Therapeutic efficacy of antimalarial drugs targeting DosRS signaling in Mycobacterium abscessus.

A search for alternative Mycobacterium abscessus treatments led to our interest in the two-component regulator DosRS, which, in Mycobacterium tuberculosis, is required for the bacterium to establish a state of nonreplicating, drug-tolerant persistence in response to a variety of host stresses. We show here that the genetic disruption of dosRS impairs the adaptation of M. abscessus to hypoxia, resulting in decreased bacterial survival after oxygen depletion, reduced tolerance to a number of antibiotics in vitro and in vivo, and the inhibition of biofilm formation. We determined that three antimalarial drugs or drug candidates, artemisinin, OZ277, and OZ439, can target DosS-mediated hypoxic signaling in M. abscessus and recapitulate the phenotypic effects of genetically disrupting dosS. OZ439 displayed bactericidal activity comparable to standard-of-care antibiotics in chronically infected mice, in addition to potentiating the activity of antibiotics used in combination. The identification of antimalarial drugs as potent inhibitors and adjunct inhibitors of M. abscessus in vivo offers repurposing opportunities that could have an immediate impact in the clinic.

Re-evaluating pretomanid analogues for Chagas disease: Hit-to-lead studies reveal both in vitro and in vivo trypanocidal efficacy.

Phenotypic screening of a 900 compound library of antitubercular nitroimidazole derivatives related to pretomanid against the protozoan parasite Trypanosoma cruzi (the causative agent for Chagas disease) identified several structurally diverse hits with an unknown mode of action. Following initial profiling, a first proof-of-concept in vivo study was undertaken, in which once daily oral dosing of a 7-substituted 2-nitroimidazooxazine analogue suppressed blood parasitemia to low or undetectable levels, although sterile cure was not achieved. Limited hit expansion studies alongside counter-screening of new compounds targeted at visceral leishmaniasis laid the foundation for a more in-depth assessment of the best leads, focusing on both drug-like attributes (solubility, metabolic stability and safety) and maximal killing of the parasite in a shorter timeframe. Comparative appraisal of one preferred lead (58) in a chronic infection mouse model, monitored by highly sensitive bioluminescence imaging, provided the first definitive evidence of (partial) curative efficacy with this promising nitroimidazooxazine class.

Inhibition of Cytomegalovirus Replication with Extended-Half-Life Synthetic Ozonides.

Artesunate (AS), a semisynthetic artemisinin approved for malaria therapy, inhibits human cytomegalovirus (HCMV) replication in vitro, but therapeutic success in humans has been variable. We hypothesized that the short in vivo half-life of AS may contribute to the different treatment outcomes. We tested novel synthetic ozonides with longer half-lives against HCMV in vitro and mouse cytomegalovirus (MCMV) in vivo Screening of the activities of four ozonides against a pp28-luciferase-expressing HCMV Towne recombinant identified OZ418 to have the best selectivity; its effective concentration inhibiting viral growth by 50% (EC50) was 9.8 ± 0.2 µM, and cytotoxicity in noninfected human fibroblasts (the concentration inhibiting cell growth by 50% [CC50]) was 128.1 ± 8.0 µM. In plaque reduction assays, OZ418 inhibited HCMV TB40 in a concentration-dependent manner as well as a ganciclovir (GCV)-resistant HCMV isolate. The combination of OZ418 and GCV was synergistic in HCMV inhibition in vitro Virus inhibition by OZ418 occurred at an early stage and was dependent on the cell density at the time of infection. OZ418 treatment reversed HCMV-mediated cell cycle progression and correlated with the reduction of HCMV-induced expression of pRb, E2F1, and cyclin-dependent kinases 1, 2, 4, and 6. In an MCMV model, once-daily oral administration of OZ418 had significantly improved efficacy against MCMV compared to that of twice-daily oral AS. A parallel pharmacokinetic study with a single oral dose of OZ418 or AS showed a prolonged plasma half-life and higher unbound concentrations of OZ418 than unbound concentrations of AS. In summary, ozonides are proposed to be potential therapeutics, alone or in combination with GCV, for HCMV infection in humans.

Assessing drug efficacy against Plasmodium falciparum liver stages in vivo.

Malaria eradication necessitates new tools to fight the evolving and complex Plasmodium pathogens. These tools include prophylactic drugs that eliminate Plasmodium liver stages and consequently prevent clinical disease, decrease transmission, and reduce the propensity for resistance development. Currently, the identification of these drugs relies on in vitro P. falciparum liver stage assays or in vivo causal prophylaxis assays using rodent malaria parasites; there is no method to directly test in vivo liver stage activity of candidate antimalarials against the human malaria-causing parasite P. falciparum. Here, we use a liver-chimeric humanized mouse (FRG huHep) to demonstrate in vivo P. falciparum liver stage development and describe the efficacy of clinically used and candidate antimalarials with prophylactic activity. We show that daily administration of atovaquone-proguanil (ATQ-PG; ATQ, 30 mg/kg, and PG, 10 mg/kg) protects 5 of 5 mice from liver stage infection, consistent with the use in humans as a causal prophylactic drug. Single-dose primaquine (60 mg/kg) has similar activity to that observed in humans, demonstrating the activity of this drug (and its active metabolites) in FRG huHep mice. We also show that DSM265, a selective Plasmodial dihydroorotate dehydrogenase inhibitor with causal prophylactic activity in humans, reduces liver stage burden in FRG huHep mice. Finally, we measured liver stage-to-blood stage transition of the parasite, the ultimate readout of prophylactic activity and measurement of infective capacity of parasites in the liver, to show that ATQ-PG reduces blood stage patency to below the limit of quantitation by quantitative PCR (qPCR). The FRG huHep model, thus, provides a platform for preclinical evaluation of drug candidates for liver stage causal prophylactic activity, pharmacokinetic/pharmacodynamics studies, and biological studies to investigate the mechanism of action of liver stage active antimalarials.

Medium-term Outcomes after Whole-gland High-intensity Focused Ultrasound for the Treatment of Nonmetastatic Prostate Cancer from a Multicentre Registry Cohort.

BACKGROUND: High-intensity focused ultrasound (HIFU) is a minimally-invasive treatment for nonmetastatic prostate cancer. OBJECTIVE: To report medium-term outcomes in men receiving primary whole-gland HIFU from a national multi-centre registry cohort. DESIGN, SETTING, AND PARTICIPANTS: Five-hundred and sixty-nine patients at eight hospitals were entered into an academic registry. INTERVENTION: Whole-gland HIFU (Sonablate 500) for primary nonmetastatic prostate cancer. Redo-HIFU was permitted as part of the intervention. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Our primary failure-free survival outcome incorporated no transition to any of the following: (1) local salvage therapy (surgery or radiotherapy), (2) systemic therapy, (3) metastases, or (4) prostate cancer-specific mortality. Secondary outcomes included adverse events and genitourinary function. RESULTS AND LIMITATIONS: Mean age was 65 yr (47-87 yr). Median prostate-specific antigen was 7.0 ng/ml (interquartile range 4.4-10.2). National Comprehensive Cancer Network low-, intermediate-, and high-risk disease was 161 (28%), 321 (56%), and 81 (14%), respectively. One hundred and sixty three of 569 (29%) required a total of 185 redo-HIFU procedures. Median follow-up was 46 (interquartile range 23-61) mo. Failure-free survival at 5 yr after first HIFU was 70% (95% confidence interval [CI]: 64-74). This was 87% (95% CI: 78-93), 63% (95% CI: 56-70), and 58% (95% CI: 32-77) for National Comprehensive Cancer Network low-, intermediate-, and high-risk groups, respectively. Fifty eight of 754 (7.7%) had one urinary tract infection, 22/574 (2.9%) a recurrent urinary tract infection, 22/754 (3%) epididymo-orchitis, 227/754 (30%) endoscopic interventions, 1/754 (0.13%) recto-urethral fistula, and 1/754 (0.13%) osteitis pubis. Of 206 known to be pad-free pre-HIFU, 183/206 (88%) remained pad free, and of 236 with good baseline erectile function, 91/236 (39%) maintained good function. The main limitation is lack of long-term data. CONCLUSIONS: Whole-gland HIFU is a repeatable day-case treatment that confers low rates of urinary incontinence. Disease control at a median of just under 5 yr of follow-up demonstrates its potential as a treatment for nonmetastatic prostate cancer. Endoscopic interventions and erectile dysfunction rates are similar to other whole-gland treatments. PATIENT SUMMARY: In this report we looked at the 5-yr outcomes following whole-gland high-intensity focused ultrasound treatment for prostate cancer and found that cancer control was acceptable with a low risk of urine leakage. However, risk of erectile dysfunction and further operations was similar to other whole-gland treatments like surgery and radiotherapy.

Haemoglobin degradation underpins the sensitivity of early ring stage Plasmodium falciparum to artemisinins.

Current first-line artemisinin antimalarials are threatened by the emergence of resistant Plasmodium falciparum. Decreased sensitivity is evident in the initial (early ring) stage of intraerythrocytic development, meaning that it is crucial to understand the action of artemisinins at this stage. Here, we examined the roles of iron (Fe) ions and haem in artemisinin activation in early rings using Fe ion chelators and a specific haemoglobinase inhibitor (E64d). Quantitative modelling of the antagonism accounted for its complex dependence on the chemical features of the artemisinins and on the drug exposure time, and showed that almost all artemisinin activity in early rings (>80%) is due to haem-mediated activation. The surprising implication that haemoglobin uptake and digestion is active in early rings is supported by identification of active haemoglobinases (falcipains) at this stage. Genetic down-modulation of the expression of the two main cysteine protease haemoglobinases, falcipains 2 and 3, renders early ring stage parasites resistant to artemisinins. This confirms the important role of haemoglobin-degrading falcipains in artemisinin activation, and shows that changes in the rate of artemisinin activation could mediate high-level artemisinin resistance.

Inhibitors of plasmodial serine hydroxymethyltransferase (SHMT): cocrystal structures of pyrazolopyrans with potent blood- and liver-stage activities.

Several of the enzymes related to the folate cycle are well-known for their role as clinically validated antimalarial targets. Nevertheless for serine hydroxymethyltransferase (SHMT), one of the key enzymes of this cycle, efficient inhibitors have not been described so far. On the basis of plant SHMT inhibitors from an herbicide optimization program, highly potent inhibitors of Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) SHMT with a pyrazolopyran core structure were identified. Cocrystal structures of potent inhibitors with PvSHMT were solved at 2.6 Å resolution. These ligands showed activity (IC50/EC50 values) in the nanomolar range against purified PfSHMT, blood-stage Pf, and liver-stage P. berghei (Pb) cells and a high selectivity when assayed against mammalian cell lines. Pharmacokinetic limitations are the most plausible explanation for lack of significant activity of the inhibitors in the in vivo Pb mouse malaria model.

Endochin-like quinolones are highly efficacious against acute and latent experimental toxoplasmosis.

Toxoplasma gondii is a widely distributed protozoan pathogen that causes devastating ocular and central nervous system disease. We show that the endochin-like quinolone (ELQ) class of compounds contains extremely potent inhibitors of T. gondii growth in vitro and is effective against acute and latent toxoplasmosis in mice. We screened 50 ELQs against T. gondii and selected two lead compounds, ELQ-271 and ELQ-316, for evaluation. ELQ-271 and ELQ-316, have in vitro IC(50) values of 0.1 nM and 0.007 nM, respectively. ELQ-271 and ELQ-316 have ED(50) values of 0.14 mg/kg and 0.08 mg/kg when administered orally to mice with acute toxoplasmosis. Moreover, ELQ-271 and ELQ-316 are highly active against the cyst form of T. gondii in mice at low doses, reducing cyst burden by 76-88% after 16 d of treatment. To investigate the ELQ mechanism of action against T. gondii, we demonstrate that endochin and ELQ-271 inhibit cytochrome c reduction by the T. gondii cytochrome bc(1) complex at 8 nM and 31 nM, respectively. We also show that ELQ-271 inhibits the Saccharomyces cerevisiae cytochrome bc(1) complex, and an M221Q amino acid substitution in the Q(i) site of the protein leads to >100-fold resistance. We conclude that ELQ-271 and ELQ-316 are orally bioavailable drugs that are effective against acute and latent toxoplasmosis, likely acting as inhibitors of the Q(i) site of the T. gondii cytochrome bc(1) complex.

Preclinical comparison of intravenous melphalan pharmacokinetics administered in formulations containing either (SBE)7 m-ß-cyclodextrin or a co-solvent system.

The aim of this work was to evaluate the impact of sulfobutyl ether ß-cyclodextrin ((SBE)(7 m)-ß-CD; Captisol(®)) on the in vivo pharmacokinetics of melphalan in rats. Melphalan is a chemically unstable antineoplastic drug which in the current commercial formulation (Alkeran(®) for Injection) has some limitations with regard to solubility, stability and biocompatibility. Melphalan formulations containing (SBE)(7 m)-ß-CD have previously been evaluated in vitro and shown to significantly reduce the rate of degradation and to simplify the reconstitution procedure for lyophilised melphalan. In this study, melphalan was administered intravenously in rats in formulations that either contain (SBE)(7 m)-ß-CD or a co-solvent system (i.e. the commercial formulation). Pharmacokinetic parameters, including half-life, volume of distribution, clearance and extent of renal elimination of melphalan were essentially unchanged between the two formulations. These findings indicate that the pharmacokinetics of melphalan are not altered in the presence of (SBE)(7 m)-ß-CD consistent with a rapid shift in the equilibrium to the fully dissociated drug from the fraction associated with the cyclodextrin host molecule upon intravenous administration.

Identification of an antimalarial synthetic trioxolane drug development candidate.

The discovery of artemisinin more than 30 years ago provided a completely new antimalarial structural prototype; that is, a molecule with a pharmacophoric peroxide bond in a unique 1,2,4-trioxane heterocycle. Available evidence suggests that artemisinin and related peroxidic antimalarial drugs exert their parasiticidal activity subsequent to reductive activation by haem, released as a result of haemoglobin digestion by the malaria-causing parasite. This irreversible redox reaction produces carbon-centred free radicals, leading to alkylation of haem and proteins (enzymes), one of which--the sarcoplasmic-endoplasmic reticulum ATPase PfATP6 (ref. 7)--may be critical to parasite survival. Notably, there is no evidence of drug resistance to any member of the artemisinin family of drugs. The chemotherapy of malaria has benefited greatly from the semi-synthetic artemisinins artemether and artesunate as they rapidly reduce parasite burden, have good therapeutic indices and provide for successful treatment outcomes. However, as a drug class, the artemisinins suffer from chemical (semi-synthetic availability, purity and cost), biopharmaceutical (poor bioavailability and limiting pharmacokinetics) and treatment (non-compliance with long treatment regimens and recrudescence) issues that limit their therapeutic potential. Here we describe how a synthetic peroxide antimalarial drug development candidate was identified in a collaborative drug discovery project.

Perioperative melatonin secretion in patients undergoing coronary artery bypass grafting.

UNLABELLED: Melatonin, a neurohormone, plays an important role in adjusting the "biological clock" in humans. We sought to describe perioperative patterns of melatonin secretion in patients undergoing coronary artery bypass grafting surgery with cardiopulmonary bypass (CPB). After IRB approval and written informed consent, 12 male patients scheduled for elective coronary artery bypass grafting under hypothermic CPB were enrolled in the study. During anesthesia, patients' eyes were carefully covered to prevent light effects. Blood samples were taken at specific time points during surgery, every 3 h in the immediate postoperative period, and for 24 h from 6:00 PM of Postoperative Day 2 until 6:00 PM of Postoperative Day 3. Plasma melatonin and cortisol concentrations were measured by radioimmunoassay and enzyme-linked immunosorbent assay, respectively. During surgery, plasma melatonin concentrations were below the minimum sensitivity concentration, yet small concentrations, without circadian variation, were detected during the immediate postoperative period. During Postoperative Days 2 and 3, circadian secretion patterns of melatonin were present in 10 patients and showed an inverse correlation with light intensity (r = 0.480; P < 0.01). Plasma cortisol concentrations in the immediate postoperative period were significantly larger than those before the induction of anesthesia (P < 0.01). Only three patients regained circadian secretion of cortisol. We concluded that melatonin and cortisol secretion was disrupted during cardiac surgery with CPB and in the immediate postoperative period. However, circadian rhythms of melatonin were present in most patients from Postoperative Day 2. Only 30% of the patients regained circadian rhythm of cortisol secretion. IMPLICATIONS: Melatonin is a hormone that plays an important role in adjusting the biological clock in humans and that regulates secretion of various other hormones. We studied melatonin secretion in patients undergoing cardiac surgery with cardiopulmonary bypass. Melatonin secretion was disturbed during and immediately after surgery but had recovered a circadian rhythm 24 h later, raising the question of whether melatonin should be supplemented before cardiac surgery.