Comparison of in vivo efficacy of BCX-1777 and cyclosporin in xenogeneic graft-vs.-host disease: the role of dGTP in antiproliferative action of BCX-1777.
Purine nucleoside phosphorylase (PNP) deficiency in humans produces a relatively selective depletion of T-cells. Inhibitors of PNP are therefore of interest as potential T-cell selective immunosuppressive agents. BCX-1777 is a potent inhibitor of PNP and in vitro T-cell proliferation. Inhibition of human T-cells by BCX-1777 and deoxyguanosine (dGuo) is accompanied by deoxyguanosine triphosphate (dGTP) accumulation. Unlike human T-cells, mouse, rat, dog and monkey T-cells are neither inhibited (IC50>100 microM) nor accumulate dGTP in the presence of BCX-1777 and dGuo. Cells pretreated with BCX-1777 and dGuo for 24 h (to elevate dGTP levels) prior to stimulation demonstrated 80% inhibition similar to the inhibition observed with cells treated with BCX-1777 and dGuo during the stimulation and proliferation process. This further confirms that inhibition of T-cells is due to the accumulation of dGTP in these cells. Deoxynucleotide (dNTP) analysis of the cells treated with BCX-1777 and dGuo for 48 h showed no significant change in deoxycytidine triphosphate (dCTP) and deoxyadenosine triphosphate (dATP) pools. However, a decrease (2-fold) in thymidine triphosphate (dTTP) pools, and a large increase in dGTP pools (15-fold) were observed. Results from various groups have shown that alteration in the dNTP supply results in DNA fragmentation and cell death with characteristics of apoptosis. Indeed, apoptosis is observed in human T-lymphocytes treated with BCX-1777 and dGuo. To compare the in vivo efficacy of BCX-1777 with another potent T-cell inhibitor, cyclosporin, these drugs were tested in a xenogeneic graft-vs.-host disease model (XGVHD). In this model, human lymphocytes are engrafted into severe combined immunodeficient mice (SCID) mice inducing severe XGVHD. The efficacy of BCX-1777 in the XGVHD model was comparable to cyclosporin and a combination of BCX-1777 and cyclosporin treatment showed a trend towards increased efficacy compared to cyclosporin alone. These results suggest that BCX-1777 may be useful for the treatment of disease characterized by activated T-cell responses.
Banti
Shanta
S
Department of Biological Sciences, BioCryst Pharmaceuticals, Inc, Birmingham, AL 35244, USA. sbantia@biocryst.com
Miller
Patrick J
PJ
Parker
Cynthia D
CD
Ananth
Sandya L
SL
Horn
LaShun L
LL
Babu
Yarlagadda S
YS
Sandhu
Jasbir S
JS
D000818:Animals; D016572:Cyclosporine / Q000494:pharmacology / Q000627:therapeutic use*; D003848:Deoxyguanine Nucleotides / Q000378:metabolism*; D004285:Dogs; D004359:Drug Therapy, Combination; D006086:Graft vs Host Disease / Q000139:chemically induced / Q000188:drug therapy* / Q000378:metabolism; D006131:Growth Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D007166:Immunosuppressive Agents / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use*; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008252:Macaca fascicularis; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D011684:Purine Nucleosides; D011744:Pyrimidinones / Q000494:pharmacology / Q000627:therapeutic use*; D011758:Pyrroles / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015996:Survival Rate; D014183:Transplantation, Heterologous / Q000276:immunology*
D003848:Deoxyguanine Nucleotides; D006131:Growth Inhibitors; D007166:Immunosuppressive Agents; D011684:Purine Nucleosides; D011744:Pyrimidinones; D011758:Pyrroles; C113101:forodesine; D016572:Cyclosporine; C029603:deoxyguanosine triphosphate