Pharmacokinetic, Pharmacodynamic, and Drug-Interaction Profile of the Hepatitis C Virus NS5B Polymerase Inhibitor Sofosbuvir

Antivirals in COVID-19: A Focus on Pediatric Cardiac Patients

The COVID-19 pandemic created an unprecedented public health crisis, driven by its rapid global spread and the urgent need for worldwide collaborative interventions to contain it. This urgency spurred the search for therapeutic agents to prevent or manage the infection. Among these, various types of antivirals emerged as a prominent treatment option, supported by a wealth of observational studies and randomized controlled trials. The results from such studies conflict, with some concluding efficacy and others the lack thereof, with variability also occurring depending on the severity of COVID-19 in the studied population. In addition, many agents have been explored using randomized controlled trials-the gold standard in evaluating the efficacy of an intervention-to only a limited degree, with most of the evidence behind their use concluded using observational studies. Thus, the sheer volume of data has made it challenging to resolve inconsistencies and determine true efficacy. Furthermore, there is a paucity in the literature regarding the use of antivirals in the pediatric population infected with COVID-19, with their use being extrapolated from the results of studies done on adult patients. As such, additional trials are needed to solidify the effectiveness of antivirals in managing COVID-19, particularly in the underexplored and especially vulnerable pediatric cardiac patients. Therefore, utilizing the results from randomized controlled trials, this narrative review evaluates the rationale behind the use of antivirals, summarizes the findings from the literature, and concludes with a focused discussion on their application in pediatric cardiac patients.

Remdesivir is active in vitro against tick-borne encephalitis virus and selects for resistance mutations in the viral RNA-dependent RNA polymerase

BACKGROUND

Tick-borne encephalitis (TBE) is a neurological disease caused by the tick-borne encephalitis virus (TBEV). Despite available vaccines, breakthrough infections occur, some fatal.

OBJECTIVES

As no antiviral therapy for TBE is currently approved, this study evaluated the in vitro activity of already licenced remdesivir (RDV) and sofosbuvir (SOF) for possible drug repurposing against TBEV.

METHODS

TBEV was cultured in A549 cells, and the inhibitory effects of RDV (GS-5734), its parent nucleotide GS-441524, and SOF (GS-7977) were assessed.

RESULTS

After 78 h, RDV demonstrated significantly lower EC50 values than SOF (0.14 vs. 11 µM) based on TBEV RNA levels measured by RT-qPCR. RDV also had a lower mean EC50 (0.55 µM) compared to GS-441524 and SOF (>8.9 and 13.1 µM, respectively) using crystal violet staining after 5 days. After 11 passages of TBEV in the presence of RDV, emergence of virus with a higher EC50 (1.32 vs. 0.55 µM) was detected with two mutations (L3122F and Y3278F) in NS5, the viral RNA-dependent RNA polymerase (RdRp), and one substitution in envelope (E) protein (E402G). Similarly, SOF resistance appeared after 20 passages, increasing EC50 values (35.5 vs. 10 µM).

CONCLUSION

RDV exhibits potent in vitro antiviral activity against TBEV via specific targeting of the viral RdRp as confirmed by the emergence of resistance-associated double NS5 substitutions in vitro in the presence of RDV. While the potential in vivo implications of the observed RDV resistance remain to be determined, these in vitro data support further assessment of RDV for the treatment of TBEV infection.

Sofosbuvir: A comprehensive profile

Sofosbuvir, a nucleotide analogue, is an antiviral medication that belongs to the class of direct-acting antivirals (DAAs). It is primarily used in the treatment of chronic hepatitis C virus (HCV) infections. Sofosbuvir works by inhibiting the replication of HCV, disrupting its ability to produce RNA and effectively reducing the viral load in the body. This chapter offers a comprehensive examination of sofosbuvir, including its nomenclature, physiochemical attributes, synthesis, and thermal analysis. Furthermore, it presents various analytical methods employed for both spectrophotometric and chromatographic assessments of sofosbuvir in different matrices.

Improved Outcomes of Liver Transplantation in Patients With Hepatitis C, Following the Introduction of Innovative Antiviral Therapies

Background

The treatment landscape for hepatitis C virus (HCV) underwent a significant shift with the introduction of direct-acting antiviral (DAA) medications in late 2013. This study aimed to evaluate the impact of DAAs on liver transplantation outcomes, examining both the benefits and any potential drawbacks associated with their use.

Methods and materials

A retrospective registry analysis of the United Network for Organ Sharing database was done for liver transplants in patients diagnosed with hepatitis C, that were performed in the United States from January 2000 to May 2020.

Results

The study was divided into two subgroups, based on the timing of the new DAA medication that FDA approved. The only significant difference between the two cohorts is the recipient's age. The data analysis showed a significant overall 5-year graft survival improvement in the 2014-2020 group compared with the 2000-2013 group, from a mean of 64.8% in 2000-2013 to a mean of 76% in 2014-2020 (P < 0.001). Interestingly, when we compared the 5-year graft survivals with recipients who had a donor above age 50, the graft survival rate difference was even more significant (74% vs. 56%, P < 0.001) as some studies have shown a suboptimal graft outcome when the donor age is above 40 years old. Not only has the utilization of donation after circulatory death livers increased significantly after 2014 but the graft survival in this cohort has also been significantly higher (P < 0.001).

Conclusion

The emergence of DAAs in 2013 marked a watershed moment in the management of HCV offering high cure rates, minimal side effects, and shorter treatment durations to a point that the short- and long-term outcomes of liver transplantation for HCV is almost equal to the other causes of liver transplantation.

Drug-Drug Interactions Between HIV Antivirals and Concomitant Drugs in HIV Patients: What We Know and What We Need to Know

Highly active antiretroviral therapy has led to a significant increase in the life expectancy of people living with HIV. The trade-off is that HIV-infected patients often suffer from comorbidities that require additional treatment, increasing the risk of Drug-Drug Interactions (DDIs), the clinical relevance of which has often not been determined during registration trials of the drugs involved. Therefore, it is important to identify potential clinically relevant DDIs in order to establish the most appropriate therapeutic approaches. This review aims to summarize and analyze data from studies published over the last two decades on DDI-related adverse clinical outcomes involving anti-HIV drugs and those used to treat comorbidities. Several studies have examined the pharmacokinetics and tolerability of different drug combinations. Protease inhibitors, followed by nonnucleoside reverse transcriptase inhibitors and integrase inhibitors have been recognized as the main players in DDIs with antivirals used to control co-infection, such as Hepatitis C virus, or with drugs commonly used to treat HIV comorbidities, such as lipid-lowering agents, proton pump inhibitors and anticancer drugs. However, the studies do not seem to be consistent with regard to sample size and follow-up, the drugs involved, or the results obtained. It should be noted that most of the available studies were conducted in healthy volunteers without being replicated in patients. This hampered the assessment of the clinical burden of DDIs and, consequently, the optimal pharmacological management of people living with HIV.

Efficacy of 8-week daclatasvir-sofosbuvir regimen in chronic hepatitis C: a systematic review and meta-analysis

BACKGROUND

The high rates of the sustained virologic response 12 weeks after treatment (SVR12) in real world settings provoked the adoption of shortened courses of the costly direct-acting antivirals (DAAs) regimens. This study provides, to our knowledge, the first systematic review and meta-analysis for the efficacy of the shortened 8-week course of sofosbuvir (SOF) plus daclatasvir (DCV), the most accessible DAAs in the low-middle income countries (LMICs).

METHODS

We performed a proportion meta-analysis to determine a reliable rate of SVR12 by pooling all studies that evaluated the results of the 8-week regimen of DCV + SOF. In addition, we applied sensitivity analyses using two imputation paradigms: a conservative approach, and a pragmatic approach to avoid overestimating the efficacy of the 8-week regimen in studies that followed a response-guided treatment (RGT) approach.

RESULTS

Six studies with a total of 159 patients were included. The pooled SVR12 rate ranged from 91 to 97% in the included scenarios. The pragmatic scenario showed that the pooled SVR12 was 97% (95% confidence interval (CI) 91%; 100%) with lower variability as assessed by the prediction interval. The conservative approach revealed an SVR12 of 93% (95% CI 84%; 95%).

CONCLUSION

The 8-week course of 60 mg DCV with SOF provided a comparable SVR12 to the standard 12-week regimen in treatment-naïve, non-HIV co-infected patients with a minimum estimated efficacy of 90%.

Effect of carvedilol on pharmacokinetics of sofosbuvir and its metabolite GS-331007: role of P-glycoprotein

Sofosbuvir (SOF) is a P-glycoprotein (P-gp) substrate, and carvedilol (CAR) is an inhibitor of P-gp, suggesting that it may affect the oral pharmacokinetics and safety of SOF. The current study investigated the pharmacokinetic interaction of CAR with SOF and its metabolite, GS-331007, and the possible consequent toxicities in rats. To assess the pharmacokinetics of SOF and GS-331007, rats were divided into three groups; all received a single oral dose of SOF preceded with saline (SAL), verapamil (VER) as a standard P-gp inhibitor, or CAR, respectively. The serosal, plasma, and hepatic tissue contents of SOF and GS-331007 were assessed using LC-MS/MS. Renal and hepatic toxicities were assessed using biochemical and histopathological tests. Serosal and plasma concentrations of SOF and GS-331007 were increased in the presence of CAR, suggesting a significant inhibitory effect of CAR on intestinal P-gp. Simultaneously, the pharmacokinetic profile of SOF showed a significant increase in the Cmax, AUC(0-t), AUC (0-∞), t1/2, and a reduction in its apparent oral clearance. While the pharmacokinetic profile of GS-331007 was not significantly affected. However, this notable elevation in drug oral bioavailability was corroborated by a significant alteration in renal functions. Hence, further clinical investigations are recommended to ensure the safety and dosing of CAR/SOF combination.

Viral replication organelles: the highly complex and programmed replication machinery

Viral infections usually induce the rearrangement of cellular cytoskeletal proteins and organelle membrane structures, thus creating independent compartments [termed replication organelles (ROs)] to facilitate viral genome replication. Within the ROs, viral replicases, including polymerases, helicases, and ligases, play functional roles during viral replication. These viral replicases are pivotal in the virus life cycle, and numerous studies have demonstrated that the viral replicases could be the potential targets for drugs development. Here, we summarize primarily the key replicases within viral ROs and emphasize the advancements of antiviral drugs targeting crucial viral replicases, providing novel insights into the future development of antiviral strategies.

Identifying Gaps in the Treatment Guidelines for Hepatitis C in Peru to Meet International Standards: A Narrative Review

Hepatitis C virus still represents a major cause of morbidity and mortality worldwide. In Peru, two national practice guidelines for the management of this infection were published more than 5 years ago; however, the latest breakthroughs in the treatment make it necessary to update these guidelines. We reviewed the most recent recommendations of the international guidelines and compared them with the current Peruvian guidelines. We found major differences, such as the use of Glecaprevir/Pibrentasvir as a first-line therapy, which is contemplated in the World Health Organization guideline, and recommended by American and European guidelines, but is not considered in the Peruvian guidelines. Another crucial difference lies in the management of patients with chronic kidney disease, who are treated nowadays with a variety of direct-acting antivirals, with no restrictions on the use of Sofosbuvir-based regimens in first-world countries, an approach that has not been adopted in Peru. We believe that standardization of the recommendations of the Peruvian guidelines is imperative, including the new therapeutic strategies that have emerged in recent years. We also suggest conducting a cost effectiveness analysis in the Peruvian context to allow for the implementation of new antivirals, and to achieve a better control of hepatitis C in the country.

Investigating the effect of polymerase inhibitors on cellular proliferation: Computational studies, cytotoxicity, CDK1 inhibitory potential, and LC-MS/MS cancer cell entrapment assays

Directly acting antivirals (DAAs) are a breakthrough in the treatment of HCV. There are controversial reports on their tendency to induce hepatocellular carcinoma (HCC) in HCV patients. Numerous reports have concluded that the HCC is attributed to patient-related factors while others are inclined to attribute this as a DAA side-effect. This study aims to investigate the effect of polymerase inhibitor DAAs, especially daclatasivir (DLT) on cellular proliferation as compared to ribavirin (RBV). The interaction of DAAs with variable cell-cycle proteins was studied in silico. The binding affinities to multiple cellular targets were investigated and the molecular dynamics were assessed. The in vitro effect of the selected candidate DLT on cancer cell proliferation was determined and the CDK1 inhibitory potential in was evaluated. Finally, the cellular entrapment of the selected candidates was assessed by an in-house developed and validated LC-MS/MS method. The results indicated that polymerase inhibitor antiviral agents, especially DLT, may exert an anti-proliferative potential against variable cancer cell lines. The results showed that the effect may be achieved via potential interaction with the multiple cellular targets, including the CDK1, resulting in halting of the cellular proliferation. DLT exhibited a remarkable cell permeability in the liver cancer cell line which permits adequate interaction with the cellular targets. In conclusion, the results reveal that the polymerase inhibitor (DLT) may have an anti-proliferative potential against liver cancer cells. These results may pose DLT as a therapeutic choice for patients suffering from HCV and are liable to HCC development.

Obesity and its Relationship with Covid-19: A Review of the Main Pharmaceutical Aspects

Important physiological changes are observed in patients with obesity, such as intestinal permeability, gastric emptying, cardiac output, and hepatic and renal function. These differences can determine variations in the pharmacokinetics of different drugs and can generate different concentrations at the site of action, which can lead to sub therapeutic or toxic concentrations. Understanding the physiological and immunological processes that lead to the clinical manifestations of COVID-19 is essential to correlate obesity as a risk factor for increasing the prevalence, severity, and lethality of the disease. Several drugs have been suggested to control COVID- 19 like Lopinavir, Ritonavir, Ribavirin, Sofosbuvir, Remdesivir, Oseltamivir, Oseltamivir phosphate, Oseltamivir carboxylate, Hydroxychloroquine, Chloroquine, Azithromycin, Teicoplanin, Tocilizumab, Anakinra, Methylprednisolone, Prednisolone, Ciclesonide and Ivermectin. Similarly, these differences between healthy people and obese people can be correlated to mechanical factors, such as insufficient doses of the vaccine for high body mass, impairing the absorption and distribution of the vaccine that will be lower than desired or can be linked to the inflammatory state in obese patients, which can influence the humoral immune response. Additionally, different aspects make the obese population more prone to persistent symptoms of the disease (long COVID), which makes understanding these mechanisms fundamental to addressing the implications of the disease. Thus, this review provides an overview of the relationship between COVID-19 and obesity, considering aspects related to pharmacokinetics, immunosuppression, immunization, and possible implications of long COVID in these individuals.

Prevention, Diagnosis, Evaluation, and Treatment of Hepatitis C in Chronic Kidney Disease: Synopsis of the Kidney Disease: Improving Global Outcomes 2022 Clinical Practice Guideline

DESCRIPTION

The Kidney Disease: Improving Global Outcomes (KDIGO) 2022 clinical practice guideline on prevention, diagnosis, evaluation, and treatment of hepatitis C in chronic kidney disease (CKD) is an update of the 2018 guideline from KDIGO.

METHODS

The KDIGO Work Group (WG) updated the guideline, which included reviewing and grading new evidence that was identified and summarized. As in the previous guideline, the WG used the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach to appraise evidence and rate the strength of recommendations and used expert judgment to develop recommendations. New evidence led to updating of recommendations in the chapters on treatment of hepatitis C virus (HCV) infection in patients with CKD (Chapter 2), management of HCV infection before and after kidney transplant (Chapter 4), and diagnosis and management of kidney disease associated with HCV infection (Chapter 5). Recommendations in chapters on detection and evaluation of hepatitis C in CKD (Chapter 1) and prevention of HCV transmission in hemodialysis units (Chapter 3) were not updated because of an absence of significant new evidence.

RECOMMENDATIONS

The 2022 updated guideline includes 43 graded recommendations and 20 ungraded recommendations, 7 of which are new or modified on the basis of the most recent evidence and consensus among the WG members. The updated guidelines recommend expanding treatment of hepatitis C with sofosbuvir-based regimens to patients with CKD glomerular filtration rate categories G4 and G5, including those receiving dialysis; expanding the donor pool for kidney transplant recipients by accepting HCV-positive kidneys regardless of the recipient's HCV status; and initiating direct-acting antiviral treatment of HCV-infected patients with clinical evidence of glomerulonephritis without requiring kidney biopsy. The update also addresses the use of immunosuppressive regimens in such patients.

Cell-Dependent Activation of ProTide Prodrugs and Its Implications in Antiviral Studies

The ProTide prodrug design is a powerful tool to improve cell permeability and enhance the intracellular activation of nucleotide antiviral analogues. Previous in vitro studies showed that the activation of ProTide prodrugs varied in different cell lines. In the present study, we investigated the activation profiles of two antiviral prodrugs tenofovir alafenamide (TAF) and sofosbuvir (SOF) in five cell lines commonly used in antiviral research, namely, Vero E6, Huh-7, Calu-3, A549, and Caco-2. We found that TAF and SOF were activated in a cell-dependent manner with Vero E6 being the least efficient and Huh-7 being the most efficient cell line for activating the prodrugs. We also demonstrated that TAF was activated at a significantly higher rate than SOF. We further analyzed the protein expressions of the activating enzymes carboxylesterase 1, cathepsin A, histidine triad nucleotide-binding protein 1, and the relevant drug transporters P-glycoprotein and organic anion-transporting polypeptides 1B1 and 1B3 in the cell lines using the proteomics data extracted from the literature and proteome database. The results revealed significant differences in the expression patterns of the enzymes and transporters among the cell lines, which might partially contribute to the observed cell-dependent activation of TAF and SOF. These findings highlight the variability of the abundance of activating enzymes and transporters between cell lines and emphasize the importance of selecting appropriate cell lines for assessing the antiviral efficacy of nucleoside/nucleotide prodrugs.

Mechanisms and Clinical Significance of Pharmacokinetic Drug Interactions Mediated by FDA and EMA-approved Hepatitis C Direct-Acting Antiviral Agents

The treatment of patients infected with the hepatitis C virus (HCV) has been revolutionised by the development of direct-acting antiviral agents (DAAs) that target specific HCV proteins involved in viral replication. The first DAAs were associated with clinical problems such as adverse drug reactions and pharmacokinetic drug-drug interactions (DDIs). Current FDA/EMA-approved treatments are combinations of DAAs that simultaneously target the HCV N5A-protein, the HCV N5B-polymerase and the HCV NS3/4A-protease. Adverse events and DDIs are less likely with these DAA combinations but several DDIs of potential clinical significance remain. Much of the available information on the interaction of DAAs with CYP drug-metabolising enzymes and influx and efflux transporters is contained in regulatory summaries and is focused on DDIs of likely clinical importance. Important DDIs perpetrated by current DAAs include increases in the pharmacokinetic exposure to statins and dabigatran. Some mechanistic information can be deduced. Although the free concentrations of DAAs in serum are very low, a number of these DDIs are likely mediated by the inhibition of systemic influx transporters, especially OATP1B1/1B3. Other DDIs may arise by DAA-mediated inhibition of intestinal efflux transporters, which increases the systemic concentrations of some coadministered drugs. Conversely, DAAs are victims of DDIs mediated by cyclosporin, ketoconazole, omeprazole and HIV antiretroviral drug combinations, especially when boosted by ritonavir and, to a lesser extent, cobicistat. In addition, concurrent administration of inducers, such as rifampicin, carbamazepine and efavirenz, decreases exposure to some DAAs. Drug-drug interactions that increase the accumulation of HCV N3/4A-protease inhibitors like grazoprevir may exacerbate hepatic injury in HCV patients.

Fitness-Dependent, Mild Mutagenic Activity of Sofosbuvir for Hepatitis C Virus

The concept of a mild mutagen was coined to describe a minor mutagenic activity exhibited by some nucleoside analogues that potentiated their efficacy as antiretroviral agents. In the present study, we report the mild mutagen activity of sofosbuvir (SOF) for hepatitis C virus (HCV). Serial passages of HCV in human hepatoma cells, in the presence of SOF at a concentration well below its cytotoxic concentration 50 (CC50) led to pre-extinction populations whose mutant spectra exhibited a significant increase of C→U transitions, relative to populations passaged in the absence of SOF. This was reflected in an increase in several diversity indices that were used to characterize viral quasispecies. The mild mutagenic activity of SOF was largely absent when it was tested with isogenic HCV populations that displayed high replicative fitness. Thus, SOF can act as a mild mutagen for HCV, depending on HCV fitness. Possible mechanisms by which the SOF mutagenic activity may contribute to its antiviral efficacy are discussed.

Structure-Based Drug Design of RdRp Inhibitors against SARS-CoV-2

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a worldwide pandemic since 2019, spreading rapidly and posing a significant threat to human health and life. With over 6 billion confirmed cases of the virus, the need for effective therapeutic drugs has become more urgent than ever before. RNA-dependent RNA polymerase (RdRp) is crucial in viral replication and transcription, catalysing viral RNA synthesis and serving as a promising therapeutic target for developing antiviral drugs. In this article, we explore the inhibition of RdRp as a potential treatment for viral diseases, analysing the structural information of RdRp in virus proliferation and summarizing the reported inhibitors' pharmacophore features and structure-activity relationship profiles. We hope that the information provided by this review will aid in structure-based drug design and aid in the global fight against SARS-CoV-2 infection.

Concomitant Treatment of Tuberculosis and Hepatitis C Virus in Coinfected Patients Using Serum Drug Concentration Monitoring

Background

Concern for drug-drug interactions leading to treatment failure and drug-resistant strains have discouraged clinicians from attempting concomitant treatment of hepatitis C virus (HCV) and tuberculosis (TB). Increased metabolism of direct-acting antivirals (DAAs) by rifamycins has hindered concurrent use. Development of an assay for ledipasvir and sofosbuvir (LDV/SOF) serum concentrations for therapeutic drug monitoring (TDM) can ensure adequate therapy. We present the first cases of concomitant therapy of active TB and HCV with rifamycin-containing regimens and DAAs using TDM.

Methods

Using TDM, we aim to determine whether concomitant therapy with rifamycin-containing regimens and DAAs is safe and effective for patients coinfected with TB and HCV. Five individuals with TB and HCV who experienced transaminitis before or during TB therapy were concomitantly treated with rifamycin-containing regimens and LDV/SOF. Therapeutic drug monitoring was performed for LDV, SOF, and rifabutin during therapy. Baseline laboratory tests and serial liver enzymes were performed. Hepatitis C virus viral load and mycobacterial sputum cultures were obtained upon completion of therapy to determine efficacy of therapy.

Results

All patients were found to have nondetectable HCV viral loads and negative mycobacterial sputum cultures upon completion of therapy. No clinically significant adverse effects were reported.

Conclusions

These cases illustrate concomitant use of LDV/SOF and rifabutin in patients with HCV/TB coinfection. Utilizing serum drug concentration monitoring to guide dosing, correction of transaminitis were achieved, which allowed the use rifamycin-containing TB therapy. These findings suggest that concomitant therapy of TB/HCV is possible, safe, and effective.

Newly diagnosed hepatitis C infection after pancreas transplantation with multiple treatment failures

This case represents the first report of a detected hepatitis C virus (HCV) infection following a pancreas transplantation that failed two different sofosbuvir (SOF)-based treatments. We present the case of a woman in her 30s with a history of kidney transplantation, who developed viremic symptoms 3 months after pancreas transplantation and with two subsequent negative HCV antibody tests. Further work-up revealed a positive HCV RNA test (genotype 1A, treatment naive). Two different direct-acting antiviral agents regimes with SOF failed in our case, and the patient achieved a sustained virological response with a 16-week course of glecaprevir/pibrentasvir.

Development and validation of LC-MS/MS methods for the simultaneous quantification of sofosbuvir and its major metabolite (GS-331007) in blood plasma and cerebrospinal and seminal fluid: Application to a pilot clinical trial with a focus on Zika

Zika still poses a threat to global health owing to its association with serious neurological conditions and the absence of a vaccine and treatment. Sofosbuvir, an anti-hepatitis C drug, has shown anti-Zika effects in animal and cell models. Thus, this study aimed to develop and validate novel LC-MS/MS methods for the quantification of sofosbuvir and its major metabolite (GS-331007) in human plasma and cerebrospinal (CSF) and seminal fluid (SF), and apply the methods to a pilot clinical trial. The samples were prepared by liquid-liquid extraction and separated using isocratic mode on Gemini C₁₈ columns. Analytical detection was performed using a triple quadrupole mass spectrometer equipped with an electrospray ionization source. The validated ranges for sofosbuvir were 0.5-2,000 ng/mL (plasma) and 0.5-100 ng/mL (CSF and SF), while for the metabolite they were 2.0-2,000 ng/mL (plasma), 5.0-200 ng/mL (CSF) and 10-1,500 ng/mL (SF). The intra-day and inter-day accuracies (90.8-113.8%) and precisions (1.4-14.8%) were within the acceptance range. The developed methods fulfilled all validation parameters concerning selectivity, matrix effect, carryover, linearity, dilution integrity, precision, accuracy and stability, confirming the suitability of the method for the analysis of clinical samples.

The relation between SNPs in the NME1 gene and response to sofosbuvir in Egyptian patients with chronic HCV

Background

Hepatitis C virus (HCV) infection is considered one of the most urgent health problems in the world, with an incidence of approximately 71 million patients and 399,000 deaths per year from related liver diseases. In this study, we examined the association between 2 single nucleotide polymorphisms (SNPs) in the nucleoside diphosphate kinase 1 (NME1) gene (encoding one of the sofosbuvir metabolizing enzymes) and the response to the sofosbuvir plus daclatasvir regimen in Egyptian HCV-infected patients.

Results

Our data showed a similarity in the distribution of the CC, CT, and TT genotypes of NME1 rs2302254 C/T (p  =  0.847) and the CC, TC, and TT genotypes of NME1 rs16949649 T/C (p  =  0.937) among patients who were either treatment responders or relapsers. Based on the univariate and multivariate logistic regression analyses of the significant predictors for sustained virological response (SVR), five factors showed a robust predictive potency for the treatment outcome: age, fasting blood glucose level, platelets, albumin, and alpha-fetoprotein. Strikingly, there was a significant correlation between the rs16949649T/C polymorphism and serum creatinine (p  =  0.023). Higher creatinine levels were observed among the CC carriers than the TC or TT carriers.

Conclusions

The 2 studied SNPs of NME1 had no significant association with SVR in Egyptian HCV-infected patients; however, the noticeable relation between rs16949649T/C and creatinine level might represent a foundation for future studies on the renal extra-hepatic manifestation of HCV and SNPs of NME1 gene.

Over 40 Years of Fosmidomycin Drug Research: A Comprehensive Review and Future Opportunities

To address the continued rise of multi-drug-resistant microorganisms, the development of novel drugs with new modes of action is urgently required. While humans biosynthesize the essential isoprenoid precursors isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) via the established mevalonate pathway, pathogenic protozoa and certain pathogenic eubacteria use the less well-known methylerythritol phosphate pathway for this purpose. Important pathogens using the MEP pathway are, for example, Plasmodium falciparum, Mycobacterium tuberculosis, Pseudomonas aeruginosa and Escherichia coli. The enzymes of that pathway are targets for antiinfective drugs that are exempt from target-related toxicity. 2C-Methyl-D-erythritol 4-phosphate (MEP), the second enzyme of the non-mevalonate pathway, has been established as the molecular target of fosmidomycin, an antibiotic that has so far failed to be approved as an anti-infective drug. This review describes the development and anti-infective properties of a wide range of fosmidomycin derivatives synthesized over the last four decades. Here we discuss the DXR inhibitor pharmacophore, which comprises a metal-binding group, a phosphate or phosphonate moiety and a connecting linker. Furthermore, non-fosmidomycin-based DXRi, bisubstrate inhibitors and several prodrug concepts are described. A comprehensive structure-activity relationship (SAR) of nearly all inhibitor types is presented and some novel opportunities for further drug development of DXR inhibitors are discussed.

The world prevalence, associated risk factors and mortality of hepatitis C virus infection in hemodialysis patients: a meta-analysis

BACKGROUND

The worldwide burden of HCV infection among hemodialysis patients has not been systematically examined.

METHODS

A systematic literature search was conducted in MEDLINE and Scopus to determine the worldwide prevalence of HCV infection, risk factors, and clinical outcomes among hemodialysis patients. Random-effect models and meta-regressions were used to generate pooled estimates and assess heterogeneity.

RESULTS

Four hundred and seven studies with 1,302,167 participants were analyzed. The pooled prevalence of HCV infection was 21%. The highest prevalence was observed in Africa (28%) and low-income countries (48.5%). A significant prevalence decline was observed following the publication year and was also inversely related to GDP and total population of each country. Factors associated with HCV positivity included younger age, longer dialysis duration, more blood transfusions, and dialyzer reuse. The pooled unadjusted hazard ratio for all-cause mortality was 1.12 (95% CI 1.03-1.22), and the adjusted hazard ratio was 1.21 (95% CI 1.12-1.30) in HCV-infected compared to non-HCV infected patients.

CONCLUSIONS

HCV infection among hemodialysis patients is a worldwide shared burden and is associated with a higher risk of death. Avoiding unnecessary blood transfusion and dialyzer reuse should be encouraged to prevent HCV transmission in hemodialysis units.

Sofosbuvir-based hepatitis C therapies in patients with chronic and end-stage kidney disease

Sofosbuvir (SOF), a nucleotide inhibitor of the hepatitis C virus (HCV) polymerase, is a component of several all-oral HCV therapies. GS-331007, SOF's predominant metabolite, is renally eliminated and accumulates 5- to 20-fold in patients with advanced chronic kidney disease (CKD) or undergoing hemodialysis (HD), respectively. Preclinical data did not determine whether these exposures represented a risk for toxicity. Therefore subjects with advanced CKD were not included in registrational studies and SOF was not initially approved for use in advanced CKD. Nevertheless, after initial licensing, off-label use of SOF at full or reduced doses was reported in patients with kidney disease. Two clinical trials of SOF-containing therapies were conducted in patients with end-stage kidney disease, demonstrating safety and efficacy. These led to expanded US Food and Drug Administration approval in 2019 for the use of SOF-containing regimens in patients with advanced CKD, including dialysis dependence. Even so, given the availability of protease inhibitor-containing direct-acting antiviral regimens, there was a reluctance by some practitioners to use SOF-containing regimens in moderate to severe kidney disease. Here we review the existing data on SOF's pharmacokinetics, toxicology, efficacy and safety in patients with kidney disease. Data from both clinical trials and real-world practice settings indicate that in patients with moderate to severe kidney disease, full-dose SOF-based regimens have high rates of efficacy and acceptable safety and tolerability profiles, without increased risk for cardiac adverse events or clinically meaningful changes in kidney function. SOF-based regimens are safe and effective in patients who have moderate to severe kidney disease, including those undergoing HD.

Serial changes in renal indices in chronic HCV patients with and without HIV co-infection receiving sofosbuvir and tenofovir-based therapies

Background

Sofosbuvir (SOF) is authorized for hepatitis C virus (HCV) patients. The nephrotoxicity of SOF on HCV mono-infected and HCV–human immunodeficiency virus (HIV) individuals receiving antiretroviral therapy (ART) remains controversial.

Methods

A prospective study including 159 HCV mono-infected and 124 HCV–HIV individuals (47 were ART naïve and 77 were tenofovir [TDF]-based ART) who presented with an estimated glomerular filtration rate (eGFR) ≥30 ml/min/1.73 m2 at baseline and were treated with SOF–daclatasvir for 12 weeks. The eGFR was estimated using the Chronic Kidney Disease Epidemiology Collaboration equation over the study period.

Results

HCV patients had a progressive decline in median levels of eGFR compared with HCV–HIV patients who were ART naïve and those receiving TDF-based ART during and after discontinuing SOF–DAC treatment (96, 109 and 114 at baseline vs 94, 117 and 108 at the end of treatment [EOT]) vs 95, 114 and 115 ml/min/1.73 m2 at 12 weeks after treatment [SVR12], respectively). Moreover, the rate of eGFR stage worsening was more pronounced in HCV mono-infected compared with HCV–HIV individuals who were ART naïve and those receiving TDF-based ART (21.4% vs 8.5% and 14.3% at EOT; 21.4% vs 2.1% and 6.5% at SVR12, respectively). Multivariable regression analysis showed that baseline variables were not independent predictors of eGFR stage worsening either at EOT or SVR12.

Conclusions

Because the changes in eGFR were minimal and not of clinical significance, and TDF was not associated with an increase in renal dysfunction, SOF-based direct-acting antivirals could be safely used in HCV mono-infected and HCV–HIV individuals, even in those on TDF-based ART.

Direct antiviral agents (DAAs) and their use in pregnant women with hepatitis C (HCV)

INTRODUCTION

Direct-Acting Antiviral Agents (DAAs) provide safer, efficacious, tolerable, and curative therapy for women with hepatitis C. Their preferred safety and efficacy profile make them potential therapies for the elimination of perinatal transmission of hepatitis C virus (HCV). However, DAAs are not currently recommended for use during pregnancy due to limited pharmacokinetic and safety data.

AREAS COVERED

This review covers the different DAA drug combinations, the available data on their pharmacodynamic and pharmacokinetic properties, how the physiology in pregnancy can potentially affect DAA drug disposition, known drug-drug interactions with DAAs, and available and planned epidemiological and pharmacokinetic studies on DAA use during pregnancy. Although no large randomized clinical trials or prospective cohort studies involving DAAs have been completed in pregnancy, the currently available studies demonstrate no significant changes in pharmacokinetics, and no major safety concerns in women with hepatitis C.

EXPERT OPINION

Initial pharmacokinetic and safety data suggest that DAAs have high efficacy and a low risk of adverse events during pregnancy. As more pharmacokinetic and epidemiologic data become available, DAAs could become a preferred option for treating HCV during pregnancy and elimination of perinatal transmission of hepatitis C virus.

SARS-CoV-2 infects human brain organoids causing cell death and loss of synapses that can be rescued by treatment with Sofosbuvir

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019 (COVID-19), which was rapidly declared a pandemic by the World Health Organization (WHO). Early clinical symptomatology focused mainly on respiratory illnesses. However, a variety of neurological manifestations in both adults and newborns are now well-documented. To experimentally determine whether SARS-CoV-2 could replicate in and affect human brain cells, we infected iPSC-derived human brain organoids. Here, we show that SARS-CoV-2 can productively replicate and promote death of neural cells, including cortical neurons. This phenotype was accompanied by loss of excitatory synapses in neurons. Notably, we found that the U.S. Food and Drug Administration (FDA)-approved antiviral Sofosbuvir was able to inhibit SARS-CoV-2 replication and rescued these neuronal alterations in infected brain organoids. Given the urgent need for readily available antivirals, these results provide a cellular basis supporting repurposed antivirals as a strategic treatment to alleviate neurocytological defects that may underlie COVID-19- related neurological symptoms.

Real-world Safety and Effectiveness of 24-week Sofosbuvir and Ribavirin Treatment in Patients Infected with Rare Chronic Hepatitis C Virus Genotypes 3, 4, 5, or 6 in Japan

Objectives Real-world evidence on the safety and effectiveness of direct-acting antivirals in patients infected with chronic hepatitis C virus (HCV) genotypes (GTs) 3, 4, 5, or 6 in Japan is limited. This prospective observational study assesses the real-world safety profile and treatment effectiveness among patients prescribed sofosbuvir with ribavirin (SOF+RBV) for HCV GT3-6 infection in Japan. Methods Adults receiving 24-week SOF+RBV treatment for HCV GT3-6 infection were prospectively enrolled and observed through 24 weeks post-treatment for treatment-emergent adverse events (AEs) considered related to SOF and/or RBV by treating physicians and for a sustained virologic response at 12 and 24 weeks post-treatment (SVR12, SVR24). Incidence rates of related AEs and serious AEs (SAEs) were calculated. Proportions of patients experiencing related AEs/SAEs and those achieving SVR12 and SVR24 were assessed overall and by baseline characteristics, including treatment experience and cirrhosis status. Results Among the 50 patients included in the safety analysis, 92% had GT3 infection. The incidence rates of related AEs and SAEs were low overall (1.52 and 0.25 per 100 person-weeks, respectively), with 6.0% and 14.0% patients experiencing AEs related to SOF or RBV, respectively. There were no marked differences in the occurrence of related AEs/SAEs by patient baseline characteristics. SVR12 and SVR24 were achieved in 83.7% (41/49) and 82.2% (37/45) of patients, respectively. Lower effectiveness was observed among treatment-experienced patients and patients with cirrhosis at baseline. Conclusions This study demonstrated that SOF+RBV treatment for HCV GT3-6 infection was safe, effective, and an important treatment option for this difficult-to-treat patient population in Japan.

Randomized clinical trial of nitazoxanide or sofosbuvir/daclatasvir for the prevention of SARS-CoV-2 infection

BACKGROUND

The COVER trial evaluated whether nitazoxanide or sofosbuvir/daclatasvir could lower the risk of SARS-CoV-2 infection. Nitazoxanide was selected given its favourable pharmacokinetics and in vitro antiviral effects against SARS-CoV-2. Sofosbuvir/daclatasvir had shown favourable results in early clinical trials.

METHODS

In this clinical trial in Johannesburg, South Africa, healthcare workers and others at high risk of infection were randomized to 24 weeks of either nitazoxanide or sofosbuvir/daclatasvir as prevention, or standard prevention advice only. Participants were evaluated every 4 weeks for COVID-19 symptoms and had antibody and PCR testing. The primary endpoint was positive SARS-CoV-2 PCR and/or serology ≥7 days after randomization, regardless of symptoms. A Poisson regression model was used to estimate the incidence rate ratios of confirmed SARS-CoV-2 between each experimental arm and control.

RESULTS

Between December 2020 and January 2022, 828 participants were enrolled. COVID-19 infections were confirmed in 100 participants on nitazoxanide (2234 per 1000 person-years; 95% CI 1837-2718), 87 on sofosbuvir/daclatasvir (2125 per 1000 person-years; 95% CI 1722-2622) and 111 in the control arm (1849 per 1000 person-years; 95% CI 1535-2227). There were no significant differences in the primary endpoint between the treatment arms, and the results met the criteria for futility. In the safety analysis, the frequency of grade 3 or 4 adverse events was low and similar across arms.

CONCLUSIONS

In this randomized trial, nitazoxanide and sofosbuvir/daclatasvir had no significant preventative effect on infection with SARS-CoV-2 among healthcare workers and others at high risk of infection.

Statins Increase the Bioavailability of Fixed-Dose Combination of Sofosbuvir/Ledipasvir by Inhibition of P-glycoprotein

BACKGROUND

Coadministration of statins and direct acting antiviral agents is frequently used. This study explored the effects of both atorvastatin and lovastatin on pharmacokinetics of a fixed-dose combination of sofosbuvir/ledipasvir "FDCSL".

METHODS

12 healthy volunteers participated in a randomized, three-phase crossover trial and were administered a single atorvastatin dose 80 mg plus tablet containing 400/90 mg FDCSL, a single lovastatin dose 40 mg plus tablet containing 400/90 mg FDCSL, or tablets containing 400/90 mg FDCSL alone. Liquid chromatography-tandem mass spectrometry was used to analyze plasma samples of sofosbuvir, ledipasvir and sofosbuvir metabolite "GS-331007" and their pharmacokinetic parameters were determined.

RESULTS

Atorvastatin caused a significant rise in sofosbuvir bioavailability as explained by increasing in AUC0-∞ and Cmax by 34.36% and 11.97%, respectively. In addition, AUC0-∞ and Cmax of GS-331007 were increased by 73.73% and 67.86%, respectively after atorvastatin intake. Similarly, co-administration of lovastatin with FDCSL increased the bioavailability of sofosbuvir, its metabolite (AUC0-∞ increase by 17.2%, 17.38%, respectively, and Cmax increase by 12.03%, 22.24%, respectively). However, neither atorvastatin nor lovastatin showed a change in ledipasvir bioavailability. Hepatic elimination was not affected after statin intake with FDCSL. Compared to lovastatin, atorvastatin showed significant increase in AUC0-∞ and Cmax of both sofosbuvir and its metabolite.

CONCLUSIONS

Both atorvastatin and lovastatin increased AUC of sofosbuvir and its metabolite after concurrent administration with FDCSL. Statins' P-glycoprotein inhibition is the attributed mechanism of interaction. The increase in sofosbuvir bioavailability was more pronounced after atorvastatin intake. Close monitoring is needed after co-administration of atorvastatin and FDCSL.

Direct-Acting Antiviral Agents for Hepatitis C Virus Infection-From Drug Discovery to Successful Implementation in Clinical Practice

Today, hepatitis C virus infection affects up to 1.5 million people per year and is responsible for 29 thousand deaths per year. In the 1970s, the clinical observation of unclear, transfusion-related cases of hepatitis ignited scientific curiosity, and after years of intensive, basic research, the hepatitis C virus was discovered and described as the causative agent for these cases of unclear hepatitis in 1989. Even before the description of the hepatitis C virus, clinicians had started treating infected individuals with interferon. However, intense side effects and limited antiviral efficacy have been major challenges, shaping the aim for the development of more suitable and specific treatments. Before direct-acting antiviral agents could be developed, a detailed understanding of viral properties was necessary. In the years after the discovery of the new virus, several research groups had been working on the hepatitis C virus biology and finally revealed the replication cycle. This knowledge was the basis for the later development of specific antiviral drugs referred to as direct-acting antiviral agents. In 2011, roughly 22 years after the discovery of the hepatitis C virus, the first two drugs became available and paved the way for a revolution in hepatitis C therapy. Today, the treatment of chronic hepatitis C virus infection does not rely on interferon anymore, and the treatment response rate is above 90% in most cases, including those with unsuccessful pretreatments. Regardless of the clinical and scientific success story, some challenges remain until the HCV elimination goals announced by the World Health Organization are met.

In-depth investigation of the Silymarin effect on the pharmacokinetic parameters of sofosbuvir, GS-331007 and ledipasvir in rat plasma using LC-MS

The use of complementary medicine (CMD) for liver support in Hepatitis C virus (HCV) patients sometimes coincides with the administration of oral antiviral drugs to eradicate the virus. This calls for a deep investigation of CMD effects on the pharmacokinetic parameters of these drugs to ensure their safety and efficacy. Silymarin (SLY), as a CMD, was selected to be given orally to healthy male rats with sofosbuvir (SFB) and ledipasvir (LED), a common regimen in HCV treatment. A new and sensitive LC-MS method was validated for the bioassay of SLY, LED, SFB and its inactive metabolite, GS-331007, in spiked plasma with lower limits of quantitation of 10, 1, 4 and 10 ng/ml, respectively. Moreover, the method was further applied to conduct a full pharmacokinetic profile of SFB, GS-331007 and ledipasvir with and without SLY. It was found that co-administration of SLY may expose the patient to unplanned high serum concentrations of SFB and LED. This could be accompanied by a decrease in SFB efficacy, potentially leading to therapeutic failure and the emergence of viral resistance.

Sofosbuvir-based direct-acting antivirals and changes in cholesterol and low density lipoprotein-cholesterol

Worsened lipid profiles were observed in chronic hepatitis C (CHC) patients during direct-acting antivirals (DAAs) treatment, among which combination drugs confounded the effect of individual ingredient on lipid. Tenofovir alafenamide (TAF) also worsened lipid profiles in HIV patients. Structural similarity between sofosbuvir (SOF) and TAF prompted us to investigate rapid increase in total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in CHC patients treated with SOF-based DAAs. A retrospective study was performed to analyze 487 CHC patients receiving DAAs with SVR12. Relative risks on elevating TC and LDL-C were analyzed by logistic regression to determine SOF-based over non-SOF-based regimens. TC or LDL-C levels at baseline, week-4 and SVR12 were compared by Wilcoxon matched-pairs signed rank test. Week 4 or SVR12 to baseline ratios of serum TC or LDL-C between regimens were compared by Mann–Whitney's test. 487 patients were treated with Harvoni (SOF-based, 206 patients), Epclusa (SOF-based, 124 patients), Maviret (non-SOF-based, 122 patients), or Zepatier (non-SOF-based, 35 patients). At week 4 during drug treatment, Harvoni, Epclusa, and Maviret induced statistically significant elevation of TC and LDL-C, but Zepatier did not. SOF-based regimens had 2.72-fold higher relative risk (RR) causing 10% elevation of TC (95% CI 1.84–4.02, p < 0.001) and 2.04-fold higher RR causing 10% elevation of LDL-C (95% CI 1.39–3.01, p < 0.001) than non-SOF-based DAAs. SOF-based DAAs were associated with significantly larger amplitude of increases in TC and LDL-C than non-SOF-based DAAs during the initial 4 weeks of treatment, but the increases were not sustained to SVR12.

Drug-Drug Interactions of Direct Oral Anticoagulants (DOACs): From Pharmacological to Clinical Practice

The direct oral anticoagulants (DOACs), dabigatran, rivaroxaban, apixaban, and edoxaban, are becoming the most commonly prescribed drugs for preventing ischemic stroke in patients with non-valvular atrial fibrillation (NVAF) and for the treatment and prevention of venous thromboembolism (VTE). Rivaroxaban was also recently approved for the treatment of patients with a recent acute coronary syndrome (ACS). Their use demonstrated to have a favorable risk-benefit profile, with significant reductions in stroke, intracranial hemorrhage, and mortality compared to warfarin, but with increased gastrointestinal bleeding. Nevertheless, their safety profile is compromised in multimorbidity patients requiring contemporary administration of several drugs. Comorbidity and polypharmacy have a high prevalence in elderly patients, who are also more susceptible to bleeding events. The combination of multiple treatments can cause relevant drug–drug interactions (DDIs) by affecting the exposure or the pharmacological activities of DOACs. Although important differences of the pharmacokinetic (PK) properties can be observed between DOACs, all of them are substrate of P-glycoprotein (P-gp) and thus may interact with strong inducers or inhibitors of this drug transporter. On the contrary, rivaroxaban and, to a lower extent, apixaban, are also susceptible to drugs altering the cytochrome P450 isoenzyme (CYP) activities. In the present review, we summarize the potential DDI of DOACs with several classes of drugs that have been reported or have characteristics that may predict clinically significant DDIs when administered together with DOACs. Possible strategies, including dosage reduction, avoiding concomitant administration, or different time of treatment, will be also discussed to reduce the incidence of DDI with DOACs. Considering the available data from specific clinical trials or registries analysis, the use of DOACs is associated with fewer clinically relevant DDIs than warfarin, and their use represents an acceptable clinical choice. Nevertheless, DDIs can be significant in certain patient conditions so a careful evaluation should be made before prescribing a specific DOAC.

Impact of Sofosbuvir-Based Direct-Acting Antivirals on Renal Function in Chronic Hepatitis C Patients With Impaired Renal Function: A Large Cohort Study From the Nationwide HCV Registry Program (TACR)

BACKGROUND & AIMS

Sofosbuvir is approved for chronic hepatitis C (CHC) patients with severe chronic kidney disease (CKD). The impact of sofosbuvir-based therapy on renal function augmentation on a real-world nationwide basis is elusive.

METHODS

The 12,995 CHC patients treated with sofosbuvir-based (n = 6802) or non-sofosbuvir-based (n = 6193) regimens were retrieved from the Taiwan nationwide real-world HCV Registry Program. Serial estimated glomerular filtration rate (eGFR) levels were measured at baseline, end of treatment (EOT), and end of follow-up (EOF) (3 months after EOT).

RESULTS

The eGFR decreased from baseline (91.4 mL/min/1.73 m2) to EOT (88.4 mL/min/1.73 m2; P < .001) and substantially recovered at EOF (88.8 mL/min/1.73 m2) but did not return to pretreatment levels (P < .001). Notably, a significant decrease in eGFR was observed only in patients with baseline eGFR ≥90 mL/min/1.73 m2 (from 112.9 to 106.4 mL/min/1.73 m2; P < .001). In contrast, eGFR increased progressively in patients whose baseline eGFR was <90 mL/min/1.73 m2 (from 70.0 to 71.5 mL/min/1.73 m2; P < .001), and this increase was generalized across different stages of CKD. The trend of eGFR amelioration was consistent irrespective of sofosbuvir usage. Multivariate adjusted analysis demonstrated that baseline eGFR >90 mL/min/1.73 m2 was the only factor independently associated with significant slope coefficient differences of eGFR (-1.98 mL/min/1.73 m2; 95% confidence interval, -2.24 to -1.72; P < .001). The use of sofosbuvir was not an independent factor associated with eGFR change.

CONCLUSIONS

Both sofosbuvir and non-sofosbuvir-based regimens restored renal function in CHC patients with CKD, especially in those with significant renal function impairment.

Sofosbuvir and risk of estimated glomerular filtration rate decline or end-stage renal disease in patients with renal impairment

BACKGROUND

Sofosbuvir, a prodrug nucleoside inhibitor of hepatitis C virus, has a predominant circulating metabolite that is renally eliminated. Whether sofosbuvir is associated with chronic kidney disease (CKD) progression is not well understood.

METHODS

We performed a retrospective analysis of patients with estimated glomerular filtration rate (eGFR) 30-89 mL/min/1.73 m2 treated with sofosbuvir in 76 Phase 2/3 registrational trials. We evaluated eGFR at each study visit. Separately, we performed a retrospective analysis of an administrative claims database (IQVIA PharMetrics Plus™) to compare the risk of incident end-stage renal disease (ESRD) associated with the use of sofosbuvir or non-sofosbuvir regimens among patients with CKD using propensity score methods. Exposure, CKD status and outcomes were determined using diagnosis and medication claim codes. Cox proportional hazards methods were used to estimate ESRD risk.

RESULTS

Among 4642 trial participants with baseline stage 2 CKD (eGFR 60-89 ml/min/1.73 m2 ) and 682 trial participants with stage 3 CKD (eGFR 30-59 ml/min/1.73 m2 ) mean (SD) eGFR improved from baseline to 4 weeks post-treatment (+0.7 [9.3] and +2.6 [8.8] ml/min/1.73 m2 , respectively; p < 0.001 each). In the second analysis, among 2042 patients with CKD receiving sofosbuvir-based regimens compared to 431 receiving non-sofosbuvir-based regimens, after adjusting for baseline covariates and weighting based on treatment propensity scores, there was no significant difference in risk of ESRD (adjusted HR = 0.85, 95% CI: 0.51-1.42).

CONCLUSIONS

Clinical trial participants with CKD did not experience worsening eGFR during sofosbuvir-based treatment, and sofosbuvir was not associated with an increased risk of ESRD in patients with CKD in a nationally-representative administrative claims database.

The Metabolic Activation of Sofosbuvir Is Impaired in an Experimental Model of NAFLD

The effect of liver steatosis on drug metabolism has been investigated in both preclinical and clinical settings, but the findings of these studies are still controversial. We here evaluated the pharmacokinetic profile of the main sofosbuvir metabolite GS-331007 in healthy animals and rats with non-alcoholic fatty liver disease (NAFLD) after the oral administration of a single 400 mg/kg dose of sofosbuvir. The plasma concentration of GS-331007 was evaluated by HPLC-MS. The expression of the two enzymes uridine monophosphate-cytidine monophosphate kinase 1 (UMP-CMPK1), and nucleoside diphosphate kinase (ND-PK), responsible for the formation of the active metabolite GS-331007-TP, were measured by qRT-PCR and Western Blot. We demonstrated that in rats with steatosis, the area under the plasma concentration-vs-time curve (AUC) and the peak plasma concentration (Cmax) of GS-331007 increased significantly whereas the expression of UMP-CMPK was significantly lower than that of healthy animals. The reduction of UMP-CMPK expression suggests an impairment of sofosbuvir activation to GS-331007-TP, giving a possible explanation for the reduction of sofosbuvir efficacy in patients affected by genotype 3 Hepatitis C virus (HCV), which is often associated with liver steatosis. Furthermore, since GS-331007 plasma concentration is altered by steatosis, it can be suggested that the plasma concentration of this metabolite may not be a reliable indicator for exposure-response analysis in patients with NAFLD.

Phosphoryl Prodrugs: Characteristics to Improve Drug Development

Phosphoryl prodrugs are key compounds in drug development. Biologically active phosphoryl compounds often have negative charges on the phosphoryl group, and as a result, frequently have poor pharmacokinetic (PK) profiles. The use of lipophilic moieties bonded to the phosphorus (or attached oxygen atoms) masks the negative charge of the phosphoryl group, cleavage releasing the active molecule. The use of prodrugs to improve the PK of active parent molecules is an essential step in drug development. This review highlights promising trends in terminal elimination half-life, C_max, clearance, oral bioavailability, and cLogP in phosphoryl prodrugs. We focus on specific prodrug families: esters, amidates, and ProTides. We conclude that moderating lipophilicity is a key part of prodrug success. This type of evaluation is important for drug development, regardless of clinical application. It is our hope that this analysis, and future ones like it, will play a significant role in prodrug evolution.

Investigation of the effect of verapamil on the regional absorption of sofosbuvir from rabbit intestine in situ

PURPOSE

Sofosbuvir, a nucleotide antiviral drug, is a Biopharmaceutics Classification System (BCS) class III prodrug suffering from limited intestinal absorption due to its high hydrophilicity and low intestinal permeability. This research aims to investigate the luminal stability of Sofosbuvir, the influence of anatomical site on its intestinal absorption and the effects of verapamil on such absorption.

METHOD

The study utilized in situ rabbit intestinal perfusion technique to examine absorption of Sofosbuvir from duodenum, jejunum, ileum and ascending colon. This was conducted both with and without verapamil.

RESULTS

The luminal stability study showed that Sofosbuvir was subjected to premature degradation with varying fractions degraded from the different intestinal segments. The in situ perfusion data showed incomplete absorption of Sofosbuvir from small and large intestinal segments. The recorded values of the absorptive clearance per unit length (Pe.A/L) of Sofosbuvir were 0.026, 0.0075, 0.0026, & 0.054 ml/min.cm for duodenum, jejunum, ileum, and ascending colon, respectively. The Pe.A/L values were ordered as colon > duodenum > jejunum > ileum. This is the opposite rank of P-gp content in the different intestinal segments. The recorded values of the length required for complete Sofosbuvir absorption (L95%) were 29.58, 128.47, 949.2 and, 13.63 cm for duodenum, jejunum, ileum, and ascending colon, respectively. Co-perfusion with verapamil significantly increased Pe.A/L and reduced the L95% of Sofosbuvir from both jejunum and ileum (P-value < 0.05).

CONCLUSION

The results indicated that the absorptive clearance of Sofosbuvir was site dependent and associated with the content of P-glycoprotein, in addition to the expected drug interactions that can occur in polymedicated hepatitis C virus (HCV) infected patients.

Breakthroughs in hepatitis C research: from discovery to cure

In the 1970s, an unknown virus was suspected for documented cases of transfusion-associated hepatitis, a phenomenon called non-A, non-B hepatitis. In 1989, the infectious transmissible agent was identified and named hepatitis C virus (HCV) and, soon enough, the first diagnostic HCV antibody test was developed, which led to a dramatic decrease in new infections. Today, HCV infection remains a global health burden and a major cause of liver cirrhosis, hepatocellular carcinoma and liver transplantation. However, tremendous advances have been made over the decades, and HCV became the first curable, chronic viral infection. The introduction of direct antiviral agents revolutionized antiviral treatment, leading to viral eradication in more than 98% of all patients infected with HCV. This Perspective discusses the history of HCV research, which reads like a role model for successful translational research: starting from a clinical observation, specific therapeutic agents were developed, which finally were implemented in national and global elimination programmes.

The impact of genetic variations in sofosbuvir metabolizing enzymes and innate immunity mediators on treatment outcome in HCV-infected patients

Hepatitis C virus (HCV) is the leading cause of liver diseases worldwide. At present, combinations of different classes of direct-acting antiviral agents (DAAs) are used as treatment options for HCV, in which sofosbuvir (SOF) is the common DAA among different therapeutic regimes. In Egypt, SOF plus daclatasvir (DCV) is the widely used anti-HCV treatment protocol. Herein, we aimed to assess the association between 3 single-nucleotide polymorphisms (SNPs) at the genes coding for 2 SOF metabolizing enzymes: histidine triad nucleotide-binding protein 1 (HINT1) rs4696/rs7728773 and nucleoside diphosphate kinase 1 (NME1) rs3760468, together with the most potent anti-HCV innate molecule, i.e., interferon lambda 3 (IFNL3) rs12979860 and the response to SOF/DCV in Egyptian patients chronically infected with genotype 4 (GT4). SNPs were genotyped using real-time PCR in DNA from patients who achieved sustained virological response (SVR) at 12 weeks post-SOF/DCV treatment (i.e., responders; n = 188), patients who failed to achieve SVR12 (i.e., non-responders; n = 109), and healthy controls (n = 62). Our results demonstrated that patients bearing HINT1 rs7728773 CT/TT (odds ratio 2.119, 95% CI 1.263-3.559, p = 0.005) and IFNL3 rs12979860 CC (odds ratio 3.995, 95% CI 2.126-7.740, p = 0.0001) were more likely to achieve SVR12. However, neither HINT1 rs4696 nor NME1 rs3760468 seems to contribute to the responsiveness to SOF/DCV. Binary regression analysis defined 5 predictor factors independently associated with SVR12: age, bilirubin, hemoglobin, early stages of fibrosis, and combined HINT1 rs7728773 and IFNL3 rs12979860 favorable and mixed genotypes (odds ratio 3.134, 95% CI 1.518-6.47, p = 0.002), and that was confirmed by the combined ROC curve for the 5 predictor factors (AUC = 0.91, 95% CI 0.869-0.95, P = 0.0001). In conclusion, these data suggest that the two SNPs have the potential in predicting the response rate to SOF/DCV treatment in patients infected with HCV GT4. This study is the first to investigate the pharmacogenetics of SOF metabolizing enzyme and introduce HINT1 rs7728773 as a novel SNP that predicts the treatment efficacy.

Evaluation of the effect of sofosbuvir and daclatasvir in hospitalized COVID-19 patients: a randomized double-blind clinical trial (DISCOVER)

Background

The combination of sofosbuvir and daclatasvir has shown preliminary efficacy for hospitalized patients with COVID-19 in four open-label studies with small sample sizes. This larger trial aimed to assess if the addition of sofosbuvir/daclatasvir to standard care improved clinical outcomes in hospitalized patients with COVID-19.

Methods

This was a placebo-controlled, double-blind, randomized clinical trial in adults hospitalized with COVID-19 at 19 hospitals in Iran. Patients were randomized to oral sofosbuvir/daclatasvir 400/60 mg once-daily or placebo in addition to standard of care. Patients were included if they had positive PCR or diagnostic chest CT, O₂ saturation <95% and compatible symptoms. The primary outcome was hospital discharge within 10 days of randomization. Secondary outcomes included mortality and time to clinical events. The trial is registered on the Iran Registry of Clinical Trials under IRCT20200624047908N1.

Results

Between July and October 2020, 1083 patients were randomized to either the sofosbuvir/daclatasvir arm (n = 541) or the placebo arm (n = 542). No significant difference was observed in the primary outcome of hospital discharge within 10 days, which was achieved by 415/541 (77%) in the sofosbuvir/daclatasvir arm and 411/542 (76%) in the placebo arm [risk ratio (RR) 1.01, 95% CI 0.95–1.08, P = 0.734]. In-hospital mortality was 60/541 (11%) in the sofosbuvir/daclatasvir arm versus 55/542 (10%) in the placebo arm (RR 1.09, 95% CI 0.77–1.54, P = 0.615). No differences were observed in time to hospital discharge or time to in-hospital mortality.

Conclusions

We observed no significant effect of sofosbuvir/daclatasvir versus placebo on hospital discharge or survival in hospitalized COVID-19 patients.

'Real-life' experience with direct-acting antiviral agents for HCV after kidney transplant

INTRODUCTIONS AND OBJECTIVES

The introduction of direct-acting antiviral (DAA) agents promises to change dramatically the management of hepatitis C in kidney transplant recipients, a patient group where the treatment of hepatitis C is historically challenging. The purpose of the current study was to assess (in a 'real-life' setting) the safety and efficacy of all-oral, interferon-free, direct-acting antiviral agents in kidney transplant recipients with HCV.

MATERIAL AND METHODS

We performed a single-arm, multi-center study in a cohort (n = 95) of kidney transplant recipients who underwent antiviral therapy with DAAs. The primary end-point was sustained virologic response (SVR) (serum HCV RNA < 15 IU/mL, 12 weeks after treatment ended; SVR12). We recorded data on on-treatment adverse events (AEs), serious AEs, and laboratory abnormalities.

RESULTS

Various regimens were adopted at the discretion of the treating physician: elbasvir/grazoprevir (n = 11), paritaprevir/ritonavir/ombitasvir/dasabuvir (PrOD) regimens ± ribavirin (n = 23), and sofosbuvir-based regimens ± ribavirin (n = 61). The SVR12 rate was 93.7% (89/95) (95% CI, 88%; 98%), according to intention-to-treat analysis; three patients without viral response (n = 3) were found. Ribavirin was administered in 8 (8.4%) allograft recipients. The frequency of drop-outs was 4.2% (4/95) (95% CI, 0.2%; 8.2%); these were related to arthralgia/myalgia (n = 2), fatigue (n = 1), and lowered estimated glomerular filtration rate (eGFR) (n = 1). There were no differences with regard to serum creatinine and eGFR before and after antiviral therapy and during follow-up in the whole cohort. The patient who interrupted antiviral treatment due to raised serum creatinine was on sofosbuvir/daclatasvir regimen; one of the four drop-outs obtained SVR.

CONCLUSIONS

All-oral, interferon-free therapy with DAAs for chronic HCV after kidney transplantation was effective and well-tolerated in a 'real-life' clinical setting. Identical results have been observed in patients with intact kidneys or advanced chronic kidney disease. Careful evaluation of kidney function over follow-up in kidney transplant recipients who received DAAs regimens is recommended. Clinical trials aimed to assess whether sustained viral response translates into improved patient/graft survival are under way.

An Updated View on the Antiviral Therapy of Hepatitis C in Chronic Kidney Disease

BACKGROUND

Hepatitis C virus infection remains common in patients with chronic kidney disease, including those on maintenance dialysis. The relationship between hepatitis C virus infection and chronic kidney disease is bi-directional; in fact, HCV is both a cause and consequence of chronic kidney disease. According to a systematic review with meta-analysis of observational studies (n = 23 studies) (n = 574,081 patients on long-term dialysis), anti-HCV positive serologic status was an independent and significant risk factor for death in patients with advanced chronic kidney disease on long-term dialysis. The overall estimate for adjusted mortality (all-cause death risk) with HCV was 1.26 (95% CI, 1.18; 1.34) (p < 0.0001). Interferon-based therapies are biased by low efficacy/safety in chronic kidney disease, but the advent of direct-acting antiviral drugs has made a paradigm shift in the treatment of HCV-infection. These medications give interruption of viral replication because they target specific non-structural viral proteins; four classes of DAAs exist-NS3/4A protease inhibitors, NS5A inhibitors, NS5B nucleoside and non-nucleoside polymerase inhibitors. All-oral, interferon-free, ribavirin-free combinations of DAAs are now available.

AIM

The goal of this narrative review is to report the available treatment options for HCV in advanced chronic kidney disease.

METHODS

We have made an extensive review of the medical literature and various research engines have been adopted.

RESULTS

Some combinations of DAAs are currently recommended for HCV in advanced CKD (including patients on maintenance dialysis): elbasvir/grazoprevir; glecaprevir/pibrentasvir; and sofosbuvir-based regimens. Solid evidence, based on registration and "real life" studies supports their efficacy (SVR rates > 90%) and safety even in patients with advanced CKD. No dosage adjustment is necessary and treatment duration is 8-12 weeks. However, recent data highlight that many patients with advanced CKD remain untreated, and numerous barriers to antiviral treatment of HCV still exist. Whether successful antiviral therapy with DAAs will translate into improved survival in the advanced CKD population is another point of future research.

Mitochondrial Genotoxicity of Hepatitis C Treatment among People Who Inject Drugs

Antiviral nucleoside analogues (ANA) are newly used therapeutics acting against the hepatitis C virus (HCV). This class of drug is well known to exhibit toxicity on mitochondrial DNA (mtDNA). People who inject drugs (PWID) are particularly affected by HCV infection and cumulated mitotoxic drug exposure from HIV treatments (antiretrovirals, ARV) and other illicit drugs. This study aims to explore the impact of direct-acting antiviral (DAA) treatments on mtDNA among PWID. A total of 470 actively injecting heroin users were included. We used quantitative PCR on whole blood to determine the mitochondrial copy number per cell (MCN) and the proportion of mitochondrial DNA deletion (MDD). These parameters were assessed before and after DAA treatment. MDD was significantly increased after HCV treatment, while MCN did not differ. MDD was even greater when subjects were cotreated with ARV. In multivariate analysis, we identified that poly-exposure to DAA and daily heroin injection or regular consumption of methamphetamines were positively associated with high MCN loss while DAA and ARV treatments or methadone use were identified as risk factors for having mtDNA deletion. These observations deserve attention since they were previously associated with premature cell ageing or cell transformation and therefore call for a long-term follow-up.

Sofosbuvir/velpatasvir for the treatment of hepatitis C in pediatric patients

Introduction: Sofosbuvir/velpatasvir is a combination of direct-acting antivirals with pangenotypic activity for treatment of chronic hepatitis C virus infection. It was approved in 2020 for use in children aged 6-17 years and in June 2021 by the United States Food and Drug Administration for the age group 3-5 years.Areas covered: A literature search of PUBMED and EMBASE was conducted on April 30th and updated on June 10th. Other citations were identified in references of available literature and from ClinicalTrials.gov. The aim of the present research was to outline and discuss the pharmacokinetics, clinical efficacy, tolerability and safety of sofosbuvir/velpatasvir, exploring its actual and potential use in children and adolescents with chronic hepatitis C virus infection.Expert opinion: Five combinations of direct-acting antivirals, of whom three with pangenotypic activity, are now approved for children. No major differences in efficacy and safety profile have been described. Limited access to treatment still is a major issue, especially in low and middle-income countries.

Evaluation of the genetic toxicity of sofosbuvir and simeprevir with and without ribavirin in a human-derived liver cell line

Direct-acting antivirals have revolutionized the treatment of chronic hepatitis C. Sofosbuvir and simeprevir are prescribed worldwide. However, there is a scarcity of information regarding their genotoxicity. Therefore, the present study assessed the cytotoxic and genotoxic effects of sofosbuvir and simeprevir, alone and combined with ribavirin. HepG2 cells were analyzed using the in vitro cytokinesis-block micronucleus cytome assay. Cells were treated for 24 h with sofosbuvir (0.011-1.511 mM), simeprevir (0.156-5.0 µM), and their combinations with ribavirin (0.250-4.0 mM). No significant differences were observed in the nuclear division cytotoxicity index, reflecting the absence of cytotoxic effects associated to sofosbuvir. However, the highest concentration of simeprevir showed a significant difference for the nuclear division cytotoxicity index. Moreover, significant results were observed for nuclear division cytotoxicity index in two combinations of sofosbuvir plus ribavirin and only in the highest combination of simeprevir plus ribavirin. Additionally, our results showed that sofosbuvir did not increase the frequency of chromosomal damage, but simeprevir significantly increased the frequency of micronuclei at the highest concentrations. The combination index demonstrated that both sofosbuvir and simeprevir produced antagonism to the genotoxic effects of ribavirin. In conclusion, our results showed that simeprevir, but not sofosbuvir, has genotoxic effects in HepG2 cells.

Recent advances in the chromatographic determination of the most commonly used anti-hepatitis C drug sofosbuvir and its co-administered drugs in human plasma

Sofosbuvir is a direct-acting antiviral drug that inhibits hepatitis C virus (HCV) NS5B polymerase, which in turn affects the virus replication inside biological systems. The clinical importance of sofosbuvir is based not only on its effect on HCV but also on other lethal viruses such as Zika and severe acute respiratory syndrome coronavirus disease 2019 (SARS-COVID-19). Accordingly, there is a continuous shedding of light on the development and validation of accurate and fast analytical methods for the determination of sofosbuvir in different environments. This work critically reviews the recent advances in chromatographic methods for the analysis of sofosbuvir and/or its metabolites in pure samples, pharmaceutical dosage forms, and in the presence of other co-administered drugs to highlight the current status and future perspectives to enhance its determination in different matrixes.