How partnership should work to bring innovative medicines to patients.

Scientists increasingly find themselves working in bilateral drug development alliances. Alliances are conceptually simple, but operationally challenging, resulting in the value-eroding misalignment and delays that alliances often experience. This case study of an exemplary collaboration between a small biotech and a global biopharmaceutical company is based on 15 interviews and a lessons-learned workshop conducted with the principal alliance team members. We outline five repeatable practices identified as contributing to their success that other alliance teams can follow.

The synthesis and SAR of 2-amino-pyrrolo[2,3-d]pyrimidines: a new class of Aurora-A kinase inhibitors.

A new class of Aurora-A inhibitors have been identified based on the 2-amino-pyrrolo[2,3-d]pyrimidine scaffold. Here, we describe the synthesis and SAR of this novel series. We report compounds which exhibit nanomolar activity in the Aurora-A biochemical assay and are able to inhibit tumor cell proliferation. This study culminates in compound 30, an inhibitor with potent activity against Aurora A (IC50=0.008 microM), anti-proliferative activity against several tumor cell lines and induces polyploidy in H460 cells.

Novel 1,4-benzodiazepine-2,5-diones as Hdm2 antagonists with improved cellular activity.

The disruption of the p53-Hdm2 protein-protein interaction induces cell growth arrest and apoptosis. We have identified the 1,4-benzodiazepine-2,5-dione scaffold as a suitable template for inhibiting this interaction by binding to the Hdm2 protein. Several compounds have been made with improved potency, solubility, and cell-based activities.

Dihydroquinone ansamycins: toward resolving the conflict between low in vitro affinity and high cellular potency of geldanamycin derivatives.

Heat shock protein 90 (Hsp90) is critical for the maturation of numerous client proteins, many of which are involved in cellular transformation and oncogenesis. The ansamycins, geldanamycin (GA) and its derivative, 17-allylaminogeldanamycin (17-AAG), inhibit Hsp90. As such, the prototypical Hsp90 inhibitor, 17-AAG, has advanced into clinical oncology trials. GA and 17-AAG potently inhibit tumor cell proliferation and survival but have been reported to bind weakly to Hsp90 in vitro. Recent studies have suggested that the in vitro potency of ansamycins against Hsp90 may be enhanced in the presence of cochaperones. Here, we present evidence of an alternative explanation. Ansamycins reduced to their dihydroquinones in the presence of common reducing agents in vitro have approximately 40-fold greater affinity than the corresponding oxidized quinones. The dihydroquinone of 17-AAG is not generated in an aqueous environment in the absence of reducing agents but is produced in both tumor and normal quiescent epithelial cells. The reduced form of 17-AAG is differentiated from its oxidized form not only by the higher affinity for Hsp90 but also by a protracted K(off) rate. Therefore, the in vivo accumulation of the high-affinity dihydroquinone ansamycins in tumor cells contributes to the antitumor activity of these compounds and alters our understanding of the active species driving the efficacy of this class of compounds.

Enantiomerically pure 1,4-benzodiazepine-2,5-diones as Hdm2 antagonists.

The 1,4-benzodiazepine-2,5-dione is a suitable template to disrupt the interaction between p53 and Hdm2. The development of an enantioselective synthesis disclosed the stereochemistry of the active enantiomer. An in vitro p53 peptide displacement assay identified active compounds. These activities were confirmed in several cell-based assays including induction of the p53 regulated gene (PIG-3) and caspase activity.

Enhanced pharmacokinetic properties of 1,4-benzodiazepine-2,5-dione antagonists of the HDM2-p53 protein-protein interaction through structure-based drug design.

Guided by structure-based drug design, modification of the 1,4-benzodiazepin-2,5-dione lead compound 1 resulted in the discovery of 19, a potent and orally bioavailable antagonist of the HDM2-p53 protein-protein interaction (FP IC50 = 0.7 microM, F approximately 100%).

Benzodiazepinedione inhibitors of the Hdm2:p53 complex suppress human tumor cell proliferation in vitro and sensitize tumors to doxorubicin in vivo.

The activity and stability of the p53 tumor suppressor are regulated by the human homologue of the mouse double minute 2 (Hdm2) oncoprotein. It has been hypothesized that small molecules disrupting the Hdm2:p53 complex would allow for the activation of p53 and result in growth suppression. We have identified small-molecule inhibitors of the Hdm2:p53 interaction using our proprietary ThermoFluor microcalorimetry technology. Medicinal chemistry and structure-based drug design led to the development of an optimized series of benzodiazepinediones, including TDP521252 and TDP665759. Activities were dependent on the expression of wild-type (wt) p53 and Hdm2 as determined by lack of potency in mutant or null p53-expressing cell lines or cells engineered to no longer express Hdm2 and wt p53. TDP521252 and TDP665759 inhibited the proliferation of wt p53-expressing cell lines with average IC(50)s of 14 and 0.7 micromol/L, respectively. These results correlated with the direct cellular dissociation of Hdm2 from wt p53 observed within 15 minutes in JAR choriocarcinoma cells. Additional activities of these inhibitors in vitro include stabilization of p53 protein levels, up-regulation of p53 target genes in a DNA damage-independent manner, and induction of apoptosis in HepG2 cells. Administration of TDP665759 to mice led to an increase in p21(waf1/cip1) levels in liver samples. Finally, TDP665759 synergizes with doxorubicin both in culture and in an A375 xenograft model to decrease tumor growth. Taken together, these data support the potential utility of small-molecule inhibitors of the Hdm2:p53 interaction for the treatment of wt p53-expressing tumors.

Structure-based design, synthesis, and biological evaluation of novel 1,4-diazepines as HDM2 antagonists.

Crystallographic analysis of ligands bound to HDM2 suggested that 7-substituted 1,4-diazepine-2,5-diones could mimic the alpha-helix of p53 peptide and may represent a promising scaffold to develop HDM2-p53 antagonists. To verify this hypothesis, we synthesized and biologically evaluated 5-[(3S)-3-(4-chlorophenyl)-4-[(R)-1-(4-chlorophenyl)ethyl]-2,5-dioxo-7-phenyl-1,4-diazepin-1-yl]valeric acid (10) and 5-[(3S)-7-(2-bromophenyl)-3-(4-chlorophenyl)-4-[(R)-1-(4-chlorophenyl)ethyl]-2,5-dioxo-1,4-diazepin-1-yl]valeric acid (11). Preliminary in vitro testing shows that 10 and 11 substantially antagonize the binding between HDM2 and p53 with an IC(50) of 13 and 3.6 microM, respectively, validating the modeling predictions. Taken together with the high cell permeability of diazepine 11 determined in CACO-2 cells, these results suggest that 1,4-diazepine-2,5-diones may be useful in the treatment of certain cancers.

Discovery and cocrystal structure of benzodiazepinedione HDM2 antagonists that activate p53 in cells.

HDM2 binds to an alpha-helical transactivation domain of p53, inhibiting its tumor suppressive functions. A miniaturized thermal denaturation assay was used to screen chemical libraries, resulting in the discovery of a novel series of benzodiazepinedione antagonists of the HDM2-p53 interaction. The X-ray crystal structure of improved antagonists bound to HDM2 reveals their alpha-helix mimetic properties. These optimized molecules increase the transcription of p53 target genes and decrease proliferation of tumor cells expressing wild-type p53.

Development of a quantitative, high-throughput cell-based enzyme-linked immunosorbent assay for detection of colony-stimulating factor-1 receptor tyrosine kinase inhibitors.

Inhibitors of receptor tyrosine kinases are implicated as therapeutic agents for the treatment of many human diseases including cancer, inflammation and diabetes. Cell-based assays to examine inhibition of receptor tyrosine kinase mediated intracellular signaling are often laborious and not amenable to high-throughput cell-based screening of compound libraries. Here we describe the development of a nonradioactive, sandwich enzyme-linked immunosorbent assay (ELISA) to quantify the activation and inhibition of ligand-induced phosphorylation of the colony-stimulating factor-1 receptor (CSF-1R) in 96-well microtiter plate format. The assay involves the capture of the Triton X-100 solubilized human CSF-1R, from HEK293E cells overexpressing histidine epitope-tagged CSF-1R (CSF-1R/HEK293E), with immobilized CSF-1R antibody and detection of phosphosphorylation of the activated receptor with a phosphotyrosine specific antibody. The assay exhibited a 5-fold increase in phosphorylated CSF-1R signal from CSF-1R/HEK293E cells treated with colony-stimulating factor (CSF-1) relative to treated vector control cells. Additionally, using a histidine epitope-specific capture antibody, this method can also be adapted to quantify the phosphorylation state of any recombinantly expressed, histidine-tagged receptor tyrosine kinase. This method is a substantial improvement in throughput and quantitation of CSF-1R phosphorylation over conventional immunoblotting techniques.

Inhibition of mixed lineage kinase 3 attenuates MPP+-induced neurotoxicity in SH-SY5Y cells.

The neuropathology of Parkinson's Disease has been modeled in experimental animals following MPTP treatment and in dopaminergic cells in culture treated with the MPTP neurotoxic metabolite, MPP(+). MPTP through MPP(+) activates the stress-activated c-Jun N-terminal kinase (JNK) pathway in mice and SH-SY5Y neuroblastoma cells. Recently, it was demonstrated that CEP-1347/KT7515 attenuated MPTP-induced nigrostriatal dopaminergic neuron degeneration in mice, as well as MPTP-induced JNK phosphorylation. Presumably, CEP-1347 acts through inhibition of at least one upstream kinase within the mixed lineage kinase (MLK) family since it has been shown to inhibit MLK 1, 2 and 3 in vitro. Activation of the MLK family leads to JNK activation. In this study, the potential role of MLK and the JNK pathway was examined in MPP(+)-induced cell death of differentiated SH-SY5Y cells using CEP-1347 as a pharmacological probe and dominant negative adenoviral constructs to MLKs. CEP-1347 inhibited MPP(+)-induced cell death and the morphological features of apoptosis. CEP-1347 also prevented MPP(+)-induced JNK activation in SH-SY5Y cells. Endogenous MLK 3 expression was demonstrated in SH-SY5Y cells through protein levels and RT-PCR. Adenoviral infection of SH-SY5Y cells with a dominant negative MLK 3 construct attenuated the MPP(+)-mediated increase in activated JNK levels and inhibited neuronal death following MPP(+) addition compared to cultures infected with a control construct. Adenoviral dominant negative constructs of two other MLK family members (MLK 2 and DLK) did not protect against MPP(+)-induced cell death. These studies show that inhibition of the MLK 3/JNK pathway attenuates MPP(+)-mediated SH-SY5Y cell death in culture and supports the mechanism of action of CEP-1347 as an MLK family inhibitor.

JNK-mediated BIM phosphorylation potentiates BAX-dependent apoptosis.

Trophic factor deprivation (TFD) activates c-Jun N-terminal kinases (JNKs), culminating in coordinate AP1-dependent transactivation of the BH3-only BCL-2 proteins BIM(EL) and HRK, which in turn are critical for BAX-dependent cytochrome c release, caspase activation, and apoptosis. Here, we report that TFD caused not only induction but also phosphorylation of BIM(EL). Mitochondrially localized JNKs but not upstream activators, like mixed-lineage kinases (MLKs) or mitogen-activated protein kinase kinases (MKKs), specifically phosphorylated BIM(EL) at Ser65, potentiating its proapoptotic activity. Inhibition of the JNK pathway attenuated BIM(EL) expression, prevented BIM(EL) phosphorylation, and abrogated TFD-induced apoptosis. Conversely, activation of this pathway promoted BIM(EL) expression and phosphorylation, causing BIM- and BAX-dependent cell death. Thus, JNKs regulate the proapoptotic activity of BIM(EL) during TFD, both transcriptionally and posttranslationally.

Identification of JNK-dependent and -independent components of cerebellar granule neuron apoptosis.

Cerebellar granule neurons grown in high potassium undergo rapid apoptosis when switched to medium containing 5 mm potassium, a stimulus mimicking deafferentation. This cell death can be blocked by genetic deletion of Bax, a member of the pro-apoptotic Bcl-2 family, cycloheximide an inhibitor of macromolecular synthesis or expression of dominant-negative c-jun. These observations suggest that Bax activation is the result of c-jun target gene(s) up-regulation following trophic withdrawal. Candidate genes include the BH3-only Bcl-2 family members Dp5 and Bim. The molecular mechanisms underlying granule cell neuronal apoptosis in response to low potassium were investigated using CEP-1347 (KT7515), an inhibitor of the MLK family of JNKKK. CEP-1347 provided protection of potassium-serum-deprived granule cells, but such neuroprotection was not long term. The incomplete protection was not due to incomplete blockade of the JNK signaling pathway because c-jun phosphorylation as well as induction of c-jun RNA and protein were completely blocked by CEP-1347. Following potassium-serum deprivation the JNKK MKK4 becomes phosphorylated, an event blocked by CEP-1347. Cells that die in the presence of CEP-1347 activate caspases; and dual inhibition of caspases and MLKs has additive, not synergistic, effects on survival. A lack of synergism was also seen with the p38 inhibitor SB203580, indicating that the neuroprotective effect of the JNK pathway inhibitor cannot be explained by p38 activation. Activation of the JNK signaling pathway seems to be a key event in granule cell apoptosis, but these neurons cannot survive long term in the absence of sustained PI3 kinase signaling.

Mixed lineage kinase 3 mediates gp120IIIB-induced neurotoxicity.

Overexpression of gp120, the major coat protein of the HIV-1 virus, in central glial cells, or treatment of neurons with gp120 in culture, produces apoptotic neuronal death. Here we demonstrate that CEP-1347 (KT7515), an inhibitor of mixed lineage kinase 3 (MLK3), an upstream activator of JNK, inhibits gp120IIIB-induced apoptosis of hippocampal neurons. Furthermore, expression of wild type MLK3 in hippocampal pyramidal neurons enhanced gp120IIIB-induced neurotoxicity, whereas expression of a dominant negative MLK3 protected neurons from the toxic effects of the glycoprotein. These results indicate a role for MLK3 signaling in gp120IIIB-induced neuronal death, and suggest potential clinical utility of CEP-1347 in inhibiting the progression of AIDS dementia.

Inhibition of the c-Jun N-terminal kinase signaling pathway by the mixed lineage kinase inhibitor CEP-1347 (KT7515) preserves metabolism and growth of trophic factor-deprived neurons.

Nerve growth factor (NGF) deprivation triggers metabolic changes in sympathetic neurons that precede cell death. Here, we investigate the role of the c-Jun N-terminal kinase (JNK) pathway in downregulating neuronal metabolism. We show that, in the presence of CEP-1347 (KT7515), a small molecule known to block cell death upstream of JNK, cellular metabolism is preserved in neurons deprived of NGF. Biochemical data that are presented are consistent with the mechanism of action of CEP-1347 being the inhibition of the mixed lineage kinases (MLKs), known activators of JNK signaling. We demonstrate that CEP-1347-saved neurons continue to grow even in the absence of NGF, indicating that inhibition of the JNK pathway is permissive for neuronal growth in the absence of trophic support. These trophic effects are seen despite the fact that CEP-1347 does not stimulate several known survival kinase pathways. In addition to blocking Bax-dependent cytochrome c release, the inhibition of the JNK signaling pathway with CEP-1347 also blocks the development of competence-to-die in response to cytosolic cytochrome c. Therefore, inhibition of the JNK signaling pathway with the MLK inhibitor CEP-1347 inhibits both limbs of the apoptotic pathway. Finally, we demonstrate that neurons that have been NGF-deprived long-term but that have been kept alive by caspase inhibitors can be rescued metabolically by CEP-1347 as assessed by soma size, cytochrome c localization, and protein synthesis rates. Therefore, we conclude that, in addition to converting extracellular signals into decisions of life and death, the JNK pathway can modulate cellular metabolism directly and thereby maintain not only survival but the "quality of life" of neurons.

Discovery of CEP-1347/KT-7515, an inhibitor of the JNK/SAPK pathway for the treatment of neurodegenerative diseases.

Apoptosis has been proposed as a mechanism of cell death in Alzheimer's, Huntington's and Parkinson's diseases and the occurrence of apoptosis in these disorders suggests a common mechanism. Events such as oxidative stress, calcium toxicity, mitochondria defects, excitatory toxicity, and deficiency of survival factors are all postulated to play varying roles in the pathogenesis of the diseases. However, the transcription factor c-jun may play a role in the pathology and cell death processes that occur in Alzheimer's disease. Parkinson's disease (PD) is also a progressive disorder involving the specific degeneration and death of dopamine neurons in the nigrostriatal pathway. In Parkinson's disease, dopaminergic neurons in the substantia nigra are hypothesized to undergo cell death by apoptotic processes. The commonality of biochemical events and pathways leading to cell death in these diseases continues to be an area under intense investigation. The current therapy for PD and AD remains targeting replacement of lost transmitter, but the ultimate objective in neurodegenerative therapy is the functional restoration and/or cessation of progression of neuronal loss. This chapter will describe a novel approach for the treatment of neurodegenerative diseases through the development of kinase inhibitors that block the active cell death process at an early transcriptional independent step in the stress activated kinase cascade. In particular, preclinical data will be presented on the c-Jun Amino Kinase pathway inhibitor, CEP-1347/KT-7515, with respect to it's properties that make it a desirable clinical candidate for treatment of various neurodegenerative diseases.