Nitazoxanide pharmacokinetics and tolerability in man during 7 days dosing with 0.5 g and 1 g b.i.d

Standardization of an antiviral pipeline for human norovirus in human intestinal enteroids demonstrates nitazoxanide has no to weak antiviral activity

Human noroviruses (HuNoVs) are the leading cause of acute gastroenteritis. In immunocompetent hosts, symptoms usually resolve within 3 days; however, in immunocompromised persons, HuNoV infection can become persistent, debilitating, and sometimes life-threatening. There are no licensed therapeutics for HuNoV due to a near half-century delay in its cultivation. Treatment for chronic HuNoV infection in immunosuppressed patients anecdotally includes nitazoxanide, a broad-spectrum antimicrobial licensed for treatment of parasite-induced gastroenteritis. Despite its off-label use for chronic HuNoV infection, nitazoxanide has not been clearly demonstrated to be an effective treatment. In this study, we standardized a pipeline for antiviral testing using multiple human small intestinal enteroid lines representing different intestinal segments and evaluated whether nitazoxanide inhibits replication of five HuNoV strains in vitro. Nitazoxanide did not exhibit high selective antiviral activity against any HuNoV strain tested, indicating it is not an effective antiviral for HuNoV infection. Human intestinal enteroids are further demonstrated as a model to serve as a preclinical platform to test antivirals against HuNoVs to treat gastrointestinal disease. Abstr.

Therapeutic potential of salicylamide derivatives for combating viral infections

Since time immemorial human beings have constantly been fighting against viral infections. The ongoing and devastating coronavirus disease 2019 pandemic represents one of the most severe and most significant public health emergencies in human history, highlighting an urgent need to develop broad-spectrum antiviral agents. Salicylamide (2-hydroxybenzamide) derivatives, represented by niclosamide and nitazoxanide, inhibit the replication of a broad range of RNA and DNA viruses such as flavivirus, influenza A virus, and coronavirus. Moreover, nitazoxanide was effective in clinical trials against different viral infections including diarrhea caused by rotavirus and norovirus, uncomplicated influenza A and B, hepatitis B, and hepatitis C. In this review, we summarize the broad antiviral activities of salicylamide derivatives, the clinical progress, and the potential targets or mechanisms against different viral infections and highlight their therapeutic potential in combating the circulating and emerging viral infections in the future.

A Standardized Antiviral Pipeline for Human Norovirus in Human Intestinal Enteroids Demonstrates No Antiviral Activity of Nitazoxanide

Human noroviruses (HuNoVs) are the leading cause of acute gastroenteritis. In immunocompetent hosts, symptoms usually resolve within three days; however, in immunocompromised persons, HuNoV infection can become persistent, debilitating, and sometimes life-threatening. There are no licensed therapeutics for HuNoV due to a near half-century delay in its cultivation. Treatment for chronic HuNoV infection in immunosuppressed patients anecdotally includes nitazoxanide, a broad-spectrum antimicrobial licensed for treatment of parasite-induced gastroenteritis. Despite its off-label use for chronic HuNoV infection, nitazoxanide has not been clearly demonstrated to be an effective treatment. In this study, we established a standardized pipeline for antiviral testing using multiple human small intestinal enteroid (HIE) lines representing different intestinal segments and evaluated whether nitazoxanide inhibits replication of 5 HuNoV strains in vitro . Nitazoxanide did not exhibit high selective antiviral activity against any HuNoV strains tested, indicating it is not an effective antiviral for norovirus infection. HIEs are further demonstrated as a model to serve as a pre-clinical platform to test antivirals against human noroviruses to treat gastrointestinal disease.

Efficacy and safety of nitazoxanide in treating SARS-CoV-2 infection: a systematic review and meta-analysis of blinded, placebo-controlled, randomized clinical trials

Purpose

Nitazoxanide is a broad-spectrum antiparasitic that has been tested for COVID-19 due to its anti-inflammatory effects and in vitro antiviral activity. This study synthesized the best evidence on the efficacy and safety of nitazoxanide in COVID-19.

Methods

Searches for studies were performed in peer-reviewed and grey-literature from January 1, 2020 to May 23, 2022. The following elements were used to define eligibility criteria: (1) Population: individuals with COVID-19; (2) Intervention: nitazoxanide; (3) Comparison: placebo; (4) Outcomes: primary outcome was death, and secondary outcomes were viral load, positive RT-PCR status, serum biomarkers of inflammation, composite measure of disease progression (ICU admission or invasive mechanical ventilation), and any adverse events; (5) Study type: blinded, placebo-controlled, randomized clinical trials (RCTs). Treatment effects were reported as relative risk (RR) for dichotomous variables and standardized mean difference (SMD) for continuous variables with 95% confidence intervals (CI).

Results

Five blinded, placebo-controlled RCTs were included and enrolled individuals with mild or moderate SARS-CoV-2 infection. We found no difference between nitazoxanide and placebo in reducing viral load (SMD =  − 0.16; 95% CI − 0.38 to 0.05) and the frequency of positive RTP-PCR results (RR = 0.92; 95% CI 0.81 to 1.06). In addition, there was no decreased risk for disease progression (RR = 0.63; 95% CI 0.38 to 1.04) and death (RR = 0.81; 95% CI 0.36 to 1.78) among patients receiving nitazoxanide. Patients with COVID-19 treated with nitazoxanide had decreased levels of white blood cells (SMD =  − 0.15; 95% − 0.29 to − 0.02), lactate dehydrogenase (LDH) (SMD − 0.32; 95% − 0.52 to − 0.13), and D-dimer (SMD − 0.49; 95% CI − 0.68 to − 0.31) compared to placebo, but the magnitude of effect was considered small to moderate.

Conclusion

This systematic review showed no evidence of clinical benefits of the use of nitazoxanide to treat patients with mild or moderate COVID-19. In addition, we found a reduction in WBC, LDH, and D-dimer levels among nitazoxanide-treated patients, but the effect size was considered small to moderate.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00228-022-03380-5.

A specific turn-on fluorescence probe for determination of nitazoxanide based on feasible oxidation reaction with hypochlorite: Applying cobalt ferrite nanoparticles for pre-concentration and extraction of its metabolite from real urine samples

Nitazoxanide is an antimicrobial compound that was originally developed as an antiprotozoal drug. Recently nitazoxanide has been identified as broad-spectrum antiviral agent and redirected for the remediation of some respiratory tract viral infections. In this study, the spectrofluorimetric technique has been applied to determine Nitazoxanide (NTX) in tablets or its metabolite, tizoxanide (TZD), in human urine samples. The developed methodology is based on oxidizing NTX (non-fluorescence) into a highly fluorescent product by sodium hypochlorite. The fluorescence emission intensity was measured at 436.5 nm after fluorescence excitation at 362.5 nm. After optimizing all conditions, the analytical procedures and bio-analytical steps were evaluated and validated using ICH and FDA criteria, respectively. The method linearity, LOQ, and LOD values of NTX were 1.0-5.0 µg/mL, 0.434, and 0.143 µg/mL, respectively. The other novelty side of the presented work is the application of cobalt ferrite (CoFe₂O₄) nanoparticles (NPs) as a magnetic solid-phase for the pre-concentration and extraction process. The synthesized magnetic nanoparticles were characterized by scanning electron microscope and zeta sizer techniques. Finally, the utilized magnetic nanoparticles exhibited good recovery results for pre-concentration and extraction of NTX or its metabolite from spiked and real human urine samples, respectively.

An Open Label, Adaptive, Phase 1 Trial of High-Dose Oral Nitazoxanide in Healthy Volunteers: An Antiviral Candidate for SARS-CoV-2

Repurposing approved drugs may rapidly establish effective interventions during a public health crisis. This has yielded immunomodulatory treatments for severe coronavirus disease 2019 (COVID-19), but repurposed antivirals have not been successful to date because of redundancy of the target in vivo or suboptimal exposures at studied doses. Nitazoxanide is a US Food and Drug Administration (FDA) approved antiparasitic medicine, that physiologically-based pharmacokinetic (PBPK) modeling has indicated may provide antiviral concentrations across the dosing interval, when repurposed at higher than approved doses. Within the AGILE trial platform (NCT04746183) an open label, adaptive, phase I trial in healthy adult participants was undertaken with high-dose nitazoxanide. Participants received 1,500 mg nitazoxanide orally twice-daily with food for 7 days. Primary outcomes were safety, tolerability, optimum dose, and schedule. Intensive pharmacokinetic (PK) sampling was undertaken day 1 and 5 with minimum concentration (Cmin ) sampling on days 3 and 7. Fourteen healthy participants were enrolled between February 18 and May 11, 2021. All 14 doses were completed by 10 of 14 participants. Nitazoxanide was safe and with no significant adverse events. Moderate gastrointestinal disturbance (loose stools or diarrhea) occurred in 8 participants (57.1%), with urine and sclera discoloration in 12 (85.7%) and 9 (64.3%) participants, respectively, without clinically significant bilirubin elevation. This was self-limiting and resolved upon drug discontinuation. PBPK predictions were confirmed on day 1 but with underprediction at day 5. Median Cmin was above the in vitro target concentration on the first dose and maintained throughout. Nitazoxanide administered at 1,500 mg b.i.d. with food was safe with acceptable tolerability a phase Ib/IIa study is now being initiated in patients with COVID-19.

Early use of nitazoxanide in mild COVID-19 disease: randomised, placebo-controlled trial

Background

Nitazoxanide is widely available and exerts broad-spectrum antiviral activity in vitro. However, there is no evidence of its impact on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Methods

In a multicentre, randomised, double-blind, placebo-controlled trial, adult patients presenting up to 3 days after onset of coronavirus disease 2019 (COVID-19) symptoms (dry cough, fever and/or fatigue) were enrolled. After confirmation of SARS-CoV-2 infection using reverse transcriptase PCR on a nasopharyngeal swab, patients were randomised 1:1 to receive either nitazoxanide (500 mg) or placebo, three times daily, for 5 days. The primary outcome was complete resolution of symptoms. Secondary outcomes were viral load, laboratory tests, serum biomarkers of inflammation and hospitalisation rate. Adverse events were also assessed.

Results

From June 8 to August 20, 2020, 1575 patients were screened. Of these, 392 (198 placebo, 194 nitazoxanide) were analysed. Median (interquartile range) time from symptom onset to first dose of study drug was 5 (4–5) days. At the 5-day study visit, symptom resolution did not differ between the nitazoxanide and placebo arms. Swabs collected were negative for SARS-CoV-2 in 29.9% of patients in the nitazoxanide arm versus 18.2% in the placebo arm (p=0.009). Viral load was reduced after nitazoxanide compared to placebo (p=0.006). The percentage viral load reduction from onset to end of therapy was higher with nitazoxanide (55%) than placebo (45%) (p=0.013). Other secondary outcomes were not significantly different. No serious adverse events were observed.

Conclusions

In patients with mild COVID-19, symptom resolution did not differ between nitazoxanide and placebo groups after 5 days of therapy. However, early nitazoxanide therapy was safe and reduced viral load significantly.

This was the first study to evaluate the effect of early nitazoxanide therapy in mild COVID-19. Nitazoxanide did not accelerate symptom resolution after 5 days of therapy, but did reduce viral load significantly with no serious adverse events.https://bit.ly/37i75pr

Nitazoxanide superiority to placebo to treat moderate COVID-19 - A Pilot prove of concept randomized double-blind clinical trial

BACKGROUND

The absence of specific antivirals to treat COVID-19 leads to the repositioning of candidates' drugs. Nitazoxanide (NTZ) has a broad antiviral effect.

METHODS

This was a randomized, double-blind pilot clinical trial comparing NTZ 600 mg BID versus Placebo for seven days among 50 individuals (25 each arm) with SARS-COV-2 RT-PCR+ (PCR) that were hospitalized with mild respiratory insufficiency from May 20^th, 2020, to September 21^st, 2020 (ClinicalTrials.gov NCT04348409). Clinical and virologic endpoints and inflammatory biomarkers were evaluated. A five-point scale for disease severity (SSD) was used.

FINDINGS

Two patients died in the NTZ arm compared to 6 in the placebo arm (p = 0.564). NTZ was superior to placebo when considering SSD (p < 0001), the mean time for hospital discharge (6.6 vs. 14 days, p = 0.021), and negative PCR at day 21 (p = 0.035), whereas the placebo group presented more adverse events (p = 0.04). Among adverse events likely related to the study drug, 14 were detected in the NTZ group and 22 in placebo (p = 0.24). Among the 30 adverse events unlikely related, 21 occurred in the placebo group (p = 0.04). A decrease from baseline was higher in the NTZ group for d-Dimer (p = 0.001), US-RCP (p < 0.002), TNF (p < 0.038), IL-6 (p < 0.001), IL-8 (p = 0.014), HLA DR. on CD4⁺ T lymphocytes (p < 0.05), CD38 in CD4⁺ and CD8⁺ T (both p < 0.05), and CD38 and HLA-DR. on CD4+ (p < 0.01).

INTERPRETATION

Compared to placebo in clinical and virologic outcomes and improvement of inflammatory outcomes, the superiority of NTZ warrants further investigation of this drug for moderate COVID-19 in larger clinical trials. A higher incidence of adverse events in the placebo arm might be attributed to COVID-19 related symptoms.

Therapeutic Potential of Nitazoxanide: An Appropriate Choice for Repurposing versus SARS-CoV-2?

The rapidly growing COVID-19 pandemic is the most serious global health crisis since the "Spanish flu" of 1918. There is currently no proven effective drug treatment or prophylaxis for this coronavirus infection. While developing safe and effective vaccines is one of the key focuses, a number of existing antiviral drugs are being evaluated for their potency and efficiency against SARS-CoV-2 in vitro and in the clinic. Here, we review the significant potential of nitazoxanide (NTZ) as an antiviral agent that can be repurposed as a treatment for COVID-19. Originally, NTZ was developed as an antiparasitic agent especially against Cryptosporidium spp.; it was later shown to possess potent activity against a broad range of both RNA and DNA viruses, including influenza A, hepatitis B and C, and coronaviruses. Recent in vitro assessment of NTZ has confirmed its promising activity against SARS-CoV-2 with an EC50 of 2.12 μM. Here we examine its drug properties, antiviral activity against different viruses, clinical trials outcomes, and mechanisms of antiviral action from the literature in order to highlight the therapeutic potential for the treatment of COVID-19. Furthermore, in preliminary PK/PD analyses using clinical data reported in the literature, comparison of simulated TIZ (active metabolite of NTZ) exposures at two doses with the in vitro potency of NTZ against SARS-CoV-2 gives further support for drug repurposing with potential in combination chemotherapy approaches. The review concludes with details of second generation thiazolides under development that could lead to improved antiviral therapies for future indications.

Evaluating the efficacy of nitazoxanide in uncomplicated amebic liver abscess

BACKGROUND

Amebic liver abscess is treated successfully with metronidazole or another nitroimidazole drug followed by a luminal amebicide. Metronidazole has long been preferred, but has been associated with several adverse effects including intolerance in certain clinical situations. Mechanisms of metronidazole resistance and mutagenic potential have been described. Effects of the use of drug in pregnant women and infants of lactating women are unknown. Nitazoxanide was proven to be efficacious in treating invasive intestinal amebiasis. Therefore, the present study was undertaken to assess the efficacy and safety of nitazoxanide as compared to metronidazole in patients with uncomplicated amebic liver abscess.

METHODS

Patients with clinical and ultrasonography features suggestive of liver abscess, positive amebic serology, and/or anchovy sauce appearance on aspiration of the pus were included in the study and randomized into two parallel treatment groups. Group M received metronidazole, 2-2.5 g/day intravenous (IV), for inpatients, or 2-2.4 g/day oral, for outpatients in three divided doses for 14 days. Group N received nitazoxanide 500 mg BD per oral for 10 days.

RESULTS

A total of sixty subjects fulfilling the inclusion criteria were randomized equally into two groups, group M and group N. Number of patients achieving symptomatic clinical response (SCR) was similar in the two groups (80% vs. 76.7%, p = 1.00), though time to achieve symptomatic clinical response was significantly lower in metronidazole group as compared to that in nitazoxanide group. Greater proportion of patients achieved early clinical response (ECR) in metronidazole group as compared to nitazoxanide group. Complete resolution of abscess, at 6 months, was noted in 18 (60%) patients in the M group and 22 (73.3%) patients in the N group (p = 0.273). Metronidazole was associated with significantly greater frequency of adverse effects than nitazoxanide.

CONCLUSIONS

This study shows equivalent efficacy of nitazoxanide in uncomplicated amebic liver abscess as compared to metronidazole, with better tolerability and advantage of simultaneous luminal clearance, thus reducing chances of recurrence.

TRIAL REGISTRATION

CTRI/2019/01/017249.

Dose prediction for repurposing nitazoxanide in SARS-CoV-2 treatment or chemoprophylaxis

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been declared a global pandemic and urgent treatment and prevention strategies are needed. Nitazoxanide, an anthelmintic drug, has been shown to exhibit in vitro activity against SARS-CoV-2. The present study used physiologically based pharmacokinetic (PBPK) modelling to inform optimal doses of nitazoxanide capable of maintaining plasma and lung tizoxanide exposures above the reported SARS-CoV-2 EC90 .

METHODS

A whole-body PBPK model was validated against available pharmacokinetic data for healthy individuals receiving single and multiple doses between 500 and 4000 mg with and without food. The validated model was used to predict doses expected to maintain tizoxanide plasma and lung concentrations above the EC90 in >90% of the simulated population. PopDes was used to estimate an optimal sparse sampling strategy for future clinical trials.

RESULTS

The PBPK model was successfully validated against the reported human pharmacokinetics. The model predicted optimal doses of 1200 mg QID, 1600 mg TID and 2900 mg BID in the fasted state and 700 mg QID, 900 mg TID and 1400 mg BID when given with food. For BID regimens an optimal sparse sampling strategy of 0.25, 1, 3 and 12 hours post dose was estimated.

CONCLUSION

The PBPK model predicted tizoxanide concentrations within doses of nitazoxanide already given to humans previously. The reported dosing strategies provide a rational basis for design of clinical trials with nitazoxanide for the treatment or prevention of SARS-CoV-2 infection. A concordant higher dose of nitazoxanide is now planned for investigation in the seamless phase I/IIa AGILE trial.

Design, Synthesis, and Pharmacokinetic Evaluation of O-Carbamoyl Tizoxanide Prodrugs

BACKGROUND

The broad-spectrum antiparasitic drug nitazoxanide (N) has been repositioned as a broad-spectrum antiviral drug. Nitazoxanide's in vivo antiviral activities are mainly attributed to its metabolitetizoxanide, the deacetylation product of nitazoxanide. In reference to the pharmacokinetic profile of nitazoxanide, we proposed the hypotheses that the low plasma concentrations and the low system exposure of tizoxanide after dosing with nitazoxanide result from significant first pass effects in the liver. It was thought that this may be due to the unstable acyloxy bond of nitazoxanide.

OBJECTIVE

Tizoxanide prodrugs, with the more stable formamyl substituent attached to the hydroxyl group rather than the acetyl group of nitazoxanide, were designed with the thought that they might be more stable in plasma. It was anticipated that these prodrugs might be less affected by the first pass effect, which would improve plasma concentrations and system exposure of tizoxanide.

METHOD

These O-carbamoyl tizoxanide prodrugs were synthesized and evaluated in a mouse model for pharmacokinetic (PK) properties and in an in vitro model for plasma stabilities.

RESULTS

The results indicated that the plasma concentration and the systemic exposure of tizoxanide (T) after oral administration of O-carbamoyl tizoxanide prodrugs were much greater than that produced by equimolar dosage of nitazoxanide. It was also found that the plasma concentration and the systemic exposure of tizoxanide glucuronide (TG) were much lower than that produced by nitazoxanide.

CONCLUSION

Further analysis showed that the suitable plasma stability of O-carbamoyl tizoxanide prodrugs is the key factor in maximizing the plasma concentration and the systemic exposure of the active ingredient tizoxanide.

Zika Virus-Infected Decidual Cells Elicit a Gestational Age-Dependent Innate Immune Response and Exaggerate Trophoblast Zika Permissiveness: Implication for Vertical Transmission

Vertical transmission of the Zika virus (ZIKV) causes severe fetal defects, but the exact pathogenic mechanism is unclear. We identified up to a 10,480-fold higher expression of viral attachment factors AXL, GAS6, and PROS1 and a 3880-fold increase in ZIKV infectiousness/propagation in human term decidual stromal cells versus trophoblasts. Moreover, levels of viral attachment factors and ZIKV are significantly increased, whereas expression of innate immune response genes are significantly decreased, in human first trimester versus term decidual cells. ZIKV-infected decidual cell supernatants increased cytotrophoblasts infection up to 252-fold compared with directly infected cytotrophoblasts. Tizoxanide treatment efficiently inhibited Zika infection in both maternal and fetal cells. We conclude that ZIKV permissiveness, as well as innate immune responsiveness of human decidual cells, are gestational age dependent, and decidual cells augment ZIKV infection of primary human cytotrophoblast cultures, which are otherwise ZIKV resistant. Human decidual cells may act as reservoirs for trimester-dependent placental transmission of ZIKV, accounting for the higher Zika infection susceptibility and more severe fetal sequelae observed in early versus late pregnancy. Moreover, tizoxanide is a promising agent in preventing perinatal Zika transmission as well as other RNA viruses such as coronavirus.

Chemoprophylactic activity of nitazoxanide in experimental model of mammary gland carcinoma in rats

The current study focuses on the evaluation of the chemoprophylactic activity of nitazoxanide against the mammary gland carcinoma in experimental rats. The experimental protocol involves total 50 female Wistar albino rats of body weight 120-150 g, which were randomly categorized into five groups; Normal control (1% w/v carboxymethyl cellulose, p.o.); Toxic control (N-methyl-N-nitrosourea, MNU, 47 mg/kg i.v.); Standard (MNU, 47 mg/kg i.v. + tamoxifen, 1 mg/kg p.o.); Treatment 1 (MNU, 47 mg/kg i.v. + NTZ low-dose, 25 mg/kg p.o.); and Treatment 2 (MNU, 47 mg/kg, i.v. + NTZ high-dose, 50 mg/kg p.o.). The mammary gland carcinoma was induced by a single tail vein intravenous injection of MNU at a 47 mg/kg dose. Seven days after MNU administration, daily dosing of nitazoxanide and tamoxifen was initiated till 110th day in respective groups. The MNU toxicity was apparent with the altered electrocardiogram and heart rate variability, increased number of alveolar bud count, differentiation score, and upregulated antioxidant parameters. Nitazoxanide treatment restored the histological architecture in rats along with the reduction of alveolar buds and downregulation of oxidative stress markers as well as inflammatory markers. Therefore, nitazoxanide can be utilized as a potential chemoprophylactic agent against mammary gland carcinoma induced by MNU.

Dose prediction for repurposing nitazoxanide in SARS-CoV-2 treatment or chemoprophylaxis

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been declared a global pandemic by the World Health Organisation and urgent treatment and prevention strategies are needed. Many clinical trials have been initiated with existing medications, but assessments of the expected plasma and lung exposures at the selected doses have not featured in the prioritisation process. Although no antiviral data is currently available for the major phenolic circulating metabolite of nitazoxanide (known as tizoxanide), the parent ester drug has been shown to exhibit in vitro activity against SARS-CoV-2. Nitazoxanide is an anthelmintic drug and its metabolite tizoxanide has been described to have broad antiviral activity against influenza and other coronaviruses. The present study used physiologically-based pharmacokinetic (PBPK) modelling to inform optimal doses of nitazoxanide capable of maintaining plasma and lung tizoxanide exposures above the reported nitazoxanide 90% effective concentration (EC ₉₀ ) against SARS-CoV-2.

METHODS

A whole-body PBPK model was constructed for oral administration of nitazoxanide and validated against available tizoxanide pharmacokinetic data for healthy individuals receiving single doses between 500 mg SARS-CoV-2 4000 mg with and without food. Additional validation against multiple-dose pharmacokinetic data when given with food was conducted. The validated model was then used to predict alternative doses expected to maintain tizoxanide plasma and lung concentrations over the reported nitazoxanide EC ₉₀ in >90% of the simulated population. Optimal design software PopDes was used to estimate an optimal sparse sampling strategy for future clinical trials.

RESULTS

The PBPK model was validated with AAFE values between 1.01 SARS-CoV-2 1.58 and a difference less than 2-fold between observed and simulated values for all the reported clinical doses. The model predicted optimal doses of 1200 mg QID, 1600 mg TID, 2900 mg BID in the fasted state and 700 mg QID, 900 mg TID and 1400 mg BID when given with food, to provide tizoxanide plasma and lung concentrations over the reported in vitro EC ₉₀ of nitazoxanide against SARS-CoV-2. For BID regimens an optimal sparse sampling strategy of 0.25, 1, 3 and 12h post dose was estimated.

CONCLUSION

The PBPK model predicted that it was possible to achieve plasma and lung tizoxanide concentrations, using proven safe doses of nitazoxanide, that exceed the EC ₉₀ for SARS-CoV-2. The PBPK model describing tizoxanide plasma pharmacokinetics after oral administration of nitazoxanide was successfully validated against clinical data. This dose prediction assumes that the tizoxanide metabolite has activity against SARS-CoV-2 similar to that reported for nitazoxanide, as has been reported for other viruses. The model and the reported dosing strategies provide a rational basis for the design (optimising plasma and lung exposures) of future clinical trials of nitazoxanide in the treatment or prevention of SARS-CoV-2 infection.

Review of safety and minimum pricing of nitazoxanide for potential treatment of COVID-19

Background

Many treatments are being assessed for repurposing to treat coronavirus disease 2019 (COVID-19). One drug that has shown promising results in vitro is nitazoxanide. Unlike other postulated drugs, nitazoxanide shows a high ratio of maximum plasma concentration (C_max), after 1 day of 500 mg twice daily (BD), to the concentration required to inhibit 50% replication (EC₅₀) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (C_max : EC₅₀ roughly equal to 14:1). As such, it is important to investigate the safety of nitazoxanide for further trials. Furthermore, treatments for COVID-19 should be cheap to promote global access, but prices of many drugs are far higher than the costs of production. We aimed to conduct a review of the safety of nitazoxanide for any prior indication and calculate its minimum costs of production.

Methods

A review of nitazoxanide clinical research was conducted using EMBASE and MEDLINE databases, supplemented by ClinicalTrials.gov. We searched for phase 2 or 3 randomised controlled trials (RCTs) comparing nitazoxanide with placebo or active control for 5–14 days in participants experiencing acute infections of any kind. Data extracted were grade 1–4 and serious adverse events (AEs). Data were also extracted on gastrointestinal (GI) AEs, as well as hepatorenal and cardiovascular effects.

Active pharmaceutical ingredient cost data from 2016 to 2019 were extracted from the Panjiva database and adjusted for 5% loss during production, costs of excipients, formulation, a 10% profit margin and tax. Two dosages, at 500 mg BD and a higher dose of 1100 mg three times daily (TDS), were considered. Our estimated costs were compared with publicly available list prices from a selection of countries.

Results

Nine RCTs of nitazoxanide were identified for inclusion. These RCTs accounted for 1514 participants and an estimated 95.3 person-years-of-follow-up. No significant differences were found in any of the AE endpoints assessed, across all trials or on subgroup analyses of active- or placebo-controlled trials. Mild GI AEs increased with dose. No hepatorenal or cardiovascular concerns were raised, but few appropriate metrics were reported. There were no teratogenic concerns, but the evidence base was very limited.

Based on a weighted-mean cost of US $61/kg, a 14-day course of treatment with nitazoxanide 500 mg BD would cost $1.41. The daily cost would therefore be $0.10. The same 14-day course could cost $3944 in US commercial pharmacies, and $3 per course in Pakistan, India and Bangladesh. At a higher dose of 1100 mg TDS, our estimated cost was $4.08 per 14-day course, equivalent to $0.29 per day.

Conclusion

Nitazoxanide demonstrates a good safety profile at approved doses. However, further evidence is required regarding hepatorenal and cardiovascular effects, as well as teratogenicity. We estimate that it would be possible to manufacture nitazoxanide as generic for $1.41 for a 14-day treatment course at 500 mg BD, up to $4.08 at 1100 mg TDS. Further trials in COVID-19 patients should be initiated. If efficacy against SARS-CoV-2 is demonstrated in clinical studies, nitazoxanide may represent a safe and affordable treatment in the ongoing pandemic.

Early Bactericidal Activity Trial of Nitazoxanide for Pulmonary Tuberculosis

This study was conducted in treatment-naive adults with drug-susceptible pulmonary tuberculosis in Port-au-Prince, Haiti, to assess the safety, bactericidal activity, and pharmacokinetics of nitazoxanide (NTZ). This was a prospective phase II clinical trial in 30 adults with pulmonary tuberculosis. Twenty participants received 1 g of NTZ orally twice daily for 14 days. A control group of 10 participants received standard therapy over 14 days. The primary outcome was the change in time to culture positivity (TTP) in an automated liquid culture system. The most common adverse events seen in the NTZ group were gastrointestinal complaints and headache. The mean change in TTP in sputum over 14 days in the NTZ group was 3.2 h ± 22.6 h and was not statistically significant (P = 0.56). The mean change in TTP in the standard therapy group was significantly increased, at 134 h ± 45.2 h (P < 0.0001). The mean NTZ MIC for Mycobacterium tuberculosis isolates was 12.3 μg/ml; the mean NTZ maximum concentration (C _max) in plasma was 10.2 μg/ml. Negligible NTZ levels were measured in sputum. At the doses used, NTZ did not show bactericidal activity against M. tuberculosis Plasma concentrations of NTZ were below the MIC, and its negligible accumulation in pulmonary sites may explain the lack of bactericidal activity. (This study has been registered at ClinicalTrials.gov under identifier NCT02684240.).

Systemic and Target-Site Pharmacokinetics of Antiparasitic Agents

About one-sixth of the world's population is affected by a neglected tropical disease as defined by the World Health Organization and Center for Disease Control. Parasitic diseases comprise most of the neglected tropical disease list and they are causing enormous amounts of disability, morbidity, mortality, and healthcare costs worldwide. The burden of disease of the top five parasitic diseases has been estimated to amount to a total 23 million disability-adjusted life-years. Despite the massive health and economic impact, most drugs currently used for the treatment of parasitic diseases have been developed decades ago and insufficient novel drugs are being developed. The current review provides a compilation of the systemic and target-site pharmacokinetics of established antiparasitic drugs. Knowledge of the pharmacokinetic profile of drugs allows for the examination and possibly optimization of existing dosing schemes. Many symptoms of parasitic diseases are caused by parasites residing in different host tissues. Penetration of the antiparasitic drug into these tissues, the target site of infection, is a prerequisite for a successful treatment of the disease. Therefore, for the examination and improvement of established dosing regimens, not only the plasma but also the tissue pharmacokinetics of the drug have to be considered. For the current paper, almost 7000 scientific articles were identified and screened from which 429 were reviewed in detail and 100 were included in this paper. Systemic pharmacokinetics are available for most antiparasitic drugs but in many cases, not for all the relevant patient populations and only for single- or multiple-dose administration. Systemic pharmacokinetic data in patients with organ impairment and target-site pharmacokinetic data for relevant tissues and body fluids are mostly lacking. To improve the treatment of patients with parasitic diseases, research in these areas is urgently needed.

Nitazoxanide in the Treatment of Intestinal Parasitic Infections in Children: A Systematic Review and Meta-Analysis

OBJECTIVES

To evaluate the efficacy and safety of nitazoxanide in intestinal parasitic infections in children.

METHODS

Four databases, PubMed, EMBASE, Web of Science and Cochrane Library, have been systematically searched from the inception of each database up to March 1st, 2019. The enrolled studies were limited to randomized clinical trials in children, comparing nitazoxanide with placebo or other antiparasitic drugs. The data extraction and quality assessment of pooled studies were conducted by two reviewers independently. For meta-analysis, Stata12.0 was used and a randomized effect model or a fixed effect model was selected according to the outcomes of heterogeneity test.

RESULTS

A total of 1645 subjects in 13 randomized controlled trials (RCTs) were enrolled, including 768 cases in the trial group and 877 cases in the control group. The effect of nitazoxanide vs. placebo and other antiparasitic drugs on the excretion rate of pathogens was uncertain (OR = 2.06, 95%CI [1.01,4.20], P = 0.047; I² = 84.7%; very low quality evidence). Compared with placebo, subgroup analysis suggested that nitazoxanide could significantly improve the excretion rate of pathogens (OR = 7.01, 95%CI [1.82,26.94], P = 0.005; I² = 79.1%; moderate quality evidence), while it made little or no difference compared with antiparasitic drugs (OR = 0.72, 95%CI [0.47,1.09], P = 0.124; I² = 33.1%; low quality evidence). Meanwhile, nitazoxanide might increase the remission rate of diarrhea with OR = 5.12, 95%CI [2.00,13.08], P = 0.001; I² = 72.3%; low quality evidence). However, it might also increase the rate of adverse events (OR = 1.47, 95%CI [1.05,2.07], P = 0.026; I² = 44.7%; low quality evidence).

CONCLUSIONS

The authors are uncertain whether or not nitazoxanide could improve the excretion rate of pathogens. Based on low-certainty evidence, nitazoxanide may improve the remission rate of diarrhea in children with intestinal parasite infections, but it may be associated with an increased risk of adverse reactions. Hence, more RCTs with a low risk of bias are still needed to assess the efficacy and safety of nitazoxanide.

Tizoxanide induces autophagy by inhibiting PI3K/Akt/mTOR pathway in RAW264.7 macrophage cells

As the main metabolite of nitazoxanide, tizoxanide (TIZ) has a broad-spectrum anti-infective effect against parasites, bacteria, and virus. In this study, we investigated the effects of TIZ on autophagy by regulating the PI3K/Akt/mTOR signaling pathway. RAW264.7 macrophage cells were treated with various TIZ concentrations. Cell viability assay, transmission electron microscope, and immunofluorescence staining were used to detect the biological function of the macrophage cells, and the expression levels of the autophagy pathway-related proteins were measured by Western blot. Results revealed that TIZ promoted the conversion of LC3-I to LC3-II, the formation of autophagy vacuoles, and the degradation of SQSTM1/p62 in a concentration- and time-dependent manner in RAW264.7 cells. Treatment with TIZ increased the Beclin-1 expression level and inhibited PI3K, Akt, mTOR, and ULK1 activation. These effects were enhanced by pretreatment with rapamycin but attenuated by pretreatment with LY294002. In addition, the conversion of LC3-I to LC3-II was observed in Vero, 293T, and HepG2 cells treated with TIZ. These data suggested that TIZ may induce autophagy by inhibiting the Akt/mTOR/ULK1 signaling pathway in macrophages and other cells.

Cytoplasmic RNA Sensor Pathways and Nitazoxanide Broadly Inhibit Intracellular Mycobacterium tuberculosis Growth

To establish stable infection, Mycobacterium tuberculosis (MTb) must overcome host innate immune mechanisms, including those that sense pathogen-derived nucleic acids. Here, we show that the host cytosolic RNA sensing molecules RIG-I-like receptor (RLR) signaling proteins RIG-I and MDA5, their common adaptor protein MAVS, and the RNA-dependent kinase PKR each independently inhibit MTb growth in human cells. Furthermore, we show that MTb broadly stimulates RIG-I, MDA5, MAVS, and PKR gene expression and their biological activities. We also show that the oral FDA-approved drug nitazoxanide (NTZ) significantly inhibits intracellular MTb growth and amplifies MTb-stimulated RNA sensor gene expression and activity. This study establishes prototypic cytoplasmic RNA sensors as innate restriction factors for MTb growth in human cells and it shows that targeting this pathway is a potential host-directed approach to treat tuberculosis disease.

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MTb infection induces RNA sensor (RIG-I, MDA5, PKR) mRNA levels and activities

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RIG-I, MDA5, MAVS, and PKR restrict intracellular MTb growth in human cells

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NTZ enhances MTb-driven RNA sensor mRNA levels and RLR activities

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NTZ and NTZ derivatives inhibit intracellular MTb growth in primary human cells

Nitazoxanide Inhibits Human Norovirus Replication and Synergizes with Ribavirin by Activation of Cellular Antiviral Response

Norovirus is the main cause of viral gastroenteritis worldwide. Although norovirus gastroenteritis is self-limiting in immunocompetent individuals, chronic infections with debilitating and life-threatening complications occur in immunocompromised patients. Nitazoxanide (NTZ) has been used empirically in the clinic and has demonstrated effectiveness against norovirus gastroenteritis. In this study, we aimed at uncovering the antiviral potential and mechanisms of action of NTZ and its active metabolite, tizoxanide (TIZ), using a human norovirus (HuNV) replicon. NTZ and TIZ, collectively referred to as thiazolides (TZD), potently inhibited replication of HuNV and a norovirus surrogate, feline calicivirus. Mechanistic studies revealed that TZD activated cellular antiviral response and stimulated the expression of a subset of interferon-stimulated genes (ISGs), particularly interferon regulatory factor 1 (IRF-1), not only in a Huh7 cell-based HuNV replicon, but also in naive Huh7 and Caco-2 cells and novel human intestinal organoids. Overexpression of exogenous IRF-1 inhibited HuNV replication, whereas knockdown of IRF-1 largely attenuated the antiviral activity of TZD, suggesting that IRF-1 mediated TZD inhibition of HuNV. By using a Janus kinase (JAK) inhibitor, CP-690550, and a STAT1 knockout approach, we found that TZD induced antiviral response independently of the classical JAK-signal transducers and activators of transcription (JAK-STAT) pathway. Furthermore, TZD and ribavirin synergized to inhibit HuNV replication and completely depleted the replicons from host cells after long-term treatment. In summary, our results demonstrated that TZD combated HuNV replication through activation of cellular antiviral response, in particular by inducing a prominent antiviral effector, IRF-1. NTZ monotherapy or combination with ribavirin represent promising options for treating norovirus gastroenteritis, especially in immunocompromised patients.

Second-generation nitazoxanide derivatives: thiazolides are effective inhibitors of the influenza A virus

AIM

The only small molecule drugs currently available for treatment of influenza A virus (IAV) are M2 ion channel blockers and sialidase inhibitors. The prototype thiazolide, nitazoxanide, has successfully completed Phase III clinical trials against acute uncomplicated influenza.

RESULTS

We report the activity of seventeen thiazolide analogs against A/PuertoRico/8/1934(H1N1), a laboratory-adapted strain of the H1N1 subtype of IAV, in a cell culture-based assay. A total of eight analogs showed IC₅₀s in the range of 0.14-5.0 μM. Additionally a quantitative structure-property relationship study showed high correlation between experimental and predicted activity based on a molecular descriptor set.

CONCLUSION

A range of thiazolides show useful activity against an H1N1 strain of IAV. Further evaluation of these molecules as potential new small molecule therapies is justified.

Susceptibilities of MDR Mycobacterium tuberculosis isolates to unconventional drugs compared with their reported pharmacokinetic/pharmacodynamic parameters

Background

The second-line drugs recommended to treat drug-resistant TB are toxic, expensive and difficult to procure. Given increasing resistance, the need for additional anti-TB drugs has become more urgent. But new drugs take time to develop and are expensive. Some commercially available drugs have reported anti-mycobacterial activity but are not routinely used because supporting laboratory and clinical evidence is sparse.

Methods

We analysed 217 MDR M. tuberculosis isolates including 153 initial isolates from unique patients and 64 isolates from follow-up specimens during the course of treatment. The resazurin microdilution assay was performed to determine MICs of trimethoprim/sulfamethoxazole, mefloquine, thioridazine, clofazimine, amoxicillin/clavulanate, meropenem/clavulanate, nitazoxanide, linezolid and oxyphenbutazone. Isoniazid was used for validation. We calculated the MIC 50 and MIC 90 as the MICs at which growth of 50% and 90% of isolates was inhibited, respectively.

Results

The MIC 50 s, in mg/L, for initial isolates were as follows: trimethoprim/sulfamethoxazole, 0.2/4; mefloquine, 8; thioridazine, 4; clofazimine, 0.25; amoxicillin/clavulanate, 16/8; meropenem/clavulanate, 1/2.5; nitazoxanide, 16; linezolid, 0.25; and oxyphenbutazone, 40. The MIC 90 s, in mg/L, for initial isolates were as follows: trimethoprim/sulfamethoxazole, 0.4/8; mefloquine, 8; thioridazine, 8; clofazimine, 0.5; amoxicillin/clavulanate, 32/16; meropenem/clavulanate, 8/2.5; nitazoxanide, 16; linezolid, 0.25; and oxyphenbutazone, 60. By comparison, the MIC 90 of isoniazid was >4 mg/L, as expected. There was no evidence that previous treatment affected susceptibility to any drug.

Conclusions

Most drugs demonstrated efficacy against M. tuberculosis . When these MICs are compared with the published pharmacokinetic/pharmacodynamic profiles of the respective drugs in humans, trimethoprim/sulfamethoxazole, meropenem/clavulanate, linezolid, clofazimine and nitazoxanide appear promising and warrant further clinical investigation.

Inhalable Particles for "Pincer Therapeutics" Targeting Nitazoxanide as Bactericidal and Host-Directed Agent to Macrophages in a Mouse Model of Tuberculosis

Nitazoxanide (NTZ) has moderate mycobactericidal activity and is also an inducer of autophagy in mammalian cells. High-payload (40-50% w/w) inhalable particles containing NTZ alone or in combination with antituberculosis (TB) agents isoniazid (INH) and rifabutin (RFB) were prepared with high incorporation efficiency of 92%. In vitro drug release was corrected for drug degradation during the course of study and revealed first-order controlled release. Particles were efficiently taken up in vitro by macrophages and maintained intracellular drug concentrations at one order of magnitude higher than NTZ in solution for 6 h. Dose-dependent killing of Mtb and restoration of lung and spleen architecture were observed in experimentally infected mice treated with inhalations containing NTZ. Adjunct NTZ with INH and RFB cleared culturable bacteria from the lung and spleen and markedly healed tissue architecture. NTZ can be used in combination with INH-RFB to kill the pathogen and heal the host.

Nitazoxanide Inhibits Pilus Biogenesis by Interfering with Folding of the Usher Protein in the Outer Membrane

Many bacterial pathogens assemble surface fibers termed pili or fimbriae that facilitate attachment to host cells and colonization of host tissues. The chaperone/usher (CU) pathway is a conserved secretion system that is responsible for the assembly of virulence-associated pili by many different Gram-negative bacteria. Pilus biogenesis by the CU pathway requires a dedicated periplasmic chaperone and an integral outer membrane (OM) assembly and secretion platform termed the usher. Nitazoxanide (NTZ), an antiparasitic drug, was previously shown to inhibit the function of aggregative adherence fimbriae and type 1 pili assembled by the CU pathway in enteroaggregativeEscherichia coli, an important causative agent of diarrhea. We show here that NTZ also inhibits the function of type 1 and P pili from uropathogenicE. coli(UPEC). UPEC is the primary causative agent of urinary tract infections, and type 1 and P pili mediate colonization of the bladder and kidneys, respectively. By analysis of the different stages of the CU pilus biogenesis pathway, we show that treatment of bacteria with NTZ causes a reduction in the number of usher molecules in the OM, resulting in a loss of pilus assembly on the bacterial surface. In addition, we determine that NTZ specifically prevents proper folding of the usher β-barrel domain in the OM. Our findings demonstrate that NTZ is a pilicide with a novel mechanism of action and activity against diverse CU pathways. This suggests that further development of the NTZ scaffold may lead to new antivirulence agents that target the usher to prevent pilus assembly.

Activity of nitazoxanide and tizoxanide against Mycobacterium tuberculosis in vitro and in whole blood culture

Nitazoxanide (NTZ) and its metabolite tizoxanide (TIZ) were studied as antimycobacterial agents in vitro (in mycobacterial growth indicator tube [MGIT] cultures) and in a whole blood bactericidal assay. Both NTZ and TIZ show high protein binding. In MGIT cultures (albumin concentration = 78 μM), inhibition of Mycobacterium tuberculosis growth occurred at total drug concentrations of ≥16 μg/ml, whereas in whole blood cultures (albumin concentration = 350 μM), ≥128 μg/ml was required. Free drug fractions at these two conditions were estimated to be 69% and 2%, respectively. Co-incubation of NTZ and TIZ in human plasma for 72 h nearly completely eliminated their ability to inhibit mycobacterial growth in MGIT. Interactions with plasma proteins may limit the potential of NTZ and TIZ as drugs for human tuberculosis.

Impact of nitazoxanide on sustained virologic response in Egyptian patients with chronic hepatitis C genotype 4: a double-blind placebo-controlled trial

BACKGROUND

Nitazoxanide, approved for the treatment of Cryptosporidium parvum and Giardia lamblia, was found to inhibit hepatitis C virus replication.

AIM

The aim of this study was to assess the impact of nitazoxanide as an add-on therapy to pegylated interferon α-2a and ribavirin on sustained virologic response (SVR) in patients with chronic hepatitis C.

PATIENTS AND METHODS

A total of 200 patients with chronic hepatitis C were enrolled in the study, assigned randomly in a 1 : 1 ratio to two groups: group A (placebo group) and group B (nitazoxanide group). Five patients withdrew from the study after they signed the consent form.A total of 195 patients were evaluated: 97 patients in group A versus 98 patients in group B at a dose of 500 mg twice daily. Placebo and nitazoxanide were administered as an add-on therapy to pegylated interferon α-2a plus ribavirin following a 12-week lead-in phase. SVR was evaluated. Statistical analysis was carried out using the SPSS software.

RESULTS

The mean age of the patients in group A was 46.5 versus 45.7 years in group B. In group A, 85 out of 97 (87.6%) patients were men and in group B, 84 out of 98 (85.7%) patients were men.In group A, 59 out of 97 (60.82%) patients achieved an SVR versus 57 out of 98 (58.16%) patients in group B (P=0.70); this difference was not significant.

CONCLUSION

Our data did not show any significant impact of nitazoxanide on SVR.

Three-Dimensional Cell Culture-Based Screening Identifies the Anthelmintic Drug Nitazoxanide as a Candidate for Treatment of Colorectal Cancer

Because dormant cancer cells in hypoxic and nutrient-deprived regions of solid tumors provide a major obstacle to treatment, compounds targeting those cells might have clinical benefits. Here, we describe a high-throughput drug screening approach, using glucose-deprived multicellular tumor spheroids (MCTS) with inner hypoxia, to identify compounds that specifically target this cell population. We used a concept of drug repositioning-using known molecules for new indications. This is a promising strategy to identify molecules for rapid clinical advancement. By screening 1,600 compounds with documented clinical history, we aimed to identify candidates with unforeseen potential for repositioning as anticancer drugs. Our screen identified five molecules with pronounced MCTS-selective activity: nitazoxanide, niclosamide, closantel, pyrvinium pamoate, and salinomycin. Herein, we show that all five compounds inhibit mitochondrial respiration. This suggests that cancer cells in low glucose concentrations depend on oxidative phosphorylation rather than solely glycolysis. Importantly, continuous exposure to the compounds was required to achieve effective treatment. Nitazoxanide, an FDA-approved antiprotozoal drug with excellent pharmacokinetic and safety profile, is the only molecule among the screening hits that reaches high plasma concentrations persisting for up to a few hours after single oral dose. Nitazoxanide activated the AMPK pathway and downregulated c-Myc, mTOR, and Wnt signaling at clinically achievable concentrations. Nitazoxanide combined with the cytotoxic drug irinotecan showed anticancer activity in vivo. We here report that the FDA-approved anthelmintic drug nitazoxanide could be a potential candidate for advancement into cancer clinical trials.

Nitazoxanide, an antiviral thiazolide, depletes ATP-sensitive intracellular Ca(2+) stores

Nitazoxanide (NTZ) inhibits influenza, Japanese encephalitis, hepatitis B and hepatitis C virus replication but effects on the replication of other members of the Flaviviridae family has yet to be defined. The pestivirus bovine viral diarrhoea virus (BVDV) is a surrogate model for HCV infection and NTZ induced PKR and eIF2α phosphorylation in both uninfected and BVDV-infected cells. This led to the observation that NTZ depletes ATP-sensitive intracellular Ca(2+) stores. In addition to PKR and eIF2α phosphorylation, consequences of NTZ-mediated Ca(2+) mobilisation included induction of chronic sub-lethal ER stress as well as perturbation of viral protein N-linked glycosylation and trafficking. To adapt to NTZ-mediated ER stress, NTZ treated cells upregulated translation of Ca(2+)-binding proteins, including the ER chaperone Bip and the cytosolic pro-survival and anti-viral protein TCTP. Depletion of intracellular Ca(2+) stores is the primary consequence of NTZ treatment and is likely to underpin all antiviral mechanisms attributed to the thiazolide.

Effect of nitazoxanide in adults and adolescents with acute uncomplicated influenza: a double-blind, randomised, placebo-controlled, phase 2b/3 trial

Background

Influenza is an important cause of morbidity and mortality worldwide. Treatment options are scarce, and new drugs with novel mechanisms of action are needed. We aimed to assess the efficacy and safety of nitazoxanide, a thiazolide anti-infective, for treatment of acute uncomplicated influenza.

Methods

We did a double-blind, randomised, placebo-controlled, phase 2b/3 trial in 74 primary care clinics in the USA between Dec 27, 2010, and April 30, 2011. We enrolled participants aged 12–65 years with fever, at least one respiratory symptom, and one constitutional symptom of influenza within 48 h of symptom onset. We randomly assigned participants to receive either nitazoxanide 600 mg, nitazoxanide 300 mg, or placebo twice daily for 5 days, (ratio 1:1:1) and followed them up for 28 days. Randomisation lists were computer generated and done in blocks of three. Sponsor, investigators, study monitors, patients, and laboratory personnel were all masked to treatment allocation in the study. The primary endpoint was the time from first dose to alleviation of symptoms. The primary analysis was by intention-to-treat for participants with influenza infection confirmed by RT-PCR or culture at baseline. This trial is registered with ClinicalTrials.gov, number NCT01227421.

Findings

Of 650 participants screened, 624 (96%) were enrolled. Of these, 212 were randomly assigned to receive placebo twice a day, 201 to receive nitazoxanide 300 mg twice a day, and 211 to receive nitazoxanide 600 mg a day. The median duration of symptoms for participants receiving placebo was 116·7 h (95% CI 108·1–122·1) compared with 95·5 h (84·0–108·0; p=0·0084) for those receiving 600 mg nitazoxanide and 109·1 h (96·1–129·5, p=0·52) for those receiving 300 mg nitazoxanide. Adverse events were similar between the three groups, the most common being headache reported by 24 (11%) of 212 patients enrolled in placebo group, 12 (6%) of 201 patients in the low-dose group, and 17 (8%) of 211 patients in the high-dose group, or diarrhoea, reported by seven (3%) patients in the placebo group, four (2%) patients enrolled in the low-dose group, and 17 (8%) patients in the high-dose group.

Interpretation

Treatment with nitazoxanide 600 mg twice daily for 5 days was associated with a reduction of the duration of symptoms in participants with acute uncomplicated influenza. Further studies are warranted to confirm these findings and to assess efficacy of the drug alone or in combination with existing drugs in seriously ill patients and those at risk of influenza complications.

Funding

Romark Laboratories LC.

Analyzing the relationship of QT interval and exposure to nitazoxanide, a prospective candidate for influenza antiviral therapy--A formal TQT study

In this randomized, double-blind, placebo controlled study, the safety of therapeutic (675 mg) and supra-therapeutic (2,700 mg) doses of nitazoxanide was evaluated in accordance with the ICH E14 guidelines. Fifty six (56) subjects participated in four treatment periods and received single doses of nitazoxanide 675 mg, nitazoxanide 2,700 mg, moxifloxacin 400 mg, or placebo. For 675 mg nitazoxanide, the largest change in QTcF from baseline was observed at 12 hours post-dose with a peak value of 1.6 ms (two-sided 90% CI: -0.3, 3.6 ms). The largest negative change in QTcF was observed at 1 hour post-dose (-2.7 ms with two-sided 90% CI: -4.5, -0.8 ms). The largest change in QTcF from baseline for 2,700 mg nitazoxanide was observed at 24 hours post-dose with a peak value of 3.4 ms (two-sided CI: 1.4, 5.4 ms). These findings demonstrate that neither a single dose of 675 mg nor 2,700 mg nitazoxanide prolonged the QT interval in healthy male and female volunteers. The safety results also demonstrate that all four treatments were well-tolerated and the most frequently reported adverse events in the nitazoxanide and moxifloxacin treatment groups were gastrointestinal disorders which were as expected according to the reference safety information.

Synthesis and antiprotozoal activity of nitazoxanide-N-methylbenzimidazole hybrids

A series of a novel hybrid compounds between nitazoxanide and N-methylbenzimidazole were synthesized starting from the corresponding N-methyl-2-nitroanilines. The new hybrid compounds (1-13) were evaluated in vitro against Giardia intestinalis, Entamoeba histolytica, Trichomonas vaginalis. NTZ, MTZ and ABZ were used as drug standards. Experimental evaluations revealed all of the new compounds (1-13) were active and showed strong activity against the three protozoa, particularly with E. histolytica where the IC50 values ranged between 3 and 69 nM. Overall, compounds 2, 5, 7, 8, 9, 11 and 12 stood out with values lower than 87 nM for all three protozoa, comparatively better than the reference drugs.

Efficacy of nitazoxanide against clinical isolates of Mycobacterium tuberculosis

Nitazoxanide (NTZ) has bactericidal activity against the H37Rv laboratory strain of Mycobacterium tuberculosis with a MIC of 16 μg/ml. However, its efficacy against clinical isolates of M. tuberculosis has not been determined. We found that NTZ's MIC against 50 clinical isolates ranged from 12 to 28 μg/ml with a median of 16 μg/ml and was unaffected by resistance to first- or second-line antituberculosis drugs or a diversity of spoligotypes.

Nitazoxanide stimulates autophagy and inhibits mTORC1 signaling and intracellular proliferation of Mycobacterium tuberculosis

Tuberculosis, caused by Mycobacterium tuberculosis infection, is a major cause of morbidity and mortality in the world today. M. tuberculosis hijacks the phagosome-lysosome trafficking pathway to escape clearance from infected macrophages. There is increasing evidence that manipulation of autophagy, a regulated catabolic trafficking pathway, can enhance killing of M. tuberculosis. Therefore, pharmacological agents that induce autophagy could be important in combating tuberculosis. We report that the antiprotozoal drug nitazoxanide and its active metabolite tizoxanide strongly stimulate autophagy and inhibit signaling by mTORC1, a major negative regulator of autophagy. Analysis of 16 nitazoxanide analogues reveals similar strict structural requirements for activity in autophagosome induction, EGFP-LC3 processing and mTORC1 inhibition. Nitazoxanide can inhibit M. tuberculosis proliferation in vitro. Here we show that it inhibits M. tuberculosis proliferation more potently in infected human THP-1 cells and peripheral monocytes. We identify the human quinone oxidoreductase NQO1 as a nitazoxanide target and propose, based on experiments with cells expressing NQO1 or not, that NQO1 inhibition is partly responsible for mTORC1 inhibition and enhanced autophagy. The dual action of nitazoxanide on both the bacterium and the host cell response to infection may lead to improved tuberculosis treatment.

Tuberculosis is responsible for approximately 2 million deaths worldwide each year. Current treatment regimens require administration of multiple drugs over several months and resistance to these drugs is on the rise. Mycobacterium tuberculosis, the causative agent of the disease, can proliferate within host cells. It has been recently observed that autophagy (cellular self-eating) can kill intracellular M. tuberculosis. We report that the antiprotozoal drug nitazoxanide and its metabolite tizoxanide induce autophagy, inhibit signaling by mTORC1, a major negative regulator of autophagy, and prevent M. tuberculosis proliferation in infected macrophages. We show that nitazoxanide exerts at least some of its pharmacological effects by targeting the quinone reductase NQO1. Our results uncover a novel mechanism of action for the drug nitazoxanide, and show that pharmacological modulation of autophagy can suppress intracellular M. tuberculosis proliferation.

Thiazolides as novel antiviral agents. 1. Inhibition of hepatitis B virus replication

We report the syntheses and activities of a wide range of thiazolides [viz., 2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis B virus replication, with QSAR analysis of our results. The prototypical thiazolide, nitazoxanide [2-hydroxybenzoyl-N-(5-nitrothiazol-2-yl)amide, NTZ] 1 is a broad spectrum antiinfective agent effective against anaerobic bacteria, viruses, and parasites. By contrast, 2-hydroxybenzoyl-N-(5-chlorothiazol-2-yl)amide 3 is a novel, potent, and selective inhibitor of hepatitis B replication (EC(50) = 0.33 μm) but is inactive against anaerobes. Several 4'- and 5'-substituted thiazolides show good activity against HBV; by contrast, some related salicyloylanilides show a narrower spectrum of activity. The ADME properties of 3 are similar to 1; viz., the O-acetate is an effective prodrug, and the O-aryl glucuronide is a major metabolite. The QSAR study shows a good correlation of observed EC(90) for intracellular virions with thiazolide structural parameters. Finally we discuss the mechanism of action of thiazolides in relation to the present results.

The pharmacokinetics of nitazoxanide active metabolite (tizoxanide) in goats and its protein binding ability in vitro

The pharmacokinetics of tizoxanide (T), the active metabolite of nitazoxanide (NTZ), and its protein binding ability in goat plasma and in the solutions of albumin and alpha-1-acid-glycoprotein were investigated. The plasma and protein binding samples were analyzed using a high-performance liquid chromatography (HPLC) assay with UV detection at 360 nm. The plasma concentration of T was detectable in goats up to 24 h. Plasma concentrations vs. time data of T after 200 mg/kg oral administration of NTZ in goats were adequately described by one-compartment open model with first order absorption. As to free T, the values of t(1/2Ka), t(1/2Ke), T(max), C(max), AUC, V/F((c)), and Cl((s)) were 2.51 +/- 0.41 h, 3.47 +/- 0.32 h, 4.90 +/- 0.13 h, 2.56 +/- 0.25 microg/mL, 27.40 +/- 1.54 (microg/mL) x h, 30.17 +/- 2.17 L/kg, and 7.34 +/- 1.21 L/(kg x h), respectively. After beta-glucuronidase hydrolysis to obtain total T, t(1/2ke), C(max), T(max), AUC increased, while the V/F((c)) and Cl((s)) decreased. Study of the protein binding ability showed that T with 4 microg/mL concentration in goat plasma and in the albumin solution achieved a protein binding percentage of more than 95%, while in the solution of alpha-1-acid-glycoprotein, the percentage was only about 49%. This result suggested that T might have much more potent binding ability with albumin than with alpha-1-acid-glycoprotein, resulting from its acidic property.

Thiazolides: a new class of antiviral drugs

BACKGROUND

Thiazolides have emerged as a new class of broad-spectrum antiviral drugs, and the first thiazolide, nitazoxanide, is in late-stage clinical trials for treating chronic hepatitis C.

OBJECTIVE

To review the chemistry, pharmacology, toxicology and efficacy of thiazolides as antiviral agents with emphasis on clinical development of nitazoxanide in treating chronic hepatitis C.

METHODS

Literature search, information from Romark Laboratories and my personal experience with the discovery and development of thiazolides serve as the sources for this review.

CONCLUSIONS

Thiazolides are metabolically stable, highly bound to plasma proteins and are associated with a favorable toxicology profile. Phase II clinical trials have demonstrated efficacy and safety of nitazoxanide added to peginterferon with or without ribavirin in treating patients with chronic hepatitis C. More limited clinical data indicated potential in treating chronic hepatitis B, and three randomized controlled trials have demonstrated efficacy in reducing the duration of viral gastroenteritis. New generation thiazolides with the nitro group of nitazoxanide replaced by a non-reducible group are not active against anaerobes but retain broad-spectrum activity against viruses. Further studies are needed. Research indicates that these drugs may play an important and complementary role in combination with other classes of antiviral drugs.

Current Approaches to the Treatment of Gastrointestinal Infections: Focus on Nitazoxanide

Nitazoxanide is a broad-spectrum agent active against several protozoa, helminths, and bacteria, including C. difficile and H. pylori. It is available as an oral tablet and suspension, both with adequate bioavailability. Nitazoxanide is associated with minimal side effects, has an acceptable safety profile, and has been classified as a pregnancy category B agent. It is 99% protein bound, which could result in drug interactions. It is the preferred agent for the treatment of Cryptospordiosis and Giardiasis in immunocompetent patients and has shown promise for the treatment of rotavirus, mild to moderate initial C. difficile infection, refractory C. difficile infection, Amoebiasis, Blastocystosis, and Taenia saginata.

Thiazolides: a new class of drugs for the treatment of chronic hepatitis B and C

Nitazoxanide, the first thiazolide, was originally developed for the treatment of Cryptosporidium parvum. The antiviral activity of nitazoxanide was discovered by serendipity in patients with AIDS who were treated for cryptosporidial diarrhea and had HBV or HCV co-infection. In preliminary open-label studies of patients with chronic hepatitis B, nitazoxanide suppressed serum HBV DNA and led to loss or seroconversion of hepatitis B e antigen in the majority of patients, as well as hepatitis B surface antigen in approximately a quarter of patients. In Phase II studies of patients with chronic hepatitis C genotype 4, nitazoxanide combined with peginterferon alfa-2a, with or without ribavirin, increased the sustained virologic response rate to 79-80 versus 50% with peginterferon plus ribavirin standard of care. Randomized, controlled studies of naive and nonresponder patients with chronic hepatitis C genotype 1 and patients with chronic hepatitis B are underway, and new second generation thiazolides are being developed.

Brugia malayi: Effects of nitazoxanide and tizoxanide on adult worms and microfilariae of filarial nematodes

There is an urgent need for safe and effective antifilarials. Prior studies have shown that the nitazoxanide (NTZ) exhibits broad activity against anaerobic bacteria, protozoa, and certain intestinal helminths. We examined the effects of NTZ and tizoxanide (TZ) on Brugia malayi nematodes in vitro and in vivo. In vitro, NTZ and TZ reduced worm motility and viability in a dose-dependent manner. Worm viability was reduced by 50% with both compounds at 2.5 and 20 microg/ml killed adult worms. NTZ or TZ (5 microg/ml) significantly reduced microfilaria release. These compounds blocked worm's embryogenesis, and decreased microfilarial motility and viability. Treated worms had damaged cuticles and abnormal mitochondria. Wolbachia were not cleared by NTZ or TZ treatment. Neither NTZ nor TZ cleared adult worms or microfilariae in infected gerbils. These results show that NTZ and TZ have potent effects on B. malayi nematodes in vitro. However, they were not effective in vivo.

Nitazoxanide: clinical studies of a broad-spectrum anti-infective agent

Nitazoxanide is a new compound with broad-spectrum activity against numerous intestinal protozoa, helminths and anaerobic bacteria. It is approved for the treatment of diseases caused by Giardia intestinalis and Cryptosporidium species. The drug is well tolerated, with few side effects and requires a short course of treatment. Further investigations regarding its use in patients with AIDS is needed. Nitazoxanide represents a significant advance in the treatment of intestinal parasitic infections worldwide.

Nitazoxanide, tizoxanide and other thiazolides are potent inhibitors of hepatitis B virus and hepatitis C virus replication

Nitazoxanide (NTZ), a thiazolide anti-infective, is active against anaerobic bacteria, protozoa, and a range of viruses in cell culture models, and is currently in phase II clinical development for treating chronic hepatitis C. In this report, we characterize the activities of NTZ and its active metabolite, tizoxanide (TIZ), along with other thiazolides against hepatitis B virus (HBV) and hepatitis C virus (HCV) replication in standard antiviral assays. NTZ and TIZ exhibited potent inhibition of both HBV and HCV replication. NTZ was equally effective at inhibiting replication of lamivudine (LMV) and adefovir dipovoxil (ADV)-resistant HBV mutants and against 2'-C-methyl cytidine (2'CmeC) and telaprevir (VX-950)-resistant HCV mutants. NTZ displayed synergistic interactions with LMV or ADV against HBV, and with recombinant interferon alpha-2b (IFN) or 2'CmeC against HCV. Pre-treatment of HCV replicon-containing cells with NTZ potentiated the effect of subsequent treatment with NTZ plus IFN, but not NTZ plus 2'CmeC. NTZ induced reductions in several HBV proteins (HBsAg, HBeAg, HBcAg) produced by 2.2.15 cells, but did not affect HBV RNA transcription. NTZ, TIZ, and other thiazolides are promising new antiviral agents that may enhance current or future anti-hepatitis therapies.

Nitazoxanide: a review of its use in the treatment of gastrointestinal infections

Nitazoxanide (Alinia, Daxon, Dexidex, Paramix, Kidonax, Colufase, Annita) has in vitro activity against a variety of microorganisms, including a broad range of protozoa and helminths. Nitazoxanide is effective in the treatment of protozoal and helminthic infections, including Cryptosporidium parvum or Giardia lamblia, in immunocompetent adults and children, and is generally well tolerated. Nitazoxanide is a first-line choice for the treatment of illness caused by C. parvum or G. lamblia infection in immunocompetent adults and children, and is an option to be considered in the treatment of illnesses caused by other protozoa and/or helminths.

Nitazoxanide in the treatment of viral gastroenteritis: a randomized double-blind placebo-controlled clinical trial

BACKGROUND

Enteric viruses including noroviruses and rotavirus are leading causes of diarrhoeal disease and gastroenteritis worldwide, and there is no effective treatment.

AIM

To evaluate nitazoxanide, a thiazolide anti-infective agent, in treating viral gastroenteritis in adults and adolescents.

METHODS

50 out-patients at least 12 years of age (mean 33.5 years) presenting with diarrhoea and stool-positive by enzyme-linked immunosorbent assay for norovirus, rotavirus or adenovirus were enrolled in a double-blind, placebo-controlled clinical trial. Patients were randomly assigned either nitazoxanide 500 mg or placebo twice daily for 3 days. The primary end point was time from first dose to resolution of symptoms. Analysis was modified intent-to-treat for 45 patients, excluding five patients with other identified enteropathogens at baseline.

RESULTS

The median time from first dose to resolution of symptoms was 1.5 days (IQR: 0.5-2.5) for nitazoxanide-treated patients and 2.5 days (IQR: 1.5-4.5) for the placebo group. Significant reductions in time to resolution of symptoms were observed for all patients analysed (P < 0.0001) and for subsets of patients with rotavirus (P = 0.0052) and norovirus (P = 0.0295). The number of patients with adenovirus (n = 5) was too small to draw any conclusion. No significant adverse events were reported.

CONCLUSIONS

Nitazoxanide may play an important role in managing viral gastroenteritis in adults.

Nitazoxanide, a broad-spectrum thiazolide anti-infective agent for the treatment of gastrointestinal infections

Colonisation of the gastrointestinal tract by anaerobic bacteria, protozoa, trematodes, cestodes and/or nematodes and other infectious pathogens, including viruses, represents a major cause of morbidity and mortality in Africa, South America and southeast Asia, as well as other parts of the world. Nitazoxanide is a member of the thiazolide class of drugs with a documented broad spectrum of activity against parasites and anaerobic bacteria. Moreover, the drug has recently been reported to have a profound activity against hepatitis C virus infection. In addition, nitazoxanide exhibits anti-inflammatory properties, which have prompted clinical investigations for its use in Crohn's disease. Studies with nitazoxanide derivatives have determined that there must be significantly different mechanisms of action acting on intracellular versus extracellular pathogens. An impressive number of clinical studies have shown that the drug has an excellent bioavailability in the gastrointestinal tract, is fast acting and highly effective against gastrointestinal bacteria, protozoa and helminthes. A recent Phase II study has demonstrated viral response (hepatitis C) to monotherapy, with a low toxicity and an excellent safety profile over 24 weeks of treatment. Pre-clinical studies have indicated that there is a potential for application of this drug against other diseases, not primarily affecting the liver or the gastrointestinal tract.