ci-972 and deoxyguanosine-triphosphate

Topics: Animals; Cell Division; Deoxyguanine Nucleotides; Dose-Response Relationship, Drug; Guanine; Humans; Immunosuppressive Agents; Purine-Nucleoside Phosphorylase; Pyrimidines; Rats; Thiophenes; Tumor Cells, Cultured

An in-parallel comparison is presented of the in vitro and in vivo properties of two 9-deazaguanine analog inhibitors of purine nucleoside phosphorylase (PNP), CI-972 [8-amino-9-deaza-9-(3-thienylmethyl)guanine] and PD 141955 [9-deaza-9-(3-thienylmethyl)guanine] (published Ki values of 0.83-8.0 and 0.08 microM, respectively). Despite structural similarities, PD 141955 was considerably more potent and active in all systems studied. The respective IC50 values for inhibition of MOLT-4 cell growth in the absence and presence of 10 microM 2'-deoxyguanosine (GdR) were greater than 50 and 5.06 microM for CI-972 and 15.4 and 0.061 microM for PD 141955. PD 141955 induced accumulation of dGTP in GdR-treated MOLT-4 and CEM cells at log-lower concentrations than were required of CI-972, and the magnitude of dGTP accumulation in PD 141955-treated T cell cultures was markedly greater (e.g. 366 vs 100 pmol/10(6) CEM cells at 10 microM). PD 141955 administered orally produced a dose-dependent elevation of plasma inosine and guanosine in rats over a broad concentration range. Mean plasma inosine concentrations following a 150 mg/kg p.o. dose peaked at 6.21 and 13.2 microM in CI-972 and PD 141955-treated rats, respectively. Low levels of inosine were detectable at 50 micrograms/kg following oral administration of PD 141955.

Topics: Animals; Cell Line; Deoxyguanine Nucleotides; Dose-Response Relationship, Drug; Guanine; Guanosine; Humans; Inosine; Male; Purine-Nucleoside Phosphorylase; Pyrimidines; Rats; Rats, Inbred Strains; T-Lymphocytes; Thiophenes

CI-972 (2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3, 2-d]pyrimidin-4-one monohydrochloride, monohydrate) is a novel inhibitor of PNP (Ki = 0.83 microM) under development as a T cell-selective immunosuppressive agent. CI-972 inhibited proliferation (3H-thymidine uptake) of human MOLT-4 (T cell) but not MGL-8 (B cell) lymphoblasts with respective IC50s of 3.0 and greater than 50 microM when tested with 10 microM 2'-deoxyguanosine. Without addition of exogenous 2'-deoxyguanosine, CI-972 was not inhibitory to any human T or B lymphoblastoid cell line tested. 2'-Deoxycytidine (10 microM), but not hypoxanthine or adenine, restored MOLT-4 cell growth. Inhibition of 3H-thymidine uptake in MOLT-4 cells correlated with accumulation of dGTP, while alterations in guanine nucleotides were not observed. 2'-Deoxycytidine (10 microM) also blocked dGTP accumulation in MOLT-4 cells. CI-972 showed activity in vivo over a broad dose range: At 5-150 mg/kg p.o., CI-972 produced dose-dependent elevation of plasma inosine one hr after administration to rats (mean maximum of 2.62 vs. 0.06 microM in controls). Guanosine was also significantly elevated in a concentration-dependent manner, although the effect was not as impressive. Plasma nucleosides remained statistically-significantly elevated for up to four hr following a single oral dose of CI-972.

Topics: Animals; Cell Line; Cells, Cultured; Deoxyguanine Nucleotides; Guanosine Triphosphate; Humans; Lymphocytes; Male; Nucleosides; Purine-Nucleoside Phosphorylase; Pyrimidines; Rats; Rats, Inbred Strains; Thiophenes; Thymidine

CI-972 (2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2- d]pyrimidin-4-one monohydrochloride, monohydrate) is a competitive inhibitor of PNPase (E.C. 2.4.2.1., Ki = 0.83 microM) entering clinical trials as a T cell-selective immunosuppressive agent. Neither CI-972 (less than or equal to 50 microM) nor dGuo (less than or equal to 10 microM) inhibited [3H]Thd uptake by human MOLT-4 (T cell) or MGL-8 (B cell) lymphoblasts, but in the presence of 10 microM dGuo, the IC50 for CI-972 decreased to 3.0 microM for MOLT-4 but remained at greater than 50 microM for MGL-8. Inhibition of MOLT-4 growth was associated with an increase in dGTP that was dependent on CI-972 concentration and inhibited by 2'-deoxycytidine. Growth could not be restored by hypoxanthine or adenine. No alterations in GTP pools were noted in MOLT-4, and neither GTP nor dGTP were altered in MGL-8.

Topics: Adenine; Cell Division; Deoxycytidine; Deoxyguanine Nucleotides; DNA Replication; Guanosine Triphosphate; Humans; Hypoxanthine; Hypoxanthines; Kinetics; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Purine-Nucleoside Phosphorylase; Pyrimidines; T-Lymphocytes; Thiophenes