Synthesis, structure-activity relationships, and in vivo evaluations of substituted di-tert-butylphenols as a novel class of potent, selective, and orally active cyclooxygenase-2 inhibitors. 2. 1,3,4- and 1,2,4-thiadiazole series

Two isoforms of the cyclooxygenase (COX) enzyme have been identified: COX-1, which is expressed constitutively, and COX-2, which is induced in inflammation. Recently, it has been shown that selective COX-2 inhibitors have antiinflammatory activity and lack the GI side effects typically associated with NSAIDs. Initial mass screening and subsequent SAR studies have identified 6b (PD164387) as a potent, selective, and orally active COX-2 inhibitor. It had IC50 values of 0.14 and 100 microM against recombinant human COX-2 and purified ovine COX-1, respectively. It inhibited COX-2 activity in the J774A.1 cell line with an IC50 of 0.18 microM and inhibited COX-1 activity in platelets with an IC50 of 3.1 microM. The choline salt of compound 6b was also orally active in vivo with an ED40 of 7. 1 mg/kg in the carrageenan footpad edema (CFE) assay. In vivo studies in rats at a dose of 100 mg/kg showed that this compound inhibited gastric prostaglandin E2 (PGE2) production in gastric mucosa by 77% but caused minimal GI damage. SAR studies of this chemical series revealed that the potency and selectivity are very sensitive to minor structural changes.

Synthesis, structure-activity relationships, and in vivo evaluations of substituted di-tert-butylphenols as a novel class of potent, selective, and orally active cyclooxygenase-2 inhibitors. 1. Thiazolone and oxazolone series

Selective cyclooxygenase-2 (COX-2) inhibitors have been shown to be potent antiinflammatory agents with fewer side effects than currently marketed nonsteroidal antiinflammatory drugs (NSAIDs). Initial mass screening and subsequent structure-activity relationship (SAR) studies have identified 4b (PD138387) as the most potent and selective COX-2 inhibitor within the thiazolone and oxazolone series of di-tert-butylphenols. Compound 4b has an IC50 of 1.7 microM against recombinant human COX-2 and inhibited COX-2 activity in the J774A.1 cell line with an IC50 of 0.17 microM. It was inactive against purified ovine COX-1 at 100 microM and did not inhibit COX-1 activity in platelets at 20 microM. Compound 4b was also orally active in vivo with an ED40 of 16 mg/kg in the carrageenan footpad edema (CFE) assay and caused no gastrointestinal (GI) damage in rats at the dose of 100 mg/kg but inhibited gastric prostaglandin E2 (PGE2) production in rats' gastric mucosa by 33% following a dose of 100 mg/kg. The SAR studies of this chemical series revealed that the potency and selectivity are very sensitive to minor structural changes. A simple isosteric replacement led to the reversal of selectivity.

Caspase-3-like activity is necessary for IL-2 release in activated Jurkat T-cells

The caspase family of proteases has previously been implicated in the biochemical cascade leading to apoptotic cell death. Recently caspase-3 was reported to be cleaved into its catalytically active subunits (17 and 13 kDa) following phytohemagglutinin (PHA) activation of peripheral blood mononuclear cells (C. Miossec et al., J. Biol. Chem. 272, 13459-13462). More recently, J. M. Zapata and colleagues (J. Biol. Chem. 273, 6916-6920, 1998), however, proposed that caspase-3 activity detected during T-cell activation was due to a methodological artifact related to the composition of the cell lysis buffer. Here we show that in PHA-activated Jurkat T-cells using the recommended lysis buffer detailed by Zapata et al., a caspase-3-like protease is activated and is accompanied by cleavage of PARP and alpha-spectrin into cleavage products suggestive of caspase-3 proteolytic activation. LDH release did not increase following PHA stimulation in this paradigm. Two caspase inhibitors, carbobenzoxy-Asp-CH2OC(O)-2,6-dichlorobenzene (Z-D-DCB) and acetyl-Asp-Glu-Val-Asp-CHO, blocked IL-2 release in a dose-dependent manner. Caspase-3-like protease-generated PARP and alpha-spectrin breakdown product formation was also reduced by Z-D-DCB. In addition, Jurkat T-cells costimulated with anti-CD3 plus anti-CD28 produced significant levels of IL-2 that were also blocked by these caspase inhibitors. Importantly, IL-2 was determined in cell culture supernatants, thus avoiding a cell lysis step that might have enabled activation of caspase-3 by granzyme B. Collectively, these data support the role of caspase-3-like protease activity in Jurkat T-cell activation and demonstrate that caspase-3 like activity is necessary for IL-2 release in PHA-activated and anti-CD3/anti-CD28 costimulated Jurkat T-cells.

Effects of novel anti-inflammatory compounds on healing of acetic acid-induced gastric ulcer in rats

Nonsteroidal anti-inflammatory drugs often cause development of significant GI lesions. Selective inhibitors of prostaglandin G/H synthase/cyclooxygenase-2 (PGHS-2) enzyme and some dual inhibitors of PGHS/5-lipoxygenase (5-LO) enzymes have been reported to be potent anti-inflammatory compounds that carry a much lower risk of having GI irritating effects. We have evaluated the anti-inflammatory effect and the GI safety profile of three new anti-inflammatory compounds: the selective PGHS-2 inhibitors NS-398 and PD 138387 and the PGHS/5-LO dual inhibitor PD 137968. All the compounds tested showed an anti-inflammatory activity in the carragenan footpad edema test in rats. None of these compounds caused either gastric damage 4 h after p.o. administration of 100 mg/kg in rats or inhibition of PGE2 synthesis in the stomach. However, when administered p.o. at an effective anti-inflammatory dose to rats with pre-existing acetic acid-induced gastric ulcer, NS-398 caused a statistically significant delay of ulcer healing. No impairment of the ulcer healing was observed with the other compounds evaluated. Derivatives of 2,6-di-tert-butylphenol, whose members may act as PGHS-1/PGHS-2 inhibitors, selective PGHS-2 inhibitors or PGHS/5-LO dual inhibitors, are novel anti-inflammatory compounds that are devoid of GI irritating effects and do not affect the rate of pre-existing gastric ulcer healing.

A purine nucleoside phosphorylase (PNP) inhibitor induces apoptosis via caspase-3-like protease activity in MOLT-4 T cells

Children with congenital homozygous deficiency of purine nucleoside phosphorylase (PNP) have abnormalities in purine metabolism that result in T-cell selective immune deficiency. The mechanism of action for cell death has been attributed to intracellular accumulation of dGTP, a potent inhibitor of ribonucleotide reductase and subsequently DNA synthesis, in thymocytes and T-cells but not B-cells. However, the mode of cell death has not been determined to be either necrosis or apoptosis. To examine the involvement of apoptosis in T-cells following PNP inhibition, MOLT-4 cells, a human T cell leukemia cell line, were co-treated with the PNP inhibitor, CI-1000 (2-amino 3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]-pyrimidin-4-one HCl), and 2'-deoxyguanosine (dGuo) which resulted in a concentration-dependent loss of cell viability (trypan blue) and inhibition of tritiated thymidine ([3H]-TdR) uptake. Staining of cells with the DNA dye Hoechst 33,258 showed nuclear morphology characteristic of apoptosis. Western blots (24 h lysates) were probed with antibodies against several proteins implicated in apoptosis. Anti-PARP revealed the presence of an 85 kD PARP breakdown product while, anti-alpha-spectrin revealed the accumulation a 120 kD breakdown product, both suggestive of CPP32 cleavage (caspase-3; an ICE-like cysteine protease). Western blots also detected the loss of the intact 32 kD caspase-3 isoform, a biochemical event associated with caspase-3 activation. Corresponding fluorometric activity assays detected a marked increase in caspase-3-like activity using the substrate Ac-DEVD-MCA. Lastly, a pan caspase inhibitor (Z-D-DCB) and 2'-deoxycytidine (dCyd), which is known to prevent dGTP accumulation following PNP inhibition, were able to prevent cell death and all indicators of caspase-3-like activity in MOLT-4 cells co-treated with dGuo and CI-1000. In summary, we provided several lines of evidence for the role of apoptosis and the contribution of caspase-3-like proteases in T-cell death following PNP inhibition.

Characterization of CPP32-like protease activity following apoptotic challenge in SH-SY5Y neuroblastoma cells

We characterized the activation of interleukin-1beta-converting enzyme (ICE)-like proteases (caspases) in human neuroblastoma cells (SH-SY5Y) following challenge with staurosporine, an established agent known to induce apoptosis. Time course analyses of lactate dehydrogenase release detected a significant increase in cell death as early as 6 h that continued at least until 24 h following staurosporine treatment. Western blot analyses using anti-poly(ADP-ribose) polymerase (anti-PARP) and anti-CPP32 antibodies revealed proteolytic processing of CPP32 (an ICE homologue) as well as fragmentation of PARP as early as 3 h following staurosporine challenge. Furthermore, the hydrolysis of the CPP32 substrate acetyl-DEVD-7-amido-4-methylcoumarin was detected as early as 3 h and became maximal at 6 h after staurosporine challenge, suggesting a delayed and sustained period of CPP32-like activation. In addition, we used the first immunohistochemical examination of CPP32 and PARP in cells following an apoptotic challenge. The localization of CPP32 in untreated SH-SY5Y cells was exclusively restricted to the cytoplasm. Following staurosporine challenge there was a condensing of CPP32 immunofluorescence from the cytoplasm to a region adjacent to the plasma membrane. In contrast, PARP immunofluorescence was evenly distributed in the nucleus in untreated SH-SY5Y cells and on staurosporine challenge was found to be associated with condensed chromatin. It is important that a pan ICE inhibitor [carbobenzoxy-Asp-CH2OC(O)-2,6-dichlorobenzene] was able to attenuate lactate dehydrogenase release and PARP and CPP32 cleavage and altered immunohistochemical staining patterns for PARP and CPP32 following staurosporine challenge.

Non-erythroid alpha-spectrin breakdown by calpain and interleukin 1 beta-converting-enzyme-like protease(s) in apoptotic cells: contributory roles of both protease families in neuronal apoptosis

The cytoskeletal protein non-erythroid alpha-spectrin is well documented as an endogenous calpain substrate, especially under pathophysiological conditions. In cell necrosis (e.g. maitotoxin-treated neuroblastoma SH-SY5Y cells), alpha-spectrin breakdown products (SBDPs) of 150 kDa and 145 kDa were produced by cellular calpains. In contrast, in neuronal cells undergoing apoptosis (cerebellar granule neurons subjected to low potassium and SH-SY5Y cells treated with staurosporine), an additional SBDP of 120 kDa was also observed. The formation of the 120 kDa SBDP was insensitive to calpain inhibitors but was completely blocked by an interleukin 1 beta-converting-enzyme (ICE)-like protease inhibitor, Z-Asp-CH2OC(O)-2,6-dichlorobenzene. Autolytic activation of both calpain and the ICE homologue CPP32 was also observed in apoptotic cells. alpha-Spectrin can also be cleaved in vitro by purified calpains to produce the SBDP doublet of 150/145 kDa and by ICE and ICE homologues [ICH-1, ICH-2 and CPP32(beta)] to produce a 150 kDa SBDP. In addition, CPP32 and ICE also produced a 120 kDa SBDP. Furthermore inhibition of either ICE-like protease(s) or calpain protects both granule neurons and SH-SY5Y cells against apoptosis. Our results suggest that both protease families participate in the expression of neuronal apoptosis.

Blockade of nucleoside degradation in monkey whole blood in vitro by CI-1000, a purine nucleoside phosphorylase (PNP) inhibitor

Purine nucleosides HxR or GdR (2.5 micrograms/mL blood) were added to EDTA-treated cynomolgus monkey whole blood in vitro, alone or with the PNP inhibitor CI-1000 (1 microgram/mL), mixed, and the concentration of nucleosides remaining in plasma followed as a function of time. The half-lives of GdR and HxR in control blood were 1.2 and < 1 min, respectively, and were extended to 17.8 and 39.8 min, respectively, by coaddition of CI-1000. In contrast, a structural analog of CI-1000, CI-972, when tested in parallel at 1 microgram/mL, had markedly less effect on the breakdown of either nucleoside. The ability of CI-1000 to retard nucleoside breakdown in blood in vitro may be a predictor of in vivo activity, and can be viewed as an early and essential biochemical consequence of PNP inhibition culminating in immunosuppression.

Evidence for a pathway independent from 2'-deoxyguanosine and reversible by IL-2 by which purine nucleoside phosphorylase inhibitors block T-cell proliferation

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.

PD 141955 and CI-972: 9-deazaguanine analog purine nucleoside phosphorylase inhibitors. I. Suppression of the human mixed lymphocyte reaction (MLR)

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.

PD 141955 and CI-972: 9-deazaguanine analog purine nucleoside phosphorylase inhibitors. II. Effects on nucleoside catabolism in human and rat blood in vitro

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.

Comparative in vitro and in vivo activities of two 9-deazaguanine analog inhibitors of purine nucleoside phosphorylase, CI-972 and PD 141955

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.

Inhibitors of human purine nucleoside phosphorylase. Synthesis of pyrrolo[3,2-d]pyrimidines, a new class of purine nucleoside phosphorylase inhibitors as potentially T-cell selective immunosuppressive agents. Description of 2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d] pyrimidin-4-one

Purine nucleoside phosphorylase (PNP) is a purine-metabolizing enzyme in the purine cascade and has been a target for drug design for sometime. A series of potent human PNP inhibitors, pyrrolo[3,2-d]pyrimidines (9-deazaguanines), has been synthesized and evaluated in the enzyme assay and in the cell line assay using MOLT-4 (T-cell) and MGL-8 (B-cell) lymphoblasts for selectivity. One of the compounds, 2,6-diamino-3,5- dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]pyrimidine-4-one (11c; CI-972), was found to be moderately potent, competitive, and reversible inhibitor of PNP with Ki = 0.83 microM. It was also found to be selectively cytotoxic to MOLT-4 lymphoblasts (IC50 = 3.0 microM) but not to MGL-8 lymphoblasts and was evaluated further. Compound 11c (CI-972) is under development in the clinic.

Inhibitors of human purine nucleoside phosphorylase. Synthesis and biological activities of 8-amino-3-benzylhypoxanthine and related analogues

A series of 3-substituted hypoxanthines (6-10, 14-17) and related analogues (22, 23) have been synthesized as inhibitors of purine nucleoside phosphorylase (PNP), which may conceivably act as T-cell-selective immunosuppressive agents with potential utility in autoimmune disorders such as rheumatoid arthritis, in organ transplantations, and in T-cell leukemias. The compounds were evaluated for their PNP activity by a radiochemical assay and also for their cytotoxic effects on a T-lymphoblastoid cell line (MOLT-4). Appropriate substitutions on 3-benzylhypoxanthine (7a) (IC50 in PNP assay, 112 microM; IC50 in MOLT-4 assay, 204.2 microM) increase potency: 8-amino (17a; 42.6, 65.2), 2-hydroxy (9a; 13.4, 28.6), 2-amino (10a; 11.4, 29.1), and 2,8-diamino (16a; 5.0, 11.9). Variation of the 3-aryl substituents of 16a as in 16b-d has thus far failed to further increase potency. Replacement of the 6-oxygen function in 7a with the analoguous nitrogen or sulfur functions, as in 22a and 23a, resulted in little change in activity. Other variations including the increase of the 3-aliphatic chain length as in 6h and 7h (n = 2), the substitution of the phenyl ring with electron-withdrawing groups as in 7e-g, and replacement of the 2-hydrogen with methylthio as in 8a and 14a resulted in decrease of activity. The values for 16a-d represent moderate but significant activities, as compared to the most active inhibitor presently known, 8-amino-9-thienylguanine (1c; 0.17, 0.82). 2,8-Diamino-3-substituted hypoxanthines (16a-d) represent a novel structural type hitherto unreported in the literature, and efficient methodologies for their synthesis were developed in the present studies. The formation of the aminoimidazole moiety occurred through a base-catalyzed 1,5-(O----N)-carbamimidoyl rearrangement (13 to 14, 20 to 16).

The biochemistry and pharmacology of PD 116124 (8-amino-2'-nordeoxyguanosine), an inhibitor of purine nucleoside phosphorylase (PNP)

PD 116124 (8-amino-2'-nordeoxyguanosine; 2,8-diamino-1,9-dihydro-9- ([2-hydroxy-1-(hydroxymethyl)ethoxy]methyl)-6H-purin-6-one) is a competitive, reversible inhibitor of human purine nucleoside phosphorylase with an apparent inhibition constant of 0.41 microM. In a cell line system using human MOLT-4 and CEM T lymphoblasts and human MGL-8 and NC-37 B lymphoblasts, PD 116124 failed to inhibit [3H]thymidine uptake at concentrations up to 500 microM. However, in the presence of 10 microM 2'-deoxyguanosine (dGuo), a noninhibitory dGuo concentration by itself, PD 116124 produced potent inhibition of growth of both T cell lines but not of either B cell line. Significant elevation of intracellular 2'-deoxyguanosine triphosphate was observed in both inhibited T cell lines but not in either B cell line. Greater and more sustained accumulation of 2'-deoxyguanosine triphosphate was observed in T lymphoblasts cultured with PD 116124 plus dGuo than with dGuo only. PD 116124 was only weakly inhibitory in human mixed lymphocyte cultures (IC50 approximately equal to 1420 microM), but in the presence of 10 microM dGuo, the IC50 for PD 116124 was reduced to 108.7 microM. Administration of PD 116124 p.o. to normal male Wistar rats caused dose-dependent elevation of plasma inosine up through 500 mg/kg. Maximal inosine elevation occurred at 30 min after dosing, and elevation was significant even 24 hr after dosing. Guanosine was also elevated, although not in a dose-dependent manner. Administration of PD 116124 i.v. produced marked and statistically significant elevation of both inosine and guanosine.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of interleukin-2 production and lymphocyte responsiveness by the cell activation inhibitor, CI-959

CI-959 (5-methoxy-3-(1-methylethoxy)-N-1H-tetrazol-5-yl-benzo [b]-thiophene-2-carboxamide), an antiallergy compound, blocked release of IL-2 from Con A stimulated rat splenocytes and human lymphocytes with respective IC50s of 19.1 and 23.1 microM. Inhibition of IL-2 production required the presence of CI-959 in culture medium for the first 9 hr. CI-959 also inhibited Con A-stimulated rat and human lymphocyte proliferation with IC50s of 4.7 and 5.4 microM, respectively. Inhibition of the Con A proliferative response could not be overcome by exogenous recombinant human IL-2 (300 units/ml) in either the rat or human systems. Although potent in the human mixed lymphocyte reaction (IC50 = 3.5 microM), CI-959 was less effective in blocking the PHA response (IC50 = 43.9 microM), and had minimal effect on the release of IL-1 and TNF alpha from LPS-stimulated human monocytes. These findings suggest that CI-959 selectively inhibits some lymphocyte functions, as opposed to monocyte functions, and that among these is the production of IL-2.

Selective in vitro inhibition of human MOLT-4 T lymphoblasts by the novel purine nucleoside phosphorylase inhibitor, CI-972

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.

Biochemical and pharmacological properties of CI-972, a novel 9-deazaguanine analog purine nucleoside phosphorylase (PNP) inhibitor

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.

Pyrrolo[3,2-d]pyrimidines, a new class of purine nucleoside phosphorylase (PNP) inhibitors as potential T-cell selective immunosuppressive agents

Previously, we have described the synthesis and biological activity of 2,8-diamino-1,9-dihydro-9-(2-thienylmethyl)-6H-purin-6-one (PD 119229; Cl-950) as a potent and competitive PNP inhibitor. As a part of our continuing efforts to develop a PNP inhibitor for autoimmune diseases, we have synthesized a series of pyrrolo[3,2-d]pyrimidines as PNP inhibitors. In this series, 2,6-diamino-3,5-dihydro-7-(3- thienylmethyl)-4H-pyrrolo-[3,2-d]pyrimidin-4-one (Cl-972) was found to be a potent, competitive inhibitor of PNP with Ki of 0.83 microM. It was also found to be selectively cytotoxic to human MOLT-4 (T cell) (IC50 = 3.0 microM) but non-toxic to MGL-8 (B cell) lymphoblasts. Cl-972 is under development as a potential T-cell selective immunosuppressive agent. Synthesis and biological activities of the series are discussed.

The antiinflammatory effects of adenosine receptor agonists on the carrageenan-induced pleural inflammatory response in rats

Adenosine and adenosine receptor agonists have a variety of inhibitory effects on the generation of inflammatory mediators by neutrophils and other cell types. In human neutrophils stimulated with the chemotactic peptide FMLP, adenosine agonists inhibit O2- generation and degranulation. Because these findings suggest that the agonists may have potential as antiinflammatory agents, several compounds were evaluated for effects on the exudative and cellular phases of carrageenan-induced pleural inflammation in rats. All of the agonists tested inhibited both parameters of the inflammatory response. Inhibition appeared to correlate better with binding to the A1 than to the A2 receptor and was reversible by a known adenosine receptor antagonist, 8-phenyltheophylline. In mechanistic studies, R-N-(1-methyl-2-phenylethyl)adenosine, a standard A1 selective agonist, reversed the drop in circulating neutrophil count that occurs after injection of carrageenan. These results suggest that the agonists may prevent cell emigration by inhibiting adhesion to the endothelium or diapedesis. In addition (R)-N-(1-methyl-2-phenylethyl)adenosine had weak inhibitory effects on superoxide production by FMLP-stimulated rat neutrophils. Control studies showed that the effects of the agonists were not the result of agonist-induced hypotension nor corticosterone production by the adrenal glands. These findings indicate that adenosine receptor agonists are effective new pharmacologic tools for the study of inflammatory processes.

The antiinflammatory effects of adenosine receptor agonists on the carrageenan-induced pleural inflammatory response in rats

Adenosine and adenosine receptor agonists have a variety of inhibitory effects on the generation of inflammatory mediators by neutrophils and other cell types. In human neutrophils stimulated with the chemotactic peptide FMLP, adenosine agonists inhibit O2- generation and degranulation. Because these findings suggest that the agonists may have potential as antiinflammatory agents, several compounds were evaluated for effects on the exudative and cellular phases of carrageenan-induced pleural inflammation in rats. All of the agonists tested inhibited both parameters of the inflammatory response. Inhibition appeared to correlate better with binding to the A1 than to the A2 receptor and was reversible by a known adenosine receptor antagonist, 8-phenyltheophylline. In mechanistic studies, R-N-(1-methyl-2-phenylethyl)adenosine, a standard A1 selective agonist, reversed the drop in circulating neutrophil count that occurs after injection of carrageenan. These results suggest that the agonists may prevent cell emigration by inhibiting adhesion to the endothelium or diapedesis. In addition (R)-N-(1-methyl-2-phenylethyl)adenosine had weak inhibitory effects on superoxide production by FMLP-stimulated rat neutrophils. Control studies showed that the effects of the agonists were not the result of agonist-induced hypotension nor corticosterone production by the adrenal glands. These findings indicate that adenosine receptor agonists are effective new pharmacologic tools for the study of inflammatory processes.

In vitro effects of the antiallergy compound, CI-949, on interleukin-1 and 2 release, and on mitogen and alloantigen responsiveness

CI-949 (5-methoxy-3-(1-methylethoxy)-1-phenyl-N-1H-tetrazol-5-yl-1H -indole- 2-carboxamide, L-arginine salt), an antiallergy compound, was found to be a weak inhibitor of IL-1 release from LPS-stimulated murine peritoneal exudate cells and human peripheral blood leukocytes, with IC50S of 186.2 and 267.9 microM, respectively. CI-949 was also a poor inhibitor of release of IL-2 from Con A-stimulated rat splenocytes (37% inhibition at 100 microM). CI-949 did produce concentration-related inhibition of the response of human lymphocytes to PHA and Con A (IC50S = 44.7 and 21.5 microM, respectively) as well as in the mixed lymphocyte reaction (MLR) (IC50 = 16.8 microM). The clinical significance of these latter findings is unknown at present.

Preliminary report on 8-amino-9-(2-thienylmethyl)guanine (PD 119,229), a novel and potent purine nucleoside phosphorylase inhibitor

PD 119,229 [8-amino-9-(2-thienylmethyl)guanine] is a novel and potent inhibitor of human erythrocyte purine nucleoside phosphorylase (PNP) with a Ki of 0.067 microM. In a cell line assay using human MOLT-4 (T cell) and MGL-8 (B cell) lymphoblasts, PD 119,229 alone had no effect on the growth of either cell line at the highest concentration tested (100 microM). However, in the presence of a nontoxic concentration of 2'-deoxyguanosine (10 microM), the IC50 values of PD 119,229 for MOLT-4 and MGI-8 40-fold either cell line at the highest concentration tested (100 microM). However, in the presence of a nontoxic concentration of 2'-deoxyguanosine (10 microM), the IC50 values of PD 119,229 for MOLT-4 and MGI-8 were 0.9 and greater than 100 microM, respectively. The inhibition of growth of MOLT-4 was accompanied by a 40-fold increase in dGTP and a two-fold reduction in GTP, while no alteration in nucleotide profile was noted in MGL-8. Both the inhibition of growth of MOLT-4 and the accumulation of dGTP were substantially prevented by coaddition of 2'-deoxycytidine.

The topical anti-inflammatory effects of a topical preparation of meclofenamic acid on carrageenan-induced footpad swelling in mice

A topical preparation of meclofenamic acid (Meclomen) was tested for anti-inflammatory activity in a murine model of carrageenan footpad oedema. The preparation significantly inhibited swelling when applied to the carrageenan-injected paw. Maximum inhibition was observed 4-5 h after carrageenan injection. The topical effects could not be attributed to systemic absorption because the preparation was more inhibitory when applied topically to the carrageenan-injected paw than to a distant site or orally.

Synthesis of 8-amino-3-deazaguanine via imidazole precursors. Antitumor activity and inhibition of purine nucleoside phosphorylase

8-Amino-3-deazaguanine (15), an analogue of both 3-deazaguanine (1) and 8-aminoguanine (6), an antitumor agent and a purine nucleoside phosphorylase (PNP) inhibitor, respectively, was synthesized from the ammonolysis of an imidazole precursor, methyl 2-(benzoylamino)-5-(cyanomethyl)-1H-imidazole-4-carboxylate (13). The requisite imidazole, methyl 2-(benzoylamino)-4-(methoxycarbonyl)-1H-imidazole-5-acetate (11), was prepared from the monoheterocyclic rearrangement of dimethyl 3-[(5-phenyl-1,2,4-oxadiazol-3-yl)amino]-2-pentenedioate (10) by NaH/DMF. Ammonolysis and subsequent dehydration of 11 provided the penultimate imidazole intermediate 13. Its deprotected (NaOMe/100 degrees C) product, methyl 2-amino-5-(cyanomethyl)-1H-imidazole-4-carboxylate (14), was also converted to 15. 8-Amino-3-deazaguanine, as its methanesulfonic acid (mesylate 7), exhibited an inhibition constant (IC50) of 9.9 microM against isolated mammalian PNP. It was a very weak inhibitor of T and B cell growth and did not enhance 2'-deoxyguanosine toxicity in the same cells. 8-Amino-3-deazaguanine mesylate was not significantly active in L1210 cells in vitro or L1210 leukemic mice. Thus, the amino group introduced in the 8-position of 3-deazaguanine enhances its PNP activity but diminishes its antitumor activity.

Inhibitors of human purine nucleoside phosphorylase. Synthesis, purine nucleoside phosphorylase inhibition, and T-cell cytotoxicity of 2,5-diaminothiazolo[5,4-d]pyrimidin-7(6H)-one and 2,5-diaminothiazolo[4,5-d]pyrimidin-7(6H)-one. Two thio isosteres of 8-aminoguanine

8-Aminoguanine is a potent inhibitor of purine nucleoside phosphorylase (PNP) and also a substrate of PNP. Two thio isosteres of 8-aminoguanine, 2,5-diaminothiazolo[5,4-d]pyrimidin-7(6H)-one (2) and 2,4-diaminothiazolo[4,5-d]pyrimidin-7(6H)-one (3), which cannot be substrates of PNP, were synthesized and evaluated for their inhibitory activity against PNP. They were found to be weak inhibitors of PNP and to be noncytotoxic for MOLT-4 T-cells in culture.

Rat haptoglobin: method of quantitation and response to antiarthritic therapy in collagen arthritis

Concentrations of the acute phase reactant haptoglobin were quantitated in the serum of rats using a commercially available antihuman haptoglobin radial immunodiffusion kit. That this antiserum reacted with rat haptoglobin was shown through the techniques of Ouchterlony immunodiffusion and immunoelectrophoresis. Haptoglobin levels were increased seven days after immunization of rats with type II collagen plus incomplete Freund's adjuvant (ICFA) and peaked on day 14. However, even six weeks post-immunization the concentration of haptoglobin was elevated in arthritic rats. A significant correlation was observed between the concentration of serum haptoglobin and the severity of disease (arthritic index) in rats immunized six weeks previously with type II collagen plus ICFA. The effects of antiinflammatory and antirheumatic therapy on arthritic index and serum haptoglobin concentration were determined using a therapeutic dosing protocol. Under these conditions, the known antiarthritic effects of nonsteroidal antiinflammatory drugs, steroids and immunosuppressive agents in this model were confirmed. Of these agents, only the nonsteroidal drugs reduced serum haptoglobin; hydrocortisone, cyclophosphamide and azathioprine elevated haptoglobin. Aurothioglucose, auranofin, and chloroquine, members of the class of disease-modifying antirheumatic drugs, had a general tendency to exacerbate disease, but had minimal effect on serum haptoglobin. D-Penicillamine had little effect on arthritic index and haptoglobin. These results suggest that, while haptoglobin levels do correlate with the intensity of hindpaw swelling, measurement of haptoglobin may not be an accurate indicator of the underlying disease processes in the collagen arthritis model.

Effects of pentostatin (2'deoxycoformycin), an inhibitor of adenosine deaminase, on type II collagen-induced arthritis in rats

Pentostatin (2'-deoxycoformycin), a potent inhibitor of adenosine deaminase, was administered therapeutically to rats with type II collagen-induced arthritis and the effects on hindpaw swelling, serum haptoglobin concentration, and anticollagen antibody titer determined. Daily intraperitoneal administration of pentostatin at 10.0 or 1.0 mg/kg/day for three weeks produced significant enhancement of hind-paw swelling and elevation of serum haptoglobin. Continuous subcutaneous infusion of pentostatin at 1.0 or 0.1 mg/kg/day had the same effects. None of the dosing regimens had any effect on anticollagen antibody titer.

The role of neutrophils in type II collagen-induced arthritis in rats

Type II collagen-induced arthritis is a pathologic process mediated, in part, by humoral immune mechanisms. Because many antibody-mediated reactions are neutrophil-dependent, the role of this cell population was examined in collagen arthritis. In rats depleted of neutrophils with rabbit anti-rat neutrophil antiserum (ANS), swelling and inflammation associated with the arthritis response were maximally reduced by 65% (P less than 0.001). ANS treatment had no detectable effect on delayed hypersensitivity or antibody response to Type II collagen. Also, levels of peripheral blood monocytes, lymphocytes, and platelets were unaffected. Treatment with normal rabbit serum (NS) had no detectable effect on any of the inflammatory or immune parameters tested nor on circulating levels of monocytes, lymphocytes, or platelets. These results suggest that further study of the functions of neutrophils in rat collagen arthritis may be of help in our understanding of the role of this cell population in human arthritis.

Effects of antiarthritic compounds on type II collagen-induced arthritis in rats

The therapeutic effects of a variety of agents on established lesions of type II collagen arthritis in rats were tested. Drug activity was determined using an Arthritic Index, which consisted of a rank score ranging from 0 to 8 (0 to 4 in each hind paw) based on hind paw swelling and redness, and by measuring titers of antibody to type II collagen. Four of five non-steroidal antiinflammatory drugs (NSAIDs), phenylbutazone, benoxaprofen, indomethacin and isoxicam, reduced swelling. Of the NSAIDs, only acetylsalicylic acid was inactive. None of these drugs reduced levels of antibody to type II collagen as determined by an ELISA procedure. One of two immunosuppressive drugs, cyclophosphamide, and a steroid, hydrocortisone acetate, significantly inhibited hind paw inflammation. The other immunosuppressive, azathioprine, did not significantly reduce swelling. Also, cyclophosphamide lowered levels of antibody to type II collagen. Five antirheumatic agents, auranofin, levamisole, D-penicillamine, chloroquine and aurothioglucose, were tested and none inhibited the disease process. Of these five, only auranofin inhibited antibody titer to type II collagen. In conclusion, although rat type II collagen arthritis did not detect standard antirheumatic drugs, this model detected the activity of several standard NSAIDs, an immunosuppressive, and a steroid. In addition, the level of antibody to type II collagen was neither a selective nor sensitive indicator of the efficacy of standard antiarthritic agents.

Heterogeneity of lymphocyte subpopulations in severe combined immunodeficiency. Evidence against a stem cell defect

Surface markers typical of T and B lymphocytes were present on varying proportions of peripheral blood lymphocytes from three infants with severe combined immunodeficiency disease. Despite this, functions mediated by T and B cells were either absent or very minimal in all three, including cell-mediated responses in vivo; the in vitro proliferative response to mitogens, allogeneic cells, or antigens; effector cell function in lymphocyte-antibody lymphocytolytic interaction assays; and in vitro synthesis of IgG, IgA, and IgM. In contrast, mononuclear cells from one of the infants were tested and found capable of lysing both human and chicken antibody-coated erythrocyte targets normally. Co-cultivation experiments with unrelated normal control lymphocytes failed to demonstrate suppressor cell activity for immunoglobulin synthesis in these infants. Augmentations of immunoglobulin production from 310 to 560% over that expected on the basis of individual culture data were noted in co-cultures of one of the infants' cells with two different unrelated normal control cells. These findings suggest that that infant may have had a T helper cell defect or that his T cells were unable to produce soluble factors necessary for B cell differentiation. The finding of cells with differentiation markers characteristic of T and B lymphocytes in each of these patients, though in variable quantities, is further evidence for heterogeneity among patients with the clinical syndrome of severe combined immunodeficiency and argues against the concept that their immunodeficiency was due to a stem cell defect.

Correction of severe combined immunodeficiency by fetal liver cells

As an alternative to bone-marrow transplantation, two infants with severe combined immunodeficiency who had no histocompatible donors were given intraperitoneal infusions of fresh liver cells from fetuses of eight and nine to 10 weeks. Transient graft-versus-host disease began at 42 and 52 days, respectively. Both infants had rises in T cells and declines in B cells by three months. No functional immunologic improvement occurred in the first infant, who died of pulmonary disease 10 months later. Clinical and functional immunologic improvement occurred in the other, who is now 19 months after transplantation. Lymphocyte responses to phytohemagglutinin and pokeweed mitogen were noted by three months, to concanavalin A by five months, and to allogeneic cells by eight months. Delayed cutaneous responsiveness to candida developed and IgM became norma. IgA and IgG remained low. Chimerism was demonstrated by a donor marker chromosome in metaphases from recipient lymphocytes. Fetal liver cells therefore reversed the immunodeficiency.