7), fatigue (n=6), vomiting (n=4) and blood bilirubin increased (n=4). Three patients had ≥ Grade 3 TRAEs (Grade 3 blood bilirubin increase, Grade 4 platelet count decrease and Grade 3 anemia, each in 1 patient). Three of 20 patients (15%) had anemia, an expected TRAE associated with the mechanism of IBI188. Majority of the patients (65%) had infusion related reactions (IRR). All IRRs were Grade 1–2 and able to be managed with standard IRR treatment. The clearance of IBI188 decreased with the increasing dose from 3 to 20 mg/kg and IBI188 can overcome the sink at 10 mg/kg or higher dose level. The PK analysis at 30 mg/kg is ongoing. The 10 mg/kg maintenance dose resulted in T cells receptor occupancy above 80%. After multiple administrations (≥ 3 times, including the priming dose), the RBC and T cells receptor occupancy tends to be stable and maintained around 90%. The receptor occupancy analysis at 20 mg/kg and 30 mg/kg is ongoing.
Conclusions IBI188 was well tolerated at 1 mg/kg priming dose following by the maintenance dose up to 30 mg/kg.
Trial Registration NCT03763149
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