Alemtuzumab-Cyclosporine Versus Tacrolimus-Methotrexate-Sirolimus for Graft-Versus-Host Disease Prophylaxis in Reduced Intensity Allogeneic Hematopoietic Stem Cell Transplantation from Unrelated Donors: Final Results of a Randomized Trial

Introduction: Allogeneic hematopoietic stem cell transplantation (alloHSCT) can provide a curative therapy for hematological malignancies but may result in complications such as relapse, infection, and acute and chronic graft versus host disease (GVHD). Two divergent approaches to GVHD prophylaxis (post-HSCT depletion of donor lymphocytes vs. suppression of immune activation) in a reduced-intensity, matched-unrelated donor setting were compared in a randomized, open label, phase 2 prospective trial (NCT00520130), powered to assess the incidence of severe cGVHD using NIH criteria.

Methods: Hematological malignancy patients received disease-specific induction chemotherapy DA-EPOCH-FR or FLAG (Salit et al, JCO 2012; 30:830) for disease control and host lymphodepletion to CD4+ cell target <100/µl. All patients received identical conditioning with concurrent fludarabine (30 mg/m2/d x4) and cyclophosphamide (1200 mg/m2/d x4), followed by mobilized T-replete peripheral blood allograft from a matched unrelated donor. Patients were randomized to receive alemtuzumab 20 mg/d x5 and cyclosporine (AC) or tacrolimus, sirolimus, and methotrexate (TMS).

Results: 81 pts (NHL=25, HL=8, CLL=18, AML/MDS=10, CML=3, CTCL/PTCL=5, ALL=4, MM=2, other=6), median age 50 yrs (range, 21-71) were included in the study (AC=42, TMS=39). The two arms were similar in age, gender, disease, relapse risk (Kahl), HCT-comorbidity index, and donor HLA match (8/8 or 7/8). Median time to neutrophil engraftment was 9 vs. 11 days in AC vs. TMS, respectively (p=0.017). There were no differences in platelet recovery (p=0.96). One case of graft failure occurred in a myeloma patient on the AC arm.

D100 mortality probabilities were 12% (95% CI, 5-25) and 10% (95% CI, 4-24) in AC and TMS, respectively (p=0.20). Median survival in AC was 18.8 mo and 41.7 mo in TMS, with a median follow-up of 53 mo in AC and 50.6 mo in TMS. 3yr OS was comparable: AC 42% (95% CI, 28-57) vs. TMS 58% (95% CI, 42-73) (p=0.20). The 3yr malignancy progression rate was higher in the AC arm (AC 51% (95% CI, 34-65) vs. TMS 21% (95% CI, 10-35), p= 0.0062). 3yr relapse related mortality rates were 29% (95% CI, 16-44) vs. 14% (95% CI, 5-29) (p=0.067) and non-relapse mortality 29% (95% CI, 16-43) vs. 28% (95% CI, 14-43) (p=0.75) in AC vs. TMS, respectively.  The most common grade ≥3 adverse events (CTCAE 4.03) within 100 d post-transplant were infections (22%) with more viral infections in the AC arm (p=0.0007). Reactivation of CMV occurred earlier in the AC arm, incidence 58% (95% CI, 42-71) vs. 24% (95% CI, 12-38) by D100 (p=0.035).

Rates of aGVHD were similar; Gr II-IV at 6 mo in AC 38% (95% CI, 23-53) vs. TMS 41% (95% CI, 26-57) (p=0.59); Gr III-IV at 6 mo AC 21% (95% CI, 11-35) vs. TMS 13% (95% CI, 5-26) (p=0.61). In contrast, significantly lower rates of any grade cGVHD occurred in the AC arm compared to TMS at 36 mo (27% (95% CI, 14-41) vs. 59% (95% CI, 40-74)) (p=0.0076). The incidence of severe cGVHD was strikingly different: AC 5% (95% CI, 1-15) vs. TMS 31% (95% CI, 16-47) (p=0.0007). In the Cox model, the only prognostic factor for severe or any cGVHD was the TMS treatment arm, HR 6.8 (95% CI, 1.5-30.3, p=0.012) and HR 2.3 (95% CI, 1.1-4.8, p=0.026), respectively.

Lymphocyte recovery (ALC 500/µL) was markedly delayed in AC, median 76 vs. 16 d (p<0.0001). NK-cell recovery was disparate during the first month (p <0.0001, D28: 31 vs. 270/µl), but similar thereafter. B-cell reconstitution was negligible in both through 6 mo. AC resulted in profound and prolonged deficit in T cells. CD4+ cells were significantly reduced in AC vs. TMS through 1 yr (p <0.0001, D28: 21 vs. 285/µl, 1yr: 131 vs. 447/µl). CD8+ disparity persisted for 6 mo (p<0.0001, D28: 6 vs. 205/µl, 6 mo: 58 vs. 429/µl). Naïve T-cells were significantly reduced in AC through 6 mo (p<0.0001, median naïve cell frequency (AC vs TMS) Treg 2.8 vs 8.4%; nonTreg CD4+ 1.0 vs 23.7%; CD8+ 2.9 vs 20.0%). Assessment of CD4+ and CD8+ TCR Vβ repertoire diversity by spectratyping demonstrated significantly lower diversity in AC at 6 mo (p=0.003).

Conclusions: This prospective, randomized trial demonstrates that the use of AC when compared with TMS led to a significant reduction in incidence of severe and overall cGVHD. These two GVHD prophylaxis regimens had similar incidences of aGVHD but very different effects on post-alloHSCT immune reconstitution, infection and relapse. Future strategies for cGVHD prevention will need to further address these issues.