Discovery and Toxicological Profiling of Aminopyridines as Orally Bioavailable Selective Inhibitors of PI3-Kinase γ.

Using a novel physiologically relevant in vitro human whole blood neutrophil shape change assay, an aminopyrazine series of selective PI3Kγ inhibitors was identified and prioritized for further optimization. Severe solubility limitations associated with the series leading to low oral bioavailability and poor exposures, especially at higher doses, were overcome by moving to an aminopyridine core. Compound 33, with the optimal balance of on-target activity, selectivity, and pharmacokinetic parameters, progressed into in vivo studies and demonstrated good efficacy (10 mg/kg) in a rat model of airway inflammation. Sufficient exposures were achieved at high doses to support toxicological studies, where unexpected inflammatory cell infiltrates in cardiovascular tissue prevented further compound development.

Preclinical metabolism and pharmacokinetics of NVS-CRF38, a potent and orally bioavailable corticotropin-releasing factor receptor 1 antagonist.

1. The pharmacokinetic properties and metabolism of NVS-CRF38 [7-(3,5-dimethyl-1H-1,2,4-triazol-1-yl)-3-(4-methoxy-2-methylphenyl)-2,6-dimethylpyrazolo[5,1-b]oxazole], a novel corticotropin-releasing factor receptor 1 (CRF1) antagonist, were determined in vitro and in animals. 2. NVS-CRF38 undergoes near complete absorption in rats and dogs. In both species the compound has low hepatic extraction and is extensively distributed to tissues. 3. In rat and human hepatic microsomes and cryopreserved hepatocytes from rat, dog, monkey and human, NVS-CRF38 was metabolised to form O-desmethyl NVS-CRF38 (M7) and several oxygen adducts (M1, M3, M4, M5 and M6). In hepatocytes further metabolites were observed, specifically the carboxylic acid (M2) and conjugates (sulphate and glucuronide) of M7. 4. Formation of primary metabolites in hepatocytes was blocked by the cytochrome P450 enzyme (P450) suicide inhibitor 1-aminobenzotriazole, implicating P450 enzymes in the primary metabolism of this compound. 5. NVS-CRF38 is weakly bound to plasma proteins from rat (fub = 0.19), dog (fub = 0.25), monkey (fub = 0.20) and humans (fub = 0.23). Blood-to-plasma partition for NVS-CRF38 approaches unity in rat and human blood. 6. The hepatic clearance of NVS-CRF38 in humans is predicted to be low (extraction ratio ∼ 0.2) based on scaling from drug depletion profiles in hepatic microsomes.

7-tert-Butyl-6-(4-chloro-phenyl)-2-thioxo-2,3-dihydro-1H-pyrido[2,3-d]pyrimidin-4-one, a classic polymodal inhibitor of transient receptor potential vanilloid type 1 with a reduced liability for hyperthermia, is analgesic and ameliorates visceral hypersensitivity.

The therapeutic potential of transient receptor potential vanilloid type 1 (TRPV1) antagonists for chronic pain has been recognized for more than a decade. However, preclinical and clinical data revealed that acute pharmacological blockade of TRPV1 perturbs thermoregulation, resulting in hyperthermia, which is a major hurdle for the clinical development of these drugs. Here, we describe the properties of 7-tert-butyl-6-(4-chloro-phenyl)-2-thioxo-2,3-dihydro-1H-pyrido[2,3-d]pyrimidin-4-one (BCTP), a TRPV1 antagonist with excellent analgesic properties that does not induce significant hyperthermia in rodents at doses providing maximal analgesia. BCTP is a classic polymodal inhibitor of TRPV1, blocking activation of the human channel by capsaicin and low pH with IC(50) values of 65.4 and 26.4 nM, respectively. Similar activity was observed with rat TRPV1, and the inhibition by BCTP was competitive and reversible. BCTP also blocked heat-induced activation of TRPV1. In rats, the inhibition of capsaicin-induced mechanical hyperalgesia was observed with a D(50) value of 2 mg/kg p.o. BCTP also reversed visceral hypersensitivity and somatic inflammatory pain, and using a model of neuropathic pain in TRPV1 null mice we confirmed that its analgesic properties were solely through the inhibition of TRPV1. We were surprised to find that BCTP administered orally induced only a maximal 0.6°C increase in core body temperature at the highest tested doses (30 and 100 mg/kg), contrasting markedly with N-[4-({6-[4-(trifluoromethyl)phenyl]pyrimidin-4-yl}oxy)-1,3-benzothiazol-2-yl]acetamide (AMG517), a clinically tested TRPV1 antagonist, which induced marked hyperthermia (>1°C) at doses eliciting submaximal reversal of capsaicin-induced hyperalgesia. The combined data indicate that TRPV1 antagonists with a classic polymodal inhibition profile can be identified where the analgesic action is separated from the effects on body temperature.

Direct arylations of 2H-indazoles on water.

The efficient palladium-catalyzed synthesis of a range of substituted 2H-Indazoles via C-H arylation is reported. Reactions are performed on water and provide a direct and mild route toward 2,3-diaryl indazoles of widespread biological significance.

Overcoming hERG issues for brain-penetrating cathepsin S inhibitors: 2-cyanopyrimidines. Part 2.

We describe here orally active and brain-penetrant cathepsin S selective inhibitors, which are virtually devoid of hERG K(+) channel affinity, yet exhibit nanomolar potency against cathepsin S and over 100-fold selectivity to cathepsin L. The new non-peptidic inhibitors are based on a 2-cyanopyrimidine scaffold bearing a spiro[3.5]non-6-yl-methyl amine at the 4-position. The brain-penetrating cathepsin S inhibitors demonstrate potential clinical utility for the treatment of multiple sclerosis and neuropathic pain.

Discovery of orally bioavailable cathepsin S inhibitors for the reversal of neuropathic pain.

Cathepsin S inhibitors are well-known to be an attractive target as immunological therapeutic agents. Recently, our gene expression analysis identified that cathepsin S inhibitors could also be effective for neuropathic pain. Herein, we describe the efficacy of selective cathepsin S inhibitors as antihyperalgesics in a model of neuropathic pain in rats after oral administration.

Direct arylations on water: synthesis of 2,5-disubstituted oxazoles balsoxin and texaline.

An efficient two-step palladium catalysed synthesis of 2,5-disubstituted oxazoles is reported.

Naphthalen-1-yl-(4-pentyloxynaphthalen-1-yl)methanone: a potent, orally bioavailable human CB1/CB2 dual agonist with antihyperalgesic properties and restricted central nervous system penetration.

Selective activation of peripheral cannabinoid CB1 receptors has the potential to become a valuable therapy for chronic pain conditions as long as central nervous system effects are attenuated. A new class of cannabinoid ligands was rationally designed from known aminoalkylindole agonists and showed good binding and functional activities at human CB1 and CB2 receptors. This has led to the discovery of a novel CB1/CB2 dual agonist, naphthalen-1-yl-(4-pentyloxynaphthalen-1-yl)methanone (13), which displays good oral bioavailability, potent antihyperalgesic activity in animal models, and limited brain penetration.

Identification and biological characterization of 6-aryl-7-isopropylquinazolinones as novel TRPV1 antagonists that are effective in models of chronic pain.

Vanilloid receptor 1 (VR1, TRPV1) is a cation-selective ion channel that is expressed on primary afferent neurons and is upregulated following inflammation and nerve damage. Blockers of this channel may have utility in the treatment of chronic nociceptive and neuropathic pain. Here, we describe the optimization from a high throughput screening hit, of a series of 6-aryl-7-isopropylquinazolinones that are TRPV1 antagonists in vitro. We also demonstrate that one compound is active in vivo against capsaicin-induced hyperalgesia and in models of neuropathic and nociceptive pain in the rat.

Potent and orally bioavailable non-peptide antagonists at the human bradykinin B(1) receptor based on a 2-alkylamino-5-sulfamoylbenzamide core.

The bradykinin B(1) receptor is rapidly induced after inflammation or tissue trauma and appears to play an important role in the maintenance of hyperalgesia in inflammatory conditions. Here, we describe the optimization process to identify novel, potent non-peptide human B(1) receptor antagonists based on a 2-alkylamino-5-sulfamoylbenzamide core. Optimized derivatives are selective, functional B(1) antagonists with low nanomolar affinity and exhibit oral bioavailability in animals.

Investigations into the Manzamine Alkaloid Biosynthetic Hypothesis.

The biomimetic synthesis of a pentacyclic alkaloid (keramaphidin B, 1), an intermediate in the biogenetic pathway to the manzamine alkaloids, has been achieved. Compound 1 was formed by an intramolecular Diels-Alder reaction of macrocycle 2 in buffer followed by reduction with NaBH4 . This reaction provides the first direct expeimental evidence for the authors' biosynthetic hypothesis.