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Recently, the fungal sphingolipid glucosylceramide (GlcCer) synthesis has emerged as a highly promising new target for drug discovery of next-generation antifungal agents, and we found two aromatic acylhydrazones as effective inhibitors of GlcCer synthesis based on HTP screening. In the present work, we have designed libraries of new aromatic acylhydrazones, evaluated their antifungal activities (MIC(80) and time-kill profile) against C. neoformans and performed an extensive SAR study, which led to the identification of five promising lead compounds, exhibiting excellent fungicidal activities with very large selectivity index. Moreover, two compounds demonstrated broad spectrum antifungal activity against six other clinically relevant fungal strains. These five lead compounds were examined for their synergism/cooperativity with five clinical drugs against seven fungal strains and very encouraging results were obtained, e.g., the combination of all five lead compounds with voriconazole exhibited either synergistic or additive effect to all seven fungal strains.

Fungal infections are a universal problem and are routinely associated with high morbidity and mortality rates in immunocompromised patients. Existing therapies comprise five different classes of antifungal agents, four of which target the synthesis of ergosterol and cell wall glucans. However, the currently available antifungals have many limitations, including poor oral bioavailability, narrow therapeutic indices, and emerging drug resistance resulting from their use, thus making it essential to investigate the development of novel drugs which can overcome these limitations and add to the antifungal armamentarium. Advances have been made in antifungal drug discovery research and development over the past few years as evidenced by the presence of several new compounds currently in various stages of development. In the following minireview, we provide a comprehensive summary of compounds aimed at one or more novel molecular targets. We also briefly describe potential pathways relevant for fungal pathogenesis that can be considered for drug development in the near future.

The incidence of invasive fungal infections is rising due to the increase in susceptible populations. Current clinically available drugs have therapeutic limitations due to toxicity, a narrow spectrum of activity, and, more importantly, the consistent rise of fungal species that are intrinsically resistant or that develop resistance due to prolonged therapy. Thus, there is an urgent need for new broad-spectrum antifungal agents with low toxicity and a novel mechanism of action. We previously reported a new class of potent antifungal compounds, acylhydrazones, that target the fungal sphingolipid pathway. Based upon our initial lead molecules, (E)-N′-(5-bromo-2-hydroxybenzylidene)-2-methylbenzohydrazide and D13, we performed a structure-activity relationship study, synthesizing ca. 300 new compounds. Of these, 5 compounds were identified to be the most promising for further studies, based on their broad-spectrum activity and low toxicity in mammalian cells lines. Among these top 5 lead compounds, we report here the impressive in vivo activity of 2,4-dibromo-N′-(5-bromo-2-hydroxybenzylidene)benzohydrazide (SB-AF-1002) in several models of systemic fungal infection. Our data show that SB-AF-1002 is efficacious and outperforms current standard-of-care drugs in models of invasive fungal infections, such as cryptococcosis, candidiasis, and aspergillosis. Specifically, animals treated with SB-AF-1002 not only survived the infection but also showed a clearing of fungal cells from key organs. Moreover, SB-AF-1002 was very effective in an aspergillosis model as a prophylactic therapy. SB-AF-1002 also displayed acceptable pharmacokinetic properties in mice, similar to those of the parent compound, D13. These results clearly indicate that our novel acylhydrazones constitute a new class of highly potent and efficacious antifungal agents which warrant further development for the treatment of invasive fungal infections.

The central nervous system (CNS) is the major area that is affected by aging. Alzheimer's disease (AD), Parkinson's disease (PD), brain cancer, and stroke are the CNS diseases that will cost trillions of dollars for their treatment. Achievement of appropriate blood-brain barrier (BBB) penetration is often considered a significant hurdle in the CNS drug discovery process. On the other hand, BBB penetration may be a liability for many of the non-CNS drug targets, and a clear understanding of the physicochemical and structural differences between CNS and non-CNS drugs may assist both research areas. Because of the numerous and challenging issues in CNS drug discovery and the low success rates, pharmaceutical companies are beginning to deprioritize their drug discovery efforts in the CNS arena. Prompted by these challenges and to aid in the design of high-quality, efficacious CNS compounds, we analyzed the physicochemical property and the chemical structural profiles of 317 CNS and 626 non-CNS oral drugs. The conclusions derived provide an ideal property profile for lead selection and the property modification strategy during the lead optimization process. A list of substructural units that may be useful for CNS drug design was also provided here. A classification tree was also developed to differentiate between CNS drugs and non-CNS oral drugs. The combined analysis provided the following guidelines for designing high-quality CNS drugs: (i) topological molecular polar surface area of76 Å(2) (25-60 Å(2)), (ii) at least one (one or two, including one aliphatic amine) nitrogen, (iii) fewer than seven (two to four) linear chains outside of rings, (iv) fewer than three (zero or one) polar hydrogen atoms, (v) volume of 740-970 Å(3), (vi) solvent accessible surface area of 460-580 Å(2), and (vii) positive QikProp parameter CNS. The ranges within parentheses may be used during lead optimization. One violation to this proposed profile may be acceptable. The chemoinformatics approaches for graphically analyzing multiple properties efficiently are presented.

CEP-26401 [irdabisant; 6-{4-[3-((R)-2-methyl-pyrrolidin-1-yl)-propoxy]-phenyl}-2H-pyridazin-3-one HCl] is a novel, potent histamine H₃ receptor (H₃R) antagonist/inverse agonist with drug-like properties. High affinity of CEP-26401 for H₃R was demonstrated in radioligand binding displacement assays in rat brain membranes (K(i) = 2.7 ± 0.3 nM) and recombinant rat and human H₃R-expressing systems (K(i) = 7.2 ± 0.4 and 2.0 ± 1.0 nM, respectively). CEP-26401 displayed potent antagonist and inverse agonist activities in [³⁵S]guanosine 5'-O-(γ-thio)triphosphate binding assays. After oral dosing of CEP-26401, occupancy of H₃R was estimated by the inhibition of ex vivo binding in rat cortical slices (OCC₅₀ = 0.1 ± 0.003 mg/kg), and antagonism of the H₃R agonist R-α-methylhistamine- induced drinking response in the rat dipsogenia model was demonstrated in a similar dose range (ED₅₀ = 0.06 mg/kg). CEP-26401 improved performance in the rat social recognition model of short-term memory at doses of 0.01 to 0.1 mg/kg p.o. and was wake-promoting at 3 to 30 mg/kg p.o. In DBA/2NCrl mice, CEP-26401 at 10 and 30 mg/kg i.p. increased prepulse inhibition (PPI), whereas the antipsychotic risperidone was effective at 0.3 and 1 mg/kg i.p. Coadministration of CEP-26401 and risperidone at subefficacious doses (3 and 0.1 mg/kg i.p., respectively) increased PPI. These results demonstrate potent behavioral effects of CEP-26401 in rodent models and suggest that this novel H₃R antagonist may have therapeutic utility in the treatment of cognitive and attentional disorders. CEP-26401 may also have therapeutic utility in treating schizophrenia or as adjunctive therapy to approved antipsychotics.

Optimization of a novel series of pyridazin-3-one histamine H(3) receptor (H(3)R) antagonists/inverse agonists identified 6-{4-[3-(R)-2-methylpyrrolidin-1-yl)propoxy]phenyl}-2H-pyridazin-3-one (8a, CEP-26401; irdabisant) as a lead candidate for potential use in the treatment of attentional and cognitive disorders. 8a had high affinity for both human (K(i) = 2.0 nM) and rat (K(i) = 7.2 nM) H(3)Rs with greater than 1000-fold selectivity over the hH(1)R, hH(2)R, and hH(4)R histamine receptor subtypes and against an in vitro panel of 418 G-protein-coupled receptors, ion channels, transporters, and enzymes. 8a demonstrated ideal pharmaceutical properties for a CNS drug in regard to water solubility, permeability and lipophilicity and had low binding to human plasma proteins. It weakly inhibited recombinant cytochrome P450 isoforms and human ether-a-go-go-related gene. 8a metabolism was minimal in rat, mouse, dog, and human liver microsomes, and it had good interspecies pharmacokinetic properties. 8a dose-dependently inhibited H(3)R agonist-induced dipsogenia in the rat (ED(50) = 0.06 mg/kg po). On the basis of its pharmacological, pharmaceutical, and safety profiles, 8a was selected for preclinical development. The clinical portions of the single and multiple ascending dose studies assessing safety and pharmacokinetics have been completed allowing for the initiation of a phase IIa for proof of concept.

The optimization of the dihydronaphthyl[3,4-a]pyrrolo[3,4-c]carbazole-5-one R(2) and R(12) positions led to the identification of the first MLK1 and MLK3 subtype-selective inhibitors within the MLK family. Compounds 14 (CEP-5104) and 16 (CEP-6331) displayed good potency for MLK1 and MLK3 inhibition with a greater than 30- to 100-fold selectivity for related family members MLK2 and DLK. Compounds 14 and 16 were orally active in vivo in a mouse MPTP biochemical efficacy model that was comparable to the first-generation pan-MLK inhibitor 1 (CEP-1347). The MLK1 structure-activity relationships were supported by the first-reported X-ray crystal structure of MLK1 bound with 16.

toward kinase inhibitor discovery, with the result that several kinase inhibitors have been approved as drugs since 2001. The commercial success of imatinib (N-(4-methyl-3-(4-(pyridin-3yl)pyrimidin-2-ylamino)phenyl)-4-((4-methylpiperazin-1-l)methyl)benzamide) has provided a clear incentive for the continued pursuit of kinase inhibitor design.

An immobilized Staurosporine aglycone isostere where one of the indole nitrogen atoms was replaced by carbon has been sequentially functionalized to generate compounds inhibiting TrkA kinase. In the first phase, initial screening of a library of C13-hydroxymethyl-7-oxo-indenopyrrolocarbazoles resulted in several potent compounds, one of which was further optimized to generate the corresponding carbamates on solid phase. Some of the major carbamate diastereomers were found to be several-fold more potent than their alcohol parents. Synthesis, SAR analysis, kinase selectivity, and anti-tumor properties of a TrkA inhibitor (12a) are discussed.

Structural modification of the indolecarbazole natural product (+)K-252a identified structural requirements for MLK activity and a novel series of potent fused pyrrolocarbazole MLK1/3 inhibitors. The SAR revealed that the lactam regiochemistry, the shape of the heterocycle, and aryl rings B and F are important to MLK activity. Heteroatom and alkyl replacement of the N-12 and/or N-13 indole nitrogen atoms identified the nonplanar dihydronaphthyl[3,4-a]pyrrolo[3,4-c]carbazole-7-one (8) and corresponding 5,7-dione (7) as potent cell-permeable MLK1/3 family-selective leads with in vitro activity comparable to that of (+)K-252a and determined them to be 2- to 3-fold more potent than the aglycone natural product K-252c.

The modern drug discovery process is steadily becoming more information driven. Structural, physicochemical and ADME-Tox property profiles of reference (successful) ligands, along with structural information of their target proteins, have been extremely useful for early-stage drug discovery. Recently, databases of known biologically active ligands (knowledge bases) have become more focused toward different protein-target classes. The number of new chemoinformatics tools used to analyze structures and properties of successful molecules has also increased enormously. Scientists in this area are exploring new physicochemical properties and appropriate drug sets to understand druglike properties. In this review, the various uses of the ligand knowledge bases in the drug discovery process have been critically reviewed.

A series of potent 1,2-benzothiazine 1,1-dioxide alpha-ketoamide inhibitors of calpain I is described.

A series of potent vascular endothelial growth factor R2 (VEGF-R2) tyrosine kinase inhibitors from a new indenopyrrolocarbazole template is reported. The structure-activity relationships for a series of 9-alkoxymethyl-12-(3-hydroxypropyl)indeno[2,1-a]pyrrolo[3,4-c]carbazole-5-ones revealed an optimal R9 substitution with ethoxymethyl 19 (VEGF-R2 IC(50) = 4 nM) and isopropoxymethyl 21 (VEGF-R2 IC(50) = 8 nM) being the most potent inhibitors in the series. The VEGF-R2 activity was reduced appreciably by increasing the size of the R9 alkoxy group or by alpha-methyl branching adjacent to the ring. The combined R9 alkoxymethyl and N12 hydroxypropyl substitutions were required for potent VEGF-R2 activity, and the corresponding thioether analogues were weaker than their ether counterparts. Compound 21 (R9 isopropoxymethyl, CEP-5214) was identified as a potent, low-nanomolar pan inhibitor of human VEGF-R tyrosine kinases, displaying IC(50) values of 16, 8, and 4 nM for VEGF-R1/FLT-1, VEGF-R2/KDR, and VEGF-R3/FLT-4, respectively, with cellular activity equivalent to the isolated enzyme activity. Compound 21 exhibited good selectivity against numerous tyrosine and serine/threonine kinases including PKC, Tie2, TrkA, CDK1, p38, JNK, and IRK. To increase water solubility and oral bioavailability, the N,N-dimethylglycine ester 40 was prepared. In pharmacokinetic studies in mice and rats, increased plasma levels of 21 were observed after oral administration of 40. Compound 21 demonstrated significant in vivo antitumor activity in numerous tumor models and was advanced into phase I clinical trials as the water-soluble N,N-dimethylglycine ester prodrug 40 (CEP-7055).

A modified core structure of indolo[2,3-a]carbazole template has been immobilized. EtMgBr was identified as a substrate compatible base providing solid-phase dianion formation. Depending upon the nature of the electrophile, the core structure has been selectively functionalized to generate a library of kinase inhibitors.

A series of irreversible inhibitors of recombinant calpain has been synthesized and their rates of inactivation have been evaluated against calpain and cathepsin B, respectively. The design of the inhibitors was based on the quiescent affinity label concept. By choosing the appropriate affinity group and by employing leaving groups derived from N-hydroxy coupling reagents, good inhibitors of calpain with high rates of inactivation have been identified. However, poor aqueous stability limits their therapeutic utility.

A series of potent P2-achiral, P'-extended alpha-ketoamide inhibitors of calpain I is described.

Dipeptidyl phosphorus compounds were synthesized as potential bioisosteric mimics of peptide alpha-ketoesters and alpha-ketoacids. alpha-Ketophosphonate Cbz-Leu-Leu-P(O)(OCH3)2 (1b), containing an alpha-ketoester bioisostere, inhibits human calpain I with an IC50 = 0.43 microM. The potency of 1b compares very favorably with that of alpha-ketoester Cbz-Leu-Leu-CO2Et (IC50 = 0.60 microM). Monomethyl ketophosphonate Cbz-Leu-Leu-P(O)(OH)(OCH3) (1a, IC50 = 5.2 microM), an alpha-ketoacid mimic, is less potent. Dibutyl and dibenzyl alpha-ketophosphonates 1c,e,f are much less potent calpain inhibitors than dimethyl alpha-ketophosphonate 1b. alpha-Ketophosphinate 1g (IC50 = 0.37 microM) and alpha-ketophosphine oxide 1h (IC50 = 0.35 microM) are also potent calpain inhibitors.

A series of 3,9 disubstituted [(alkylthio)methyl]- and (alkoxymethyl)-K-252a derivatives was synthesized with the aim of enhancing and separating the neurotrophic properties from the undesirable NGF (trk A kinase) and PKC inhibitory activities of K-252a. Data from this series reveal that substitution in the 3- and 9-positions of K-252a with these groups reduces trk A kinase inhibitory properties approximately 100- to500-fold while maintaining or in certain cases enhancing the neurotrophic activity. From this research, 3,9-bis[(ethylthio)methyl]-K-252a (8) was identified as a potent and selective neurotrophic agent in vitro as measured by enhancement of choline acetyltransferase activity in embryonic rat spinal cord and basal forebrain cultures. Compound 8 was found to have weak kinase inhibitory activity for trk A, protein kinase C1 protein kinase A, and myosin light chain kinase. On the basis of the in vitro profile, 8 was evaluated in in vivo models suggestive of neurological diseases. Compound 8 was active in preventing degeneration of cholinergic neurons of the nucleus basalis magnocellularis (NBM) and reduced developmentally programmed cell death (PCD) of female rat spinal nucleus of the bulbocavernosus motoneurons and embryonic chick lumbar motoneurons.

The syntheses and biological activities of novel nonpeptidic calpain inhibitors 2–3, 12, and 14, derived from 2-naphthalenethiol, are described.

Novel and potent, xanthene derived reversible aldehyde (7c) and α-ketocarboxamide (10a), and irreversible fluoromethyl ketone (10b) inhibitors of recombinant human calpain I are described.

We report on a series of potent and selective dipeptide fluoromethyl ketone inhibitors of recombinant human calpain I. Compound 4f, having a tetrahydroisoquinoline containing urea motif as N-terminus capping group, is the most potent member ( k obs I = 276,000 M−1 s−1) of this class. This compound was shown to prefer calpain I by >36-fold and approximately 4-fold over the related cysteine proteases, cathepsin B and cathepsin L, respectively.

Potent and selective α-ketocarbonyl ( 8a–b ) and boronic ester ( 11 ) derived inhibitors of the chymotrypsin-like activity of proteasome , first member of a newly identified class of threonine proteases, are described.

A practical synthesis of the title compounds ( 3a-c, e ) from commercially available 3-hydroxy-2-pyridine carboxylic acid ( 4 ) is reported. The key step in the synthetic sequence involves a Pd-catalyzed cross coupling reaction of the triflate 6 with the appropriate alkyl or aryl derivatives to generate the substituted picolinic acid esters 7a-b, 8 and 11 . Catalytic reduction of these picolinic acid esters provided the title compounds in good yields.

A series of permanently charged benzo[b]quinolizinium cations having lower lipophilicity than MK-801 or phencyclidine (PCP) were synthesized. Data relating agonist independent block of N-methyl-D-aspartic acid (NMDA) ion channels to log D are described. Closed channel access is predicted to result in a more noncompetitive profile of antagonism compared to selective open channel blockers, which are uncompetitive inhibitors. Reduced closed channel block may underlie the absence of PCP or MK-801-like behavioral side effects observed for benzo[b]-quinolizinium cations.

The synthesis and in vitro and in vivo evaluation of 12,13-cycloalkyl-6,11-ethanobenzo[b]-quinolizidines, a new class of noncompetitive N-methyl-D-aspartate (NMDA) antagonists acting at the PCP site on the NMDA receptor complex, is reported. Structure-activity relationship studies led to the identification of 10-hydroxy-(6 alpha,11 alpha,11 alpha beta,12R*,13S*)-1,3,4,6,11,11a,13,14,15,16-decahydro-12H- 6,11[1',2']-endo-cyclopenta-2H-pyrido[1,2-b]isoquinoline hydrobromide (5h) and 9-hydroxy-(6 alpha,11 alpha,11a beta,12R*,13S*)- 1,3,4,6,11,11a,13,14,15,16-decahydro-12H-6,11-[1',2']-endo-cycl ope nta-2H- pyrido[1,2-b]isoquinoline hydrobromide (5i), the most potent members of this series with Ki values of 2.3 +/- 0.2 and 2.3 +/- 0.5 nM, respectively. Molecular modeling studies revealed that this series of compounds occupies both lipophilic sites of the Andrews PCP receptor model and shares structural features which are common to other classes of known noncompetitive NMDA antagonists such as MK-801.

A series of 2,3,3a,4,9,9a-hexahydro-9,4-(iminomethano)-1H-benz[f]indenes was prepared and their ability to displace [3H]TCP was measured. The 5-amino derivatives 5 and 12b were the most potent members of this series with Ki values of 14 nM and 8 nM respectively. The orientation of the cyclopentane ring was crucial for binding potency, with the endo isomer 12a >10 times more potent than the exo-isomer 13.

6,11-Ethano-12,12-diaryl-6,11-dihydrobenzo[b]quinolizinium cations 8, a novel class of N-methyl-D-aspartate (NMDA) antagonists acting at the phencyclidine site, have been identified. Structure-activity relationship studies around the lead compound 8a led to the identification of 12g (WIN 67870-2), one of the most potent compounds in this series. Compound 12g has a Ki = 1.8 +/- 0.2 nM vs [3H]TCP binding, has 700-fold selectivity for binding to the open state of the NMDA receptor-ionophore, and was devoid of MK-801- and PCP-like behavioral effects in rats. Compound 12g was neuroprotective in cultured mouse cortical neurons and exhibited antiischemic activity in a rat middle cerebral artery occlusion/reperfusion model of focal ischemia.

A substantial body of evidence supports the utility of antiangiogenesis inhibitors as a strategy to block or attenuate tumor-induced angiogenesis and inhibition of primary and metastatic tumor growth in a variety of solid and hematopoietic tumors. Given the requirement of tumors for different cytokine and growth factors at distinct stages of their growth and dissemination, optimal antiangiogenic therapy necessitates inhibition of multiple, complementary, and nonredundant angiogenic targets. 11-(2-Methylpropyl)-12,13-dihydro-2-methyl-8-(pyrimidin-2-ylamino)-4H-indazolo[5,4-a]pyrrolo[3,4-c]carbazol-4-one (11b, CEP-11981) is a potent orally active inhibitor of multiple targets (TIE-2, VEGF-R1, 2, and 3, and FGF-R1) having essential and nonredundant roles in tumor angiogenesis and vascular maintenance. Outlined in this article are the design strategy, synthesis, and biochemical and pharmacological profile for 11b, which completed Phase I clinical assessing safety and pharmacokinetics allowing for the initiation of proof of concept studies.

CEP-26401 [irdabisant; 6-{4-[3-((R)-2-methyl-pyrrolidin-1-yl)-propoxy]-phenyl}-2H-pyridazin-3-one HCl] is a novel, potent histamine H₃ receptor (H₃R) antagonist/inverse agonist with drug-like properties. High affinity of CEP-26401 for H₃R was demonstrated in radioligand binding displacement assays in rat brain membranes (K(i) = 2.7 ± 0.3 nM) and recombinant rat and human H₃R-expressing systems (K(i) = 7.2 ± 0.4 and 2.0 ± 1.0 nM, respectively). CEP-26401 displayed potent antagonist and inverse agonist activities in [³⁵S]guanosine 5'-O-(γ-thio)triphosphate binding assays. After oral dosing of CEP-26401, occupancy of H₃R was estimated by the inhibition of ex vivo binding in rat cortical slices (OCC₅₀ = 0.1 ± 0.003 mg/kg), and antagonism of the H₃R agonist R-α-methylhistamine- induced drinking response in the rat dipsogenia model was demonstrated in a similar dose range (ED₅₀ = 0.06 mg/kg). CEP-26401 improved performance in the rat social recognition model of short-term memory at doses of 0.01 to 0.1 mg/kg p.o. and was wake-promoting at 3 to 30 mg/kg p.o. In DBA/2NCrl mice, CEP-26401 at 10 and 30 mg/kg i.p. increased prepulse inhibition (PPI), whereas the antipsychotic risperidone was effective at 0.3 and 1 mg/kg i.p. Coadministration of CEP-26401 and risperidone at subefficacious doses (3 and 0.1 mg/kg i.p., respectively) increased PPI. These results demonstrate potent behavioral effects of CEP-26401 in rodent models and suggest that this novel H₃R antagonist may have therapeutic utility in the treatment of cognitive and attentional disorders. CEP-26401 may also have therapeutic utility in treating schizophrenia or as adjunctive therapy to approved antipsychotics.

A series of 2,3,3a,4,9,9a-hexahydro-9,4-(iminomethano)-1H-benz[f]indenes was prepared and their ability to displace [3H]TCP was measured. The 5-amino derivatives 5 and 12b were the most potent members of this series with Ki values of 14 nM and 8 nM respectively. The orientation of the cyclopentane ring was crucial for binding potency, with the endo isomer 12a >10 times more potent than the exo-isomer 13.

A practical synthesis of the title compounds ( 3a-c, e ) from commercially available 3-hydroxy-2-pyridine carboxylic acid ( 4 ) is reported. The key step in the synthetic sequence involves a Pd-catalyzed cross coupling reaction of the triflate 6 with the appropriate alkyl or aryl derivatives to generate the substituted picolinic acid esters 7a-b, 8 and 11 . Catalytic reduction of these picolinic acid esters provided the title compounds in good yields.

Tandem alkylation/cyclization of indenopyrrolocarbazole 4a, a C12 carbon analogue of indolocarbazole K252c, was carried out by general solid-phase and solution-phase methods. Alkylation of fused pyrroloindenylcarbazole 4a derivatives with appropriate monoacetals of diketones afforded the corresponding C12-substituted acetal alcohols. Acid-catalyzed cyclization of these adducts yielded C12,N13-bridged tetrahydrofuran, pyran, and dioxane compounds 10-13.

A variety of heterocyclic analogs of Win 54954 have been synthesized and tested in vitro against human rhinovirus type 14 (HRV-14) in a plaque reduction assay. The more active compounds were tested against 14 additional serotypes, and the concentration which inhibited 80% of the serotypes tested (MIC80) was measured. One compound, 37, exhibited activity comparable to Win 59454. Physicochemical as well as electrostatic parameters were calculated and the results subjected to a QSAR analysis in an effort to explain differences in activity observed between these compounds; however, no meaningful correlation with biological activity was found with any of these parameters.

Using unlabeled androsterone as starting material, 5α-[16,16-2H2]androstan-3α-ol-17-one was synthesized by exchange using deuterated potassium methoxide. This labeled androsterone product was reduced by sodium borodeuteride, which gave predominantly trideuterated 5α-androstane-3α,17β-diol. The labeled androstanediol was conjugated with glucuronide by using the Koenig-Knorr reaction with methyl-I-bromo-I-deoxy-2,3,4-tri-O-acetyl-α-D-glucopyranosuronate. The dominant product was identified by thermospray high-performance liquid chromatography/mass spectrometry (MS) and electrospray MS as 5α-[16,16,17-2H3]androstane-3α,17β-diol,17β-glucuronide.

An efficient resolution of (±)-trans-2'-hydroxy-5,9-dimethyl-6,7-benzomorphan has been developed employing (—)-(R)- and (+)-(S)-O-acetylmandelic acids. Measurement of optical rotations on the resolved bases, NMR analyses of diastereomeric urea derivatives, as well as gas chromatographic analyses of diastereomeric amide derivatives indicate a net improvement over previous resolution methodology and an enantiomeric excess ≥ 99%. © 1992 Wiley-Liss, Inc.

toward kinase inhibitor discovery, with the result that several kinase inhibitors have been approved as drugs since 2001. The commercial success of imatinib (N-(4-methyl-3-(4-(pyridin-3yl)pyrimidin-2-ylamino)phenyl)-4-((4-methylpiperazin-1-l)methyl)benzamide) has provided a clear incentive for the continued pursuit of kinase inhibitor design.

The ubiquitin-proteasome pathway plays a central role in regulation of the production and destruction of cellular proteins. These pathways mediate proliferation and cell survival, particularly in malignant cells. The successful development of the 20S human proteasome inhibitor bortezomib for the treatment of relapsed and refractory multiple myeloma has established this targeted intervention as an effective therapeutic strategy. Herein, the potent, selective, and orally bioavailable threonine-derived 20S human proteasome inhibitor that has been advanced to preclinical development, [(1R)-1-[[(2 S,3 R)-3-hydroxy-2-[(6-phenylpyridine-2-carbonyl)amino]-1-oxobutyl]amino]-3-methylbutyl]boronic acid 20 (CEP-18770), is disclosed.

This overview unit describes the core activities involved in the drug discovery and development process, from target identification - including preclinical biology, medicinal and process chemistry - to pharmacokinetics and metabolism (ADME), and also activities related to the to the drug approval process. The latter include the activities related to the filing of an IND (Investigational New Drug) application and also Phases I - III of clinical trials that form the basis of an NDA (New Drug Application) submission, as well as post-marketing Phase IV activities as required by the U.S. Food and Drug Administration (FDA) and the European and Japanese counterparts.

KDR kinase inhibition is considered to play an important role in regulating angiogenesis, which is vital for the survival and proliferation of tumor cells. Recently we disclosed a structure-based kinase inhibitor design strategy which led to the identification of a new class of VEGFR-2/KDR kinase inhibitors bearing heterocyclic substituted pyrazolones as the core template. Instability in a rat S9 preparation and poor iv PK profiles for most of these inhibitors necessitated exploration of new pyrazolones to identify new analogs with improved metabolic stability. Optimization of the heterocyclic moiety led to the identification of the thiadiazole series of pyrazolones (D) as potent VEGFR-2/KDR kinase inhibitors. SAR modifications, kinase selectivity profiling, and structural elements for improved PK properties were explored. Oral bioavailability up to 29% was achieved in the rat. Modeling results based on the Glide XP docking approach supported our postulation regarding the interaction of the lactam segment of the pyrazolones with the hinge region of the KDR kinase.

Structural analysis of the essential binding elements of the oxindole-based kinase inhibitor (1) led to the identification of a novel class of heterocyclic-substituted pyrazolones. Knoevenagel condensation of a variety of activated methylene nucleophiles with indole or pyrrole carboxaldehydes provided a focused library of molecules, each containing elements of kinase pharmacophore probe. Initial screening for VEGFR-2 kinase inhibition eliminated several of the probes. Identification of an active pyrazolone motif and further optimization resulted in several highly potent VEGFR-2 inhibitors with cellular efficacy, anti-angiogenic activity ex vivo in rat aortic ring explant cultures, and oral anti-tumor efficacy in nude mice.

A new procedure for protecting the amide, lactam, urea, and carbamate NH group with a triphenylmethyl (Tr) group is described. The utility of this method is illustrated with molecules that contain other functional groups. A mild deprotection using trifluoroacetic acid makes this a useful method for attaching amide groups on resin for combinatorial synthesis.

Tandem alkylation/cyclization of indenopyrrolocarbazole 4a, a C12 carbon analogue of indolocarbazole K252c, was carried out by general solid-phase and solution-phase methods. Alkylation of fused pyrroloindenylcarbazole 4a derivatives with appropriate monoacetals of diketones afforded the corresponding C12-substituted acetal alcohols. Acid-catalyzed cyclization of these adducts yielded C12,N13-bridged tetrahydrofuran, pyran, and dioxane compounds 10-13.

A series of irreversible inhibitors of recombinant calpain has been synthesized and their rates of inactivation have been evaluated against calpain and cathepsin B, respectively. The design of the inhibitors was based on the quiescent affinity label concept. By choosing the appropriate affinity group and by employing leaving groups derived from N-hydroxy coupling reagents, good inhibitors of calpain with high rates of inactivation have been identified. However, poor aqueous stability limits their therapeutic utility.

Prodrug esters of the indolocarbazole CEP-751 (KT-6587) were prepared with the goal of identifying water soluble, stable but cleavable forms for intravenous dosing. A dipeptide proform Lys-beta-Ala (16, CEP-2563/KT-8391) was identified for advancement to clinical trials.

Calpain I, an intracellular cysteine protease, has been implicated in the neurodegeneration following an episode of cerebral ischemia. In this paper, we report on a series of peptidomimetic ketomethylene and carbamethylene inhibitors of recombinant human calpain I (rh calpain I). Our study reveals that the -NHCO-moiety (possible hydrogen-bonding site) at the P2-P3 region of a potent tripeptide or a dipeptide inhibitor of calpain I is not a strict requirement for enzyme recognition. Compounds 7d ((R)-2-isobutyl-4-oxo-4-(9-xanthenyl)butanoic acid ((S)-1-formyl-3-methyl)butyl amide), 31 ((R)-2-isobutyl-4-(2-sulfonylnaphthyl)butyric acid ((S)1-formyl-3-methyl)butyl amide) and 34 ((R)-2-isobutyl-4-(2-sulfoxylnaphthyl)butyric acid ((S)-1-formyl-3-methyl)butyl amide) which exhibited good activity in the enzyme assay, also inhibited calpain I in a human cell line.

Calpain I, an intracellular cysteine protease, has been implicated in the neurodegeneration following an episode of stroke. In this paper, we report on a series of potent dipeptide fluoromethyl ketone inhibitors of recombinant human calpain I (rh calpain I). SAR studies revealed that while calpain I tolerates a variety of hydrophobic groups at the P1 site, Leu at P2 is preferred. However, the nature of the N-terminal capping group has a significant effect on the inhibitory activity of this series of compounds. Compound 4e [(1,2,3,4-tetrahydroisoquinolin-2-yl)carbonyl-Leu-D,L-Phe-CH2F+ ++], having a tetrahydroisoquinoline containing urea as the N-terminal capping group, is the most potent dipeptide fluoromethyl ketone inhibitor of calpain I (with a second-order rate constant for inactivation of 276,000 M-1 s-1) yet reported; tripeptide 4k (Cbz-Leu-Leu-D,L-Phe-CH2F) is equipotent. A number of compounds presented in this study displayed excellent selectivity for calpain I over cathepsins B and L, two related cysteine proteases. Compounds which exhibited good inhibitory activity in the assay against isolated rh calpain I also inhibited intracellular calpain I in a human cell line. Thus, in an intact cell assay, compounds 4e and 4k inhibited calpain I with IC50 values of 0.2 and 0.1 microM, respectively. Finally, we also disclose the first example of fluorination of a dipeptide enol silyl ether to generate the corresponding dipeptide fluoromethyl ketone.