Graham Charles Bloomfield

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.

Development of isoform selective PI3-kinase inhibitors as pharmacological tools for elucidating the PI3K pathway

Using a parallel synthesis approach to target a non-conserved region of the PI3K catalytic domain a pan-PI3K inhibitor 1 was elaborated to provide alpha, delta and gamma isoform selective Class I PI3K inhibitors 21, 24, 26 and 27. The compounds had good cellular activity and were selective against protein kinases and other members of the PI3K superfamily including mTOR and DNA-PK.

Synthesis of 2,9,10-trioxatricyclo[4.3.1.0]decane analogues of resiniferatoxin

Structurally simplified analogues of the daphnane diterpene resiniferatoxin (RTX)1, possessing the unusual 2,9,10-trioxatricyclo[4.3.1.0]decane system have been synthesised stereoselectively from cyclohexa-1,3-diene: functionalisation of the diene afforded the anti-epoxide, 1,4-di-O-benzyl-t-2,t-3-epoxycyclohexane-r-1,c-4-diol 4, the ring-opening of which was examined using various organo-metallic reagents; organoaluminium species were found to be the most efficient to effect this reaction. When trimethylsilyl (in place of benzyl) ethers were used to protect the diol, selective deprotection of 1,4-di-O-trimethylsilyl-2-O-(p-tolylsulfonyl)-c-3-[3-(tert-butyldiphenylsilyloxy)-prop-1-ynyl]cyclohexane-r-1,t-2,c-4-triol 16 was achieved using citric acid in methanol—the equatorially disposed trimethylsilyl ether was found to be more easily cleaved than the axially orientated one. Formation of the tricyclic orthoester was achieved by the generation of a dioxolenium ion from 1-O-phenylacetyl-2-O-(p-tolylsulfpnyl)-c-3-[3-(tert-butyldiphenylsilyloxy)-prop-1-ynyl]cyclohexane-r-1,t-2,c-4-triol 19, by heating in 2,4,6-trimethylpyridine, with in situ intramolecular trapping by the suitably orientated hydroxy group to give 1-benzyl-7-(3-tert-butyldiphenylsilyloxyprop-1-ynyl)-2,9,10-trioxatricyclo[4.3.1.0] decane 20.

The stereoselective synthesis of 2,9,10-trioxatricyclo[4.3.1.0]decane analogues of resiniferatoxin

Structurally simplified analogues of the diterpene resiniferatoxin possessing a 2,9,10-trioxatricyclo[4.3.1.0]decane system are synthesised stereoselectively from cyclohexa-1,3-diene.