ORLANDO – The use of the CCR5 antagonist maraviroc for 90 days is safe and effective for graft-versus-host disease (GVHD) prophylaxis in patients undergoing allogeneic stem cell transplantation, according to findings from a phase II study.

An earlier study showed that CCR5 blockade using maraviroc for 33 days was associated with a low incidence of acute GVHD, as well as with absence of early liver and gut GVHD – although delayed severe cases of visceral GVHD still occurred.

The current study was performed because the prior findings raised concerns that brief blockade was insufficient for preventing GVHD over a longer period of time. The new findings show that an extended course may indeed provide additional benefits, Ran Reshef, MD, reported at the combined annual meetings of the Center for International Blood & Marrow Transplant Research and the American Society for Blood and Marrow Transplantation.

In 37 high-risk patients who received allogeneic stem cell transplantation from unrelated donors using fludarabine/busulfan (Flu/Bu2) conditioning followed by peripheral blood stem cells, maraviroc was given at a dose of 300 mg twice daily, in addition to standard tacrolimus and methotrexate.

The 180-day rates of grade 2-4 and grade 3-4 acute GVHD (the primary endpoint of the study) in these patients were 27% and 5%, respectively. These rates were very similar to the 24% and 6% rates seen in the first study at 6 months after 30 days of maraviroc treatment, said Dr. Reshef of Columbia University Medical Center, New York.

The earlier results were “driven not so much by a reduction in the rates of skin GVHD, but by low rates of visceral GVHD of the gut and the liver – with a striking absence of gut and liver GVHD in the first 100 days,” he said.

Dr. Reshef also noted that the current study had a less favorable donor mix, as no matched related donors were included because of the earlier study’s very low rates of GVHD – with or without maraviroc – in those with related donors, who composed a third of donors.

Long-term follow-up of results from the earlier study, with comparison of a large contemporary control cohort, showed that “there is in fact an impact ... on grade 2-4 and grade 3-4 [GVHD], although the number of events is small, and the study was not powered enough to reach statistical significance,” Dr. Reshef said. The rates of chronic GVHD did not differ between the study subjects and contemporary controls, he noted.

At 100 days in the current study, there were no cases of liver GVHD, two cases of mild upper-GI GVHD, and one case of severe gut GVHD. At 1 year, the disease relapse rate was “fairly reasonable” at 30%, nonrelapse mortality was 12% with only one case of death from GVHD, and the incidence of chronic GVHD was 8%, which was significantly lower than in the prior study, he said.

The low rate of chronic GVHD led to a GVHD/relapse-free survival (GRFS) rate of 49%.

“To put this in context, the [Center for International Blood & Marrow Transplant Research] data for reduced-intensity transplants ... have shown 25% for acute myeloid leukemia and 12% for myelodysplastic syndrome,” he said. “So, we feel that these are by far improved numbers, compared with this benchmark.”

To determine which patients develop GVHD despite chemotaxis blockade and why, Dr. Reshef and his colleagues developed a pharmacodynamic assay to assess the activity of maraviroc in fresh blood samples. They found that those with insufficient CCR5 blockade on day 0 were those with higher incidence of severe acute GVHD, nonrelapse mortality, GRFS, and overall survival.

The investigators performed pharmacokinetic analysis using combined data from both trials to improve understanding of why some patients have insufficient CCR5 blockade. This showed significant variability in day 0 trough of maraviroc among patients (median of 65 ng/mL, range 12-316 ng/mL); levels above the median were associated with a significantly lower incidence of acute grade 2-4 GVHD and a trend toward improved GRFS.

These studies of maraviroc, which was originally developed for the treatment of HIV infection, were done to test the belief that blocking lymphocyte migration might prevent GVHD without interfering with graft-versus-tumor activity. Based on the earlier findings, Dr. Reshef and his colleagues hypothesized that treatment up to day 90 would decrease the rate to less than 30%, from a historical rate of 52%.

Patients in the study were high risk by virtue of age (median, 64 years), HLA matching (matched unrelated, 84%; mismatched unrelated, 16%), and comorbidities (comorbidity index greater than 2 in 49%). Underlying diseases were acute leukemia (78%), myelodysplastic syndrome (16%), and myeloproliferative neoplasm and cutaneous T-cell lymphomas (3% each).

At a median follow-up of 21 months, the 3-month course of maraviroc was well tolerated. Eight patients did not complete treatment because of disease relapse (five patients), skin reaction (one patient), early infection-related death (one patient), or poor tolerance of oral drugs (one patient). Neutrophil, platelet, and T-cell engraftment were similar to historical controls, and rates of infections were also similar, Dr Reshef noted.

“To conclude, an extended course of maraviroc up to day 90 is feasible and safe in the majority of patients,” he said. “This study confirms the effect of CCR5 blockade on visceral GVHD. I’m still awaiting a randomized study to confirm that further.

“A long course of maraviroc does not necessarily affect the rates of acute GVHD, but may help reduce chronic GVHD and improve GRFS,” Dr. Reshef said. “We should look further into the pharmacodynamic and pharmacokinetic variables.”

Dr. Reshef reported receiving research funding from Pfizer.

sworcester@frontlinemedcom.com

Extended maraviroc helps prevent graft-versus-host disease