Patrick J Miller

Publications (2)4.75 Total impact

• Article: 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.

  Shanta Banti, Patrick J Miller, Cynthia D Parker, Sandya L Ananth, LaShun L Horn, Yarlagadda S Babu, Jasbir S Sandhu
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  ABSTRACT: 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.
  International Immunopharmacology 06/2002; 2(7):913-23. · 2.38 Impact Factor
• Article: Purine nucleoside phosphorylase inhibitor BCX-1777 (Immucillin-H)—a novel potent and orally active immunosuppressive agent

  Shanta Bantia, Patrick J Miller, Cynthia D Parker, Sandya L Ananth, LaShun L Horn, John M Kilpatrick, Philip E Morris, Tracy L Hutchison, John A Montgomery, Jasbir S Sandhu
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  ABSTRACT: Patients with purine nucleoside phosphorylase (PNP) deficiency present a selective T-cell immunodeficiency. Inhibitors of PNP are, therefore, of interest as potential T-cell selective immunosuppressive agents. BCX-1777 is a potent inhibitor of PNP from various species including human, mouse, rat, monkey and dog, with IC50 values ranging from 0.48 to 1.57 nM. BCX-1777, in the presence of 2′-deoxyguanosine (dGuo, 3–10 μM), inhibits human lymphocyte proliferation activated by various agents such as interleukin-2 (IL-2), mixed lymphocyte reaction (MLR) and phytohemagglutinin (PHA) (IC50 values <0.1–0.38 μM). BCX-1777 is a 10–100-fold more potent inhibitor of human lymphocyte proliferation than other known PNP inhibitors like PD141955 and BCX-34. Nucleotide analysis of human lymphocytes indicate that inhibition of proliferation by BCX-1777 correlates with dGTP levels in the cells. BCX-1777 has excellent oral bioavailability (63%) in mice. At a single dose of 10 mg/kg in mice, BCX-1777 elevates dGuo to approximately 5 μM. BCX-1777 was not effective in mouse T-cell models such as delayed type hypersensitivity (DTH) and splenomegaly because mouse T-cells do not accumulate dGTP as do human T-cells. However, in the human peripheral blood lymphocyte severe combined immunodeficiency (hu-PBL-SCID) mouse model, BCX-1777 was effective in prolonging the life span 2-fold or more. This is the first known example of a PNP inhibitor that elevates dGuo in mice similar to the levels observed in PNP-deficient patients. Furthermore, these dGuo levels are also required for in vitro T-cell inhibition by BCX-1777. Thus, BCX-1777 represents a novel class of selective immunosuppressive agents that could have therapeutic utility in various T-cell disorders.
  International Immunopharmacology 06/2001; · 2.38 Impact Factor