Herwig Pongratz

Synthetic 2-aroylindole derivatives as a new class of potent tubulin-inhibitory, antimitotic agents.

A new class of simple synthetic antimitotic compounds based on 2-aroylindoles was discovered. (5-Methoxy-1H-2-indolyl)-phenylmethanone (1) as well as analogous 3-fluorophenyl- (36) and 3-methoxyphenyl (3) derivatives displayed high cytotoxicity of IC(50) = 20 to 75 nM against the human HeLa/KB cervical, SK-OV-3 ovarian, and U373 astrocytoma carcinoma cell lines. The inhibition of proliferation correlated with the arrest in the G2/M phase of the cell cycle. In in vitro assays with tubulin isolated from bovine brain, in general antiproliferative activity correlated with inhibition of tubulin polymerization. Thus, the antimitotic activity of 2-aroylindoles is explained by interference with the mitotic spindle apparatus and destabilization of microtubules. In contrast to colchicine, vincristine, nocodazole, or taxol, 1 did not significantly affect the GTPase activity of beta-tubulin. Interestingly, selected compounds inhibited angiogenesis in the chorioallantoic membrane (CAM) assay. In xenograft experiments, 1 was highly active after oral administration at 200 mg/kg against the human amelanocytic melanoma MEXF 989 in athymic nude mice. We conclude, that 2-aroylindoles constitute an interesting new class of antitubulin agents with the potential to be clinically developed for cancer treatment.

Design of chimeric histone deacetylase- and tyrosine kinase-inhibitors: a series of imatinib hybrides as potent inhibitors of wild-type and mutant BCR-ABL, PDGF-Rbeta, and histone deacetylases.

Inhibitors of histone deacetylases are a new class of cancer therapeutics with possibly broad applicability. Combinations of HDAC inhibitors with the kinase inhibitor 1 (Imatinib) in recent studies showed additive and synergistic effects. Here we present a new concept by combining inhibition of protein kinases and HDACs, two independent pharmacological activities, in one synthetic small molecule. In general, the HDAC inhibition profile, the potencies, and the probable binding modes to HDAC1 and HDAC6 were similar as for 6 (SAHA). Inhibition of Abl kinase in biochemical assays was maintained for most compounds, but in general the kinase selectivity profile differed from that of 1 with nearly equipotent inhibition of the wild-type and the Imatinib resistant Abl T(315)I mutant. A potent cellular inhibition of PDGFR and cytotoxicity toward EOL-1 cells, a model for idiopathic hypereosinophilic syndrome (HES), are restored or enhanced for selected analogues (12b, 14b, and 18b). Cytotoxicity was evaluated by using a broad panel of tumor cell lines, with selected analogues displaying mean IC(50) values between 3.6 and 7.1 muM.

Novel chimeric histone deacetylase inhibitors: a series of lapatinib hybrides as potent inhibitors of epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and histone deacetylase activity.

Reversible lysine-specific acetylation has been described as an important posttranslational modification, regulating chromatin structure and transcriptional activity in the case of core histone proteins. Histone deacetylases (HDAC) are considered as a promising target for anticancer drug development, with 2a as pan-HDAC inhibitor approved for cutanous T-cell lymphoma therapy and several other HDAC inhibitors currently in preclinical and clinical development. Protein kinases are a well-established target for cancer therapy with the EGFR/HER2 inhibitor 5 approved for treatment of advanced, HER2 positive breast cancer as a prominent example. In the present report, we present a novel strategy for cancer drug development by combination of EGFR/HER2 kinase and HDAC inhibitory activity in one molecule. By combining the structural features of 5 with an (E)-3-(aryl)-N-hydroxyacrylamide motif known from HDAC inhibitors like 1 or 3, we obtained selective inhibitors for both targets with potent cellular activity (target inhibition and cytotoxicity) of selected compounds 6a and 6c. By combining two distinct pharmacologically properties in one molecule, we postulate a broader activity spectrum and less likelihood of drug resistance in cancer patients.

Novel inhibitors of epidermal growth factor receptor: (4-(Arylamino)-7H-pyrrolo[2,3-d]pyrimidin-6-yl)(1H-indol-2-yl)methanones and (1H-indol-2-yl)(4-(phenylamino)thieno[2,3-d]pyrimidin-6-yl)methanones.

Several members of the quinazoline class of known tyrosine kinase inhibitors are approved anticancer agents, often showing selectivity for receptors of the HER/ErbB-family. Combining structural elements of this class with the bisindolylmethanone-structure led to a series of novel compounds. These compounds inhibited EGFR in the nanomolar range. Moreover, inhibition of EGFR autophosphorylation in intact A431 cells was shown, with IC(50) values ranging form 0.3-1μM for compound 42, and 0.1-0.3μM for 45. In a panel of 42 human tumor cell lines the sensitivity profile of the novel compounds was shown to be similar to that of the quinazoline class of tyrosine kinase inhibitors lapatinib and erlotinib (Tarceva®).

Chimerically designed HDAC- and tyrosine kinase inhibitors. A series of erlotinib hybrids as dual-selective inhibitors of EGFR, HER2 and histone deacetylases

The regulation of chromatin structure and, therefore, transcriptional activity of histone proteins by reversible lysine acetylation is an important posttranslational modification. Inhibitors of histone deacetylase (HDAC) are considered as promising new anti-neoplastic drugs. The hydroxamic acid SAHA e.g. is currently used in the treatment of advanced primary cutaneous T-cell lymphoma. The EGFR protein tyrosine kinase inhibitor erlotinib is a prominent drug in cancer chemotherapy and currently approved for treatment of non-small cell lung cancer. In this report, we present a novel strategy for cancer drug development by a combination of EGFR/HER2 kinase and HDAC inhibitory activity in one molecule. By combining two distinct pharmacological properties in one molecule, we expect a broader activity spectrum and less likelihood of drug resistance in cancer patients. The combination led to substances with both HDAC inhibitory properties and EGFR as well as HER2 kinase inhibitory activities.

ELECTRON IMPACT INDUCED FRAGMENTATION OF 4-ARYL-4,6,7,8-TETRAHYDRO-1H, 3H-QUINAZOLINE-2,5-DIONES

The mol. ions (M+×) of 4-substituted aryl-4,6,7,8-tetrahydro-1H,3H-quinazoline-2,5-diones (Biginelli compds.) (2 - 18) decomp. by loss of the substituents X of the Ph group (X = o-F; o-, m-, p-Cl, Br, OCH3, CH3; 2,3-, 2,4-, 2,6-, 3,4-dichloro) giving rise to prominent (M - ×X)+ ions at 70 and 12 eV, resp. In the cases of o-Cl and o-Br substitution, the M+× is extremely unstable. In general, metastable M+× (1st ffr) eliminates preferably H×, that of 15 (2,6-dichloro), however, exclusively a chlorine atom. As corroborated by 2H-labeling, reversible H-migration from C-4 to the Ph group takes place. The collisional activation spectra of the (M - ×X)+ ions of 3 (o-Cl) and 6 (o-Br) are identical but different from the indistinguishable spectra of the (M - ×X)+ ions of 4 (m-Cl), 5 (p-Cl), 9 (o-OCH3), 11 (p-OCH3), and 14 (p-CH3). Semiempirical MO calcns. (MOPAC 6.0, PM 3 Hamiltonian) of the M+× of all ortho-substituted derivs. support a close interaction of o-Cl and o-Br with the carbonyl oxygen, leading to elimination of these substituents and affording cyclic oxonium ions. In the other cases loss of X× is explained as a consequence of 4-H migration to the Ph group.

Marbostat 100 defines a new class of potent and selective antiinflammatory and antirheumatic histone deacetylase 6 inhibitors

Epigenetic modifiers of the histone deacetylase (HDAC) family contribute to autoimmunity, cancer, HIV infection, inflammation, and neurodegeneration. Hence, histone deacetylase inhibitors (HDACi), which alter protein acetylation, gene expression patterns, and cell fate decisions, represent promising new drugs for the therapy of these diseases. Whereas pan-HDACi inhibit all 11 Zn2+-dependent histone deacetylases (HDACs) and cause a broad spectrum of side effects, specific inhibitors of histone deacetylase 6 (HDAC6i) are supposed to have less side effects. We present the synthesis and biological evaluation of Marbostats, novel HDAC6i that contain the hydroxamic acid moiety linked to tetrahydro-β-carboline derivatives. Our lead compound Marbostat-100 is a more potent and more selective HDAC6i than previously established well-characterized compounds in vitro as well as in cells. Moreover, Marbostat-100 is well tolerated by mice and effective against collagen type II induced arthritis. Thus, Marbostat-100 represents a most selective known HDAC6i and the possibility for clinical evaluation of a HDAC isoform-specific drug.