To assess the safety, tolerability, and feasibility of adult allogeneic bone marrow–derived mesenchymal precursor cells (MPCs) in type 2 diabetes inadequately controlled with metformin either alone or with one additional oral antidiabetic agent.

The study was a dose-escalating randomized placebo-controlled trial assessing one intravenous (IV) infusion of MPCs (rexlemestrocel-L; Mesoblast Inc.) 0.3 × 10⁶/kg (n = 15), 1.0 × 10⁶/kg (n = 15), or 2.0 × 10⁶/kg (n = 15) or placebo (n = 16). Study duration was 12 weeks.

Subjects (21 women, 40 men) with a mean ± SD baseline HbA_1c 8.3 ± 1.0% (67 ± 10.9 mmol/mol), BMI 33.5 ± 5.5 kg/m², and diabetes duration 10.1 ± 6.0 years were enrolled at 18 U.S. sites. No acute adverse events (AEs) were associated with infusion. No serious AEs, serious hypoglycemia AEs, or discontinuations due to AEs over 12 weeks were found. No subjects developed donor-specific anti-HLA antibodies or became sensitized. The safety profile was comparable among treatment groups. Compared with placebo, a single IV infusion of rexlemestrocel-L reduced HbA_1c at all time points after week 1. The adjusted least squares mean ± SE dose-related differences in HbA_1c from placebo in the rexlemestrocel-L groups ranged from −0.1 ± 0.2% (−1.1 ± 2.2 mmol/mol) to −0.4 ± 0.2% (4.4 ± 2.2 mmol/mol) at 8 weeks and from 0.0 ± 0.25% to −0.3 ± 0.25% (−3.3 ± −2.7 mmol/mol) at 12 weeks (P < 0.05 for 2.0 × 10⁶/kg dose at 8 weeks). The clinical target HbA_1c <7% (53 mmol/mol) was achieved by 33% (5 of 15) of the subjects who received the 2.0 × 10⁶/kg dose vs. 0% of those who received placebo (P < 0.05).

This short-term study demonstrates the safety and feasibility of up to 246 million MPCs in subjects with type 2 diabetes.