Study design. ∗Platelet counts were assessed in part A on days 0 (4 and 8 hours after the first dose), 4, 11, 14, 28, 42, 56, 70, 84, 98, 112, 126, 134, 140, and 154; weekly throughout the washout period; and in part B at 4 and 8 hours after the first dose, on day 4, and then every 2 weeks before each sutimlimab dose. Additional platelet monitoring was performed as needed for safety monitoring or at the discretion of the investigator. If the patient’s platelet count exceeded 450 × 109/L, their next dose of sutimlimab was withheld and dosing resumed when the platelet count was <150 × 109/L. Dosing of concomitant ITP medications could be reduced at any time in patients with elevated platelet counts. ¶Patients entering part B received an additional loading dose if >17 days had elapsed since the last dose received in part A. ¤Dosing may be delayed due to high platelet levels; an additional loading dose was considered if resumption of sutimlimab treatment occurred more than 17 days after the last dose. ¥Blood samples for PK and PD analysis were taken before every sutimlimab dose and at 0.5, 1, 4, 8, and 24 hours after the first and last dose in part A. Blood was sampled weekly during washout, every 4 doses during part B, and 9 weeks after dose completion (last sample not shown on diagram). øDuring part A, clinic visits with full assessments occurred on days 0, 1, 4, 7, 11, 14 and then every 2 weeks through to the end-of-treatment visit (day 147; week 21) and the end-of-washout visit (day 196). During part B, clinic visits were on days 0 and 4 and every 2 weeks thereafter, with end-of-treatment and end-of-study visits occurring 1 week and a maximum of 9 weeks after dose completion, respectively. A-EOS, part A end of study; A-EOT, part A end of treatment; ITP, immune thrombocytopenia; IV, intravenous; LPI, last patient in; PD, pharmacodynamic; PK, pharmacokinetic.
