Allogeneic umbilical cord-derived mesenchymal stromal cells as treatment for systemic lupus erythematosus: a single-centre, open-label, dose-escalation, phase 1 study

Background: Patients with systemic lupus erythematosus (SLE) with inadequate responses to standard therapies have unmet therapeutic needs. The immunomodulatory, proangiogenic, and antifibrotic properties of mesenchymal stromal cells support their use in treating patients with SLE. We aimed to assess the safety of a single intravenous infusion of allogeneic umbilical cord-derived mesenchymal stromal cells in patients with severe SLE.

Methods: This prospective, single-centre, open-label, dose-escalation, Bayesian phase 1 study was done at the Saint-Louis University Hospital (Paris, France). Eligible patients were aged 18-70 years, were diagnosed with SLE according to American College of Rheumatology criteria with positive antinuclear antibodies, had a baseline Safety of Estrogens in Lupus Erythematosus National Assessment-SLE Disease Activity Index (SELENA-SLEDAI) score of 6 or more, and had disease that was refractory to first and second line SLE therapies. Patients were to receive a single intravenous infusion of 1 × 10⁶, 2 × 10⁶, or 4 × 10⁶ umbilical cord-derived mesenchymal stromal cells per kg (manufactured from a single umbilical cord) in cohorts of five patients per dose, starting at 2 × 10⁶ cells per kg. The primary endpoint was the rate of treatment-related severe adverse events (grade ≥3) in the first 10 days after infusion of umbilical cord-derived mesenchymal stromal cells. People with lived experience were involved in study design, patient enrolment, and dissemination of the study findings. This study is registered with ClinicalTrials.gov, NCT03562065, and the EU Clinical Trials Register, EudraCT2017-001400-29.

Findings: From May 14, 2019, to March 6, 2023, 29 patients were screened for eligibility, eight of whom were enrolled in the study. Enrolment was terminated early after inclusion of eight patients and no patients received the 1 × 10⁶ dose of umbilical cord-derived mesenchymal stromal cells. Seven (88%) of eight participants were cisgender women and one (13%) was a cisgender man. The median age was 35 years (range 26-57) and the median SLE disease duration was 12 years (5-19). All patients received at least 2 × 10⁶ cells per kg (range 2 × 10⁶ to 4 × 10⁶). No severe adverse events and three infusion-related adverse events (two grade 1 and one grade 2) occurred in two patients in the first 10 days after infusion. After 12·4 months (range 12-13) of follow-up, no treatment-related severe adverse events and three non-treatment-related severe adverse events occurred in one patient after relapse.

Interpretation: Our results suggest that a single infusion of 2 × 10⁶ cells per kg or 4 × 10⁶ cells per kg of allogeneic umbilical cord-derived mesenchymal stromal cells was safe in patients with severe SLE. Placebo-controlled trials are needed to confirm clinical efficacy and the role of B-cell modifications in clinical benefit.

Funding: Fondation du Rein, Alliance Maladies Rares AFM-Téléthon, Direction de la Recherche Clinique et de l'Innovation AP-HP, and ANR eCellFrance.