Identification of a potent and selective LAPTc inhibitor by RapidFire-Mass Spectrometry, with antichagasic activity.

BACKGROUND: Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and leads to ~10,000 deaths each year. Nifurtimox and benznidazole are the only two drugs available but have significant adverse effects and limited efficacy. New chemotherapeutic agents are urgently required. Here we identified inhibitors of the acidic M17 leucyl-aminopeptidase from T. cruzi (LAPTc) that show promise as novel starting points for Chagas disease drug discovery. METHODOLOGY/PRINCIPAL FINDINGS: A RapidFire-MS screen with a protease-focused compound library identified novel LAPTc inhibitors. Twenty-eight hits were progressed to the dose-response studies, from which 12 molecules inhibited LAPTc with IC50 < 34 µM. Of these, compound 4 was the most potent hit and mode of inhibition studies indicate that compound 4 is a competitive LAPTc inhibitor, with Ki 0.27 µM. Compound 4 is selective with respect to human LAP3, showing a selectivity index of >500. Compound 4 exhibited sub-micromolar activity against intracellular T. cruzi amastigotes, and while the selectivity-window against the host cells was narrow, no toxicity was observed for un-infected HepG2 cells. In silico modelling of the LAPTc-compound 4 interaction is consistent with the competitive mode of inhibition. Molecular dynamics simulations reproduce the experimental binding strength (-8.95 kcal/mol), and indicate a binding mode based mainly on hydrophobic interactions with active site residues without metal cation coordination. CONCLUSIONS/SIGNIFICANCE: Our data indicates that these new LAPTc inhibitors should be considered for further development as antiparasitic agents for the treatment of Chagas disease.

Development of a High-Throughput Screening Assay to Identify Inhibitors of the Major M17-Leucyl Aminopeptidase from Trypanosoma cruzi Using RapidFire Mass Spectrometry.

Leucyl aminopeptidases (LAPs) are involved in multiple cellular functions, which, in the case of infectious diseases, includes participation in the pathogen-host cell interface and pathogenesis. Thus, LAPs are considered good candidate drug targets, and the major M17-LAP from Trypanosoma cruzi (LAPTc) in particular is a promising target for Chagas disease. To exploit LAPTc as a potential target, it is essential to develop potent and selective inhibitors. To achieve this, we report a high-throughput screening method for LAPTc. Two methods were developed and optimized: a Leu-7-amido-4-methylcoumarin-based fluorogenic assay and a RapidFire mass spectrometry (RapidFire MS)-based assay using the LSTVIVR peptide as substrate. Compared with a fluorescence assay, the major advantages of the RapidFire MS assay are a greater signal-to-noise ratio as well as decreased consumption of enzyme. RapidFire MS was validated with the broad-spectrum LAP inhibitors bestatin (IC50 = 0.35 µM) and arphamenine A (IC50 = 15.75 µM). We suggest that RapidFire MS is highly suitable for screening for specific LAPTc inhibitors.

Superior outcomes and lower outpatient costs with scale-up of antiretroviral therapy at the GHESKIO clinic in Port-au-Prince, Haiti.

BACKGROUND: Treatment protocols and prices of antiretroviral therapy (ART) have changed over time. Yet, limited data exist to evaluate the impact of these changes on patient outcomes and treatment costs in resource-poor settings. METHODS: We compared patient-level data on outcomes, utilization, and cost for the first 2 years of ART for a cohort of adult patients initiating ART in 2003-2004 and a cohort initiating ART in 2006-2008 at the Haitian Group for the Study of Kaposi's Sarcoma and Opportunistic Infections clinic (GHESKIO) in Port-au-Prince, Haiti. Costs were measured from the health center perspective. Multivariate analyses were conducted to account for the potential impact of differences in disease severity at baseline. RESULTS: With the exclusion of patients who transferred care, 92% (167/181) of patients in the 2006-2008 cohort and 75% (150/200) in the 2003-2004 cohort were alive and in care at the end of the study period. The mean cost per patient for the 2-year study period was US$723 for the 2006-2008 cohort vs. US$1191 for the 2003-2004 cohort, a cost difference of US$468 (P < 0.0001). The mean cost per patient alive and in care at the end of the 2-year study period was US$744 for the 2006-2008 cohort vs. US$1489 for the 2003-2004 cohort (P < 0.0001). CONCLUSIONS: HIV treatment outcomes in Haiti have improved over time while treatment costs declined by over 50% per patient alive and in care at the end of the 2-year study period. The major drivers in the reduction of treatment costs were the lower price of ART, lower costs for laboratory testing, and lower overhead costs.