Ivermectin for onchocercal eye disease (river blindness)

Drug Repurposing: A Review of Old and New Antibiotics for the Treatment of Malaria: Identifying Antibiotics with a Fast Onset of Antiplasmodial Action

Malaria is one of the most life-threatening infectious diseases and constitutes a major health problem, especially in Africa. Although artemisinin combination therapies remain efficacious to treat malaria, the emergence of resistant parasites emphasizes the urgent need of new alternative chemotherapies. One strategy is the repurposing of existing drugs. Herein, we reviewed the antimalarial effects of marketed antibiotics, and described in detail the fast-acting antibiotics that showed activity in nanomolar concentrations. Antibiotics have been used for prophylaxis and treatment of malaria for many years and are of particular interest because they might exert a different mode of action than current antimalarials, and can be used simultaneously to treat concomitant bacterial infections.

Participants' outcomes gone missing within a network of interventions: Bayesian modeling strategies

OBJECTIVES

To investigate the implications of addressing informative missing binary outcome data (MOD) on network meta-analysis (NMA) estimates while applying the missing at random (MAR) assumption under different prior structures of the missingness parameter.

METHODS

In three motivating examples, we compared six different prior structures of the informative missingness odds ratio (IMOR) parameter in logarithmic scale under pattern-mixture and selection models. Then, we simulated 1000 triangle networks of two-arm trials assuming informative MOD related to interventions. We extended the Bayesian random-effects NMA model for binary outcomes and node-splitting approach to incorporate these 12 models in total. With interval plots, we illustrated the posterior distribution of log OR, common between-trial variance (τ2 ), inconsistency factor and probability of being best per intervention under each model.

RESULTS

All models gave similar point estimates for all NMA estimates regardless of simulation scenario. For moderate and large MOD, intervention-specific prior structure of log IMOR led to larger posterior standard deviation of log ORs compared to trial-specific and common-within-network prior structures. Hierarchical prior structure led to slightly more precise τ2 compared to identical prior structure, particularly for moderate inconsistency and large MOD. Pattern-mixture and selection models agreed for all NMA estimates.

CONCLUSIONS

Analyzing informative MOD assuming MAR with different prior structures of log IMOR affected mainly the precision of NMA estimates. Reviewers should decide in advance on the prior structure of log IMOR that best aligns with the condition and interventions investigated.

Population pharmacokinetics of oral ivermectin in venous plasma and dried blood spots in healthy volunteers

AIMS

The anthelminthic ivermectin is receiving new attention as it is being repurposed for new indications such as mass drug administrations for the treatment of scabies or in malaria vector control. As its pharmacokinetics are still poorly understood, we aimed to characterize the population pharmacokinetics of ivermectin in plasma and dried blood spots (DBS), a sampling method better suited to field trials, with special focus on the influence of body composition and enterohepatic circulation.

METHODS

We performed a clinical trial in 12 healthy volunteers who each received a single oral dose of 12 mg ivermectin, and collected peripheral venous and capillary DBS samples. We determined ivermectin concentrations in plasma and DBS by liquid chromatography tandem mass spectrometry using a fully automated and scalable extraction system for DBS sample processing. Pharmacokinetic data were analysed using non-linear mixed effects modelling.

RESULTS

A two-compartment model with a transit absorption model, first-order elimination, and weight as an influential covariate on central volume of distribution and clearance best described the data. The model estimates (inter-individual variability) for a 70 kg subject were: apparent population clearance 7.7 (25%) l h^-1 , and central and peripheral volumes of distribution 89 (10%) l and 234 (20%) l, respectively. Concentrations obtained from DBS samples were strongly linearly correlated (R²  = 0.97) with plasma concentrations, and on average 30% lower.

CONCLUSION

The model accurately depicts population pharmacokinetics of plasma and DBS concentrations over time for oral ivermectin. The proposed analytical workflow is scalable and applicable to the requirements of mass drug administrations.

Human myiasis caused by the reindeer warble fly, Hypoderma tarandi, case series from Norway, 2011 to 2016

Hypoderma tarandi causes myiasis in reindeer and caribou (Rangifer tarandus spp.) in most northern hemisphere regions where these animals live. We report a series of 39 human myiasis cases caused by H. tarandi in Norway from 2011 to 2016. Thirty-two were residents of Finnmark, the northernmost county of Norway, one a visitor to Finnmark, and six lived in other counties of Norway where reindeer live. Clinical manifestations involved migratory dermal swellings of the face and head, enlargement of regional lymph nodes, and periorbital oedema, with or without eosinophilia. Most cases of human myiasis are seen in tropical and subtropical countries, and in tourists returning from such areas. Our findings demonstrate that myiasis caused by H. tarandi is more common than previously thought. Healthcare professionals in regions where there is a likelihood of human infestation with H. tarandi (regions populated by reindeer), or treating returning travellers, should be aware of the condition. All clinicians are advised to obtain a detailed travel history when assessing patients with migratory dermal swellings. On clinical suspicion, ivermectin should be given to prevent larval invasion of the eye (ophthalmomyiasis). Since H. tarandi oviposits on hair, we suggest wearing a hat as a prevention measure.

Cytochrome P450/ABC transporter inhibition simultaneously enhances ivermectin pharmacokinetics in the mammal host and pharmacodynamics in Anopheles gambiae

Mass administration of endectocides, drugs that kill blood-feeding arthropods, has been proposed as a complementary strategy to reduce malaria transmission. Ivermectin is one of the leading candidates given its excellent safety profile. Here we provide proof that the effect of ivermectin can be boosted at two different levels by drugs inhibiting the cytochrome or ABC transporter in the mammal host and the target mosquitoes. Using a mini-pig model, we show that drug-mediated cytochrome P450/ABC transporter inhibition results in a 3-fold increase in the time ivermectin remains above mosquito-killing concentrations. In contrast, P450/ABC transporter induction with rifampicin markedly impaired ivermectin absorption. The same ketoconazole-mediated cytochrome/ABC transporter inhibition also occurs outside the mammal host and enhances the mortality of Anopheles gambiae. This was proven by using the samples from the mini-pig experiments to conduct an ex-vivo synergistic bioassay by membrane-feeding Anopheles mosquitoes. Inhibiting the same cytochrome/xenobiotic pump complex in two different organisms to simultaneously boost the pharmacokinetic and pharmacodynamic activity of a drug is a novel concept that could be applied to other systems. Although the lack of a dose-response effect in the synergistic bioassay warrants further exploration, our study may have broad implications for the control of parasitic and vector-borne diseases.

Ivermectin to reduce malaria transmission I. Pharmacokinetic and pharmacodynamic considerations regarding efficacy and safety

Ivermectin is an endectocide that has been used broadly in single dose community campaigns for the control of onchocerciasis and lymphatic filariasis for more than 30 years. There is now interest in the potential use of ivermectin regimens to reduce malaria transmission, envisaged as community-wide campaigns tailored to transmission patterns and as complement of the local vector control programme. The development of new ivermectin regimens or other novel endectocides will require integrated development of the drug in the context of traditional entomological tools and endpoints. This document examines the main pharmacokinetic and pharmacodynamic parameters of the medicine and their potential influence on its vector control efficacy and safety at population level. This information could be valuable for trial design and clinical development into regulatory and policy pathways.

Doxycycline plus ivermectin versus ivermectin alone for treatment of patients with onchocerciasis

BACKGROUND

Onchocerciasis, also known as "river blindness," is a parasitic disease that is caused by infection from the filarial nematode (roundworm), Onchocerca volvulus. Nematodes are transmitted from person to person by blackflies of the Simulium genus, which usually breed in fast flowing streams and rivers. The disease is the second leading infectious cause of blindness in endemic areas.Ivermectin (a microfilaricide) is widely distributed to endemic populations for prevention and treatment of onchocerciasis. Doxycycline, an antibiotic, targets Wolbachia organisms that are crucial to the survival of adult onchocerca (macrofilaricide). Combined treatment with both drugs is believed to cause direct microfilarial death by ivermectin and indirect macrofilarial death by doxycycline. Long-term reduction in the numbers of microfilaria in the skin and eyes and in the numbers of adult worms in the body has the potential to reduce the transmission and occurrence of onchocercal eye disease.

OBJECTIVES

The primary aim of this review was to assess the effectiveness of doxycycline plus ivermectin versus ivermectin alone for prevention and treatment of onchocerciasis. The secondary aim was to assess the effectiveness of doxycycline plus ivermectin versus ivermectin alone for prevention and treatment of onchocercal ocular lesions in communities co-endemic for onchocerciasis and Loa loa (loiasis) infection.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (Issue 7, 2015), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to July 2015), EMBASE (January 1980 to July 2015), PubMed (1948 to July 2015), Latin American and Caribbean Health Sciences Literature Database (LILACS) (1982 to July 2015), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) (last searched 1 July 2014), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 15 July 2015.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that had compared doxycycline plus ivermectin versus ivermectin alone. Participants with or without one or more characteristic signs of ocular onchocerciasis resided in communities where onchocerciasis was endemic.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility and extracted data. We used standard methodological procedures as expected by Cochrane.

MAIN RESULTS

We identified three RCTs including a total of 466 participants with a diagnosis of onchocerciasis. All trials compared doxycycline plus ivermectin versus ivermectin alone. One study investigated improvement in visual impairment at six-month follow-up; the other two studies measured microfilarial loads in skin snips to assess sustained effects of treatment at follow-up of 21 months or longer. The studies were conducted at various centers across three countries (Cameroon, Ghana, and Liberia). We judged all studies to be at overall high risk of bias because of inadequate randomization and lack of masking (one study), missing data (two studies), and selective outcome reporting (three studies).Only one study measured visual outcomes. This study reported uncertainty about the difference in the proportion of participants with improvement in visual impairment at six-month follow-up for doxycycline plus ivermectin compared with ivermectin alone (risk ratio (RR) 1.06, 95% confidence interval (95% CI) 0.80 to 1.39; 240 participants; very low-quality evidence). No participant in either group showed improvement in optic atrophy, chorioretinitis, or sclerosing keratitis at six-month follow-up. More participants in the doxycycline plus ivermectin group than in the ivermectin alone group showed improvement in iridocyclitis (RR 1.24, 95% CI 0.69 to 2.22) and punctate keratitis (RR 1.43, 95% CI 1.02 to 2.00) at six-month follow-up; however, we graded these results as very low quality.Two studies reported that a six-week course of doxycycline may result in Wolbachia depletion and macrofilaricidal and sterilizing activities in female Onchocerca worms; however, no analysis was possible because data were missing and incomplete (graded evidence as very low quality). Adverse events were reported in 16 of 135 (12%) participants in one of these studies and included itching, headaches, body pains, and vertigo; no difference between treatment groups was reported for any adverse event. The second study reported that one (1.3%) participant in the doxycycline plus ivermectin group had bloody diarrhea after treatment was initiated.

AUTHORS' CONCLUSIONS

Available evidence on the effectiveness of doxycycline plus ivermectin compared with ivermectin alone in preventing and treating onchocerciasis is unclear. Limited evidence of very low quality from two studies indicates that a six-week course of doxycycline followed by ivermectin may result in more frequent macrofilaricidal and microfilaricidal activity and sterilization of female adult Onchocerca compared with ivermectin alone; however, effects on vision-related outcomes are uncertain. Future studies should consider the effectiveness of treatments in preventing visual acuity and visual field loss and their effects on anterior and posterior segment lesions, particularly chorioretinitis. These studies should report outcomes in a uniform and consistent manner at follow-up of three years or longer to allow detection of meaningful changes in vision-related outcomes.

Modelling the impact of ivermectin on River Blindness and its burden of morbidity and mortality in African Savannah: EpiOncho projections

Background

The African Programme for Onchocerciasis Control (APOC) has refocused its goals on the elimination of infection where possible, seemingly achievable by 15–17 years of annual mass distribution of ivermectin in some African foci. Previously, APOC had focused on the elimination of onchocerciasis as a public health problem. Timeframes have been set by the World Health Organization, the London Declaration on Neglected Tropical Diseases and the World Bank to achieve these goals by 2020–2025.

Methods

A novel mathematical model of the dynamics of onchocercal disease is presented which links documented associations between Onchocerca volvulus infection and the prevalence and incidence of morbidity and mortality to model outputs from our host age- and sex-structured onchocerciasis transmission framework (EpiOncho). The model is calibrated for African savannah settings, and used to assess the impact of long-term annual mass administration of ivermectin on infection and ocular and skin disease and to explore how this depends on epidemiological and programmatic variables.

Results

Current onchocerciasis disease projections, which do not account for excess mortality of sighted individuals with heavy microfilarial loads, underestimate disease burden. Long-term annual ivermectin treatment is highly effective at reducing both the morbidity and mortality associated with onchocerciasis, and this result is not greatly influenced by treatment coverage and compliance. By contrast, impact on microfilarial prevalence and intensity is highly dependent on baseline endemicity, treatment coverage and systematic non-compliance.

Conclusions

The goals of eliminating morbidity and infection with ivermectin alone are distinctly influenced by epidemiological and programmatic factors. Whilst the former goal is most certainly achievable, reaching the latter will strongly depend on initial endemicity (the higher the endemicity, the greater the magnitude of inter-treatment transmission), advising caution when generalising the applicability of successful elimination outcomes to other areas. The proportion of systematic non-compliers will become far more influential in terms of overall success in achieving elimination goals.

Prevention and control of neglected tropical diseases: overview of randomized trials, systematic reviews and meta-analyses

OBJECTIVE

To analyse evidence from randomized controlled trials (RCTs) on the prevention and control of neglected tropical diseases (NTDs) and to identify areas where evidence is lacking.

METHODS

The Cochrane Central Register of Controlled Trials and PubMed were searched for RCTs and the Cochrane Database of Systematic Reviews and PubMed were searched for meta-analyses and systematic reviews, both from inception to 31 December 2012.

FINDINGS

Overall, 258 RCTs were found on American trypanosomiasis, Buruli ulcer, dengue, geohelminth infection, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, rabies, schistosomiasis or trachoma. No RCTs were found on cysticercosis, dracunculiasis, echinococcosis, foodborne trematodes, or human African trypanosomiasis. The most studied diseases were geohelminth infection (51 RCTs) and leishmaniasis (46 RCTs). Vaccines, chemoprophylaxis and interventions targeting insect vectors were evaluated in 113, 99 and 39 RCTs, respectively. Few addressed how best to deliver preventive chemotherapy, such as the choice of dosing interval (10) or target population (4), the population coverage needed to reduce transmission (2) or the method of drug distribution (1). Thirty-one publications containing 32 systematic reviews (16 with and 16 without meta-analyses) were found on American trypanosomiasis, dengue, geohelminths, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis or trachoma. Together, they included only 79 of the 258 published RCTs (30.6%). Of 36 interventions assessed, 8 were judged effective in more than one review.

CONCLUSION

Few RCTs on the prevention or control of the principal NTDs were found. Trials on how best to deliver preventive chemotherapy were particularly rare.