Hans-Willi Krell

Anti-Invasive, Antitumoral, and Antiangiogenic Efficacy of a Pyrimidine-2,4,6-trione Derivative, an Orally Active and Selective Matrix Metalloproteinases Inhibitor

Purpose: The implication of matrix metalloproteinases (MMPs) in the major stages of cancer progression has fueled interest in the design of synthetic MMP inhibitors (MMPIs) as a novel anticancer therapy. Thus far, drugs used in clinical trials are broad-spectrum MMPIs the therapeutic index of which proved disappointingly low. The development of selective MMPIs for tumor progression-associated MMPs is, thus, likely to offer improved therapeutic possibilities. Experimental Design: The anti-invasive capacity of a series of pyrimidine-trione derivatives was tested in vitro in a chemoinvasion assay, and the most potent compound was further evaluated in vivo in different human tumor xenograft models. The activity of this novel selective MMPI was compared with BB-94, a broad-spectrum inhibitor. Results: Ro-28-2653, an inhibitor with high selectivity for MMP-2, MMP-9, and membrane type 1 (MT1)-MMP, showed the highest anti-invasive activity in vitro. In vivo, Ro-28-2653 reduced the growth of tumors induced by the inoculation of different cell lines producing MMPs and inhibited the tumor-promoting effect of fibroblasts on breast adenocarcinoma cells. Furthermore, Ro-28-2653 reduced tumor vascularization and blocked angiogenesis in a rat aortic ring assay. In contrast, BB-94 up-regulated MMP-9 expression in tumor cells and promoted angiogenesis in the aortic ring assay. Conclusion: Ro-28-2653, a selective and orally bioavailable MMPI with inhibitory activity against MMPs expressed by tumor and/or stromal cells, is a potent antitumor and antiangiogenic agent. In contrast to broad-spectrum inhibitors, the administration of Ro-28-2653 was not associated with the occurrence of adverse side effects that might hamper the therapeutic potential of these drugs.

Human meprin alpha and beta homo-oligomers: cleavage of basement membrane proteins and sensitivity to metalloprotease inhibitors.

Meprin is a zinc endopeptidase of the astacin family, which is expressed as a membrane-bound or secreted protein in mammalian epithelial cells, in intestinal leucocytes and in certain cancer cells. There are two types of meprin subunits, alpha and beta, which form disulphide-bonded homo- and hetero-oligomers. Here we report on the cleavage of matrix proteins by hmeprin (human meprin) alpha and beta homo-oligomers, and on the interactions of these enzymes with inhibitors. Despite their completely different cleavage specificities, both hmeprin alpha and beta are able to hydrolyse basement membrane components such as collagen IV, nidogen-1 and fibronectin. However, they are inactive against intact collagen I. Hence the matrix-cleaving activity of hmeprin resembles that of gelatinases rather than collagenases. Hmeprin is inhibited by hydroxamic acid derivatives such as batimastat, galardin and Pro-Leu-Gly-hydroxamate, by TAPI-0 (tumour necrosis factor alpha protease inhibitor-0) and TAPI-2, and by thiol-based compounds such as captopril. Therapeutic targets for these inhibitors are MMPs (matrix metalloproteases), TACE (tumour necrosis factor alpha-converting enzyme) and angiotensin-converting enzyme respectively. The most effective inhibitor of hmeprin alpha in the present study was the naturally occurring hydroxamate actinonin ( K(i)=20 nM). The marked variance in the cleavage specificities of hmeprin alpha and beta is reflected by their interaction with the TACE inhibitor Ro 32-7315, whose affinity for the beta subunit (IC50=1.6 mM) is weaker by three orders of magnitude than that for the alpha subunit ( K(i)=1.6 microM). MMP inhibitors such as the pyrimidine-2,4,6-trione derivative Ro 28-2653 that are more specific for gelatinases do not bind to hmeprin, presumably due to the subtle differences in the mode of zinc binding and active-site structure between the astacins and the MMPs.

The new synthetic matrix metalloproteinase inhibitor (Roche 28-2653) reduces tumor growth and prolongs survival in a prostate cancer standard rat model.

The therapeutic efficacy of synthetic inhibitors of matrix-metalloproteinases (MMPs) in various cancers has been demonstrated. A novel inhibitor, Ro 28-2653, with high selectivity for MMP2, MMP9 and membrane type 1-MMP was evaluated in an orthotopic prostate cancer rat model. Efficacy was determined by recording tumor growth and survival endpoints. Prostate cancer was induced by inoculating R3327 Dunning tumor cells (MatLyLu) into the ventral lobe of the prostates of 148 Copenhagen rats. Daily oral treatment with Ro 28-2653 (10–300 mg/kg per day) was started on day 1 or on day 6 after tumor cell injection. Animals were sacrificed on day 20 for determination of tumor weights. For survival studies, rats received daily oral Ro 28-2653 (100 mg/kg per day) or vehicle for up to 30 days. Tumor induction was successful in 100% of the animals. Ro 28-2653 reproducibly reduced the tumor weights by up to 90% in a dose-dependent manner. In addition, an inhibitory effect in rats with established tumors (treatment start at day 6) was shown. A significantly prolonged survival of Ro 28-2653-treated rats was also demonstrated. Selective inhibition of MMP activity is a novel therapeutic approach, which bears promise for studies in patients with prostate cancer.

A pentacyclic aurora kinase inhibitor (AKI-001) with high in vivo potency and oral bioavailability.

Aurora kinase inhibitors have attracted a great deal of interest as a new class of antimitotic agents. We report a novel class of Aurora inhibitors based on a pentacyclic scaffold. A prototype pentacyclic inhibitor 32 (AKI-001) derived from two early lead structures improves upon the best properties of each parent and compares favorably to a previously reported Aurora inhibitor, 39 (VX-680). The inhibitor exhibits low nanomolar potency against both Aurora A and Aurora B enzymes, excellent cellular potency (IC50 < 100 nM), and good oral bioavailability. Phenotypic cellular assays show that both Aurora A and Aurora B are inhibited at inhibitor concentrations sufficient to block proliferation. Importantly, the cellular activity translates to potent inhibition of tumor growth in vivo. An oral dose of 5 mg/kg QD is well tolerated and results in near stasis (92% TGI) in an HCT116 mouse xenograft model.

Research on MMP Inhibitors with Unusual Scaffolds

Synthetic inhibitors of matrix metalloproteases have been developed using hydroxamate, N-carboxyalkyl, phosphonamidate, phosphinate, thiol, and other groups, each as a ligand for the active-site zinc atom of metalloproteases. Several of these inhibitors have been crystallized in complexes with the catalytic domains of various matrix metalloproteinases (MMPs).