Design, synthesis and biological evaluation of suramin-derived dual antagonists of the proinflammatory G protein-coupled receptors P2Y2 and GPR17.

Dual- or multi-target drugs are particularly promising for the treatment of complex diseases such as (neuro)inflammatory disorders. In the present study, we identified dual antagonists for two related pro-inflammatory G protein-coupled receptors (GPCRs), the purinergic receptor P2Y2 receptor, and the orphan receptor GPR17. Based on the lead compound suramin small molecules were designed, synthesized, and modified, including benzenesulfonate, benzenesulfonamide, dibenzamide and diphenylurea derivatives. Structure-activity relationship studies identified 3-nitrophenyl 4-benzamidobenzenesulfonic acid derivatives as dual P2Y2R/GPR17 antagonists. In particular, 3-nitrophenyl 4-(4-chlorobenzamido)benzenesulfonate (14l, IC50 3.01 µM at P2Y2R, and 3.37  µM at GPR17) and 3-nitrophenyl-4-(2-chlorobenzamido)benzenesulfonate (14m, IC50 3.17 µM at P2Y2R, and 1.67 µM at GPR17) exhibited dual antagonistic activity. Compound 14l was shown to act as an allosteric antagonist at both receptors. In addition, GPR17-selective antagonists were identified including 3-nitrophenyl 4-benzamidobenzenesulfonate (14a, IC50 3.20 µM) and 3-nitrophenyl 4-(3-(trifluoromethyl)benzamido)benzenesulfonate (14f, IC50 3.88 µM). The developed antagonists were selective versus other closely related P2Y receptors. They were found to possess high chemical and metabolic stability in human liver microsomes and therefore present good starting points for developing potent multi-target drugs with potential applications in inflammatory diseases.

Bis(benzofuran-thiazolidinone)s and bis(benzofuran-thiazinanone)s as inhibiting agents for chikungunya virus.

There are currently still no approved antiviral drugs to treat or prevent chikungunya virus (CHIKV) infections despite the fact that this arbovirus continues to cause outbreaks in Africa, Asia, and South- and Central-America. Thus 20 new conjugated compounds in the families of bis(benzofuran-1,3-thiazolidin-4-one)s and bis(benzofuran-1,3-thiazinan-4-one)s were designed based on the structural features of suramin. These new compounds were synthesized by chemical methods and their structures were confirmed spectroscopically. In CPE reduction assays, six of these new bis-conjugates inhibited CHIKV replication in Vero E6 cells with EC50 in the range of 1.9-2.7 µM and selectivity index values of ∼75 or higher. These results and compounds provide a starting point for further optimization, design, and synthesis of new antiviral agents for this (re)emerging disease.

A small-molecule screen identifies the antitrypanosomal agent suramin and analogues NF023 and NF449 as inhibitors of STAT5a/b.

The transcription factor STAT5a is a potential target for tumor therapy. We present a fluorescence polarization-based, high-throughput screen of chemical libraries containing natural products and known bioactive molecules, for the identification of small-molecule inhibitors of the STAT5a SH2 domain. This screen identified suramin, a drug used to treat African trypanosomiasis, and its analogues NF023 and NF449 as inhibitors of the SH2 domains of STAT5a/b. Our data extend the known in vitro targets of suramin and analogues to include members of the STAT protein family.

A Continuous, Fluorogenic Sirtuin 2 Deacylase Assay: Substrate Screening and Inhibitor Evaluation.

Sirtuins are important regulators of lysine acylation, which is implicated in cellular metabolism and transcriptional control. This makes the sirtuin class of enzymes interesting targets for development of small molecule probes with pharmaceutical potential. To achieve detailed profiling and kinetic insight regarding sirtuin inhibitors, it is important to have access to efficient assays. In this work, we report readily synthesized fluorogenic substrates enabling enzyme-economical evaluation of SIRT2 inhibitors in a continuous assay format as well as evaluation of the properties of SIRT2 as a long chain deacylase enzyme. Novel enzymatic activities of SIRT2 were thus established in vitro, which warrant further investigation, and two known inhibitors, suramin and SirReal2, were profiled against substrates containing ε-N-acyllysine modifications of varying length.

Structural bases of norovirus RNA dependent RNA polymerase inhibition by novel suramin-related compounds.

Noroviruses (NV) are +ssRNA viruses responsible for severe gastroenteritis; no effective vaccines/antivirals are currently available. We previously identified Suramin (9) as a potent inhibitor of NV-RNA dependent RNA polymerase (NV-RdRp). Despite significant in vitro activities versus several pharmacological targets, Suramin clinical use is hampered by pharmacokinetics/toxicity problems. To improve Suramin access to NV-RdRp in vivo, a Suramin-derivative, 8, devoid of two sulphonate groups, was synthesized, achieving significant anti-human-NV-RdRp activity (IC50 = 28 nM); the compound inhibits also murine NV (mNV) RdRp. The synthesis process led to the isolation/characterization of lower molecular weight intermediates (3-7) hosting only one sulphonate head. The crystal structures of both hNV/mNV-RdRps in complex with 6, were analyzed, providing new knowledge on the interactions that a small fragment can establish with NV-RdRps, and establishing a platform for structure-guided optimization of potency, selectivity and drugability.

Synthesis and structure-activity relationships of suramin-derived P2Y11 receptor antagonists with nanomolar potency.

Selective and potent P2Y(11) receptor antagonists have yet to be developed, thus impeding an evaluation of this G protein-coupled receptor mainly expressed on immune cells. Taking suramin with moderate inhibitory potency as a template, 18 ureas with variations of the methyl groups of suramin and their precursors were functionally tested at P2Y(11), P2Y(1), and P2Y(2) receptors. Fluorine substitution of the methyl groups of suramin led to the first nanomolar P2Y(11) antagonist (8f, NF157, pK(i): 7.35). For selectivity, 8f was also tested at various P2X receptors. 8f displayed selectivity for P2Y(11) over P2Y(1) (>650-fold), P2Y(2) (>650-fold), P2X(2) (3-fold), P2X(3) (8-fold), P2X(4) (>22-fold), and P2X(7) (>67-fold) but no selectivity over P2X(1). QSAR studies confirm that residues with favored resonance and size parameters in the aromatic linker region can indeed lead to an increased potency as is the case for 8f. A symmetric structure linking two anionic clusters seems to be required for bioactivity. 8f may be helpful for studies evaluating the physiological role of P2Y(11) receptors.

Suramin analogues with a 2-phenylbenzimidazole moiety as partial structure; potential anti HIV- and angiostatic drugs, 2: Sulfanilic acid-, benzenedisulfonic acid-, and naphthalenetrisulfonic acid analogues.

The synthesis of suramin analogues bearing a 2-phenyl-benzimidazole moiety is described. Aminoarene sulfonic acids 2a-e are acylated with 3,4-dinitrobenzoyl chloride 3 yielding the amides 4a-e which are hydrogenated to the corresponding diamines 5a-e. These are treated with 3-nitrobenzaldehyde, yielding the azomethines 7a-e and their isomers 8a-e and 9a-e. Key step in the synthesis of the target compounds 12a-e is the oxidation of the azomethines with oxygen to the benzimidazoles 10a-e. These are hydrogenated to the amines 11a-e reacting with phosgene to yield the symmetric ureas 12a-e. Results of the anti-HIV, cytostatic, and antiangiogenic screening are presented.

Inhibition of human immunodeficiency virus type I reverse transcriptase by suramin-related compounds.

Ninety analogues of suramin have been examined for their ability to inhibit the exogenous reverse transcriptase (RT) of human immunodeficiency virus type I (HIV-I). Of these compounds, 57 inhibited the poly(rC).oligo(dG)-dependent RT activity. Three classes of dose-response curves could be discriminated. Allocation of a compound to one class did not correspond with obvious structural features. Twenty-four substances were superior to suramin in our RT inhibition assay. The RT-inhibitory activity of these compounds did not correlate with their effect against filariae or trypanosomes. Preliminary antiviral evaluation in susceptible human T cells inoculated with HIV-I demonstrated in vitro therapeutic efficacy for some compounds with lower drug-related cellular toxicity than suramin. Certain structural features relevant for the RT-inhibitory effect of these compounds were recognized. Predictions are made for the design of more effective RT inhibitors. Such compounds will help to understand the molecular mechanism of reverse transcription and might be useful in the therapy of retroviral infections.