LAUSR

We conducted a multicenter interventional study to assess the efficacy of Therakos ECP to treat steroid‐resistant graft‐vs‐host disease (SRes‐GVHD) after allogeneic HSCT and to identify biomarkers of GVHD response. A total of 62 patients were treated for acute SRes‐GVHD (n = 37) or chronic SRes‐GVHD (n = 25). Median time to best response was 35 days (range, 28‐85) and 90 days (range, 27‐240) in acute and chronic SRes‐GVHD, respectively. Overall, 27 patients (72.9%) with SRes‐aGVHD responded to treatment (40.5% CR and 32.4% PR). The response rate was significantly higher in grade I‐II than in grade III‐IV aGVHD (100% vs 50.0%, respectively, P‐value = .001). In chronic SRes‐GVHD, 22 patients (88%) achieved a clinical response (24.0% CR and 64% PR). Response was higher in moderate than in severe SRes‐cGVHD (100% vs 75%, P = .096). In both acute and chronic SRes‐GVHD patients, the percentage of peripheral blood CD3+CD4+ was higher and CD3+CD8+ lower in responding than nonresponding patients. Acute SRes‐GVHD responding patients presented a higher number of Treg cells (CD4+CD25+CD127low/−) at day 0 (P = .028) than nonresponding patients, differences that were maintained over the observation period. Phenotypic analysis of T‐cell maturation showed a trend toward reduction in TCD8 naive cells, along with an increased percentage of TCD8 Mem Efect T cells after starting ECP in responding patients. None of the studied serum cytokines displayed statistically significant changes in either acute or chronic SRes‐GVHD. ECP is an effective treatment for patients with SRes‐GVHD. Biomarkers could help guide decision‐making on ECP treatment initiation and duration.