Objective <p>Magrolimab (ONO-7913) is an anti-cluster of differentiation 47 (CD47) monoclonal antibody. This was a phase 1, open-label, uncontrolled, dose-escalation study that assessed the tolerability and safety of intravenous magrolimab (priming dose: 1&#xa0;mg/kg; maintenance dose: 20&#xa0;mg/kg [Cohort 1] or 30&#xa0;mg/kg [Cohort 2]; 28-day treatment cycle) in Japanese adult patients with histologically or cytologically confirmed advanced or metastatic solid tumors, ≥ 1 measurable lesion, an Eastern Cooperative Oncology Group performance score of 0–1, and an expected survival ≥ 3 months.</p> Results <p>Seven patients were enrolled and received magrolimab (Cohort 1, <i>n</i> = 4; Cohort 2, <i>n</i> = 3) with the median follow-up of 170.0 (34–491) days. All 7 patients discontinued the magrolimab monotherapy, and 4 (57.1%) patients completed the study as per the protocol. No dose-limiting toxicities were observed in both cohorts, and the maximum tolerated dose was not reached. All patients experienced treatment-emergent adverse events (TEAEs) but not any serious adverse events, TEAEs leading to treatment discontinuation or interruption, or TEAE-related deaths. No complete or partial responses occurred, while the disease control rate was 42.9% (best overall response: stable disease, <i>n</i> = 3; disease progression, <i>n</i> = 3; not evaluable, <i>n</i> = 1). Magrolimab was well tolerated in Japanese patients with advanced or metastatic solid tumors.</p> <p><i>Trial registration</i>: NCT04403308, submitted on May 21, 2020.</p>