ci-972 and 9-deaza-9-(3-thienylmethyl)guanine

Patients with homozygous deficiency of purine nucleoside phosphorylase (PNP) present with a T-cell selective immune deficiency. To elucidate the potential use of PNP inhibitors in the therapy of cutaneous T-cell lymphomas (CTCLs) the authors studied the effects of CI-1000 (formerly PD141955-2) and CI-972 on a T-cell line MyLa established from a patient with mycosis fungoides. Both PNP inhibitors had significant, dose-dependent, inhibitory effects on the proliferation of the T-cell line. CI-1000 (ED50: 3.7 microM) was approximately six-fold more potent in blocking 3H-thymidine uptake than CI-972 (ED50: 22.5 microM). The inhibitory effect of either substance could not be increased by addition of deoxyguanosine. Flow cytometric analysis revealed that both PNP inhibitors caused a block in the S-phase of the cell cycle. The inhibitory effect on proliferation was reversible partially by addition of IL-2. When testing proliferation inhibition of both substances on an IL-2-dependent T-cell line (SeAx), their inhibitory effects were reduced significantly. These data document a mechanism of action of the PNP inhibitors independent of deoxyguanosine and partially reversible by IL-2. The authors' observations suggest the potential use of PNP inhibitors in the therapy of cutaneous T-cell lymphomas and provide evidence for a pathway independent from deoxyguanosine by which PNP inhibitors might function in T cells.

Topics: Cell Cycle; Cell Line; Deoxyguanosine; Flow Cytometry; Guanine; Humans; Interleukin-2; Interleukin-7; Lymphocyte Activation; Mycosis Fungoides; Purine-Nucleoside Phosphorylase; Pyrimidines; S Phase; Sezary Syndrome; T-Lymphocytes; Thiophenes; Time Factors

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

Inhibitors of purine nucleoside phosphorylase (PNP) are of interest as potential T-cell-selective immunosuppressive agents and for other uses. PD 141955 (9-deaza-9-(3-thienylmethyl)guanine; 2-amino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]pyrimidin -4-one) is 12- to 100-fold more potent than CI-972 (8-amino-9-deaza-9-(3-thienylmethyl)guanine; 2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]pyrim idin-4- one) in PNP enzyme inhibition assays. In the human MLR, PD 141955 has IC50s of 2.8 and 12.8 microM in the presence and absence, respectively, of 15 microM GdR (means from 10 assays), while the IC50s of CI-972 tested in parallel are > 30 microM. Concentration-dependent accumulation of dGTP occurs in PD 141955-treated MLRs under conditions in which CI-972 lacks detectable activity. Thus, consistent with its greater PNP inhibitory activity in a cell free system, PD 141955 is significantly more potent than CI-972 in its ability to suppress the MLR.

Topics: Cells, Cultured; Guanine; Humans; Immunosuppressive Agents; Lymphocyte Culture Test, Mixed; Purine-Nucleoside Phosphorylase; Pyrimidines; T-Lymphocytes; Thiophenes

Patients with deficiency in purine nucleoside phosphorylase (PNP) have elevated levels of the PNP substrates inosine, guanosine, and (rarely) 2'-deoxyguanosine (GdR) in their plasma and urine. GdR is critical because it serves as a precursor of dGTP, which blocks T-cell replication, thus leading to T-cell-selective immune dysfunction. We adapted these findings to the study of PNP inhibitors in human and rat blood in vitro. Blood was spiked with GdR (2.5 micrograms/ml) and the effects of PD 141955 (9-deaza-9-(3-thienylmethyl)guanine; 2-amino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]pyrimidin -4-one) and CI-972 (8-amino-9-deaza-9-(3-thienylmethyl)guanine; 2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]pyrim idin-4- one) on GdR catabolism were determined. GdR was metabolized 89 times faster in human blood than in rat blood (half-life = 12.0 +/- 1.4 s in human blood). When PD 141955 (1 microgram/ml) was added to human blood before spiking, the GdR half-life increased to > 60 min. In contrast, CI-972 (1 microgram/ml) extended the GdR half-life to 7.2 +/- 1.7 min. Both PD 141955 and CI-972 at 1 microgram/ml significantly retarded GdR catabolism from rat blood.

Topics: Animals; Chromatography, High Pressure Liquid; Deoxyguanosine; Guanine; Half-Life; Humans; Immunosuppressive Agents; Purine-Nucleoside Phosphorylase; Pyrimidines; Rats; Thiophenes

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