Jacob Kaizerman

Potent and highly selective hypoxia-activated achiral phosphoramidate mustards as anticancer drugs.

A series of achiral hypoxia-activated prodrugs were synthesized on the basis of the DNA cross-linking toxin of the prodrug, ifosfamide. The hypoxia-selective cytotoxicity of several of the compounds was improved over previously reported racemic mixtures of chiral bioreductive phosphoramidate prodrugs. Prodrugs activated by 2-nitroimidazole reduction demonstrated up to 400-fold enhanced cytotoxicity toward H460 cells in culture under hypoxia versus their potency under aerobic conditions. Compounds were further assessed for their stability to cytochrome P450 metabolism using a liver microsome assay. The 2-nitroimidazole containing lead compound 3b (TH-302) was selectively potent under hypoxia and stable to liver microsomes. It was active in an in vivo MIA PaCa-2 pancreatic cancer orthotopic xenograft model as a monotherapy and demonstrated dramatic efficacy when used in combination with gemcitabine, extending survival with one of eight animals tumor free at day-44. Compound 3b has emerged as a promising antitumor agent that shows excellent in vivo efficacy and is currently being evaluated in the clinic.

DNA binding ligands targeting drug-resistant Gram-positive bacteria. Part 2: C-terminal benzimidazoles and derivatives.

The synthesis and in vitro potency of DNA minor-groove binding antibacterials lacking the C-terminal amide bond are described. The crescent shaped molecules bear the positively charged amino group at an internal pyrrole unit instead of the C-terminus. Three structural parameters were investigated: the N-terminal unit, the internal amino group, and the C-terminal ring system. Several compounds demonstrated good in vitro potency against various Gram-positive bacteria and some molecules were moderately active against Escherichia coli, a representative Gram-negative strain.

DNA Binding Ligands with Excellent Antibiotic Potency Against Drug-Resistant Gram-Positive Bacteria

An efficient synthesis of DNA binding molecules consisting of four heterocyclic carboxamide units and various substituents at both termini is described. The minor-groove binding ligands showed excellent activity against a broad range of Gram-positive bacteria; no cross-resistance to known antibacterial drugs was observed.

Design of 1-piperazinyl-4-arylphthalazines as potent Smoothened antagonists

The Hedgehog (Hh) signaling pathway regulates cell proliferation and differentiation in developing tissues, and abnormal activation of the Hh pathway has been linked to several tumor subsets. As a transducer of Hh signaling, the GPCR-like protein Smoothened (Smo) is a promising target for disruption of unregulated Hh signaling. A series of 1-amino-4-arylphthalazines was developed as potent and orally bioavailable inhibitors of Smo. A representative compound from this class demonstrated significant tumor volume reduction in a mouse medulloblastoma model.

Optimization of novel di-substituted cyclohexylbenzamide derivatives as potent 11 beta-HSD1 inhibitors.

Novel 4,4-disubstituted cyclohexylbenzamide inhibitors of 11beta-HSD1 were optimized to account for liabilities relating to in vitro pharmacokinetics, cytotoxicity and protein-related shifts in potency. A representative compound showing favorable in vivo pharmacokinetics was found to be an efficacious inhibitor of 11beta-HSD1 in a rat pharmacodynamic model (ED(50)=10mg/kg).

Addressing PXR liabilities of phthalazine-based hedgehog/smoothened antagonists using novel pyridopyridazines

Pyridopyridazine antagonists of the hedgehog signaling pathway are described. Designed to optimize our previously described phthalazine smoothened antagonists, a representative compound eliminates a PXR liability while retaining potency and in vitro metabolic stability. Moreover, the compound has improved efficacy in a hedgehog/smoothened signaling mouse pharmacodynamic model.

Discovery of amide replacements that improve activity and metabolic stability of a bis-amide smoothened antagonist hit

A bis-amide antagonist of Smoothened, a seven-transmembrane receptor in the Hedgehog signaling pathway, was discovered via high throughput screening. In vitro and in vivo experiments demonstrated that the bis-amide was susceptible to N-acyl transferase mediated amide scission. Several bioisosteric replacements of the labile amide that maintained in vitro potency were identified and shown to be metabolically stable in vitro and in vivo.

Synthesis and optimization of novel 4,4-disubstituted cyclohexylbenzamide derivatives as potent 11β-HSD1 inhibitors

The synthesis and SAR of a series of 4,4-disubstituted cyclohexylbenzamide inhibitors of 11β-HSD1 are described. Optimization rapidly led to potent, highly selective, and orally bioavailable inhibitors demonstrating efficacy in both rat and non-human primate ex vivo pharmacodynamic models.

Abstract 2351: CDK4/FLT3 dual inhibitors as potential therapeutics for acute myeloid leukemia.

CDK4 is a cyclin D dependent kinase that promotes cell cycle progression in a broad range of tumor types by phosphorylating the tumor suppressor retinoblastoma protein (Rb) and releasing transcription factor E2F. Critical involvement of the cyclin D-CDK4-Rb pathway in carcinogenesis is strongly supported by a large amount of genetic evidence. In addition, promoter methylation with consequent silencing of expression of the CDK4 inhibitor, p15, has been reported in 44-60% of acute myeloid leukemia (AML) patients. It is also well established that constitutive activation of the tyrosine kinase FLT3 via mutation contributes to the development of AML, with 30% of AML carrying such activating mutations. FLT3 tyrosine kinase inhibitors used as single agents reduce peripheral blood and bone marrow blasts in only a minority of AML patients, and the effect tends to be transient. This may be due to insufficient FLT3 inhibition, the selection of drug-resistant clones, or the independence of the cell on FLT3 signaling for proliferation and survival. In preclinical models, a synergistic effect of CDK4 inhibition and FLT3 inhibition resulting in increased apoptosis of AML cell lines was reported (Wang et al., Blood, 2007). From a HTS hit through SAR optimization led to AM-5992, a potent and orally bioavailable dual inhibitor of CDK4 and FLT3 including all FLT3 mutants reported to date. AM-5992 inhibits the proliferation of a panel of human tumor cell lines including MDA-MB-435(Rb+), colo-205(Rb+), U937(FLT3WT) and induced cell death in MOLM13(FLT3ITD), MV4-11(FLT3ITD), and even in MOLM13(FLT3ITD, D835Y) which exhibits resistance to a number of FLT3 inhibitors currently under clinical development. In mouse models of leukemia using cells with the FLT3ITD mutation, AM-5992 treatment at 150 mpk qd on days 6-16 after leukemia cell injection significantly reduced the leukemia burden and prolonged survival 11 days over that of vehicle controls. Collectively, these data support the hypothesis that simultaneously inhibition of CDK4 and FLT3 may improve the durability of clinical response in AML; and consequently that this hypothesis should be tested in the clinic. Citation Format: Zhihong Li, Kang Dai, Kathleen Keegan, Ji Ma, Mark Ragains, Jacob Kaizerman, Dustin McMinn, Jiasheng Fu, Benjamin Fisher, Michael Gribble, Lawrence R. McGee, John Eksterowicz, Cong Li, Lingming Liang, Margaret Weidner, Justin Huard, Robert Cho, Timothy Carlson, Grace M. Alba, David Hollenback, John Hill, Darrin Beaupre, Alexander Kamb, Dineli Wickramasinghe, Julio C. Medina. CDK4/FLT3 dual inhibitors as potential therapeutics for acute myeloid leukemia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2351. doi:10.1158/1538-7445.AM2013-2351