Discovery and Optimization of Anthranilic Acid Sulfonamides as Inhibitors of Methionine Aminopeptidase-2:  A Structural Basis for the Reduction of Albumin Binding

Abstract

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.

Correlation of tumor growth suppression and methionine aminopetidase-2 activity blockade using an orally active inhibitor

“…The correlation of inhibition of proliferation with broad methionine processing is supported by previous studies (10,21). We have been able to expand this observation and provide more specific molecular characterization.…”

“…The antiproliferative activity of A-800141 was not limited to endothelial cells, as originally proposed for fumagillin and TNP-470 (16), but extended to many tumor cell lines as well, which is described in detail elsewhere (25). The antiproliferative activity of the sulfonamide series of inhibitors has been shown to correlate tightly with their cellular activity inhibiting MetAP2 enzyme function (21). The effect of MetAP2 inhibitors was cytostatic; treated cells were arrested in the G 1 phase of cell cycle without apoptosis.…”

“…We have shown that a rationally designed bestatin-type inhibitor of MetAP2, A-357300, induces cytostasis by cell cycle arrest at the G 1 phase in endothelial cells and certain tumor cells, and that this MetAP2 inhibitor blocks angiogenesis and shows potent antitumor efficacy in carcinoma, sarcoma, and neuroblastoma murine models (10,19). More recently, we have reported that the most potent and selective MetAP2 inhibitors we discovered thus far are compounds of an anthranilic acid aryl sulfonamide series, originally identified by mass spectrometrybased affinity selection screening (20)(21)(22). Initial screening hits were modified with the aid of multiple crystal structures compared obtained with A-357300 (10).…”

“…1). The aryl sulfonamide portion of A-800141 occupies a hydrophobic cleft on the enzyme surface adjacent to the active site, which is solventexposed on one edge, allowing the introduction of the (Z)-3-diethylamino-prop-1-enyl group, which improves the solubility and modulates the albumin-binding properties of A-800141 (21).…”

Ectopic expression of methionine aminopeptidase-2 causes cell transformation and stimulates proliferation

“…To characterize the sensitivity of tumor cells to MetAP2 inhibition, we tested a panel of tumor lines with three distinct chemical classes of MetAP2 inhibitors: an irreversible inhibitor TNP-470 (Ingber et al, 1990;Griffith et al, 1997;Sin et al, 1997), a bestatin inhibitor A-357300 (Wang et al, 2003a) and a sulfonamide inhibitor A-800141 (Sheppard et al, 2006). In monolayer culture, the growth of these tumor cells was partially inhibited by these MetAP2 inhibitors, with maximal inhibition in the range of 33-80% for all agents (Table 1; Figure 1a).…”