Design and synthesis of nonpeptidic, small molecule inhibitors for the Mycobacterium tuberculosis protein tyrosine phosphatase PtpB

Abstract

The design and synthesis of new inhibitor analogues for the Mycobacterium tuberculosis (Mtb) phosphatase PtpB is described. Analogues were synthesized by incorporation of two common and effective phosphate mimetics, the isothiazolidinone (IZD) and the difluoromethylphosphonic acid (DFMP). The basic scaffold of the inhibitor was identified from structure-activity relationships established for a previously published isoxazole inhibitor, while the phosphate mimetics were chosen based on their proven cell permeability and activity when incorporated into previously reported inhibitors for the phosphatase PTP1B. The inhibitory activity of each compound was evaluated, and each was found to have low or submicromolar affinity for PtpB. (Mtb). Each year, nearly 2 million deaths occur out of over 13 million active cases of TB, 1 and current treatment of drug-sensitive strains requires 6-9 months to fully eradicate the infection. New Mtb drugs that act on novel targets are needed to shorten treatment time and address the emergence of antibiotic resistance. Mtb PtpB is a secreted virulence factor that functions within human macrophages, and chemical interference with PtpB function has been shown to reduce bacterial loads in an Mtb macrophage infection model. 2 PtpB is attractive as a therapeutic target due to its localization outside of the unusually thick mycobacterial cell wall, which is difficult to penetrate and leads to long treatment times for tuberculosis (TB). Tuberculosis (TB) is a chronic, infectious disease caused by Mycobacterium tuberculosisWe previously reported the development of isoxazole carboxylic acid inhibitor 1 for PtpB, using the substrate activity screening (SAS) method, a novel fragment-based approach for the identification of phosphatase inhibitors (Figure 1). 3 Development of the isoxazole inhibitor revealed that ortho substituents are preferred for optimal PtpB binding, with the cyclohexyl group providing the most favorable enzyme interactions. In order to compare binding affinity and cell activity, we desired a route to analogueous inhibitors incorporating other commonly used phosphate mimetics. NIH-PA Author ManuscriptA variety of phosphate isosteres have been reported and could be introduced in place of the isoxazole,4 but many contain at least two acidic sites and lead to inhibitors with poor cellular permeability. 5 We therefore chose two phosphate mimetics that have been effectively used in inhibitors of PTP1B, a human phosphatase targeted for diabetes treatment, with good cell permeability and activity, namely the isothiazolidinone (IZD) and difluoromethylphosphonic acid (DFMP) mimetics ( Figure 2). The monoanionic IZD 6 phosphate mimetic was developed by Incyte through structure-based design, 6g while the DFMP pharmacophore is a commonly used phosphate mimetic that has been investigated extensively in the literature. 7 Despite being dianionic, the DFMP isostere has recently been shown by Merck to be cell permeable and orally bioavailable in animals when incorporated into nonpeptid...

LmxM.22.0250-Encoded Dual Specificity Protein/Lipid Phosphatase Impairs Leishmania mexicana Virulence In Vitro

“…Importantly, mycobacteria with inhibited MptpB or ablated mptpB gene are severely defective in their ability to survive in activated mouse macrophages and in guinea pigs [24,25]. It has been hypothesized that MptpB dephosphorylates the P-Tyr residues of the myelin basic protein, thus enabling the mycobacteria to survive within its host [23,26]. Similarly, the virulence of Listeria monocytogenes strains lacking the lmo1800 gene, which encodes a secreted tyrosine phosphatase LipA, is severely attenuated in vivo [22].…”

Zinc(II) Complexes of Acylpyrazolones Decorated with a Cyclohexyl Group Display Antiproliferative Activity Against Human Breast Cancer Cells

“…For example, a cyclohexyl group was found to play a role in small isoxazole-based inhibitors for the Mycobacterium tuberculosis phosphatase, providing the most favorable enzyme interactions. [47,48] Also the ancillary N 2 -donor ligands shown in Figure 1 were chosen to finely tune the whole hydrophobicity and solubility in polar solvents of the Zn II complexes. The antiproliferative and pro-apoptotic potential of the Zn II complexes sufficiently soluble in DMSO/water was investigated against human breast cancer cell line MCF-7 cultured in an in vitro membrane platform.…”

“…In more detail, the replacement of the long and flexible aliphatic chain in the acyl moiety with a compact cyclohexyl group may introduce further differentiations in the solubility of the zinc complexes in polar solvents such as DMSO, usually employed for biologic experiments, and also in the steric hindrance. For example, a cyclohexyl group was found to play a role in small isoxazole‐based inhibitors for the Mycobacterium tuberculosis phosphatase, providing the most favorable enzyme interactions , . Also the ancillary N 2 ‐donor ligands shown in Figure were chosen to finely tune the whole hydrophobicity and solubility in polar solvents of the Zn II complexes.…”

Wzy-Dependent Bacterial Capsules as Potential Drug Targets

“…These are mainly developed for the treatment of non-pathogenic diseases such as diabetes mellitus, cancer, and neural disorders. As potential drugs against pathogens, there has been some success in targeting PTPs in both Gram-positive and -negative organisms, for example Mycobacterium tuberculosis [102][103][104] and Yersinia pestis [105,106]. Although demonstrably viable as drug targets, and increasingly specific compounds are under development, there are as of yet no clinically approved PTP inhibitors available.…”