Mycobacterial Protein Tyrosine Phosphatases A and B Inhibitors Augment the Bactericidal Activity of the Standard Anti-tuberculosis Regimen

Abstract

Novel drugs are required to shorten the duration of treatment for tuberculosis (TB) and to combat the emergence of drug resistance. One approach has been to identify and target Mycobacterium tuberculosis (Mtb) virulence factors, which promote the establishment of TB infection and pathogenesis. Mtb produces a number of virulence factors, including two protein tyrosine phosphatases (PTPs), mPTPA and mPTPB, to evade the antimicrobial functions of host macrophages. To assess the therapeutic potential of targeting the virulent Mtb PTPs, we developed highly potent and selective inhibitors of mPTPA (L335-M34) and mPTPB (L01-Z08) with drug-like properties. We tested the bactericidal activity of L335-M34 and L01-Z08 alone or together in combination with the standard antitubercular regimen of isoniazid-rifampicin-pyrazinamide (HRZ) in the guinea pig model of chronic TB infection, which faithfully recapitulates some of the key histological features of human TB lesions. Following a single dose of L335-M34 50mg/kg and L01-Z08 20 mg/kg, plasma levels were maintained at levels 10-fold greater than the biochemical IC50 for 12–24 hours. Although neither PTP inhibitor alone significantly enhanced the antibacterial activity of HRZ, dual inhibition of mPTPA and mPTPB in combination with HRZ showed modest synergy, even after 2 weeks of treatment. After 6 weeks of treatment, the degree of lung inflammation correlated with the bactericidal activity of each drug regimen. This study highlights the potential utility of targeting Mtb virulence factors, and specifically the Mtb PTPs, as a strategy for enhancing the activity of standard anti-TB treatment.

Targeting Tyrosine Phosphatases: Time to End the Stigma

“…Fragment-based optimization of SPAA also led to discovery of L335-M34, a selective inhibitor of Mycobacterium tuberculosis ( Mtb ) LMPTP (mPTPA), an Mtb virulence factor[17]. L335-M34 does not inhibit human LMPTP, and decreased bacterial load in Mtb -infected macrophages (IC 90 =1.38 μM), without displaying in vitro anti- Mtb activity[17].…”

“…L335-M34 does not inhibit human LMPTP, and decreased bacterial load in Mtb -infected macrophages (IC 90 =1.38 μM), without displaying in vitro anti- Mtb activity[17]. Importantly, L335-M34 displayed oral bioavailability when administered to guinea pigs without causing weight loss or overt toxicity.…”

Decavanadate Inhibits Mycobacterial Growth More Potently Than Other Oxovanadates

“…cells during growth. This suggest that the reduction is likely to come from the excretion of siderophores (Hider and Kong, 2010 ) or proteins such as the reported protein tyrosine phosphatases from mycobacteria (Beresford et al, 2009 ; Dutta et al, 2016 ). Since we also carried out such studies of supernatant that had been heated (see Supplemental Material ), such a product is either a very heat stable protein or a siderophore-type of material.…”

Drugging the Undruggable: Therapeutic Potential of Targeting Protein Tyrosine Phosphatases

“…50 Dual inhibition of mPTPA and mPTPB with 10 and 8 enhances the antitubercular activity of the first-line regimen and improves lung pathology in the guinea pig model. 50 Compound 11 (Figure 5) represents the most potent and selective mPTPB inhibitor, with a K i of 7.9 nM and more than 10,000-fold preference for mPTPB over a large panel of 25 phosphatases. 51 11 also exhibits excellent cellular activity and specificity in blocking mPTPB function in macrophage.…”