The discovery of BMS-737 as a potent, CYP17 lyase-selective inhibitor for the treatment of castration-resistant prostate cancer.

We report herein, the discovery of BMS-737 (compound 33) as a potent, non-steroidal, reversible small molecule inhibitor demonstrating 11-fold selectivity for CYP17 lyase over CYP17 hydroxylase, as well as a clean xenobiotic CYP profile for the treatment of castration-resistant prostate cancer (CRPC). Extensive SAR studies on the initial lead 1 at three different regions of the molecule resulted in the identification of BMS-737, which demonstrated a robust 83% lowering of testosterone without any significant perturbation of the mineralocorticoid and glucocorticoid levels in cynomologous monkeys in a 1-day PK/PD study.

Design, synthesis and biological evaluation of phenol-linked uncialamycin antibody-drug conjugates.

Uncialamycin is one of the structurally simpler and newer members of enediyne family of natural products. It exhibits highly potent activity against several types of bacteria and cancer cells. Described herein is a strategy for the targeted delivery of this cytotoxic agent to tumors using an antibody-drug conjugate (ADC) approach. Central to the design of ADC were the generation of potent and chemically stable uncialamycin analogues and attachment of protease cleavable linkers to newly realized phenolic handles to prepare linker-payloads. Conjugation of the linker-payloads to tumor targeting antibody, in vitro activity and in vivo evaluation are presented.

Development of a series of novel o-phenylenediamine-based indoleamine 2,3-dioxygenase 1 (IDO1) inhibitors.

A novel series of o-phenylenediamine-based inhibitors of indoleamine 2,3-dioxygenase (IDO) has been identified. IDO is a heme-containing enzyme, overexpressed in the tumor microenvironment of many cancers, which can contribute to the suppression of the host immune system. Synthetic modifications to a previously described diarylether series resulted in an additional degree of molecular diversity which was exploited to afford compounds that demonstrated significant potency in the HeLa human cervical cancer IDO1 assay. .

Identification and optimization of a novel series of indoleamine 2,3-dioxygenase inhibitors.

The discovery of a series of structurally-novel biaryl urea IDO inhibitors is described. Optimization of a micromolar hit through iterative cycles of synthesis and screening in an assay measuring IDO-mediated intracellular conversion of tryptophan to kynurenine led to potent inhibitors with favorable selectivity and metabolic stability profiles.

Macrocyclic pyrrolobenzodiazepine dimers as antibody-drug conjugate payloads.

Macrocyclic pyrrolobenzodiazepine dimers were designed and evaluated for use as antibody-drug conjugate payloads. Initial structure-activity exploration established that macrocyclization could increase the potency of PBD dimers compared with non-macrocyclic analogs. Further optimization overcame activity-limiting solubility issues, leading to compounds with highly potent (picomolar) activity against several cancer cell lines. High levels of in vitro potency and specificity were demonstrated with an anti-mesothelin conjugate.

[2.2.1]-Bicyclic sultams as potent androgen receptor antagonists.

This letter describes the discovery, synthesis, SAR, and biological activity of [2.2.1]-bicyclic sultams as potent antagonists of the androgen receptor. Optimization of the series led to the identification of compound 25, which displayed robust pharmacodynamic effects in rats after oral dosing.

Pharmacology of smac mimetics; chemotype differentiation based on physical association with caspase regulators and cellular transport.

Cellular levels of inhibitor of apoptosis (IAP) proteins are elevated in multiple human cancers and their activities often play a part in promoting cancer cell survival by blocking apoptotic pathways, controlling signal transduction pathways and contributing to resistance. These proteins function through interactions of their BIR (baculoviral IAP repeat) protein domains with pathway components and these interactions are endogenously antagonized by Smac/Diablo (second mitochondrial activator of caspases/direct IAP binding protein with low isoelectric point). This report describes development of synthetic smac mimetics (SM) and compares their binding, antiproliferative and anti-tumor activities. All dimeric antagonists inhibit in vitro smac tetrapeptide binding to recombinant IAP proteins, rescue IAP-bound caspase-3 activity and show anti-proliferative activity against human A875 melanoma cells. One heterodimeric SM, SM3, binds tightly to IAP proteins in vitro and slowly dissociates (greater than two hours) from these protein complexes compared to the other antagonists. In addition, in vitro SM anti-proliferation potency is influenced by ABCB1 transporter (ATP-binding cassette, sub-family B; MDR1, P-gp) activities and one antagonist, SM5, does not appear to be an ABCB1 efflux pump substrate. All dimeric smac mimetics inhibit the growth of human melanoma A875 tumors implanted in athymic mice at well-tolerated doses. One antagonist, SM4, shows broad spectrum in vivo anti-tumor activity and modulates known pharmacodynamic markers of IAP antagonism. These data taken together demonstrate the range of diverse dimeric IAP antagonist activities and supports their potential as anticancer agents.

BMS-871: a novel orally active pan-Notch inhibitor as an anticancer agent.

This Letter describes synthesis, SAR, and biological activity of (2-oxo-1,4-benzodiazepin-3-yl)-succinamides as inhibitors of γ-secretase mediated signaling of Notch receptors. Optimization of this series led to the identification of BMS-871 (compound 30) which displayed robust in vivo efficacy in Notch-dependent leukemia and solid tumor xenograft models.

Hyperdynamic microtubules, cognitive deficits, and pathology are improved in tau transgenic mice with low doses of the microtubule-stabilizing agent BMS-241027.

Tau is a microtubule (MT)-stabilizing protein that is altered in Alzheimer's disease (AD) and other tauopathies. It is hypothesized that the hyperphosphorylated, conformationally altered, and multimeric forms of tau lead to a disruption of MT stability; however, direct evidence is lacking in vivo. In this study, an in vivo stable isotope-mass spectrometric technique was used to measure the turnover, or dynamicity, of MTs in brains of living animals. We demonstrated an age-dependent increase in MT dynamics in two different tau transgenic mouse models, 3xTg and rTg4510. MT hyperdynamicity was dependent on tau expression, since a reduction of transgene expression with doxycycline reversed the MT changes. Treatment of rTg4510 mice with the epothilone, BMS-241027, also restored MT dynamics to baseline levels. In addition, MT stabilization with BMS-241027 had beneficial effects on Morris water maze deficits, tau pathology, and neurodegeneration. Interestingly, pathological and functional benefits of BMS-241027 were observed at doses that only partially reversed MT hyperdynamicity. Together, these data suggest that tau-mediated loss of MT stability may contribute to disease progression and that very low doses of BMS-241027 may be useful in the treatment of AD and other tauopathies.

Novel pyrrolo[2,1-f][1,2,4]triazin-4-amines: Dual inhibitors of EGFR and HER2 protein tyrosine kinases.

A novel series of 5-((4-aminopiperidin-1-yl)methyl)-pyrrolo[2,1-f][1,2,4]triazin-4-amines with small aniline substituents at the C4 position were optimized for dual EGFR and HER2 protein tyrosine kinase inhibition. Compound 8l exhibited promising oral efficacy in both EGFR and HER2-driven human tumor xenograft models.

Discovery of Orally Active Isofuranones as Potent, Selective Inhibitors of Hematopoetic Progenitor Kinase 1.

While the discovery of immune checkpoint inhibitors has led to robust, durable responses in a range of cancers, many patients do not respond to currently available therapeutics. Therefore, an urgent need exists to identify alternative mechanisms to augment the immune-mediated clearance of tumors. Hematopoetic progenitor kinase 1 (HPK1) is a serine-threonine kinase that acts as a negative regulator of T-cell receptor (TCR) signaling, to dampen the immune response. Herein we describe the structure-based discovery of isofuranones as inhibitors of HPK1. Optimization of the chemotype led to improvements in potency, selectivity, plasma protein binding, and metabolic stability, culminating in the identification of compound 24. Oral administration of 24, in combination with an anti-PD1 antibody, demonstrated robust enhancement of anti-PD1 efficacy in a syngeneic tumor model of colorectal cancer.

Regioselective synthesis of folate receptor-targeted agents derived from epothilone analogs and folic acid.

Efficient regioselective syntheses of conjugates of folic acid and cytotoxic agents derived from natural epothilones are described. These folate receptor (FR) targeting compounds are water soluble and incorporate a hydrophilic peptide-based spacer unit and a reducible self-immolative disulfide-based linker system between the FR-targeting ligand and the parent drug.

Total Synthesis of Meayamycin and O-Acyl Analogues.

A short, scalable total synthesis of meayamycin is described by an approach that entails a longest linear sequence of 12 steps (22 steps overall) from commercially available chiral pool materials (ethyl l-lactate, BocNH-Thr-OH, and d-ribose) and introduces the most straightforward preparation of the right-hand subunit detailed to date. The use of the approach in the divergent synthesis of a representative series of O-acyl analogues is exemplified.

Discovery of anticancer agents of diverse natural origin.

A collaborative multidisciplinary research project is described in which new natural product anticancer drug leads are obtained from a diverse group of organisms, constituted by tropical plants, aquatic cyanobacteria, and filamentous fungi. Information is provided on how these organisms are collected and processed. The types of bioassays are indicated in which crude extracts of these acquisitions are tested. Progress made in the isolation of lead bioactive secondary metabolites from three tropical plants is discussed.

Identification and optimization of a novel series of [2.2.1]-oxabicyclo imide-based androgen receptor antagonists.

A novel series of [2.2.1]-oxabicyclo imide-based compounds were identified as potent antagonists of the androgen receptor. Molecular modeling and iterative drug design were applied to optimize this series. The lead compound [3aS-(3aalpha,4beta,5beta,7beta,7aalpha)]-4-(octahydro-5-hydroxy-4,7-dimethyl-1,3-dioxo-4,7-epoxy-2H-isoindol-2-yl)-2-iodobenzonitrile was shown to have potent in vivo efficacy after oral dosing in the CWR22 human prostate tumor xenograph model.

Discovery of 4-Azaindole Inhibitors of TGFßRI as Immuno-oncology Agents.

The multifunctional cytokine TGFß plays a central role in regulating antitumor immunity. It has been postulated that inhibition of TGFß signaling in concert with checkpoint blockade will provide improved and durable immune response against tumors. Herein, we describe a novel series of 4-azaindole TGFß receptor kinase inhibitors with excellent selectivity for TGFß receptor 1 kinase. The combination of compound 3f and an antimouse-PD-1 antibody demonstrated significantly improved antitumor efficacy compared to either treatment alone in a murine tumor model.

Preclinical antitumor activity of BMS-599626, a pan-HER kinase inhibitor that inhibits HER1/HER2 homodimer and heterodimer signaling.

PURPOSE: The studies described here are intended to characterize the ability of BMS-599626, a small-molecule inhibitor of the human epidermal growth factor receptor (HER) kinase family, to modulate signaling and growth of tumor cells that depend on HER1 and/or HER2. EXPERIMENTAL DESIGN: The potency and selectivity of BMS-599626 were assessed in biochemical assays using recombinant protein kinases, as well as in cell proliferation assays using tumor cell lines with varying degrees of dependence on HER1 or HER2 signaling. Modulation of receptor signaling was determined in cell assays by Western blot analyses of receptor autophosphorylation and downstream signaling. The ability of BMS-599626 to inhibit receptor heterodimer signaling in tumor cells was studied by receptor coimmunoprecipitation. Antitumor activity of BMS-599626 was evaluated using a number of different xenograft models that represent a spectrum of human tumors with HER1 or HER2 overexpression. RESULTS: BMS-599626 inhibited HER1 and HER2 with IC50 of 20 and 30 nmol/L, respectively, and was highly selective when tested against a broad panel of diverse protein kinases. Biochemical studies suggested that BMS-599626 inhibited HER1 and HER2 through distinct mechanisms. BMS-599626 abrogated HER1 and HER2 signaling and inhibited the proliferation of tumor cell lines that are dependent on these receptors, with IC50 in the range of 0.24 to 1 micromol/L. BMS-599626 was highly selective for tumor cells that depend on HER1/HER2 and had no effect on the proliferation of cell lines that do not express these receptors. In tumor cells that are capable of forming HER1/HER2 heterodimers, BMS-599626 inhibited heterodimerization and downstream signaling. BMS-599626 had antitumor activity in models that overexpress HER1 (GEO), as well as in models that have HER2 gene amplification (KPL4) or overexpression (Sal2), and there was good correlation between the inhibition of receptor signaling and antitumor activity. CONCLUSIONS: BMS-599626 is a highly selective and potent inhibitor of HER1 and HER2 kinases and inhibits tumor cell proliferation through modulation of receptor signaling. BMS-599626 inhibits HER1/HER2 receptor heterodimerization and provides an additional mechanism of inhibiting tumors in which receptor coexpression and heterodimerization play a major role in driving tumor growth. The preclinical data support the advancement of BMS-599626 into clinical development for the treatment of cancer.

Constitutively active receptor tyrosine kinases as oncogenes in preclinical models for cancer therapeutics.

Receptor tyrosine kinases (RTK) remain an area of therapeutic interest because of their role in epithelial tumors, and experimental models specific to these targets are highly desirable. Chimeric receptors were prepared by in-frame fusion of the CD8 extracellular sequence with the cytoplasmic sequences of RTKs. A CD8HER2 fusion protein was shown to form disulfide-mediated homodimers and to transform fibroblasts and epithelial cells. CD8RTK fusion proteins transform rat kidney epithelial cells and impart phenotypes that may reflect signaling specificity inherent in the native receptors. Transgenic expression of CD8HER2 and CD8Met in mice resulted in the formation of salivary and mammary gland tumors. The transgenic tumors allow the derivation of allograft tumors and cell lines that are sensitive to inhibition by small molecule kinase inhibitors. This approach provides excellent cell and tumor models for the characterization of signaling properties of diverse RTKs and for the evaluation of rationally designed antagonists targeting these kinases.

Synergistic inhibition of Aß production by combinations of γ-secretase modulators.

Alzheimer's disease is associated with the accumulation of amyloid-ß (Aß) in the brain. In particular, the 42-amino acid form, Aß1-42, is thought to play a key role in the disease. It is therefore of interest that diverse compounds, known as γ-secretase modulators (GSM), can selectively decrease Aß1-42 production without inhibiting the production of other forms of Aß. Here we describe the novel discovery of synergistic inhibition of Aß by certain combinations of GSMs. Cell cultures were treated with pairwise combinations of GSMs to determine how Aß peptide production was affected. Analysis of isobolograms and calculation of the combination index showed that BMS-869780 and GSM-2 were highly synergistic. Additional combinations of GSMs revealed that inhibition of Aß occurred only when one GSM was of the "acid GSM" structural class and the other was of the "non-acid GSM" class. A total of 15 representative acid/non-acid GSM combinations were shown to inhibit Aß production, whereas 10 pairwise combinations containing two acid GSMs or containing two non-acid GSMs did not inhibit Aß. We also discovered that lasalocid, a natural product, is a potent GSM. Lasalocid is unique in that it did not synergize with other GSMs. Synergism did not translate in vivo perhaps because of biochemical differences between the cell culture model and brain. These findings reinforce the pharmacological differences between different structural classes of GSMs, and may help to exploit the potential of γ-secretase as a drug target.

Apoptotic and cytostatic farnesyltransferase inhibitors have distinct pharmacology and efficacy profiles in tumor models.

BMS-214662 and BMS-225975 are tetrahydrobenzodiazepine-based farnesyltransferase inhibitors (FTIs) that have nearly identical structures and very similar pharmacological profiles associated with farnesyltransferase (FT) inhibition. Despite their similar activity against FT in vitro and in cells, these compounds differ dramatically in their apoptotic potency and tumor-regressing activity in vivo. BMS-214662 is the most potent apoptotic FTI known and exhibits curative responses in mice bearing a variety of staged human tumor xenografts such as HCT-116 human colon tumor. By contrast, BMS-225975 does not cause tumor regression and at best causes partial tumor growth inhibition in staged HCT-116 human colon tumor xenografts. Lack of tumor regression activity in BMS-225975 was attributable to its relatively weak apoptotic potency, not to poor cell permeability or pharmacokinetics. Both compounds were equally effective in inhibiting Ras processing and causing accumulation of a variety of nonfarnesylated substrates of FT in HCT-116 cells. Because BMS-225975 has poor apoptotic activity compared with BMS-214662 but inhibits FT to the same extent as BMS-214662, it is very unlikely that FT inhibition alone can account for the apoptotic potency of BMS-214662. Clearly distinct patterns of sensitivities in a cell line panel were obtained for the apoptotic FTI BMS-214662 and the cytostatic FTI BMS-225975. Activation of the c-Jun-NH(2)-terminal kinase pathway was readily observed with BMS-214662 but not with BMS-225975. We developed a highly sensitive San-1 murine xenograft tumor model that is particularly useful for evaluating the in vivo activity of cytostatic FTIs such as BMS-225975.