Purine Nucleoside Phosphorylase Inhibitor Research Articles

Purine nucleoside phosphorylase inhibition ameliorates age-associated lower urinary tract dysfunctions.

In the aging population, lower urinary tract (LUT) dysfunction is common and often leads to storage and voiding difficulties classified into overlapping symptom syndromes. Despite prevalence and consequences of these syndromes, LUT disorders continue to be undertreated simply because there are few therapeutic options. LUT function and structure were assessed in aged (>25 months) male and female Fischer 344 rats randomized to oral treatment with a purine nucleoside phosphorylase (PNPase inhibitor) 8-aminoguanine (8-AG) or vehicle for 6 weeks. The bladders of aged rats exhibited multiple abnormalities: tactile insensitivity, vascular remodeling, reduced collagen-fiber tortuosity, increased bladder stiffness, abnormal smooth muscle morphology, swelling of mitochondria, and increases in urodamaging purine metabolites. Treatment of aged rats with 8-AG restored all evaluated histological, ultrastructural, and physiological abnormalities toward that of a younger state. 8-AG is an effective treatment that ameliorates key age-related structural and physiologic bladder abnormalities. Because PNPase inhibition blocks metabolism of inosine to hypoxanthine and guanosine to guanine, likely uroprotective effects of 8-AG are mediated by increased bladder levels of uroprotective inosine and guanosine and reductions in urodamaging hypoxanthine and xanthine. These findings demonstrate that 8-AG has translational potential for treating age-associated LUT dysfunctions and resultant syndromes in humans.

Purine Nucleoside Phosphorylase Inhibitors as Novel Immuno-Oncology Agent and Vaccine Adjuvant

Purine Nucleoside Phosphorylase (PNP) deficiency in humans causes lymphopenia and this provided the rationale for developing PNP inhibitors as immunosuppressive agents. However, carefulre-evaluation of clinical history of PNP deficient patients and clinical experience with PNP inhibitors together with new experimental data suggest inhibition of PNP may have immune activating effects through elevation of guanosine and activation of various toll-like receptors (TLRs). This paper proposes a mechanism of action for the immune activating effects of PNP inhibition.

Computer-aided rational design of acyclovir analogs to inhibit purine nucleoside phosphorylase

Purine nucleoside phosphorylase (PNP) is one of the major enzymes in the purine salvage pathway. It is responsible for the elevation of deoxyguanosine, and thus considered as the potent target in T-cell lymphoma. The present study examined acyclovir, reported as a low-affinity PNP inhibitor, for the rational design of new acyclovir derivatives by incorporating halogens, hydroxyl, and bulky amino groups. The molecular actions of designed derivatives were investigated by employing density functional theory, molecular docking, and binding energy calculations. The results revealed that the newly designed compounds were highly stable and showed more affinity to PNP than the parent compound, acyclovir. The quantum mechanics and molecular docking studies suggested that modification of side chains with bulky polar groups provided better binding affinities than substitutions with halogens. The resultant derivatives have strong polar interactions like His257 and Tyr88. Furthermore, the designed derivatives were within the ideal range of ADMET (absorption, distribution, metabolism, elimination, and toxicity) analysis. Considering that, these findings recommend further validation of designed acyclovir derivatives in wet lab confirmatory analysis with the emphasis on the further improvements in the treatment of T-cell-mediated diseases.

Propolis Exerts an Anti-Inflammatory Effect on PMA-Differentiated THP-1 Cells via Inhibition of Purine Nucleoside Phosphorylase.

Previous research has shown that propolis has immunomodulatory activity. Propolis extracts from different geographic origins were assessed for their anti-inflammatory activities by investigating their ability to alter the production of tumour necrosis factor-α (TNF-α) and the cytokines interleukin-1β (IL-1β), IL-6 and IL-10 in THP-1-derived macrophage cells co-stimulated with lipopolysaccharide (LPS). All the propolis extracts suppressed the TNF-α and IL-6 LPS-stimulated levels. Similar suppression effects were detected for IL-1β, but the release of this cytokine was synergised by propolis samples from Ghana and Indonesia when compared with LPS. Overall, the Cameroonian propolis extract (P-C) was the most active and this was evaluated for its effects on the metabolic profile of unstimulated macrophages or macrophages activated by LPS. The levels of 81 polar metabolites were identified by liquid chromatography (LC) coupled with mass spectrometry (MS) on a ZIC-pHILIC column. LPS altered the energy, amino acid and nucleotide metabolism in THP-1 cells, and interpretation of the metabolic pathways showed that P-C reversed some of the effects of LPS. Overall, the results showed that propolis extracts exert an anti-inflammatory effect by inhibition of pro-inflammatory cytokines and by metabolic reprogramming of LPS activity in macrophage cells, suggesting an immunomodulatory effect.

Fused Heterocyclic Systems with an s-Triazine Ring. 34. Development of a Practical Approach for the Synthesis of 5-Aza-isoguanines.

Purine isosteres present excellent opportunities in drug design and development. Using isosteres of natural purines as scaffolds for the construction of new therapeutic agents has been a valid strategy of medicinal chemistry. Inspired by the similarity to isoguanine, we attempted to develop a practical method for the preparation of 5-aza-isoguanines. Several synthetic approaches were explored to establish a robust general protocol for the preparation of these compounds. The significant difference in the reactivity of the C-5 and C-7 electrophilic centers of 1,2,4-triazolo[1,5-a][1,3,5]triazines (5-azapurines) towards nucleophiles was demonstrated. The most practical and general method for the preparation of 5-aza-isoguanines involved a regioselective reaction of ethoxycarbonyl isothiocyanate with a 5-aminotriazole. The intramolecular ring closure of the resulted product followed by the S-methylation afforded 7-methylthio-2-phenyl-1,2,4-triazolo[1,5-a][1,3,5]triazin-5-one, which could be effectively aminated with various amines. The resulted 5-aza-isoguanines resemble a known purine nucleoside phosphorylase inhibitor and could be interesting for further investigations as potential anticancer agents.

Inhibiting PNP for the therapy of hyperuricemia in Lesch-Nyhan disease: Preliminary in vitro studies with analogues of immucillin-G.

Lesch-Nyhan disease (LND) is a rare X-linked genetic disorder, with complete hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency, uric acid (UA), hypoxanthine and xanthine accumulation, and a devastating neurologic syndrome. UA excess, causing renal failure, is commonly decreased by xanthine oxidoreductase (XOR) inhibitors, such as allopurinol, yielding a xanthine and hypoxanthine increase. Xanthine accumulation may result in renal stones, while hypoxanthine excess seems involved in the neurological disorder. Inhibition of purine nucleoside phosphorylase (PNP) represents a different strategy for lowering urate. PNP catalyzes the cleavage of purine ribo- and d-ribo-nucleosides into ribose/deoxyribose phosphate and free bases, starting catabolism to uric acid. Clinical trials demonstrated that PNP inhibitors, initially developed as anticancer drugs, lowered UA in some gouty patients, in association or not with allopurinol. The present study tested the reliability of an analogue of immucillin-G (C1a), a PNP inhibitor, as a therapy for urate, hypoxanthine, and xanthine excess in LND patients by blocking hypoxanthine production upstream. The therapeutic aim is to limit the administration of XOR inhibitors to LND patients by supplying the PNP inhibitor in low doses, avoiding d-nucleoside toxicity. We report studies conducted in primary cultures of skin fibroblasts from controls and LND patients grown in the presence of the PNP inhibitor. Cell viability, oxypurine release in culture medium, and endocellular nucleotide pattern have been monitored in different growth conditions (inhibitor concentration, time, added inosine). Our results demonstrate effective PNP inhibition by low inhibitor concentration, with reduced hypoxanthine release, and no appreciable toxicity in control or patient cells, suggesting a new therapeutic strategy for LND hyperuricemia.

8-Aminoguanine Induces Diuresis, Natriuresis, and Glucosuria by Inhibiting Purine Nucleoside Phosphorylase and Reduces Potassium Excretion by Inhibiting Rac1.

Background8‐Aminoguanosine and 8‐aminoguanine are K+‐sparing natriuretics that increase glucose excretion. Most effects of 8‐aminoguanosine are due to its metabolism to 8‐aminoguanine. However, the mechanism by which 8‐aminoguanine affects renal function is unknown and is the focus of this investigation.Methods and ResultsBecause 8‐aminoguanine has structural similarities with inhibitors of the epithelial sodium channel (ENaC), Na+/H+ exchangers, and adenosine A1 receptors, we examined the effects of 8‐aminoguanine on ENaC activity in mouse collecting duct cells, on intracellular pH of human proximal tubular epithelial cells, on responses to a selective A1‐receptor agonist in vivo, and on renal excretory function in A1‐receptor knockout rats. These experiments showed that 8‐aminoguanine did not block ENaC, Na+/H+ exchangers, or A1 receptors. Because Rac1 enhances activity of mineralocorticoid receptors and some guanosine analogues inhibit Rac1, we examined the effects of 8‐aminoguanine on Rac1 activity in mouse collecting duct cells. Rac1 activity was significantly inhibited by 8‐aminoguanine. Because in vitro 8‐aminoguanine is a purine nucleoside phosphorylase (PNPase) inhibitor, we examined the effects of a natriuretic dose of 8‐aminoguanine on urinary excretion of PNPase substrates and products. 8‐Aminoguanine increased and decreased, respectively, urinary excretion of PNPase substrates and products. Next we compared in rats the renal effects of intravenous doses of 9‐deazaguanine (PNPase inhibitor) versus 8‐aminoguanine. 8‐Aminoguanine and 9‐deazaguanine induced similar increases in urinary Na+ and glucose excretion, yet only 8‐aminoguanine reduced K+ excretion. Nsc23766 (Rac1 inhibitor) mimicked the effects of 8‐aminoguanine on K+ excretion.Conclusions8‐Aminoguanine increases Na+ and glucose excretion by blocking PNPase and decreases K+ excretion by inhibiting Rac1.

Abstract 067: Mechanism of Action of 8-Aminoguanine on Renal Excretory Function

The endogenous purines 8-aminoguanosine and 8-aminoguanine (8-AG) are K + -sparing natriuretics that increase glucose excretion and attenuate salt-induced hypertension. Most effects of 8-aminoguanosine are not direct, but require conversion in the systemic circulation to 8-AG (i.e., 8-aminoguanosine is a prodrug/prohormone). However, the mechanism of action by which 8-AG affects renal excretory function is unknown and is the subject of this investigation. Because 8-AG has structural similarities with inhibitors of epithelial Na + channels (ENaC), Na + /H + exchangers (NHE), and adenosine A 1 receptors, we examined the effects of 8-AG on amiloride-sensitive ENaC activity in mouse collecting duct cells, on intracellular pH of human renal proximal tubule epithelial cells, and on in vivo (in rats) pharmacological responses to 2-chloro-N 6 -cyclopentyladenosine (A 1 -receptor agonist). 8-AG did not block ENaC, NHE, or A 1 receptors. Because Rac1 enhances activity of mineralocorticoid receptors and some guanosine analogues inhibit Rac1, we examined the effects of 8-AG on Rac1 activity in mouse collecting duct cells. Rac1 activity was significantly ( P =0.024) inhibited by 8-AG (30 μM; from 2.5 ± 0.7 to 1.7 ± 0.7 arbitrary units). Because 8-AG is an inhibitor of purine nucleoside phosphorylase (PNPase; metabolizes inosine to hypoxanthine and guanosine to guanine), we compared the renal effects (in rats) of approximately equipotent intravenous doses of 8-AG (33.5 μmol/kg) vs. 9-deazaguanine (9-DG; 67 μmol/kg; PNPase inhibitor). 8-AG and 9-DG induced similar increases in urinary Na + (μmol/30 min; 8-AG, from 4.4 ± 2.0 to 38 ± 17; 9-DG, from 5.6 ± 3.3 to 34 ± 8.6) and glucose (μg/30 min; 8-AG, from 31 ± 17 to 225 ± 77; 9-DG, from 6.9 ± 3.9 to 144 ± 81) excretion. Intravenous 8-AG increased urinary excretion of guanosine and inosine (PNPase substrates), yet decreased excretion of guanine and hypoxanthine (PNPase products). 8-AG reduced K + excretion (μmol/30 min; 8-AG, from 29 ± 6.6 to 5.4 ± 1.7) whereas 9-DG did not. However, the Rac1 inhibitor Nsc23766 (9.4 μmol/kg) mimicked the effects of 8-AG on K + excretion (μmol/30 min; from 40 ± 7.1 to 18 ± 6.5). Conclusion: Likely 8-AG increases Na + and glucose excretion by blocking PNPase and decreases K + excretion by inhibiting Rac1.

Multicenter phase 1/2 study of forodesine in patients with relapsed peripheral T cell lymphoma

Peripheral T cell lymphomas are an aggressive group of non-Hodgkin lymphomas with poor outcomes for most subtypes and no accepted standard of care for relapsed patients. This study evaluated the efficacy and safety of forodesine, a novel purine nucleoside phosphorylase inhibitor, in patients with relapsed peripheral T cell lymphomas. Patients with histologically confirmed disease, progression after ≥ 1 prior treatment, and an objective response to last treatment received oral forodesine 300 mg twice-daily. The primary endpoint was objective response rate (ORR). Secondary endpoints included duration of response, progression-free survival (PFS), overall survival (OS), and safety. Forty-eight patients (median age, 69.5 years; median of 2 prior treatments) received forodesine. In phase 1 (n = 3 evaluable), no dose-limiting toxicity was observed during the first 28 days of forodesine treatment. In phase 2 (n = 41 evaluable), the ORR for the primary and final analyses was 22% (90% CI 12–35%) and 25% (90% CI 14–38%), respectively, including four complete responses (10%). Median PFS and OS were 1.9 and 15.6 months, respectively. The most common grade 3/4 adverse events were lymphopenia (96%), leukopenia (42%), and neutropenia (35%). Dose reduction and discontinuation due to adverse events were uncommon. Secondary B cell lymphoma developed in five patients, of whom four were positive for Epstein-Barr virus. In conclusion, forodesine has single-agent activity within the range of approved therapies in relapsed peripheral T cell lymphomas, with a manageable safety profile, and may represent a viable treatment option for this difficult-to-treat population.

Hydroxyl-related differences for three dietary flavonoids as inhibitors of human purine nucleoside phosphorylase

In this work, the hydroxyl-related differences of binding properties and inhibitory activities of dietary flavonoids, namely chrysin, baicalein and apigenin against purine nucleoside phosphorylase (PNP) were investigated. It was found that the hydroxylation on position C4′ of chrysin (→apigenin) mildly decreased the binding affinities for PNP, whereas on the position C6 of chrysin (→baicalein) significantly increased binding affinities. Comparatively, the hydroxylation on position C4′ and C6 greatly improved their PNP inhibitory effects. The IC50 values of apigenin and baicalein were 6.09 × 10−5 M and 8.94 × 10−5 M, respectively, which is significantly lower than that of chrysin (2.13 × 10−4 M). Results from molecular modeling revealed that there are two binding sites, i.e. active site (major) and tryptophan site (minor) on PNP, and the binding of these flavonoids might induce a serious conformational destabilization of PNP as a result of altering the micro-environment and morphology by flavonoids.

Forodesine in the treatment of relapsed/refractory peripheral T-cell lymphoma: an evidence-based review.

T-cell lymphoma is a rare hematologic malignancy with an incidence rate between 10% and 20% of that of non-Hodgkin lymphomas. Patients with peripheral T-cell lymphoma (PTCL) generally have a poor prognosis when treated with cyclophosphamide, doxorubicin, vincristine, and prednisolone (CHOP)/CHOP-like chemotherapy; once relapse occurs, it is mostly regarded as an incurable disease. To overcome the chemorefractoriness of PTCL, several novel agents have been developed. Since the first approval of pralatrexate, a dihydrofolate reductase inhibitor, for relapsed/refractory PTCL by the US Food and Drug Administration, several new agents, such as romidepsin (histone deacetylase inhibitor), brentuximab vedotin (antibody–drug conjugate targeting CD30), chidamide (histone deacetylase inhibitor), and mogamulizumab (anti-CC chemokine receptor 4 monoclonal antibody), have been approved as a therapeutic option for relapsed/refractory PTCL in several countries, including the US, Europe, China, and Japan. Forodesine is a novel, potent purine nucleoside phosphorylase inhibitor that is effective against T-cell malignancies. Although the clinical development of forodesine was discontinued in the US and Europe, a multicenter Phase I/II study of oral forodesine for relapsed PTCL was recently completed in Japan. The overall response rate was 24% (10 of 41 patients), which included four patients with complete response. In general, the toxicity of forodesine is manageable. As the study met the primary end point, forodesine was approved for the treatment of relapsed/refractory PTCL in Japan in March 2017, which was the first approval of forodesine in the world. As forodesine is an oral formulation, it is more convenient than other novel intravenous agents approved for PTCL. However, it is necessary to appropriately manage opportunistic infections and secondary lymphomas possibly associated with long-lasting lymphocytopenia caused by forodesine. In this manuscript, we have summarized the currently available evidence for forodesine and discussed the clinical implications for PTCL treatment.

Genetic resistance to purine nucleoside phosphorylase inhibition in Plasmodium falciparum

Plasmodium falciparum causes the most lethal form of human malaria and is a global health concern. The parasite responds to antimalarial therapies by developing drug resistance. The continuous development of new antimalarials with novel mechanisms of action is a priority for drug combination therapies. The use of transition-state analog inhibitors to block essential steps in purine salvage has been proposed as a new antimalarial approach. Mutations that reduce transition-state analog binding are also expected to reduce the essential catalytic function of the target. We have previously reported that inhibition of host and P. falciparum purine nucleoside phosphorylase (PfPNP) by DADMe-Immucillin-G (DADMe-ImmG) causes purine starvation and parasite death in vitro and in primate infection models. P. falciparum cultured under incremental DADMe-ImmG drug pressure initially exhibited increased PfPNP gene copy number and protein expression. At increased drug pressure, additional PfPNP gene copies appeared with point mutations at catalytic site residues involved in drug binding. Mutant PfPNPs from resistant clones demonstrated reduced affinity for DADMe-ImmG, but also reduced catalytic efficiency. The catalytic defects were partially overcome by gene amplification in the region expressing PfPNP. Crystal structures of native and mutated PfPNPs demonstrate altered catalytic site contacts to DADMe-ImmG. Both point mutations and gene amplification are required to overcome purine starvation induced by DADMe-ImmG. Resistance developed slowly, over 136 generations (2136 clonal selection). Transition-state analog inhibitors against PfPNP are slow to induce resistance and may have promise in malaria therapy.

Immucillins in Infectious Diseases.

The Immucillins are chemically stable analogues that mimic the ribocation and leaving-group features of N-ribosyltransferase transition states. Infectious disease agents often rely on ribosyltransferase chemistry in pathways involving precursor synthesis for nucleic acids, salvage of nucleic acid precursors, or synthetic pathways with nucleoside intermediates. Here, we review three infectious agents and the use of the Immucillins to taget enzymes essential to the parasites. First, DADMe-Immucillin-G is a purine nucleoside phosphorylase (PNP) inhibitor that blocks purine salvage and shows clinical potential for treatment for the malaria parasite Plasmodium falciparum, a purine auxotroph requiring hypoxanthine for purine nucleotide synthesis. Inhibition of the PNPs in the host and in parasite cells leads to apurinic starvation and death. Second, Helicobacter pylori, a causative agent of human ulcers, synthesizes menaquinone, an essential electron transfer agent, in a pathway requiring aminofutalosine nucleoside hydrolysis. Inhibitors of the H.pylori methylthioadenosine nucleosidase (MTAN) are powerful antibiotics for this organism. Synthesis of menaquinone by the aminofutalosine pathway does not occur in most bacteria populating the human gut microbiome. Thus, MTAN inhibitors provide high-specificity antibiotics for H.pylori and are not expected to disrupt the normal gut bacterial flora. Third, Immucillin-A was designed as a transition state analogue of the atypical PNP from Trichomonas vaginalis. In antiviral screens, Immucillin-A was shown to act as a prodrug. It is active against filoviruses and flaviviruses. In virus-infected cells, Immucillin-A is converted to the triphosphate, is incorporated into the viral transcript, and functions as an atypical chain-terminator for RNA-dependent RNA polymerases. Immucillin-A has entered clinical trials for use as an antiviral. We also summarize other Immucillins that have been characterized in successful clinical trials for T-cell lymphoma and gout. The human trials support the potential development of the Immucillins in infectious diseases.

1,N6-ethenoadenine and other Fluorescent Nucleobase Analogues as Substrates for Purine-Nucleoside Phosphorylases: Spectroscopic and Kinetic Studies.

Purine-nucleoside phosphorylase (PNP) is known as a tool for the synthesis of various nucleosides and nucleoside analogues. Mechanism, properties, molecular diversity and inhibitors of PNP, particularly these of pharmacological significance, are briefly characterized. UV and fluorescence spectroscopy was used for kinetic experiments, and HPLC chromatography for product analyses. Applications of various forms of PNP to synthesis of selected fluorescent nucleosides, particularly ribosides of 1,N6-ethenoadenine and various 8-azapurines (triazolo[4,5-d]pyrimidines) are reviewed. Different specificity of various PNP forms is described towards nucleobase and analogue substrates as well as variable ribosylation sites observed in some reactions, with a possibility to further modify these features via the site-directed mutagenesis. Present and future applications of the fluorescent or fluorogenic ribosides are discussed, with particular emphasis on biochemical and clinical analyses with improved sensitivity.

Intracellular rebinding of transition-state analogues provides extended in vivo inhibition lifetimes on human purine nucleoside phosphorylase

Purine nucleoside phosphorylase (PNP) is part of the human purine salvage pathway. Its deficiency triggers apoptosis of activated T-cells, making it a target for T-cell proliferative disorders. Transition-state analogues of PNP bind with picomolar (pm) dissociation constants. Tight-binding PNP inhibitors show exceptionally long lifetimes on the target enzyme. We solve the mechanism of the target residence time by comparing functional off-rates in vitro and in vivo We report in vitro PNP-inhibitor dissociation rates (t½) from 3 to 31 min for seven Immucillins with dissociation constants of 115 to 6 pm Treatment of human erythrocytes with DADMe-Immucillin-H (DADMe-ImmH, 22 pm) causes complete inhibition of PNP. Loss of [14C]DADMe-ImmH from erythrocytes during multiple washes is slow and biphasic, resulting from inhibitor release and rebinding to PNP catalytic sites. The slow phase gave a t½ of 84 h. Loss of [14C]DADMe-ImmH from erythrocytes in the presence of excess unlabeled DADMe-ImmH increased to a t½ of 1.6 h by preventing rebinding. Thus, in human erythrocytes, rebinding of DADMe-ImmH is 50-fold more likely than diffusional loss of the inhibitor from the erythrocyte. Humans treated with a single oral dose of DADMe-ImmH in phase 1 clinical trials exhibit regain of PNP activity with a t½ of 59 days, corresponding to the erythropoiesis rate in humans. Thus, the PNP catalytic site recapture of DADMe-ImmH is highly favored in vivo We conclude that transition-state analogues with picomolar dissociation constants exhibit long lifetimes on their targets in vivo because the probability of the target enzyme recapturing inhibitor molecules is greater than diffusional loss to the extracellular space.

Identification of a novel putative inhibitor of the Plasmodium falciparum purine nucleoside phosphorylase: exploring the purine salvage pathway to design new antimalarial drugs.

Malaria, a tropical parasitic disease caused by Plasmodium spp., continues to place a heavy social burden, with almost 200 million cases and more than 580,000 deaths per year. Plasmodium falciparum purine nucleoside phosphorylase (PfPNP) can be targeted for antimalarial drug design since its inhibition kills malaria parasites both in vitro and in vivo. Although the currently known inhibitors of PfPNP, immucillins, are orally available and of low toxicity to animals and humans, to the best of our knowledge, none of these compounds has entered clinical trials for the treatment of malaria. Using a pharmacophore-based virtual screening coupled to a consensual molecular docking approach, we identified 59 potential PfPNP inhibitors that are predicted to be orally absorbed in a Caco-2 cell model. Although most of these compounds are predicted to have high plasma protein binding levels, poor water solubility (except for compound 25) and CYP3A4 metabolic stability (except for 4, 7 and 8), four structures (4, 7, 8 and 25) remain as potential leads because of their plausible interaction with a specific hydrophobic pocket of PfPNP, which would confer them higher selectivity for PfPNP over human PNP. Additionally, both predicted Gibbs free energies for binding and molecular dynamics suggest that compound 4 may form a more stable complex with PfPNP than 5[Formula: see text]-methylthio-immucillin-H, a potent and selective inhibitor of PfPNP.

In Vitro Immunomodulatory Activity of a Transition-State Analog Inhibitor of Human Purine Nucleoside Phosphorylase in Cutaneous Leishmaniasis.

Cutaneous leishmaniasis (CL) is the most common clinical form of American tegumentary leishmaniasis caused by Leishmania (Viannia) braziliensis. CL is associated with a strong Th1 immune response. This exacerbated inflammatory response is correlated with severity of disease and delays the healing time of the ulcer. The fourth-generation immucillin derivative (DI4G), a potent inhibitor of purine nucleoside phosphorylase, has been proposed as a promising agent in the treatment of diseases associated with T cell activation. Herein, we evaluated the in vitro immunomodulatory activity of DI4G in cells of patients presenting with CL. Peripheral blood mononuclear cells (PBMC) from CL patients were stimulated with soluble leishmania antigen (SLA), in the presence or absence of DI4G, and IFN-γ, TNF, CXCL9, and CXCL10 levels were determined by ELISA. Lymphocyte proliferation in the presence or absence of DI4G was also evaluated, using flow cytometry. DI4G was able to decrease (p < 0.05) IFN-γ production but did not change the TNF, CXCL9, and CXCL10 levels. DI4G decreased (p < 0.05) the lymphoproliferative response mediated by CD8+ T cells, but not that by CD4+ T cells. DI4G is able to attenuate the exaggerated immune response in CL, exhibiting immunomodulatory activity in IFN-γ production and in CD8+ T cell proliferation.

Chemoenzymatic Synthesis of Modified 2′-Deoxy-2′-fluoro-β-d-arabinofuranosyl Benzimidazoles and Evaluation of Their Activity Against Herpes Simplex Virus Type 1

1-(2′-Deoxy-2′-fluoro-β- d -arabinofuranosyl)benzimidazoles containing 4,6-difluoro-, 4,5,6-trifluoro-, 5-fluoro-6-methoxy-, and 5-methoxy-4,6-difluorobenzimidazole fragments were synthesized by using purine nucleoside phosphorylase-catalyzed chemoenzymatic approach. As expected, enzymatic synthesis of nucleosides proceeds in lower yields of target compounds in comparison with the synthesis of ribo- and 2′-deoxyribobenzimidazoles (40–55% vs 60–90%). The compounds obtained were tested against the herpes simplex virus type 1, by using the Vero E6 cells. 5-Methoxy-4,6-difluoro-1-β- d -(2′-deoxy-2′-fluoroarabinofuranosyl)benzimidazole did not show any antiviral activity, when used in nontoxic concentration. All other nucleosides proved to exhibit a selective antiherpes activity. In contrast, it was shown that benzimidazole-β- d -arabinofuranosides of both di- and trisubstituted derivatives, having substituents in positions 4–6 of the benzene ring, as well as unsubstituted compounds, cannot be synthesized by enzymatic transglycosylation. 1-(β- d -Arabinofuranosyl)benzimidazole was obtained through glycosylation of N -trimethylsilylbenzimidazole with 1-chloro-2,3,5- O -methoxymethyl- d -arabinose. The behavior of this compound, as inhibitor of purine nucleoside phosphorylase (PNP) E. сoli , was investigated . 1-(β- d -Arabinofuranosyl)benzimidazole was found to belong to a mixed type of inhibitors of PNP. This fact explains why all attempts to perform enzymatic arabinosylation of 4,6-di-, 5,6-di-, and 4,5,6-trisubstituted benzimidazoles failed.

Phase 1/2 study of forodesine in patients with relapsed peripheral t-cell lymphoma (PTCL).

7542Background: Forodesine, a potent purine nucleoside phosphorylase inhibitor, induces apoptosis mainly in T cells. Forodesine at relatively low dose was feasible but the response rate was not suf...

Treatment of hyperuricemia in gout: current therapeutic options, latest developments and clinical implications.

Despite being the most common type of inflammatory arthritis, gout is often poorly managed. Except for febuxostat and pegloticase, research in new therapeutic agents for the management of hyperuricemia in gout remained insufficient for several decades. With emerging evidence of possible roles of hyperuricemia in cardiometabolic comorbidities, as well as more convincing evidence regarding poor outcomes (e.g. disability, recurrent hospital admissions) in patients with uncontrolled gout, several agents are current under development. Increasing knowledge regarding renal urate transporters has resulted in the development of new generation uricosurics such as lesinurad and arhalofenate. This review aims at discussing current therapeutic strategies for gout, as well as their limitations and the possible role of emerging agents in the chronic management of hyperuricemia in gout. Drugs in phases I and II of development will be discussed, along with new agents and therapeutic classes, such as purine nucleoside phosphorylase inhibitors and dual-action drugs. These new developments are encouraging, and will hopefully contribute to a more adequate management of hyperuricemia in gout.