Discovery and Preclinical Pharmacology of an Oral Bromodomain and Extra-Terminal (BET) Inhibitor Using Scaffold-Hopping and Structure-Guided Drug Design

Inhibition of the bromodomain and extra-terminal (BET) family of adaptor proteins is an attractive strategy for targeting transcriptional regulation of key oncogenes, such as c-MYC. Starting with the screening hit 1, a combination of structure-activity relationship and protein structure-guided drug design led to the discovery of a differently oriented carbazole 9 with favorable binding to the tryptophan, proline, and phenylalanine (WPF) shelf conserved in the BET family. Identification of an additional lipophilic pocket and functional group optimization to optimize pharmacokinetic (PK) properties culminated in the discovery of 18 (BMS-986158) with excellent potency in binding and functional assays. On the basis of its favorable PK profile and robust in vivo activity in a panel of hematologic and solid tumor models, BMS-986158 was selected as a candidate for clinical evaluation.

[Downregulation of large conductance calcium-activated potassium channels in paraventricular nucleus contributes to sympathoexcitation in rats with chronic heart failure]

Objective: To elucidate the association between large conductance calcium-activated potassium channels (BK_Ca) in the paraventricular hypothalamic nucleus (PVN) and sympathetic outflow in rats with chronic heart failure (CHF) . Methods: Male Wistar rats (6-7 weeks old) were randomized to sham operated group and CHF group (coronary artery ligation) . Two weeks after operation, BK_Ca inhibitor Iberiotoxin (IBTX) was infused into PVN by osmotic minipumps, rats were divided into following groups: sham+aCSF, CHF+aCSF, sham+low dose IBTX (0.125 nmol/nl) , CHF+low dose IBTX, sham+moderate dose IBTX (1.25 nmol/nl) , CHF+moderate dose IBTX, sham+ high dose IBTX (12.5 nmol/nl) , and CHF+high dose IBTX (n=6 each) . Additional rats were grouped as follows: sham+vehicle, sham+KCNMB4 knockdown (by rAAV2-KCNMB4 shRNA virus injection in PVN) , CHF+vehicle, CHF+ KCNMB4 knockdown group (n=6 each) . The cardiac function was determined by echocardiography, left ventricular hemodynamics were measured invasively, renal sympathetic nerve activity (RSNA) was recorded at 6 weeks after coronary artery ligation or sham operation. The contents of norepinephrine (NE) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) in plasma were determined by enzyme-linked immunosorbent assay. The protein and mRNA expression of KCNMB4 in PVN were measured by immunofluorescence staining, Western blot, and real-time PCR, mRNA expression of BK_Ca in PVN was detected by real-time PCR. Results: Compared with the sham operation group, the cardiac function of the heart failure group was significantly reduced (P<0.05) , and the plasma NE and the serum NT-proBNP were significantly elevated (P<0.05) . The protein and mRNA expression of KCNMB4 in PVN were obviously down-regulated in CHF rats (P<0.05) . After perfusion of IBTX or KCNMB4 knockdown by microinjection of rAAV2-KCNMB4 shRNA virus,right ventricular weight/body weight and lung weight/body weight ratio as well as left ventricular end-diastolic diameter were increased and left ventricular ejection fraction was decreased (all P<0.05) , the sympathetic driving indexes was increased in sham rats, changes of these parameters further aggravated in CHF rats (P<0.05) . KCNMB4 knockdown further downregulated protein expression in PVN of CHF rats. Conclusion: Downregulation and blunted function of BK_Ca in PVN may contribute to sympathoexcitation and deterioration of cardiac function in rats with chronic heart failure.

Discovery of Clinical Candidate BMS-906024: A Potent Pan-Notch Inhibitor for the Treatment of Leukemia and Solid Tumors

Structure-activity relationships in a series of (2-oxo-1,4-benzodiazepin-3-yl)-succinamides identified highly potent inhibitors of γ-secretase mediated signaling of Notch1/2/3/4 receptors. On the basis of its robust in vivo efficacy at tolerated doses in Notch driven leukemia and solid tumor xenograft models, 12 (BMS-906024) was selected as a candidate for clinical evaluation.

Abstract 1643: BMS-983970, an oral pan-Notch inhibitor for the treatment of cancer

Deregulation of the Notch pathway has been shown to be oncogenic in numerous tissue types including T-cell acute lymphoblastic leukemia (T-ALL), breast cancer, non-small cell lung cancer, and colorectal carcinoma. Notch signal activation can cause uncontrolled proliferation, restrict differentiation leading to increased self-renewal capacity, evasion of apoptosis, and enhancement of angiogenesis and metastasis. There is increasing evidence that Notch plays a role in the maintenance and survival of cancer stem cells. γ-Secretase mediates the Notch signaling pathway by releasing the Notch intracellular domain (NICD) which translocates to the nucleus and binds to the transcription factor CSL to activate transcription of various target genes. BMS-906024 is a potent pan-Notch inhibitor that demonstrated robust anti-tumor activity at tolerated doses in multiple tumor xenograft models. It is being evaluated in Phase 1 clinical studies. BMS-906024 is being administered IV (once weekly) in the clinic and the projected human efficacious dose is 4 - 6 mg. Based on the preclinical data, the projected human half-life of BMS-906024 is in the 37 h - 124 h range.

This presentation will describe further structure-activity relationships in the 1,4-benzodiazepinone series that culminated in the identification of BMS-983970 as an oral-pan-Notch inhibitor. Pharmacokinetic properties and in vivo evaluation of BMS-983970 in T-ALL and solid tumor xenograft models will be presented.

Citation Format: Ashvinikumar V. Gavai, Yufen Zhao, Daniel O'Malley, Brian Fink, Claude Quesnelle, Derek Norris, Libing Chen, Soong-Hoon Kim, Wen-Ching Han, Patrice Gill, Weifang Shan, Aaron Balog, Andrew Tebben, Richard Rampulla, Dauh-Rurng Wu, Yingru Zhang, Arvind Mathur, Haiqing Wang, Zheng Yang, Qian Ruan, Robin Moore, David Rodrigues, Asoka Ranasinghe, Celia D'Arienzo, Ching Kim Tye, Ching Su, Gerry Everlof, Melissa Yarde, Mary Ellen Cvijic, Krista Menard, Mei-Li Wen, George Trainor, Bruce Fischer, John Hunt, Gregory Vite, Richard Westhouse, Francis Lee. BMS-983970, an oral pan-Notch inhibitor for the treatment of cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1643. doi:10.1158/1538-7445.AM2014-1643

Abstract B195: Synergy between ixabepilone (Ixa) and trastuzumab (TZ): Investigation of the role of microtubule-associated protein (MAP-tau) and III tubulin (βIII) in HER2-positive (HER2+) breast cancer (BC)

Background and rationale: Historically, patients with aggressive HER2+ BC have a poor response to chemotherapy, including antimicrotubule agents. Elevated III levels have been reported in HER2+ BC. Introduction of the HER2+ targeted agent TZ, in combination with taxane based chemotherapy, greatly improved the outcomes of these patients. The novel antimicrotubule agent Ixa has broad preclinical and clinical efficacy in BC tumors, including those that overexpress III, a predictor of taxane resistance. Previous reports in BC cell lines and tumors have shown an inverse correlation between Ixa/taxane sensitivity and MAP-tau. We set out to evaluate the activity of Ixa in combination with TZ and explore the relationship between III and MAPtau expression and Ixa response in HER2+ BC. Here we provide preclinical evidence of synergy with Ixa plus TZ and preclinical and clinical evidence of the contribution of MAP-tau and III in HER2+ BC.

Methods: In preclinical studies with HER2+ human BC cell lines BT-474 and KPL-4 the effects of drug exposure were determined by a vital dye uptake assay (MTS) or a colony formation assay. Gene (Affymetrix HG U133A v2.0 Gene Chips) and protein expression (immunoblotting) changes in cells exposed to TZ or estradiol (E2; control) were assessed. BT-474 and KPL-4 subcutaneous tumors in mice were also assessed. Using intrinsic gene clustering, microarray expression data from 134 breast tumors from the Ixa monotherapy neoadjuvant BC trial CA163-080 (080) were subtyped as HER2-enriched, basal-, luminal- or normal-like, and III/MAP-tau expression was assessed by subtype.

Results: Ixa exhibited synergistic activity in combination with TZ in vitro (HER2+ BT-474 cell line). Synergy was also demonstrated in BT-474 and KPL-4 human BC xenografts in mice; 75% complete response (CR) was achieved in BT-474, compared with 0% CR and 25% partial response (PR) with Ixa alone, and 0% CR and 0% PR with TZ alone. Exposure of BT-474 cells to TZ for 24 hours caused down regulation of MAP-tau, relative to E2. Analysis of clinical tumor samples from 080 demonstrated that HER2-enriched tumors have elevated III, but reduced MAP-Tau levels relative to luminal-like and normal-like subtypes (P&lt;0.0001).

Conclusions: Ixa and TZ demonstrated synergy in HER2+ BC models. The ability of TZ to down regulate MAP-tau may explain, at least partially, the synergistic activity seen in the clinical setting when TZ is combined with antimicrotubule agents. Retrospective analysis of the 080 trial revealed that III was over- and MAP-tau was under-expressed, in HER2-enriched tumors relative to other BC subtypes. In two Phase 2 studies, Ixa was safe and effective when combined with TZ for the treatment of HER2+ BC patients. This data supports further exploration of III/MAP-tau expression and Ixa response in HER2+ BC in the clinical setting.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B195.

Synergistic antitumor activity of ixabepilone (BMS-247550) plus bevacizumab in multiple in vivo tumor models

PURPOSE

Angiogenesis is a critical step in the establishment, growth, and metastasis of solid tumors, and combination of antiangiogenic agents with chemotherapy is an attractive therapeutic option. We investigated the potential of ixabepilone, the first in a new class of antineoplastic agents known as epothilones, to synergize with antiangiogenic agents to inhibit tumor growth.

EXPERIMENTAL DESIGN

In vitro and in vivo cytotoxicity of ixabepilone as single agent and in combination with two targeted antiangiogenic agents, bevacizumab or sunitinib, were examined in preclinical tumor models. Direct effects of the agents against endothelial cells was also examined and compared with the effects of paclitaxel as single agent and in combination with bevacizumab.

RESULTS

Ixabepilone showed robust synergistic antitumor activity in combination with bevacizumab and sunitinib in preclinical in vivo models derived from breast, colon, lung, and kidney cancers. The synergistic antitumor effect was greater with ixabepilone compared with paclitaxel. Furthermore, ixabepilone was more effective than paclitaxel at killing endothelial cells expressing P-glycoprotein in vitro and inhibiting endothelial cell proliferation and tumor angiogenesis in vivo.

CONCLUSIONS

Ixabepilone may enhance the antitumor effects of antiangiogenic therapy by direct cytotoxicity and also indirectly via the killing of tumor-associated endothelial cells. Given that ixabepilone has reduced susceptibility to drug efflux pumps compared with taxanes, these data may explain the increased antiangiogenic and antitumor activity of ixabepilone in combination with antiangiogenic agents. Phase II studies to assess the efficacy and safety of ixabepilone plus bevacizumab in locally recurrent or metastatic breast cancer are planned.

Dasatinib (BMS-354825) pharmacokinetics and pharmacodynamic biomarkers in animal models predict optimal clinical exposure

PURPOSE

Chronic myeloid leukemia (CML) is caused by reciprocal translocation between chromosomes 9 and 22, forming BCR-ABL, a constitutively activated tyrosine kinase. Imatinib mesylate, a selective inhibitor of BCR-ABL, represents current frontline therapy for CML; however, emerging evidence suggests that drug resistance to imatinib may limit its long-term success. To improve treatment options, dasatinib (BMS-354825) was developed as a novel, oral, multi-targeted kinase inhibitor of BCR-ABL and SRC family kinases. To date, dasatinib has shown promising anti-leukemic activity in preclinical models of CML and in phase I/II clinical studies in patients with imatinib-resistant or imatinib-intolerant disease.

EXPERIMENTAL DESIGN

The pharmacokinetic and pharmacodynamic biomarkers of dasatinib were investigated in K562 human CML xenografts grown s.c. in severe combined immunodeficient mice. Tumoral levels of phospho-BCR-ABL/phospho-CrkL were determined by Western blot.

RESULTS

Following a single oral administration of dasatinib at a preclinical efficacious dose of 1.25 or 2.5 mg/kg, tumoral phospho-BCR-ABL/phospho-CrkL were maximally inhibited at approximately 3 hours and recovered to basal levels by 24 hours. The time course and extent of the inhibition correlated with the plasma levels of dasatinib in mice. Pharmacokinetic/biomarker modeling predicted that the plasma concentration of dasatinib required to inhibit 90% of phospho-BCR-ABL in vivo was 10.9 ng/mL in mice and 14.6 ng/mL in humans, which is within the range of concentrations achieved in CML patients who responded to dasatinib treatment in the clinic.

CONCLUSIONS

Phospho-BCR-ABL/phospho-CrkL are likely to be useful clinical biomarkers for the assessment of BCR-ABL kinase inhibition by dasatinib.

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.

Tumor development by transgenic expression of a constitutively active insulin-like growth factor I receptor

The insulin-like growth factor I receptor (IGF-IR) is a transmembrane tyrosine kinase that is essential to growth and development and also thought to provide a survival signal for the maintenance of the transformed phenotype. There has been increasing interest in further understanding the role of IGF-I signaling in cancer and in developing receptor antagonists for therapeutic application. We describe herein a novel animal model that involves transgenic expression of a fusion receptor that is constitutively activated by homodimerization. Transgenic mice that expressed the activated receptor showed aberrant development of the mammary glands and developed salivary and mammary adenocarcinomas as early as 8 weeks of age. Xenograft tumors and a cell line were derived from the transgenic animals and are sensitive to inhibition by a novel small-molecule inhibitor of the IGF-IR kinase. This new model should provide new opportunities for further understanding how aberrant IGF-IR signaling leads to tumorigenesis and for optimizing novel antagonists of the receptor kinase.

Discovery of N-(2-chloro-6-methyl- phenyl)-2-(6-(4-(2-hydroxyethyl)- piperazin-1-yl)-2-methylpyrimidin-4- ylamino)thiazole-5-carboxamide (BMS-354825), a dual Src/Abl kinase inhibitor with potent antitumor activity in preclinical assays

A series of substituted 2-(aminopyridyl)- and 2-(aminopyrimidinyl)thiazole-5-carboxamides was identified as potent Src/Abl kinase inhibitors with excellent antiproliferative activity against hematological and solid tumor cell lines. Compound 13 was orally active in a K562 xenograft model of chronic myelogenous leukemia (CML), demonstrating complete tumor regressions and low toxicity at multiple dose levels. On the basis of its robust in vivo activity and favorable pharmacokinetic profile, 13 was selected for additional characterization for oncology indications.

Discovery of N-(2-chloro-6-methyl- phenyl)-2-(6-(4-(2-hydroxyethyl)- piperazin-1-yl)-2-methylpyrimidin-4- ylamino)thiazole-5-carboxamide (BMS-354825), a dual Src/Abl kinase inhibitor with potent antitumor activity in preclinical assays

A series of substituted 2-(aminopyridyl)- and 2-(aminopyrimidinyl)thiazole-5-carboxamides was identified as potent Src/Abl kinase inhibitors with excellent antiproliferative activity against hematological and solid tumor cell lines. Compound 13 was orally active in a K562 xenograft model of chronic myelogenous leukemia (CML), demonstrating complete tumor regressions and low toxicity at multiple dose levels. On the basis of its robust in vivo activity and favorable pharmacokinetic profile, 13 was selected for additional characterization for oncology indications.

Fentanyl-selective polymeric membrane electrode

A poly (vinyl chloride) membrane electrode with dibutyl phthalate as plasticizer based on a fentanyl-tetrakis(4-chlorophenyl)borate ion-pair complex for the determination of fentanyl citrate in injections is described. A linear response over the range 1 x 10(-5) mol.dm-3 to 1 x 10(-2) mol.dm-3 drug with a slope of 59.3 +/- 0.6 mV/decade was established. The optimum pH range was 1 to 6. The lower detection limit was 8 x 10(-6) mol.dm-3 fentanyl citrate (2.7 micrograms cm-3 fentanyl). There were negligible interferences from a number of inorganic cations, structural analogues, and some common drug additives used in injections. The electrode proposed has been successfully applied to determine fentanyl citrate in injections. The results correlated well with those obtained by the United States Pharmacopoeia standard procedure.

Construction and performance characteristics of new fentanyl-selective plastic membrane electrode

The construction and performance characteristics of an ion-selective electrode for fentanyl-drug cation, based on an ion-pair complex with tetrakis[3,5-bis-(trifluoromethyl)phenyl]borate anion in a PVC matrix were studied. A linear response for 1 x 10(-5) mol dm-3 to 1 x 10(-2) mol dm-3 drug with a slope of 57.9 +/- 0.5 mV/decade was established. The optimum pH range was 2 to 6. The lower detection limit was 6.29 x 10(-6) mol dm-3 fentanyl citrate (2.1165 micrograms cm-3 fentanyl). There were negligible interferences from a number of inorganic cations, structural analogues, and some common drug additives in injections. The electrode proposed has been successfully applied to determine fentanyl citrate in injections. The results correlated well with those obtained by the United States Pharmacopoeia standard procedure.

Plastic membrane electrode for the potentiometric determination of pethidine hydrochloride in pharmaceutical preparations

A novel poly(vinyl chloride) membrane electrode with dibutyl phthalate as plasticizer based on the pethidine-tetraphenylborate ion-association complex as ion-exchange site for the determination of pethidine hydrochloride in injections and tablets was developed. A linear response for 1 x 10(-5) to 1 x 10(-2) mol/L drug with a slope of 51.77 mV/decade was established. The optimum pH range was 2-8. The lower detection limit was 2.18 x 10(-6) mol/L. There were negligible interferences from a number of inorganic and organic cations and some common drug excipients. The electrode proposed had been successfully applied to determine pethidine hydrochloride in tablets and injections. The results correlated well with those obtained by the United States Pharmacopoeia standard procedure.

Potentiometric sensor for methylene blue based on methylene blue-silicotungstate ion association and its pharmaceutical applications

A methylene blue (MB) poly(vinyl chloride) membrane sensor based on MB-silicotungstate (SLT) ion association as electroactive material was described. The linear response covered the range 1 x 10(-3)-1 x 10(-6) mol x dm(-3) MB solution, with a slope 52.0+/-0.8 mV decade(-1) (pH range 3.0-10.0). The detection limit was 7.65 x 10(-7) mol x dm(-3). The electrode showed stability, good reproducibility and fast response. Interferences from common inorganic cations, some organic base were negligible. These characteristics of the electrode enabled it to be used successfully for the determination of MB in injection. There was a good agreement for the results of MB content in injection between potentiometric method and USP standard procedure.

An affinity column method for determination of the immunoreactivity of 131I-chimeric L6 monoclonal antibody and comparison to in vivo tumor localization

An affinity column method was developed to determine the immunoreactivity of 131I-ChiL6 (chimeric L6 monoclonal antibody), a candidate for radioimmunotherapy. This method involved assessing the binding of the radiolabeled antibody to antigen containing membranes bound to a Reacti-gel agarose matrix. The immunoreactivity determined by the affinity column method correlated to other in vitro binding assays including the Lindmo infinite antigen excess method. In tumor-bearing mice which had been injected with 131I-ChiL6, which possessed high immunoreactivities (90-82%), a high tumor uptake (13.5-10.5% ID/g) was observed. A decrease in tumor uptake (5.2-4.8% ID/g) was observed with 131I-ChiL6 samples of low immunoreactivity (42% and 31%, respectively). While a moderate loss of immunoreactivity (4-18%) of the 131I-ChiL6 samples could be detected by the affinity column method, the loss of tumor uptake in vivo observed was not as significant. This method was found to be an efficient and sensitive method for detecting damage to the antibody during radiolabeling and applicable as a quality control method for clinical trials. This rapid method, compared to the other in vitro binding assays (including the Lindmo infinite antigen excess method) has distinct advantages as a quality control method since it requires less manipulation and can be semi-automated.

Site-specifically modified 111In labelled antibodies give low liver backgrounds and improved radioimmunoscintigraphy

Site-specific modification of monoclonal antibodies at their oligosaccharide had previously been demonstrated to produce excellent 111In imaging in a xenograft model using a Brown Norway (BN) rat lymphoma and a rat anti-BN MHC monoclonal antibody [Lee C. et al. Fed. Proc. Abstr. 43 3014 (1984)]. These results are due, in part, to lack of liver uptake, so we wanted to evaluate the extent of hepatic uptake observed with different monoclonal antibodies in normal mice. Biodistribution data were obtained for four monoclonal antibodies by first modifying each antibody at its carbohydrate with a diethylenetriaminepentaacetic acid (DTPA) derivative. The antibodies were then labelled with 111In and injected into normal mice. Images were obtained 24 h post-injection, and at 48 h the mice were dissected and the tissue-to-blood (T:B) ratios determined. T:B ratios were approximately 1 (or less) for every organ evaluated, indicating minimal non-specific uptake into these organs. Data is also presented for the BN-rat system which shows excellent localization into the tumor xenograft and low non-specific organ uptake. These data indicate that modification of antibodies site-specifically at their oligosaccharide results in minimal non-specific uptake into non-target tissues and enhanced localization into the tumor target, and that this may represent a preferred method for production of 111In labelled antibodies.