AT1001 for the Treatment of COVID-19 Related MIS-C

This is a Phase 2a (Proof of Concept), randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of AT1001 for use in hospitalized pediatric patients diagnosed with MIS-C. Eligible participants (N=20) will be treated with AT1001 or matching placebo orally four times a day (QID) for up to 21 days as an add-on to standard of care. The study includes three phases: * Screening/Baseline: The main purpose of this phase is to determine if the participant meets entry criterion after obtaining informed consent and obtain baseline assessments. * Treatment: Eligible participants will be treated with AT1001 or matching placebo 10 μg/kg/dose QID up to 500 μg/dose (rounded to the nearest 50 μg) for 21 days as an add-on to standard of care for MIS-C. * Follow-up through 24 weeks: The participant will return for a follow-up visits during weekly clinic visits during Week 1 through Week 3, with monthly telemedicine visits at Week 4, Week 8, Week 16 and Week 20, and clinic visits at Week 12 and Week 24. Safety monitoring, including physical examination, vitals, and clinical laboratory testing will be performed during the screening phase, periodically during treatment phase and at the follow-up phase. Adverse events and concomitant medications will be recorded during the entire study. Total duration of the participants' participation in the study is approximately 24 weeks (with 21 days treatment period). Total duration of the study is projected to be 12 months, dependent on enrollment timeline.