Prevention of Graft-Versus-Host Disease by Inhibition of Lymphocyte Trafficking Using a CCR5 Antagonist

Abstract 673 Inhibition of lymphocyte trafficking early after allogeneic stem cell transplantation (SCT) could limit T cell interactions with antigen-presenting cells and migration to target tissues. This represents a novel strategy to prevent GvHD without interfering with GvL activity. CCR5 is a chemokine receptor expressed on effector T-cells and immature dendritic cells and binds 3 ligands - CCL3, CCL4 and RANTES (CCL5). Accumulating evidence from animal models and clinical observations implicates CCR5 as pivotal in the pathogenesis of GvHD. Genomic analyses suggest that the same CCR5 polymorphisms that confer resistance to HIV infection also correlate with a lower susceptibility to acute GvHD. Maraviroc (MVC; Selzentry®, Pfizer) is the first oral CCR5 antagonist in clinical use. We hypothesized that modulating T-cell trafficking early after allogeneic SCT via CCR5 blockade would limit GvHD. We therefore performed preclinical and clinical testing of MVC as GvHD prophylaxis. Our goals were to 1) determine in vitro activity of MVC on chemotaxis, 2) determine the feasibility, safety and appropriate dose of MVC as part of GvHD prophylaxis, and 3) demonstrate biological activity of MVC through immune pharmacodynamic assays. In vitro, MVC fully inhibited CCR5 internalization by CCL3 and RANTES even at concentrations as low as 1 μM. Using RANTES as a chemotactic trigger, MVC caused dose-dependent inhibition of lymphocyte chemotaxis by up to 53% at MVC 1mM. To address concerns that MVC might impair hematopoiesis, we demonstrated that CCR5 was not expressed on the surface of bone marrow- and peripheral blood-derived CD34+ cells. Moreover, when CD34+ cells were plated in methylcellulose, formation of CFU-GEMM and CFU-GM was not affected by the presence of MVC 1μM; CFU-E and BFU-E were slightly decreased compared to controls. Based on these and other data, we enrolled 19 pts in a phase I/II study of reduced intensity conditioned allogeneic SCT with MVC GvHD prophylaxis. Pts received fludarabine 120mg/m 2 and IV busulfan 6.4 mg/kg followed by peripheral blood stem cells from matched related (n=6), matched unrelated (n=10) and 1-antigen mismatched unrelated (n=3) donors. In addition to standard GvHD prophylaxis with tacrolimus and methotrexate, MVC at escalating dose levels was given from day -2 to +30. Median age was 63 (range 21–74). Indications for SCT were AML/MDS (9), NHL (4), myelofibrosis (2), CLL, aplastic anemia, Hodgkin lymphoma and myeloma (1 each). Pharmacokinetic analysis on 6 pts at each dose revealed that the 300 mg and 150 mg bid dose levels resulted in mean Cavg of 536 and 118 ng/ml, respectively. 3/6 patients at 150mg did not reach the targeted minimum Cavg (100 ng/ml), while the 300mg dose level resulted in adequate Cavg in 6/6 patients and was used as the phase II dose. MVC was well tolerated; 3 pts did not complete the entire course because of transient LFT abnormalities (1) or mucositis (2). The median time to ANC>500/μL was 15 d (range 10–21) and to platelets>20k/μL was 13 d (range 11–24) with no graft rejections. The median donor chimerism at day 100 was 97% (range 83–100%). A day 100-landmark analysis in evaluable pts demonstrated that the cumulative incidence of acute GvHD grade 2–4 was 27% (grade 3–4; 9%) in this high-risk population. Importantly, by day 100 all cases of acute GvHD involved only the skin without liver or intestinal involvement. At a median follow up of 186 days, 3/19 patients relapsed (2 AML, 1 NHL) and 6/19 patients died (3 disease-related, 1 neutropenic sepsis, 1 SOS, 1 unrelated). There were no GvHD-related deaths. To explore potential mechanisms, we tested the capacity of patient serum to inhibit CCR5 internalization and chemotaxis. Patient serum from multiple time points (trough, 1, 2, 3, 4, 6 hr post dose) effectively prevented internalization of CCR5 by RANTES. In addition, in vitro chemotaxis of normal donor T-cells in response to RANTES was significantly impaired in the presence of patient serum from day 0 (on MVC) as compared to day 60 (off MVC). In summary, inhibition of lymphocyte trafficking to peripheral tissues represents a novel strategy to modulate and possibly reduce acute GvHD in allogeneic SCT. MVC at 300mg bid was well tolerated and biologically active in pharmacodynamic assays. Patients receiving MVC exhibited limited GvHD by day 100 without excessive relapses. The phase II portion of the trial is ongoing. Disclosures: Off Label Use: Off label use of maraviroc (Selzentry) will be discussed. Frey: Pfizer, Inc.: Speakers Bureau. Vonderheide: Pfizer, Inc.: Research Funding. Porter: Pfizer, Inc.: Research Funding.