Mesenchymal stromal cells plus basiliximab, calcineurin inhibitor as treatment of steroid-resistant acute graft-versus-host disease: a multicenter, randomized, phase 3, open-label trial

Background: Steroid-resistant (SR) acute graft-versus-host disease (aGVHD) lacks standard second-line treatment. Mesenchymal stromal cells (MSCs) have potential efficacy in SR aGVHD. We aimed to assess the efficacy and safety of MSCs combined with basiliximab and calcineurin inhibitor as second-line therapy for SR aGVHD. Methods: A randomized phase 3 trial involved 203 SR aGVHD patients at nine centers in China (September 2014-March 2019). Participants were randomized at a 1:1 ratio to receive second-line therapy with (n = 101) or without (n = 102) MSCs. The primary endpoint was the overall response (OR) at day 28. Secondary and safety endpoints included durable OR at day 56, failure-free survival, overall survival (OS), chronic GVHD (cGVHD), infection, hematological toxicity and relapse. Results: Of 203 patients, 198 (97.5%; mean age, 30.1 years; 40.4% women) completed the study. The OR at day 28 was higher in the MSC group than the control group (82.8% [82 patients] vs. 70.7% [70]; odds ratio, 2.00; 95% confidence interval [Cl], 1.01-3.94; P=0.043). The durable OR at day 56 was also higher in the MSC group (78.8% [78 patients] vs. 64.6% [64]; odds ratio, 2.02; 95% CI, 1.08-3.83; P= 0.027). The median failure-free survival was longer in the MSC group compared with control (11.3 months vs. 6.0 months; hazard ratio (HR) 0.68; 95% CI, 0.48-0.95, P= 0.024). The 2-year cumulative incidence of cGVHD was 39.5% (95% CI, 29.3-49.4%) and 62.7% (51.4-72.1%) in the MSC and control groups (HR 0.55, 95% CI, 0.36-0.84; P= 0.005). Within 180 days after study treatments, the most common grade 3 and 4 adverse events were infections (65 [65.7%] in the MSC group vs. 78 [78.8%] in the control group) and hematological toxicity (37 [37.4%] vs. 53 [53.5%]). The 3-year cumulative incidence of tumor relapse was 10.1% (95% CI, 5.2-17.1) and 13.5% (7.5-21.2%) in the MSC and control groups, respectively (HR 0.75, 95% CI, 0.34-1.67, P= 0.610). Conclusions: MSCs plus second-line treatments increase the efficacy of SR aGVHD, decrease drug toxicity of secondl-ine drugs and cGVHD without increasing relapse, and are well-tolerated. MSCs could be recommended as a second-line treatment option for aGVHD patients.

Automated summary

This study evaluated the efficacy and safety of combining mesenchymal stromal cells (MSCs) with basiliximab and calcineurin inhibitor as second-line therapy for steroid-resistant acute graft-versus-host disease (SR aGVHD). Results showed that MSCs plus second-line treatments improved overall response and durable overall response, prolonged failure-free survival, and reduced the incidence of chronic GVHD. The study also found that the combination therapy did not increase the risk of tumor relapse and was well-tolerated.