Abstract
Background: Blocking lymphocyte trafficking after allogeneic stem cell transplantation (alloSCT) may prevent graft-versus-host disease (GvHD) without interfering with graft-versus-tumor (GvT) activity. We previously reported that brief (up to day+30) CCR5 blockade using maraviroc (MVC, Pfizer) after reduced-intensity conditioned (RIC) alloSCT resulted in a low incidence of acute GvHD and absence of early liver and gut GvHD, although delayed GvHD still occurred. We designed a phase II study to test the hypothesis that extended administration of MVC would be feasible, safe and provide protection against late-onset GvHD without impairing immune reconstitution or GvT responses.
Patients and Methods: In April 2013 we initiated a 37-patient (pt) phase II study to test an extended course of MVC in recipients of RIC alloSCT from unrelated donors. Pts receive fludarabine 120 mg/m2 and busulfan i.v. 6.4 mg/kg followed by peripheral blood stem cells. MVC 300 mg b.i.d. is orally administered from day -3 to day +90 in addition to standard prophylaxis with tacrolimus and methotrexate. The primary endpoint is the cumulative incidence of grade 2-4 acute GvHD by day 180. As of July 2014 we enrolled 20 pts at high risk for transplant-related toxicity by virtue of age (median=64, range 55–72), donor source (matched unrelated 80%, single-antigen mismatch unrelated 20%) or comorbidities (comorbidity index: low 15%, intermediate 35%, high 50%). Underlying diseases were AML (16), MDS, MPD, ALL and CTCL (1 each).
Feasibility and Safety: The median follow-up on surviving patients is 5.7 months. The 3-month course of MVC was well tolerated with no increased toxicity; two pts did not complete their treatment due to early disease relapse and one patient discontinued therapy due to a skin reaction with eosinophilia where the histological features favored a drug reaction and the attribution to MVC was possible. Postural hypotension, a known dose-dependent toxicity, was observed in one pt who completed the course with a 50% dose reduction.
Engraftment and Immune Reconstitution: The median time to ANC>500/μL was 12 d (range 10-21) and platelets>20k/μL was 14 d (range 9-28). The median whole blood and T-cell donor chimerism levels at day 100 were 95% (range 12–100%) and 80% (range 23–94%) respectively, which are similar to historical rates. Median CD4 counts on day 30 were 341 (range 206-424). Only 3/16 evaluable pts had Ig levels<500 mg/dL in the first 100 days.
GvHD: Sixteen pts are evaluable with > 3 mo of follow-up. The day-180 cumulative incidence rates (± s.e.) of grade 2-4 and grade 3-4 acute GvHD are 25 ± 11% and 6 ± 6% respectively (Fig. 1). Of patients who developed acute GvHD in the first 180 days, there have been no cases of liver GvHD, 2 cases of stage 1 steroid-responsive gut GvHD and 1 case of severe diarrhea with combined features of GvHD and leukemic infiltrates in the gut. These results are comparable to the GvHD rates in our phase I/II MVC study (grade 2-4: 23.6% and grade 3-4: 5.9%), which included related and unrelated donor transplants. These results also compare favorably with a 45% day-180 acute GvHD rate seen in similar patients treated with our standard GvHD prophylaxis alone. Notably, there has been no treatment-related mortality. Five patients have relapsed at a median of 2.6 months post-transplant (range 0.93 – 3.5), which is similar to our historical rates after RIC alloSCT.
PD analysis: We developed a phosphoflow assay to assess in real-time the activity of MVC in fresh blood samples. The assay quantifies the activation of CCR5 by measuring the phosphorylation of C-terminal serine residues as a result of CCL4 stimulation. In 15 evaluable patients, we observed diminished pCCR5 levels with CCL4 stimulation on day 0 as compared to day -6 (Fig. 2).
In summary, our preliminary results support the feasibility, safety and protective activity of the CCR5 antagonist MVC against acute GvHD, with preferential activity against visceral GvHD. Continued pt enrollment and follow-up are ongoing. Updated safety, efficacy and PD results will be presented. A multi-center study (BMT-CTN 1203) will be initiated later this year to further clarify the role of this novel strategy in improving the outcome of alloHSCT.
Cumulative Incidence of Acute GvHD
Phosphoflow shows CCR5 unresponsiveness to CCL4 stimulation on day 0
Reshef:Pfizer: Research Funding. Off Label Use: Maraviroc for graft-versus-host disease prophylaxis.
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