This study will enroll RA patients who still remained moderate-to-high disease activity after conventional synthetic DMARDs (csDMARDs) therapy. All participants are informed about the study procedures and potential risks and are required to provide written informed consent prior to study begin.~A 3+3 dose escalation design will be implemented. Three ascending dose cohorts (3 participants/cohort) will be treated successively to identify the maxium tolerated dose (MTD) and/or a recommended dose for phase II study. Dose escalation will be terminated if the dose-limiting toxicities (DLT) are observed in 2 participants during the 28-day follow-up within cohort.~DLT was defined as any ≥grade 3 non-hematological toxicity or grade 4 hemtological toxicity according to CTCAE v5.0, which was related to the investigational product determined by investigator.
BC-U001 is an allogeneic fresh human umbilical cord-derived mesenchymal stem cell product, which showed therapeutic potential for rheumatoid arthritis(RA) based on its anti-inflammatory, immunomodulatory and tissue repair activities. The primary objective of this open-label, non-randomized, dose-escalation study is to evaluate the safety and tolerability of a single intravenous infusion of BC-U001 for RA patients using a 3+3 design.