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This Letter describes the lead discovery, optimization, and biological characterization of a series of substituted 4-amino-1H-pyrazolo[3,4-d]pyrimidines as potent inhibitors of IGF1R, EGFR, and ErbB2. The leading compound 11 showed an IGF1R IC(50) of 12 nM, an EGFR (L858R) IC(50) of 31 nM, and an ErbB2 IC(50) of 11 nM, potent activity in cellular functional and anti-proliferation assays, as well as activity in an in vivo pharmacodynamic assay.

The design and enzyme activities of a novel class of imidazo[2,1-b]thiazoles is presented.

BackgroundThe insulin-like growth factor (IGF) axis is an important signaling pathway in the growth and survival of many cell and tissue types. This pathway has also been implicated in many aspects of cancer progression from tumorigenesis to metastasis. The multiple roles of IGF signaling in cancer suggest that inhibition of the pathway might yield clinically effective therapeutics.MethodsWe describe A-928605, a novel pyrazolo [3,4-d]pyrimidine small molecule inhibitor of the receptor tyrosine kinases (IGF1R and IR) responsible for IGF signal transduction. This compound was first tested for its activity and selectivity via conventionalin vitrokinome profiling and cellular IGF1R autophosphorylation. Additionally, cellular selectivity and efficacy of A-928605 were analyzed in an IGF1R oncogene-addicted cell line by proliferation, signaling and microarray studies. Finally,in vivoefficacy of A-928605 was assessed in the oncogene-addicted cell line and in a neuroblastoma model as a single agent as well as in combination with clinically approved therapeutics targeting EGFR in models of pancreatic and non-small cell lung cancers.ResultsA-928605 is a selective IGF1R inhibitor that is able to abrogate activation of the pathway bothin vitroandin vivo. This novel compound dosed as a single agent is able to produce significant growth inhibition of neuroblastoma xenograftsin vivo. A-928605 is also able to provide additive effects when used in combination with clinically approved agents directed against EGFR in non-small cell lung and human pancreatic tumor models.ConclusionThese results suggest that a selective IGF1R inhibitor such as A-928605 may provide a useful clinical therapeutic for IGF pathway affected tumors and warrants further investigation.

Emerging clinical and pre-clinical data indicate that both insulin-like growth factor receptor (IGF-IR) and members of the epidermal growth factor (EGF) family of receptor tyrosine kinases (RTKs) exhibit significant cross-talk in human cancers. Therefore, a small molecule that successfully inhibits the signaling of both classes of oncogenic kinases might provide an attractive agent for chemotherapeutic use. Herein, we disclose the structure activity relationships that led to the synthesis and biological characterization of 14, a novel small molecule inhibitor of both IGF-IR and members of the epidermal growth factor family of RTKs.

A high throughput screen of Abbott's compound repository revealed that the pyrazolo[3,4-d]pyrimidine class of kinase inhibitors possessed moderate potency for IGF-IR, a promising target for cancer chemotherapy. The synthesis and subsequent optimization of this class of compounds led to the discovery of 14, a compound that possesses in vivo IGF-IR inhibitory activity.

The anti-apoptotic protein MCL-1 is a key regulator of cancer cell survival and a known resistance factor for small-molecule BCL-2 family inhibitors such as ABT-263 (navitoclax), making it an attractive therapeutic target. However, directly inhibiting this target requires the disruption of high-affinity protein–protein interactions, and therefore designing small molecules potent enough to inhibit MCL-1 in cells has proven extremely challenging. Here, we describe a series of indole-2-carboxylic acids, exemplified by the compound A-1210477, that bind to MCL-1 selectively and with sufficient affinity to disrupt MCL-1–BIM complexes in living cells. A-1210477 induces the hallmarks of intrinsic apoptosis and demonstrates single agent killing of multiple myeloma and non-small cell lung cancer cell lines demonstrated to be MCL-1 dependent by BH3 profiling or siRNA rescue experiments. As predicted, A-1210477 synergizes with the BCL-2/BCL-XL inhibitor navitoclax to kill a variety of cancer cell lines. This work represents the first description of small-molecule MCL-1 inhibitors with sufficient potency to induce clear on-target cellular activity. It also demonstrates the utility of these molecules as chemical tools for dissecting the basic biology of MCL-1 and the promise of small-molecule MCL-1 inhibitors as potential therapeutics for the treatment of cancer.

Methionine aminopeptidase-2 (MetAP2) is a novel target for cancer therapy. As part of an effort to discover orally active reversible inhibitors of MetAP2, a series of anthranilic acid sulfonamides with micromolar affinities for human MetAP2 were identified using affinity selection by mass spectrometry (ASMS) screening. These micromolar hits were rapidly improved to nanomolar leads on the basis of insights from protein crystallography; however, the compounds displayed extensive binding to human serum albumin and had limited activity in cellular assays. Modifications based on structural information on the binding of lead compounds to both MetAP2 and domain III of albumin allowed the identification of compounds with significant improvements in both parameters, which showed good cellular activity in both proliferation and methionine processing assays.

We have screened molecules for inhibition of MetAP2 as a novel approach toward antiangiogenesis and anticancer therapy using affinity selection/mass spectrometry (ASMS) employing MetAP2 loaded with Mn 2+ as the active site metal. After a series of anthranilic acid sulfonamides with micromolar affinities was identified, chemistry efforts were initiated. The micromolar hits were quickly improved to potent nanomolar inhibitors by chemical modifications guided by insights from X-ray crystallography.

Kringle 5, a proteolytic fragment of human plasminogen has been shown to potently inhibit angiogenesis. The tetrapeptide KLYD derived from kringle 5 has been shown to capture many activities of kringle 5 in vitro. Further simplification has been achieved by replacement of the two central amino acids with a 4-aminobenzoic acid spacer group. Molecules displaying the required recognition groups on this core show similar in vitro properties to kringle 5, and are able to displace radiolabeled protein from a high affinity binding site on endothelial cells.

The reaction of N-Boc-α-amino acids with aryllithium reagents followed by removal of the nitrogen protecting group provides enantiomerically pure α-amino aryl ketones as their corresponding HCl salts. This practical two-step sequence gives rapid access to a pharmaceutically interesting class of compounds from commercially available starting materials.

Methionine aminopeptidase (MetAP)-2 has been suggested as a novel target for cancer therapy because the anticancer agent TNP-470 irreversibly inactivates the catalytic activity of this enzyme. However, the importance of MetAP2 in cell growth and tumor progression was uncertain because previous data were based on the chemically reactive TNP-470. Here we show that a rationally designed reversible MetAP2 inhibitor, A-357300, suppresses tumor growth preclinically without the toxicities observed with TNP-470. We have synthesized this bestatin-type MetAP2 inhibitor with the aid of crystal structures of the enzyme-inhibitor complexes and parallel synthesis. A-357300 induces cytostasis by cell cycle arrest at the G(1) phase selectively in endothelial cells and in a subset of tumor cells, but not in most primary cells of nonendothelial type. A-357300 inhibits angiogenesis both in vitro and in vivo and shows potent antitumor efficacy in carcinoma, sarcoma, and neuroblastoma murine models. These data affirm that MetAP2 plays a pivotal role in cell growth and establish that reversible MetAP2 inhibitors are promising novel cancer therapeutic agents.

The identity of the physiological metal cofactor for human methionine aminopeptidase-2 (MetAP2) has not been established. To examine this question, we first investigated the effect of eight divalent metal ions, including Ca(2+), Co(2+), Cu(2+), Fe(2+), Mg(2+), Mn(2+), Ni(2+), and Zn(2+), on recombinant human methionine aminopeptidase apoenzymes in releasing N-terminal methionine from three peptide substrates: MAS, MGAQFSKT, and (3)H-MASK(biotin)G. The activity of MetAP2 on either MAS or MGAQFSKT was enhanced 15-25-fold by Co(2+) or Mn(2+) metal ions in a broad concentration range (1-1000 microM). In the presence of reduced glutathione to mimic the cellular environment, Co(2+) and Mn(2+) were also the best stimulators (approximately 30-fold) for MetAP2 enzyme activity. To determine which metal ion is physiologically relevant, we then tested inhibition of intracellular MetAP2 with synthetic inhibitors selective for MetAP2 with different metal cofactors. A-310840 below 10 microM did not inhibit the activity of MetAP2-Mn(2+) but was very potent against MetAP2 with other metal ions including Co(2+), Fe(2+), Ni(2+), and Zn(2+) in the in vitro enzyme assays. In contrast, A-311263 inhibited MetAP2 with Mn(2+), as well as Co(2+), Fe(2+), Ni(2+), and Zn(2+). In cell culture assays, A-310840 did not inhibit intracellular MetAP2 enzyme activity and did not inhibit cell proliferation despite its ability to permeate and accumulate in cytosol, while A-311263 inhibited both intracellular MetAP2 and proliferation in a similar concentration range, indicating cellular MetAP2 is functioning as a manganese enzyme but not as a cobalt, zinc, iron, or nickel enzyme. We conclude that MetAP2 is a manganese enzyme and that therapeutic MetAP2 inhibitors should inhibit MetAP2-Mn(2+).

The asymmetric synthesis of the lonomycin A C 1 -C 11 synthon is described, in which the absolute stereochemical relationships were established through the use of β-keto imide aldol bond constructions, internally directed β-hydroxy ketone reduction, and diastereoselective rhodium-catalyzed hydroboration

ABT-491 (4-ethynyl- N , N -dimethyl-3-[3-fluoro-4-[(2-methyl-1 H -imidazo-[4,5- c ]pyridin-1-yl)methyl]benzoyl]-1 H -indole-1-carboxamide hydrochloride) is a novel PAF (platelet-activating factor) receptor antagonist with a K i for inhibiting PAF binding to human platelets of 0.6 nM. Binding kinetics of ABT-491 to the PAF receptor is consistent with a relatively slow off-rate of the antagonist when compared to PAF. Inhibition of PAF binding is selective and is correlated with functional antagonism of PAF-mediated cellular responses (Ca 2+ mobilization, priming, and degranulation). Administration of ABT-491 in vivo leads to potent inhibition of PAF-induced inflammatory responses (increased vascular permeability, hypotension, and edema) and PAF-induced lethality. Oral potency (ED 50 ) was between 0.03 and 0.4 mg/kg in rat, mouse, and guinea-pig. When administered intravenously in these species, ABT-491 exhibited ED 50 values between 0.005 and 0.016 mg/kg. An oral dose of 0.5 mg/kg in rat provided >50% protection for 8 h against cutaneous PAF challenge. ABT-491 administered orally was also effective in inhibiting lipopolysaccharide-induced hypotension (ED 50 =0.04 mg/kg), gastrointestinal damage (0.05 mg/kg, 79% inhibition), and lethality (1 mg/kg, 85% vs. 57% survival). The potency of this novel antagonist suggests that ABT-491 will be useful in the treatment of PAF-mediated diseases. © 1997 Elsevier Science B.V.

Kringle 5, a proteolytic fragment of human plasminogen has been shown to potently inhibit angiogenesis. The tetrapeptide KLYD derived from kringle 5 has been shown to capture many activities of kringle 5 in vitro. Further simplification has been achieved by replacement of the two central amino acids with a 4-aminobenzoic acid spacer group. Molecules displaying the required recognition groups on this core show similar in vitro properties to kringle 5, and are able to displace radiolabeled protein from a high affinity binding site on endothelial cells.

Indole compounds substituted at the 3-position by a 7-carbonyl(pyridin-3-yl)pyrrolo[1,2-c]thiazole, 7-carbonyl(pyridin-3-yl)pyrrolo[1,2-c]oxazoline, or 7-carbonyl(pyridin-3-yl)pyrrolo[1,2-c]pyrrole group are potent antagonists of PAF and are useful in the treatment of PAF-related disorders including asthma, shock, respiratory distress syndrome, acute inflammation, transplanted organ rejection, gastrointestinal ulceration, allergic skin diseases, delayed cellular immunity, parturition, fetal lung maturation, and cellular differentiation.

The insulin-like growth factor 1 receptor (IGF1R) and its ligands, IGF1 and IGF2 are associated with cell growth and resistance to apoptosis. The ErbB axis, consisting of 4 receptor tyrosine kinases (EGFR, ErbB2, ErbB3, and ErbB4) is a longstanding target of cancer chemotherapy. There is a growing body of literature suggesting that targeting a combination of the IGF and ErbB axes would be more effective than targeting either alone. A screen of Abbott's compound collection revealed a scaffold, the imidazothiazoles, which showed activity against EGFR. A similar scaffold from the literature had previously been reported to have IGF1R activity. Optimization of the imidazothiazoles, and a scaffold hop to imidazopyridines, has provided a series of compounds with amide head groups with kinase inhibitory activity against IGF1R, EGFR, and ErbB2. These compounds also demonstrated inhibition of p-IGF1R and p-EGFR in a human epidermoid carcinoma line (A-431), as well as inhibition of p-ErbB2 in a human gastric cancer cell line (N87). This poster will discuss the synthesis and optimization of the imidazothiazoles and imidazopyridines as multitargeted kinase inhibitors. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A245.

Insulin-like growth factor-1 receptor (IGF1R) and members of ErbB family (eg. EGFR, ErbB2) are receptor tyrosine kianses that play significant roles in cancer and have been pursued as drug targets for cancer therapy. There is substantial evidence for the existence of reciprocal cross-talk between IGF1R axis and ErbB axis of cellular signaling. Acquired resistance to EGFR inhibitors gefitinib and erlotinib or ErbB2 inhibitor trastuzumab has been linked to activation of IGF1R signaling through induced overexpression of IGF1R or loss of IGF binding- proteins. Additionally, synergy between IGF1R inhibition and ErbB inhibition has been demonstrated in cancer cell growth inhibition and in xenograft models. Thus, molecules targeting both IGF1R and ErbB-family might have superior anti-tumor efficacy. This poster describes the lead discovery, optimization and biological characterization of a series of substituted 4-amino-1H-pyrazolo[3,4-d]pyrimidines as potent inhibitors of IGF1R, EGFR and ErbB2. The leading compound, A-923573, showed IGF1R IC50 of 12 nM, EGFR (L858R) IC50 of 31 nM and ErbB2 IC50 of 11 nM, potent activity in cellular functional assays and anti-proliferation assays, as well as in an in vivo pharmacodynamic assay. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A248.

Studies directed toward the formation of methyl ethers in key intermediates for the synthesis of lonomycin A are described. Several highly functionalized secondary alcohols have been methylated in excellent yields using the powerful methylating reagents methyl triflate (MeOTf) and trimethyloxonium fluoroborate (Me 3 OBF 4 ).

Cycloadditions de pyrrolides d'acides pentyne-4oique et -heptyne-6oique et d'alcynes avec CpCo(CO) 2 : obtention d'η 5 -cyclopentadienyl complexes du cobalt de dihydro-5,6 pyrrolo [3,2,1-ij] quinoleines et de tetrahydro-4,5,6,7 azocino [3,2,1-hi] indoles

DURING the month of February of this year an unusual phenomenon has been observed in connexion with the coastal waters of the Pacific from the headland of Santa Elena to the north of Esmeraldas, Ecuador.