Clinical management of renal transplant patients with hepatitis C virus infection treated with cyclosporine or tacrolimus

Influence of Inflammation on Cytochromes P450 Activity in Adults: A Systematic Review of the Literature

Background: Available in-vitro and animal studies indicate that inflammation impacts cytochromes P450 (CYP) activity via multiple and complex transcriptional and post-transcriptional mechanisms, depending on the specific CYP isoforms and the nature of inflammation mediators. It is essential to review the current published data on the impact of inflammation on CYP activities in adults to support drug individualization based on comorbidities and diseases in clinical practice. Methods: This systematic review was conducted in PubMed through 7th January 2021 looking for articles that investigated the consequences of inflammation on CYP activities in adults. Information on the source of inflammation, victim drugs (and CYPs involved), effect of disease-drug interaction, number of subjects, and study design were extracted. Results: The search strategy identified 218 studies and case reports that met our inclusion criteria. These articles were divided into fourteen different sources of inflammation (such as infection, autoimmune diseases, cancer, therapies with immunomodulator…). The impact of inflammation on CYP activities appeared to be isoform-specific and dependent on the nature and severity of the underlying disease causing the inflammation. Some of these drug-disease interactions had a significant influence on drug pharmacokinetic parameters and on clinical management. For example, clozapine levels doubled with signs of toxicity during infections and the concentration ratio between clopidogrel's active metabolite and clopidogrel is 48-fold lower in critically ill patients. Infection and CYP3A were the most cited perpetrator of inflammation and the most studied CYP, respectively. Moreover, some data suggest that resolution of inflammation results in a return to baseline CYP activities. Conclusion: Convincing evidence shows that inflammation is a major factor to be taken into account in drug development and in clinical practice to avoid any efficacy or safety issues because inflammation modulates CYP activities and thus drug pharmacokinetics. The impact is different depending on the CYP isoform and the inflammatory disease considered. Moreover, resolution of inflammation appears to result in a normalization of CYP activity. However, some results are still equivocal and further investigations are thus needed.

Impact of Inflammation on Cytochromes P450 Activity in Pediatrics: A Systematic Review

Background and Objective

Cytochromes P450 (CYP) are the major enzymes involved in hepatic metabolism of drugs. Personalization of treatment in pediatrics is a major challenge, as it must not only take into account genetic, environmental, and physiological factors but also ontogeny. Published data in adults show that inflammation had an isoform-specific impact on CYP activities and we aimed to evaluate this impact in the pediatric population.

Methods

Articles listed in PubMed through 7 January, 2021 that studied the impact of inflammation on CYP activities in pediatrics were included in this systematic review. Sources of inflammation, victim drugs (CYP involved), effect of drug–disease interactions, number and age of subjects, and study design were extracted.

Results

Twenty-seven studies and case reports were included. The impact of inflammation on CYP activities appeared to be age dependent and isoform-specific, with some drug–disease interactions having significant pharmacokinetic and clinical impact. For example, midazolam clearance decreases by 70%, while immunosuppressant and theophylline concentrations increase three-fold and two-fold with intensive care unit admission and infection. Cytochrome P450 activity appears to return to baseline level when the disease is resolved.

Conclusions

Studies that have assessed the impact of inflammation on CYP activity are lacking in pediatrics, yet it is a major factor to consider to improve drug efficacy or safety. The scarce current data show that the impact of inflammation is isoform and age dependent. An effort must be made to improve the understanding of the impact of inflammation on CYP activities in children to better individualize treatment.

Impact of Acute Inflammation on Cytochromes P450 Activity Assessed by the Geneva Cocktail

Cytochromes P450 (CYP) are subject to important interindividual variability in their activity due to genetic and environmental factors and some diseases. Limited human data support the idea that inflammation downregulates CYP activities. Our study aimed to evaluate the impact of orthopedic surgery (acute inflammation model) on the activity of six human CYP. This prospective observational study was conducted in 30 patients who underwent elective hip surgery at the Geneva University Hospitals in Switzerland. The Geneva phenotyping cocktail containing caffeine, bupropion, flurbiprofen, omeprazole, dextromethorphan, and midazolam as probe drugs respectively assessing CYP1A2, 2B6, 2C9, 2C19, 2D6, and 3A activities was administered orally before surgery, day 1 (D1) and 3 (D3) postsurgery and at discharge. Capillary blood samples were collected 2 hours after cocktail intake to assess metabolic ratios (MRs). Serum inflammatory markers (CRP, IL‐6, IL‐1β, TNF‐α, and IFN‐γ) were also measured in blood. CYP1A2 MRs decreased by 53% (P < 0.0001) between baseline and the nadir at D1. CYP2C19 and CYP3A activities (MRs) decreased by 57% (P = 0.0002) and 61% (P < 0.0001), respectively, with the nadir at D3. CYP2B6 and CYP2C9 MRs increased by 120% (P < 0.0001) and 79% (P = 0.018), respectively, and peaked at D1. Surgery did not have a significant impact on CYP2D6 MR. Hip surgery was a good acute inflammation model as CRP, IL‐6, and TNF‐α peak levels were reached between D1 and day 2 (D2). Acute inflammation modulated CYP activity in an isoform‐specific manner, with different magnitudes and kinetics. Acute inflammation may thus have a clinically relevant impact on the pharmacokinetics of these CYP substrates.

Impact of direct-acting antivirals for hepatitis C virus therapy on tacrolimus dosing in liver transplant recipients

INTRODUCTION

Direct-acting antivirals (DAAs) have transformed hepatitis C virus (HCV) management post-liver transplant. As HCV clears during DAA treatment, hepatic metabolism improves, resulting in decreased tacrolimus concentrations that may require dose adjustment. The purpose of this study was to determine appropriate management of immunosuppression in liver transplant recipients during and following treatment of HCV.

METHODS

This study was a single-center retrospective analysis of 71 liver transplant recipients who were treated for HCV with DAAs. The primary outcome was change in dose-normalized tacrolimus concentrations from the start of DAA treatment to 12 weeks following therapy.

RESULTS

The mean change in log-transformed dose-normalized tacrolimus concentrations was a reduction of 0.43 ng/mL/mg (95% CI; 0.26-0.60, P < 0.0001). The greatest decrease occurred in the first 4 weeks of treatment, after which levels stabilized. The overall mean tacrolimus concentration was 4.8 ng/mL (±2.5). Two patients (3%) developed acute cellular rejection and two patients (3%) had graft loss and died.

CONCLUSION

From the start of treatment to 12 weeks post-DAA therapy, liver transplant recipients experienced a significant decrease in dose-normalized tacrolimus concentrations. In conclusion, close monitoring of tacrolimus concentrations is warranted during and following treatment with DAAs, as dose increases may be indicated in order to maintain therapeutic concentrations to prevent graft rejection.

Influence of chronic hepatitis C infection on cytochrome P450 3A4 activity using midazolam as an in vivo probe substrate

PURPOSE

Inflammation-related changes in pharmacokinetics have been described for a number of disease-states including cancer, infection, and autoimmune disorders. This study examined the impact of chronic hepatitis C infection (CHC) on the pharmacokinetics of the cytochrome P450 3A probe midazolam in patients without significant liver disease who were either treatment naïve or prior interferon null-responders.

METHODS

Data were pooled from three studies which compared the pharmacokinetics of oral midazolam in healthy volunteers (n = 107) and in treatment-naive patients (n = 35) and interferon-null responders (n = 24) with CHC but without significant liver disease. Oral midazolam was administered as a single 2 mg oral dose, followed by frequent pharmacokinetic sampling and determination of the pharmacokinetics of midazolam and its α-hydroxy metabolite. CYP3A activity was determined by the metabolic ratio (MR) of the AUC metabolite/AUC parent and compared across groups as the mean effect ratio (test/reference).

RESULTS

The midazolam MR was lower in treatment-naïve patients with CHC than in health volunteers with a mean effect ratio of 0.63 [90 % confidence interval (CI) 0.56-0.72]. The effect was more pronounced in null-responders, who demonstrated a mean MR effect ratio of 0.46 (90 % CI 0.39-0.53) compared to volunteers. The mean area under the concentration-time curve (AUCinf) for midazolam in healthy volunteers, naïve patients, and null-responders was 32.3 [coefficient of variation (CV%) 41], 36.5 (CV% 33.5), and 55.3 (CV% 36.9) ng.h/mL, respectively.

CONCLUSIONS

The results of this study demonstrate a reduction in CYP3A4 activity between healthy volunteers and patients with CHC, with interferon null-responders demonstrating the most substantial difference. These results may have implications for the pharmacotherapy of patients infected with CHC.

Effect of hepatitis C infection on tacrolimus doses and blood levels in liver transplantation recipients

BACKGROUND

In our cohort of patients with hepatitis-C virus, which is the most common indication for liver transplantation, we have noted higher relative blood levels of tacrolimus compared to patients without hepatitis-C virus.

AIM

To verify this observation and determine its clinical significance, we performed a comparison of doses and blood levels of tacrolimus in hepatitis-C virus and non- hepatitis-C virus liver transplantation recipients.

METHODS

Tacrolimus dose and trough level, as well as mean alanine aminotransferase, for all patients transplanted at our center with a deceased donor between 1/1995 and 12/1999 with hepatitis-C virus were recorded at monthly intervals during the first 24 months following transplantation and compared to patients without hepatitis-C virus.

RESULTS

The tacrolimus levels for hepatitis-C virus and non-hepatitis-C virus patients were not significantly different at any of the monthly intervals, except month 9. In addition, the overall mean tacrolimus levels for hepatitis-C virus and non-hepatitis-C virus patients were not significantly different (P = ns). However, the mean tacrolimus dose (mg/kg) was significantly higher for hepatitis-C virus patients at 12, 15, 18, 21 and 24 months, P < 0.01. The total mean tacrolimus dose in hepatitis-C virus patients was lower during year one by 39% (P = 0.018) and by 73% (P = 0.001) during year two. The total difference in cost of tacrolimus (for year one and two) administered to hepatitis-C virus patients was $4920, P = 0.03. The serum alanine aminotransferase was significantly higher in hepatitis-C virus patients at each monthly interval except month 1, P < or = 0.01.

CONCLUSIONS

Liver transplant recipients with hepatitis-C virus require significantly lower oral doses of tacrolimus to achieve the same blood levels compared to non-hepatitis-C virus patients. This difference may result in a significant reduction in the cost of tacrolimus in hepatitis-C virus patients. The most likely explanation for these findings is decreased hepatic clearance of tacrolimus caused by mild hepatic injury from recurrent hepatitis-C virus.