Andrew Dunstan

Bradyzide, a potent non-peptide B2 bradykinin receptor antagonist with long-lasting oral activity in animal models of inflammatory hyperalgesia

Bradyzide is from a novel class of rodent‐selective non‐peptide B2 bradykinin antagonists (1‐(2‐Nitrophenyl)thiosemicarbazides). Bradyzide has high affinity for the rodent B2 receptor, displacing [3H]‐bradykinin binding in NG108‐15 cells and in Cos‐7 cells expressing the rat receptor with KI values of 0.51±0.18 nM (n=3) and 0.89±0.27 nM (n=3), respectively. Bradyzide is a competitive antagonist, inhibiting B2 receptor‐induced 45Ca efflux from NG108‐15 cells with a pKB of 8.0±0.16 (n=5) and a Schild slope of 1.05. In the rat spinal cord and tail preparation, bradyzide inhibits bradykinin‐induced ventral root depolarizations (IC50 value; 1.6±0.05 nM (n=3)). Bradyzide is much less potent at the human than at the rodent B2 receptor, displacing [3H]‐bradykinin binding in human fibroblasts and in Cos‐7 cells expressing the human B2 receptor with KI values of 393±90 nM (n=3) and 772±144 nM (n=3), respectively. Bradyzide inhibits bradykinin‐induced [3H]‐inositol trisphosphate (IP3) formation with IC50 values of 11.6±1.4 nM (n=3) at the rat and 2.4±0.3 μM (n=3) at the human receptor. Bradyzide does not interact with a range of other receptors, including human and rat B1 bradykinin receptors. Bradyzide is orally available and blocks bradykinin‐induced hypotension and plasma extravasation. Bradyzide shows long‐lasting oral activity in rodent models of inflammatory hyperalgesia, reversing Freunds complete adjuvant (FCA)‐induced mechanical hyperalgesia in the rat knee joint (ED50, 0.84 μmol kg−1; duration of action >4 h). It is equipotent with morphine and diclofenac, and 1000 times more potent than paracetamol, its maximal effect exceeding that of the non‐steroidal anti‐inflammatory drugs (NSAIDs). Bradyzide does not exhibit tolerance when administered over 6 days. In summary, bradyzide is a potent, orally active, antagonist of the B2 bradykinin receptor, with selectivity for the rodent over the human receptor.

Camostat attenuates airway epithelial sodium channel function in vivo through the inhibition of a channel-activating protease

Inhibition of airway epithelial sodium channel (ENaC) function enhances mucociliary clearance (MCC). ENaC is positively regulated by channel-activating proteases (CAPs), and CAP inhibitors are therefore predicted to be beneficial in diseases associated with impaired MCC. The aims of the present study were to 1) identify low-molecular-weight inhibitors of airway CAPs and 2) to establish whether such CAP inhibitors would translate into a negative regulation of ENaC function in vivo, with a consequent enhancement of MCC. To this end, camostat, a trypsin-like protease inhibitor, provided a potent (IC50 ∼50 nM) and prolonged attenuation of ENaC function in human airway epithelial cell models that was reversible upon the addition of excess trypsin. In primary human bronchial epithelial cells, a potency order of placental bikunin > camostat > 4-guanidinobenzoic acid 4-carboxymethyl-phenyl ester > aprotinin >> soybean trypsin inhibitor = α1-antitrypsin, was largely consistent with that observed for inhibition of prostasin, a molecular candidate for the airway CAP. In vivo, topical airway administration of camostat induced a potent and prolonged attenuation of ENaC activity in the guinea pig trachea (ED50 = 3 μg/kg). When administered by aerosol inhalation in conscious sheep, camostat enhanced MCC out to at least 5 h after inhaled dosing. In summary, camostat attenuates ENaC function and enhances MCC, providing an opportunity for this approach toward the negative regulation of ENaC function to be tested therapeutically.

The design of non-peptide human bradykinin B2 receptor antagonists employing the benzodiazepine peptidomimetic scaffold

The Bradykinin B2 receptor antagonist HOE 140 (D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Tic-Oic-Arg) has been used as a template for the de novo design and synthesis of a small number of non-peptide lead compounds based on the 1,4-benzodiazepin-2-one framework. Two of the compounds have been found to exhibit moderate K(i) values of 8.9 and 9.2 microM at the human Bradykinin B2 receptor.

CONCISE AND REGIOSPECIFIC SYNTHESES OF TRI-SUBSTITUTED 1,2,4-TRIAZOLES

Abstract Novel tri-substituted 1,2,4-triazoles are synthesized via complementary, regiospecific routes as part of a lead finding exercise. A key feature of one of the syntheses is recognition of an intrinsic regioselectivity toward deprotonation in the 1-phenylguanazole substrate.

8-Aryl xanthines potent inhibitors of phosphodiesterase 5.

In clinical studies, several inhibitors of phosphodiesterase 5 (PDE5) have demonstrated utility in the treatment of erectile dysfunction. We describe herein a series of 8-aryl xanthine derivatives which function as potent PDE5 inhibitors with, in many cases, high levels of selectivity versus other PDE isoforms.

FACILE SOLID PHASE SYNTHESIS OF AN ACTIVATED DIAZO LINKER

Abstract The synthesis of a resin bound diazo species has been achieved in a highly efficient manner starting from commercially available reagents. This has produced an activated linker, providing a chemoselective method for the attachment of functionalised carboxylic acids to the solid phase via the Wang linker, in a rapid and colourometric reaction.

A solid-phase approach towards the synthesis of PDE5 inhibitors

PDE5 inhibitors based upon the xanthine scaffold 8 have been expediently synthesized using a solid-phase route. Attachment of the xanthine scaffold 8 using the Rink chloride linker 4 and N-1 functionalization using Mitsunobu chemistry is described. A library of compounds was produced in multi-milligram quantities with excellent purities and acceptable yields. The compounds were tested for their PDE5 inhibitory activity.

Design and synthesis of a library of chemokine antagonists.

A library of chemokine antagonists has been synthesized using a combination of solid and solution-phase chemistry. Structures of known chemokine antagonists were used to produce a pharmacophore which served to guide monomer selection. Several combinations of monomers have resulted in providing novel chemokine antagonists which in some cases display dual chemokine receptor antagonism.