Contributions of hepatic and intestinal metabolism and P-glycoprotein to cyclosporine and tacrolimus oral drug delivery

Calcineurin Inhibitor Associated Nephrotoxicity in Kidney Transplantation-A Transplant Nephrologist's Perspective

AIM

Calcineurin inhibitors (CNIs) have revolutionized transplant medicine, improving allograft survival but posing challenges like calcineurin inhibitor-induced nephrotoxicity (CNT). Acute CNT, often dose-dependent, leads to vasoconstriction and acute kidney injury, with treatment focusing on CNI exposure reduction. Chronic CNT manifests as progressive allograft function decline, with challenges in distinguishing it from nonspecific allograft nephropathy.

METHODS

This narrative review provides a concise overview of the clinical management of CNT, covering acute and chronic CNT. We reviewed original articles, landmark papers, and meta-analyses on CNT mitigation strategies, including CNI-sparing approaches.

RESULTS

Preventive measures include co-medications, CNI exposure monitoring, and CNI sparing strategies, such as reducing target trough levels and converting to mTOR inhibitors (mTORi) or belatacept. Despite improvements in graft function, challenges persist in demonstrating significant differences in allograft survival with CNI-sparing regimens. The paradigm shift from chronic CNT as the main cause of chronic allograft nephropathy toward rather immunologic triggered injuries and/or comorbidities as relevant contributors to allograft deterioration over time must be kept in mind.

CONCLUSION

CNIs have significantly improved kidney transplant outcomes, but their associated nephrotoxicity necessitates mitigation strategies. The decision to implement such regimens is always an individual choice balancing against the risk of immunologic injuries. Further long-term studies are needed to optimize immunosuppressive approaches and refine CNT management.

Bempedoic Acid, the First-in-Class Oral ATP Citrate Lyase Inhibitor with Hypocholesterolemic Activity: Clinical Pharmacology and Drug-Drug Interactions

Bempedoic acid is a new drug that improves the control of cholesterol levels, either as monotherapy or in combination with existing lipid-lowering therapies, and shows clinical efficacy in cardiovascular disease patients. Thus, patients with comorbidities and under multiple therapies may be eligible for bempedoic acid, thus facing the potential problem of drug-drug interactions (DDIs). Bempedoic acid is a prodrug administered orally at a fixed daily dose of 180 mg. The dicarboxylic acid is enzymatically activated by conjugation with coenzyme A (CoA) to form the pharmacologically active thioester (bempedoic acid-CoA). This process is catalyzed by very-long-chain acyl-CoA synthetase 1 (ACSVL1), expressed almost exclusively at the hepatic level. Bempedoic acid-CoA is a potent and selective inhibitor of ATP citrate lyase (ACL), a key enzyme in the biosynthetic pathway of cholesterol and fatty acids. The drug reduces low-density lipoprotein-cholesterol (LDL-C) (20-25%), non-high-density lipoprotein-cholesterol (HDL-C) (19%), apolipoprotein B (apoB) (15%), and total cholesterol (16%) in patients with hypercholesterolemia or mixed dyslipidemia. The drug has a favorable pharmacokinetics profile. Bempedoic acid and its metabolites are not substrates or inhibitors/inducers of cytochrome P450 (CYP450) involved in drug metabolism. On the other hand, bempedoic acid-glucuronide is a substrate for organic anion transporter 3 (OAT3). Bempedoic acid and its glucuronide are weak inhibitors of the OAT2, OAT3, and organic anion-transporting polypeptide 1B1 (OATP1B1) and 1B3 (OATP1B3). Thus, bempedoic acid could inhibit (perpetrator) the hepatic uptake of OATP1B1/3 substrate drugs and the renal elimination of OAT2 and OAT3 substrates and could suffer (victim) the effect of OAT3 transporter inhibitors, reducing its renal elimination. Based on these pharmacological characteristics, here, we describe the potential DDIs of bempedoic acid with concomitant medications and the possible clinical implications.

Evaluation of drug interaction between cyclosporine and lercanidipine: a descriptive study

OBJECTIVES

Cyclosporine is an immunosuppressive drug with a high potential for drug interactions that is frequently used in renal transplant patients. The purpose of this study was to assess the change in cyclosporine concentration in patients taking cyclosporine and lercanidipine concurrently.

METHODS

The potential drug interactions in renal transplant patients who received lercanidipine and cyclosporine concurrently in a university hospital between January 2008 and January 2018 were evaluated retrospectively. Patients had renal transplantation from deceased donors or living related donors. The Drug Interaction Probability Scale (DIPS) criteria were used to assess the causality of cyclosporine and lercanidipine drug interaction.

RESULTS

The study included six renal transplant patients. The median cyclosporine concentration before lercanidipine use was 325 ng/mL (min-max 101-356) and 592.5 ng/mL (min-max 198-799) thereafter (p=0.028). Serum creatinine and proteinuria levels did not change significantly during lercanidipine treatment (p=0.686 and p=0.116, respectively). According to the DIPS evaluation, cyclosporine and lercanidipine interaction was classified as "possible (score 3)".

CONCLUSIONS

Concomitant use of cyclosporine and lercanidipine increases the concentration of cyclosporine, which may result in side effects during effective treatment in renal transplant patients. Therefore, cyclosporine concentrations should definitely be monitored while patients are taking lercanidipine.

Drug-drug interactions between letermovir and tacrolimus in Japanese renal transplant recipients simulated using a physiologically based pharmacokinetic model

Letermovir (LET) is a novel antiviral agent recently approved for cytomegalovirus (CMV) prophylaxis of renal transplant patients in Japan. However, its interactions with tacrolimus (TAC), an important immunosuppressant, remain ambiguous, warranting careful evaluation considering the unique genetic and physiological characteristics of Japanese patients. Therefore, in this study, we aimed to investigate the drug-drug interactions between LET and extended-release TAC (ER-TAC) in Japanese renal transplant patients via physiologically based pharmacokinetic (PBPK) modeling. We developed PBPK models for LET and TAC, including a new model for ER-TAC, using the Simcyp simulator. We also created a virtual Japanese post-transplant population by incorporating physiological parameters specific to Japanese patients, including CYP3A5 genotypes. Our model accurately predicted the pharmacokinetics of both immediate-release and ER-TAC co-administered with LET. In the Japanese population, LET significantly increased ER-TAC exposure, with the effect varying by CYP3A5 genotype. For CYP3A5*1 carrier, the area under the curve ratio ranged from 2.33 to 2.53, while for CYP3A5*3/*3 carriers, it ranged from 2.82 to 2.86. The maximum concentration ratio was approximately 1.50 across all groups. Our findings suggest reducing the ER-TAC dose by approximately 57-60% for CYP3A5*1 carrier and 65% for CYP3A5*3/*3 carriers when co-administered with LET for Japanese renal transplant patients. Moreover, the developed model incorporating population-specific factors, such as hematocrit values and CYP3A5 genotype frequencies, is a valuable tool to evaluate complex drug interactions and guide the dosing strategies for LET and TAC in Japanese patients. Overall, this study expands the application of PBPK modeling in transplant pharmacology, contributing to the development of effective immunosuppressive strategies for Japanese renal transplant patients.

What to do when traditional rescue therapies fail in acute severe ulcerative colitis

Acute severe ulcerative colitis (ASUC) is a medical emergency that affects approximately 25% of patients with ulcerative colitis at some point in time in their lives. Outcomes of ASUC are highly variable. Approximately 30% of patients do not respond to corticosteroids and up to 50% of patients do not respond to rescue therapy (infliximab or cyclosporin) and require emergency colectomy. Data are emerging on infliximab dosing strategies, use of cyclosporin as a bridge to slower acting biologic agents and Janus kinase inhibition as primary and sequential therapy. In this review, we outline contemporary approaches to clinical management of ASUC in the setting of failure to respond to traditional rescue therapies.

From hazard to risk prioritization: a case study to predict drug-induced cholestasis using physiologically based kinetic modeling

Cholestasis is characterized by hepatic accumulation of bile acids. Clinical manifestation of cholestasis only occurs in a small proportion of exposed individuals. The present study aims to develop a new approach methodology (NAM) to predict drug-induced cholestasis as a result of drug-induced hepatic bile acid efflux inhibition and the resulting bile acid accumulation. To this end, hepatic concentrations of a panel of drugs were predicted by a generic physiologically based kinetic (PBK) drug model. Their effects on hepatic bile acid efflux were incorporated in a PBK model for bile acids. The predicted bile acid accumulation was used as a measure for a drug's cholestatic potency. The selected drugs were known to inhibit hepatic bile acid efflux in an assay with primary suspension-cultured hepatocytes and classified as common, rare, or no for cholestasis incidence. Common cholestasis drugs included were atorvastatin, chlorpromazine, cyclosporine, glimepiride, ketoconazole, and ritonavir. The cholestasis incidence of the drugs appeared not to be adequately predicted by their Ki for inhibition of hepatic bile acid efflux, but rather by the AUC of the PBK model predicted internal hepatic drug concentration at therapeutic dose level above this Ki. People with slower drug clearance, a larger bile acid pool, reduced bile salt export pump (BSEP) abundance, or given higher than therapeutic dose levels were predicted to be at higher risk to develop drug-induced cholestasis. The results provide a proof-of-principle of using a PBK-based NAM for cholestasis risk prioritization as a result of transporter inhibition and identification of individual risk factors.

Effect of Tacrolimus Formulation (Prolonged-Release vs Immediate-Release) on Its Susceptibility to Drug-Drug Interactions with St. John's Wort

Tacrolimus is metabolized by cytochrome P450 3A (CYP3A) and is susceptible to interactions with the CYP3A and P-glycoprotein inducer St. John's Wort (SJW). CYP3A isozymes are predominantly expressed in the small intestine and liver. Prolonged-release tacrolimus (PR-Tac) is largely absorbed in distal intestinal segments and is less susceptible to CYP3A inhibition. The effect of induction by SJW is unknown. In this randomized, crossover trial, 18 healthy volunteers received single oral tacrolimus doses (immediate-release [IR]-Tac or PR-Tac, 5 mg each) alone and during induction by SJW. Concentrations were quantified using ultra-high performance liquid chromatography coupled with tandem mass spectrometry and non-compartmental pharmacokinetics were evaluated. SJW decreased IR-Tac exposure (area under the concentration-time curve) to 73% (95% confidence interval 60%-88%) and maximum concentration (Cmax ) to 61% (52%-73%), and PR-Tac exposure to 67% (55%-81%) and Cmax to 69% (58%-82%), with no statistical difference between the 2 formulations. The extent of interaction appeared to be less pronounced in volunteers with higher baseline CYP3A4 activity and in CYP3A5 expressors. In contrast to CYP3A inhibition, CYP3A induction by SJW showed a similar extent of interaction with both tacrolimus formulations. A higher metabolic baseline capacity appeared to attenuate the extent of induction by SJW.

Effect of CYP3A4*22, CYP3A5*3 and POR*28 genetic polymorphisms on calcineurin inhibitors dose requirements in early phase renal transplant patients

OBJECTIVE

This study aimed to investigate the combined effect of CYP3A5*3, CYP3A4*22, and POR*28 genetic polymorphisms on tacrolimus and cyclosporine dose requirements.

METHODS

One hundred thirty renal transplant patients placed on either tacrolimus or cyclosporine were recruited, where the effect of CYP3A5*3, CYP3A4*22, and POR*28 genetic polymorphisms on their dose requirements were studied at days 14, 30, and 90 post-transplantations.

RESULTS

The POR*28 allele frequency in the studied population was 29.61%. The tacrolimus dose-adjusted trough concentration ratio (C0/D) was significantly lower in the fast metabolizers group ( CYP3A5*1/POR*28(CT/TT ) carriers) than in the poor metabolizers group ( CYP3A5*3/*3/CYP3A4*22 carriers) throughout the study (14, 30, and 90 days) ( P = 0.001, <0.001, and 0.003, respectively). Meanwhile, there was no significant effect of this gene combination on cyclosporine C0/D.

CONCLUSION

Combining the CYP3A5*3, POR*28 , and CYP3A4*22 genotypes can have a significant effect on early tacrolimus dose requirements determination and adjustments. However, it does not have such influence on cyclosporine dose requirements.

Improved LC-MS/MS method for the simultaneous quantification of tacrolimus and cyclosporine A in human blood and application to therapeutic drug monitoring

In order to facilitate therapeutic drug monitoring of tacrolimus and cyclosporine A in clinical practice, a simple, rapid, robust, sensitive and specific LC-MS/MS assay was developed and validated for the simultaneous determination of tacrolimus and cyclosporine A in human whole blood. Erythrocytes were destroyed using internal standard solution with 10% (w/v) zinc sulfate in water. The analytes were extracted from 100 μl of whole blood by protein precipitation with acetonitrile. Chromatographic separation was conducted on a Kinetex PFP column (60°C) by a gradient elution with a flow rate of 0.450 ml/min in 2.5 min. Quantitative analysis was performed using electrospray ionization and multiple reaction monitoring in positive ionization mode. The method was fully validated as per current guidelines on bioanalytical methodologies of the US Food and Drug Administration and European Medicines Agency. The method developed was applied successfully in analyzing clinical samples from patients administered tacrolimus or cyclosporine A. The sample treatment procedure was rationalized and improved to fulfill the complete target extraction. The chromatography conditions were optimized to achieve rapid and accurate quantification of both analytes. This method may be beneficial as a constructive input for the therapeutic drug monitoring of tacrolimus and cyclosporine A in obtaining individualized therapy.

Validation of a New Methodology to Create Oral Drugs beyond the Rule of 5 for Intracellular Tough Targets

Establishing a technological platform for creating clinical compounds inhibiting intracellular protein-protein interactions (PPIs) can open the door to many valuable drugs. Although small molecules and antibodies are mainstream modalities, they are not suitable for a target protein that lacks a deep cavity for a small molecule to bind or a protein found in intracellular space out of an antibody's reach. One possible approach to access these targets is to utilize so-called middle-size cyclic peptides (defined here as those with a molecular weight of 1000-2000 g/mol). In this study, we validated a new methodology to create oral drugs beyond the rule of 5 for intracellular tough targets by elucidating structural features and physicochemical properties for drug-like cyclic peptides and developing library technologies to afford highly N-alkylated cyclic peptide hits. We discovered a KRAS inhibitory clinical compound (LUNA18) as the first example of our platform technology.

Drug Interaction Between Tacrolimus and Paxlovid (Nirmatrelvir/Ritonavir) in an Adolescent with Inflammatory Bowel Disease

The coronavirus disease of 2019 (COVID-19) led to a worldwide pandemic. The emergency use of a combination of nirmatrelvir/ritonavir (paxlovid) was approved for high-risk individuals (such as immunocompromised) testing positive for the disease. We present a patient with ulcerative colitis being treated with tacrolimus, as well as ustekinumab, who was diagnosed with COVID-19 and placed on paxlovid due to her immunosuppressed state. She stopped her tacrolimus while on paxlovid and did well clinically. Tacrolimus was restarted 12 hours after completion of paxlovid, but she became symptomatic with vomiting, headache, and malaise and was found to have a toxic tacrolimus level. Tacrolimus was stopped and symptoms resolved, but levels remained elevated for a prolonged period. There is a paucity of literature on this drug-drug interaction, and with the resurgence of COVID-19, it is important to be cognizant of the potential for adverse effects and toxicity.

Pharmacogenomics of Old and New Immunosuppressive Drugs for Precision Medicine in Kidney Transplantation

Kidney transplantation is the preferred therapeutic option for end-stage kidney disease, but, despite major therapeutic advancements, allograft rejection continues to endanger graft survival. Every patient is unique due to his or her clinical history, drug metabolism, genetic background, and epigenetics. For this reason, examples of "personalized medicine" and "precision medicine" have steadily increased in recent decades. The final target of precision medicine is to maximize drug efficacy and minimize toxicity for each individual patient. Immunosuppressive drugs, in the setting of kidney transplantation, require a precise dosage to avoid either adverse events (overdosage) or a lack of efficacy (underdosage). In this review, we will explore the knowledge regarding the pharmacogenomics of the main immunosuppressive medications currently utilized in kidney transplantation. We will focus on clinically relevant pharmacogenomic data, that is, the polymorphisms of the genes that metabolize immunosuppressive drugs.

Pharmacogenetic Testing for the Pediatric Gastroenterologist: Actionable Drug-Gene Pairs to Know

Gastroenterologists represent some of the earlier adopters of precision medicine through pharmacogenetic testing by embracing upfront genotyping for thiopurine S-methyltransferase nucleotide diphosphatase (TPMT) before prescribing 6-mercaptopurine or azathioprine for the treatment of inflammatory bowel disease. Over the last two decades, pharmacogenetic testing has become more readily available for other genes relevant to drug dose individualization. Common medications prescribed by gastroenterologists for conditions other than inflammatory bowel disease now have actionable guidelines, which can improve medication efficacy and safety; however, a clear understanding of how to interpret the results remains a challenge for many clinicians, precluding wide implementation of genotype-guided dosing for drugs other than 6-mercaptopurine and azathioprine. Our goal is to provide a practical tutorial on the currently available pharmacogenetic testing options and a results interpretation for drug-gene pairs important to medications commonly used in pediatric gastroenterology. We focus on evidence-based clinical guidelines published by the Clinical Pharmacogenetics Implementation Consortium (CPIC^®) to highlight relevant drug-gene pairs, including proton pump inhibitors and selective serotonin reuptake inhibitors and cytochrome P450 (CYP) 2C19, ondansetron and CYP2D6, 6-mercaptopurine and TMPT and Nudix hydrolase 15 (NUDT15), and budesonide and tacrolimus and CYP3A5.

Morphology of the male rat gonad after in Utero exposure to immunosuppressants

The protocol for immunosuppression of pregnant women is based on immunosuppressant panels. The aim of the study was to determine the influence of commonly applied combinations of immunosuppressants to pregnant rats on the morphology of the offspring' testes. Pregnant rats were treated with cyclosporin A (CsA), mycophenolate mofetil (MMF) and prednisone (Pred) (CMG); tacrolimus (Tc), MMF and Pred (TMG); CsA, everolimus (Ev) and Pred (CEG). Testes of mature offspring underwent morphological analysis. Mainly in the testes of CMG and TMG rats the morphological and functional changes were observed: immature germ cells (GCs) in the seminiferous tubule (ST) lumen, invaginations of the basement membrane, infolding to the seminiferous epithelium (SE), the ST wall thickening, increased acidophilia of Sertoli cells' (SCs) cytoplasm, large residual bodies near the lumen, dystrophic ST and tubules look like the Sertoli cell-only syndrome, Leydig cells with abnormal cell nucleus, hypertrophy of the interstitium, blurring of the boundary between ST wall and interstitium, a reduced number of GCs in the SE, vacuolation of the SE. In the CEG there were only a reduced number of GCs in some tubules and vacuolization of SCs. The safest combination of drugs was CEG, while the TMG and CMG were gonadotoxic.

Bioavailability of tetracyclines is substantially increased by administration of cyclosporine A, a non-specific efflux-pump blocker

OBJECTIVES

To investigate how cyclosporine A, a nonspecific efflux-pump blocker, affects the plasma concentrations and oral bioavailability of tigecycline, oxytetracycline, chlortetracycline, doxycycline, minocycline, and tetracycline.

METHODS

Broiler chickens were used as an animal model. The tetracyclines (10 mg/kg BW) were administered intravenously, orally, and orally with cyclosporine A (50 mg/kg BW; administration: oral or intravenous). After administration, plasma samples were taken, and their concentrations of tetracyclines were measured using high-performance liquid chromatography coupled with tandem mass spectrometry. For pharmacokinetic analyses of mean plasma concentrations versus time, compartmental and non-compartmental analyses were used.

RESULTS

After oral administration of the tetracyclines, cyclosporine A administration (oral or intravenous) significantly (P < 0.05) increased the plasma concentrations, the bioavailability, the maximum plasma concentration, and the area under the curve of all the tetracyclines. Interestingly, the bioavailability of the tetracyclines was around two times higher after orally administering cyclosporine A than after intravenously administering it (P < 0.05).

CONCLUSIONS

Cyclosporine A administration increases the plasma concentrations of orally administered tetracyclines. Although cyclosporine A also inhibits renal and hepatic clearance, these results strongly suggest that efflux pumps in the intestinal epithelium are involved in the regulation of tetracycline absorption from the gastrointestinal tract.

Population Pharmacokinetic Analysis for Model-Based Therapeutic Drug Monitoring of Tacrolimus in Chinese Han Heart Transplant Patients

BACKGROUND AND OBJECTIVE

Tacrolimus has become the first-line immunosuppressant for preventing rejection after heart transplantation. The present study aimed to investigate genetic variants and clinical factors affecting the variability of tacrolimus in Chinese Han heart transplant patients using a population pharmacokinetic approach.

METHODS

The retrospective study included 53 hospitalized patients with 547 tacrolimus concentrations for analysis. Nonlinear mixed-effects modeling was used to develop the population pharmacokinetics model for tacrolimus in patients with heart transplants, followed by Monte Carlo simulations to design initial dosing regimens.

RESULTS

In our study, the mutation rate of CYP3A4*18B (C>T) was 27.36%. An oral one-compartment model with first-order absorption and elimination was used to describe the pharmacokinetics of tacrolimus in heart transplant patients. In the final model, the estimated apparent clearance (CL/F) and volume of distribution (V/F) were 532.5 L/h [12.20% interindividual variability, IIV] and 16.87 L (23.16% IIV), respectively. Albumin, postoperative time, and rs2242480 (CYP3A4*18B) gene polymorphisms were the significant covariates affecting CL/F, and creatinine clearance had significant effects on the V/F.

CONCLUSION

The population pharmacokinetic model of tacrolimus in heart transplant patients can better estimate the population and individual pharmacokinetic parameters of patients and can provide a reference for the design of individualized dosing regimens.

Protective effects of pomegranate (Punica granatum) and its main components against natural and chemical toxic agents: A comprehensive review

BACKGROUND

Different chemical toxicants or natural toxins can damage human health through various routes such as air, water, fruits, foods, and vegetables.

PURPOSE

Herbal medicines may be safe and selective for the prevention of toxic agents due to their active ingredients and various pharmacological properties. According to the beneficial properties of pomegranate, this paper summarized the protective effects of this plant against toxic substances.

STUDY DESIGN

In this review, we focused on the findings of in vivo and in vitro studies of the protective effects of pomegranate (Punica granatum) and its active components including ellagic acid and punicalagin, against natural and chemical toxic agents.

METHODS

We collected articles from the following databases or search engines such as Web of Sciences, Google Scholar, Pubmed and Scopus without a time limit until the end of September 2022.

RESULTS

P. granatum and its constituents have shown protective effects against natural toxins such as aflatoxins, and endotoxins as well as chemical toxicants for instance arsenic, diazinon, and carbon tetrachloride. The protective effects of these compounds are related to different mechanisms such as the prevention of oxidative stress, and reduction of inflammatory mediators including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), cyclooxygenase-2(COX-2) and nuclear factor ĸB (NF-ĸB) as well as the modulation of apoptosis, mitogen-activated protein kinase (MAPK) signaling pathways and improvement of liver or cardiac function via regulation of enzymes.

CONCLUSION

In this review, different in vitro and in vivo studies have shown that P. granatum and its active constituents have protective effects against natural and chemical toxic agents via different mechanisms. There are no clinical trials on the protective effects of P. granatum against toxic agents.

Metabolism of the areca alkaloids - toxic and psychoactive constituents of the areca (betel) nut

Areca nut (AN) is consumed by millions of people for its therapeutic and psychoactive effects, making it one of the most widely self-administered psychoactive substances in the world. Even so, AN use/abuse is associated with myriad oral and systemic side effects, affecting most organ systems in the body. Alkaloids abundant in the nut (e.g. arecoline, arecaidine, guvacoline, and guvacine), collectively called the areca alkaloids, are presumably responsible for the major pharmacological effects experienced by users, with arecoline being the most abundant alkaloid with notable toxicological properties. However, the mechanisms of arecoline and other areca alkaloid elimination in humans remain poorly documented. Therefore, the purpose of this review is to provide an in-depth review of areca alkaloid pharmacokinetics (PK) in biological systems, and discuss mechanisms of metabolism by presenting information found in the literature. Also, the toxicological relevance of the known and purported metabolic steps will be reviewed. In brief, several areca alkaloids contain a labile methyl ester group and are susceptible to hydrolysis, although the human esterase responsible remains presumptive. Other notable mechanisms include N-oxidation, glutathionylation, nitrosamine conversion, and carbon-carbon double-bond reduction. These metabolic conversions result in toxic and sometimes less-toxic derivatives. Arecoline and arecaidine undergo extensive metabolism while far less is known about guvacine and guvacoline. Metabolism information may help predict drug interactions with human pharmaceuticals with overlapping elimination pathways. Altogether, this review provides a first-of-its-kind comprehensive analysis of AN alkaloid metabolism, adds perspective on new mechanisms of metabolism, and highlights the need for future metabolism work in the field.

Elevated Tacrolimus Levels at Time of Diagnosis of COVID-19 Compared to Baseline Among Hospitalized Organ Transplant Recipients

BACKGROUND

The effect of COVID-19 on immunosuppressant drug levels in organ transplant recipients (OTRs) has not been adequately studied.

OBJECTIVE

To study the effect of COVID-19 on tacrolimus trough levels (primary outcome) in OTRs and the association of the later with acute kidney injury, bacterial infection, and oxygen requirements.

METHODS

We studied adult (>18-year-old) hospitalized OTRs with COVID-19, who were receiving tacrolimus between 3/1 and 12/16/2020.

RESULTS

Among 30 OTRs, 67% were men, 90% had a kidney transplant. Median age was 60.5 (interquartile range [IQR]: 45-68) years, median time from transplant 36 (IQR: 20-84) months. Tacrolimus troughs were higher on admission for COVID-19 than baseline (average over 6 months prior) (P = .001). Eighteen patients (60%) had admission tacrolimus trough >10, 5 (17%) >20 ng/mL. Patients with diarrhea had borderline higher tacrolimus troughs, compared to those without diarrhea (P = .09). Organ transplant recipients with a tacrolimus trough >10 ng/mL were more likely to have elevated aspartate aminotransferase on admission (P = .01) and require supplemental oxygen. (P = .026).

CONCLUSION AND RELEVANCE

Tacrolimus trough levels were elevated in most OTRs with COVID-19 at the time of hospital admission, compared to baseline. Potential mechanisms are diarrhea and hepatic involvement in COVID-19. In OTRs with COVID-19, including outpatients, immunosuppressant drug levels should be closely followed; management of immunosuppression should be individualized.

Dose-dependent bioavailability and tissue distribution of the ATR inhibitor AZD6738 (ceralasertib) in mice

PURPOSE

Ataxia telangiectasia and Rad3-related (ATR) initiates and regulates cellular responses to DNA damage, such as those caused by cancer treatments. Several ATR inhibitors (ATRi) are in clinical development including AZD6738. Therapeutic indices among ATRi may differ as a result of varying potencies and concentrations at both tumor and off-target sites. Additionally, AZD6738 contributes to anti-tumor immune responses necessitating evaluation of exposure at immunological sites.

METHODS

Using mouse models and a highly sensitive LC-MS/MS assay, the pharmacokinetics of AZD6738 were studied, including dose linearity, bioavailability, metabolism, and tissue distribution in tumor-bearing mice.

RESULTS

Initial studies identified dose-dependent bioavailability, with greater than proportional increases in exposure as dose increased resulting in a ~ twofold increase in bioavailability between the lowest and highest investigated doses. These behaviors were successfully captured with a compartmental PK model. Analysis of metabolite PK revealed decreasing metabolic ratios with increasing dose, indicative of saturable first-pass metabolism. Further analysis revealed that intestinal and gut metabolism contribute to metabolism and these saturable mechanisms. Studies of tumor and tissue distribution found rapid and extensive drug distribution to most tissues except brain and spinal cord.

CONCLUSION

The complex non-linear behavior of AZD6738 PK in mice was due to pre-systemic saturation and which appears to be recapitulated clinically at low doses. PK reported here will allow future correlation of tissue related toxicities with drug exposure as well as exposure with immunological responses. These results can also be compared with those from similar studies of other ATRi to contrast drug exposure with responses.

Extrapolation of physiologically based pharmacokinetic model for tacrolimus from renal to liver transplant patients

Physiologically based pharmacokinetic (PBPK) modeling is useful for evaluating differences in drug exposure among special populations, but it has not yet been employed to evaluate the absorption process of tacrolimus. In this study, we developed a minimal PBPK model with a compartmental absorption and transit model for renal transplant patients using available data in the literature and clinical data from our hospital. The effective permeability value of tacrolimus absorption and parameters for the single adjusting compartment were optimized via sensitivity analyses, generating a PBPK model of tacrolimus for renal transplant patients with good predictability. Next, we extrapolated the pharmacokinetics of tacrolimus for liver transplant patients by changing the population demographic parameters of the model. When the physiological parameters of a population with normal liver function were changed to those of a population with impaired hepatic function (Child-Pugh class A) in the constructed renal transplant PBPK model, the predicted tacrolimus concentrations were consistent with the observed concentrations in liver transplant patients. In conclusion, the constructed tacrolimus PBPK model for renal transplant patients could predict the pharmacokinetics in liver transplant patients by slightly reducing the hepatic function, even at three weeks post-transplantation.

Drug interaction profile of TKI alectinib allows effective and safe treatment of ALK+ lung cancer in the kidney transplant recipient

ALK targeting with tyrosine kinase inhibitors (TKIs) is a highly potent treatment option for the therapy of ALK positive non-small cell lung cancer (NSCLC). However, pharmacokinetics of TKIs leads to clinically significant drug interactions, and the interfering co-medication may hamper the anti-cancer therapeutic management. Here, we present for the first time a drug interaction profile of ALK-TKIs, crizotinib and alectinib, and immunosuppressive agent cyclosporine A in kidney transplant recipients diagnosed with ALK+ lung cancer. Based on therapeutic drug monitoring of cyclosporin A plasma level, the dose of cyclosporine A has been adjusted to achieve a safe and effective therapeutic level in terms of both cancer treatment and kidney transplant condition. Particularly, 15 years upon the kidney transplantation, the stage IV lung cancer patient was treated with the 1st-line chemotherapy, the 2nd-line ALK-TKI crizotinib followed by ALK-TKI alectinib. The successful therapy with ALK-TKIs has been continuing for more than 36 months, including the period when the patient was treated for COVID-19 bilateral pneumonia. Hence, the therapy of ALK+ NSCLC with ALK-TKIs in organ transplant recipients treated with cyclosporine A may be feasible and effective.

Effects of Postoperative Day and NR1I2 on Tacrolimus Clearance in Chinese Liver Transplant Recipients-A Population Model Approach

We aimed to explore the new biomarkers influencing tacrolimus in vivo behavior in Chinese liver transplant recipients. A total of 418 drug concentration samples of 41 liver transplant patients were collected for modeling. A population pharmacokinetic model was developed using the nonlinear mixed-effects modeling approach. The potential covariates, such as postoperative day (POD), age, body weight, hepatic and renal function, and recipient genetic polymorphisms (ABCB1, CYP3A4, CYP3A5, NR1I2) were evaluated using forward-inclusion and backward-elimination methods. A 1-compartment model was used describing the in vivo behavior of tacrolimus in liver transplant patients. The estimates of CL/F and V/F were 8.88 L/h and 495.82 L, respectively. Two covariates, POD and NR1I2 rs2276707 genotypes, were incorporated into the final population pharmacokinetic model, and they could significantly impact the CL/F: CL/F (L/h) = 8.88 × (POD/16)^0.18 × e^{0.91 × NR1I2} × e^ηCL . The model evaluation and validation indicated a stable and precise performance of the final model. The functional annotation using ENCODE data indicated that rs2276707 was located on the higher peak of the H3K4Me1 and H3K4Me3 histone marker. To our knowledge, this is the first report indicating NR1I2 rs2276707 genotypes is another biomarker impacting tacrolimus clearance in liver transplant recipients. The NR1I2 gene polymorphism may affect the in vivo behavior of tacrolimus by regulating gene expression.

Coculture with hiPS-derived intestinal cells enhanced human hepatocyte functions in a pneumatic-pressure-driven two-organ microphysiological system

Examining intestine-liver interactions is important for achieving the desired physiological drug absorption and metabolism response in in vitro drug tests. Multi-organ microphysiological systems (MPSs) constitute promising tools for evaluating inter-organ interactions in vitro. For coculture on MPSs, normal cells are challenging to use because they require complex maintenance and careful handling. Herein, we demonstrated the potential of coculturing normal cells on MPSs in the evaluation of intestine-liver interactions. To this end, we cocultured human-induced pluripotent stem cell-derived intestinal cells and fresh human hepatocytes which were isolated from PXB mice with medium circulation in a pneumatic-pressure-driven MPS with pipette-friendly liquid-handling options. The cytochrome activity, albumin production, and liver-specific gene expressions in human hepatocytes freshly isolated from a PXB mouse were significantly upregulated via coculture with hiPS-intestinal cells. Our normal cell coculture shows the effects of the interactions between the intestine and liver that may occur in vivo. This study is the first to demonstrate the coculturing of hiPS-intestinal cells and fresh human hepatocytes on an MPS for examining pure inter-organ interactions. Normal-cell coculture using the multi-organ MPS could be pursued to explore unknown physiological mechanisms of inter-organ interactions in vitro and investigate the physiological response of new drugs.

Short Bowel Syndrome and Kidney Transplantation: Challenges, Outcomes, and the Use of Teduglutide

Among patients with short bowel syndrome who commonly have kidney disease, kidney transplantation remains challenging. We describe the clinicopathologic course of a 59-year old man with short bowel syndrome secondary to Crohn's disease who underwent a deceased donor kidney transplant that was complicated by recurrent acute kidney allograft injury due to volume depletion from diarrhea, ultimately requiring the placement of permanent intravenous access for daily volume expansion at home resulting in the recovery of allograft function. Teduglutide treatment at 1.8 years post-transplant led to a dramatic decrease in diarrhea. A literature review of similar cases yielded 18 patients who underwent 19 kidney transplants. Despite high rates of complications, at the time of last follow-up (median 2.1 years [0.04-7]), 94% of the patients were still alive and 89% had functioning allografts, with a median eGFR of 37.5 [14-122] ml/min/1.73m². In conclusion, despite high rates of complications, kidney transplantation in patients with short bowel syndrome is associated with acceptable short- and midterm outcomes. Further, we report for the first time the effects of the glucagon-like peptide-2 analogue teduglutide for short bowel syndrome in a kidney transplant recipient.

Incorporating nonlinear kinetics to improve predictive performance of population pharmacokinetic models for ciclosporin in adult renal transplant recipients: A comparison of modelling strategies

BACKGROUND

Ciclosporin has been shown to follow nonlinear pharmacokinetics (PK) in renal transplant recipients who received ciclosporin (Neoral^Ⓡ, Novartis)-based triple immunosuppressive therapy. Some of these nonlinear properties have not been fully considered in population PK (popPK) analysis. Therefore, the aim of this study was to determine the potential influence of nonlinearity and the functional forms of covariates on model predictability as well as to analyse multiple nonlinear factors in the in vivo process.

METHODS

A total of 2969 ciclosporin whole-blood measurements, including 1328 pre-dose and 1641 2-h post-dose concentrations, were collected from 173 patients who underwent their first renal transplantation. Four popPK models based on different modelling strategies were developed to investigate the discrepancy between empirical and theory-based, linear and nonlinear compartmental kinetic models and empirical formulae on model predictability. Prediction and simulation-based diagnostics (prediction-corrected visual predictive checks) were performed to determine the stability and predictive performance of these four models.

RESULTS

Model predictability improved when nonlinearity was considered. The theory-based nonlinear model which incorporated nonlinear property based on known theoretical relationships performed better than the other two compartmental models. The nonlinear Michaelis-Menten model showed a remarkable improvement in predictive performance compared to the other three compartmental models. The saturated binding of ciclosporin to erythrocytes, auto-inhibition induced by the inhibitory effects of ciclosporin on cytochrome P450 3A4/P-glycoprotein may have contributed to the nonlinearity. Ciclosporin-prednisolone drug interaction should be given serious consideration in clinical settings.

CONCLUSIONS

Incorporation of nonlinear properties is likely to be a promising approach for improving ciclosporin model predictability. Theory-based modelling is helpful to improve model predictability. However, ciclosporin nonlinear kinetics resources need further investigation.

Analysis of time course and dose effect of tacrolimus on proteinuria in lupus nephritis patients

WHAT IS KNOWN AND OBJECTIVES

Tacrolimus is used to treat patients with lupus nephritis; however, its time course and dose effect on proteinuria in lupus nephritis patients remain unknown. The purpose of this study was to determine the time course and dose effect of tacrolimus on proteinuria in lupus nephritis patients via model-based meta-analysis (MBMA).

METHODS

PubMed, Web of Science, Cochrane Library and ClinicalTrials.gov databases were systematically searched for information on the efficacy of tacrolimus against proteinuria in lupus nephritis patients. Useful data were extracted to build a model for the population studied using a non-linear mixed-effect model (NONMEM). This model was applied to simulate time course of tacrolimus on proteinuria using Monte Carlo simulations.

RESULTS

Ten clinical studies that recruited 222 patients with lupus nephritis were included. Based on various diagnostic plots, we found that the established model described the observed data reasonably well. In addition, the typical E_max and ET₅₀ of tacrolimus for 24-hour proteinuria in lupus nephritis patients were -5.88 g and 0.37 months, respectively. The baseline value of 24-hour proteinuria affected E_max . No significant dose-response relationship was observed in the range of tacrolimus concentration used in the present study (3-10 ng/mL), indicating that the effect of tacrolimus on proteinuria depends on effective concentration range and not the dose. However, the time course relationship was obvious; the efficacy of tacrolimus increased over time, reaching a plateau (80% E_max ) at approximately 1.48 months from the beginning of treatment.

WHAT IS NEW AND CONCLUSION

When the concentration range of tacrolimus is maintained at 3-10 ng/mL, at least 1.48 months of treatment is required to achieve a better outcome with regard to proteinuria in lupus nephritis patients.

CYP3A5 Genotype as a Potential Pharmacodynamic Biomarker for Tacrolimus Therapy in Ulcerative Colitis in Japanese Patients

Tacrolimus has been used to induce remission in patients with steroid-refractory ulcerative colitis. It poses a problem of large individual differences in dosage necessary to attain target blood concentration and, often, this leads to drug inefficacy. We examined the difference in mRNA expression levels of ATP binding cassette transporter B1 (ABCB1) between inflamed and non-inflamed tissues, and the influence of CYP3A5 genotype on tacrolimus therapy. The mRNA expression of CYP3A4 in colonic mucosa and that of cytochrome p450 3A5 (CYP3A5) and ABCB1 in inflamed and non-inflamed areas were examined in 14 subjects. The mRNA expression levels of CYP3A5 were higher than that of CYP3A4. The mRNA expression of ABCB1 was lower in the inflamed than in the non-inflamed mucosa, despite that of CYP3A5 mRNA level being not significantly changed. Hence, the deterioration of the disease is related to the reduction of the barrier in the inflamed mucosa. The relationship between CYP3A5 genotype and blood concentration, dose, and concentration/dose (C/D) ratio of tacrolimus in 15 subjects was studied. The tacrolimus dose to maintain equivalent blood concentrations was lower in CYP3A5*3/*3 than in CYP3A5*1 carriers, and the C/D ratio was significantly higher in the latter. Thus, CYP3A5 polymorphism information played a role in determining the initial dose of tacrolimus. Furthermore, since the effect of tacrolimus appears earlier in CYP3A5*3/*3 than in CYP3A5*1/*1 and *1/*3, it seems necessary to change the evaluation time of therapeutic effect by CYP3A5 genotype. Additionally, the relationship between CYP3A5 genotype and C/D ratio of tacrolimus in colonic mucosa was investigated in 10 subjects. Tacrolimus concentration in the mucosa was two-fold higher in CYP3A5*3/*3 than in CYP3A5*1 carriers, although no significant difference in tacrolimus-blood levels was observed. Therefore, the local concentration of tacrolimus affected by CYP3A5 polymorphism might be related to its therapeutic effect.

Importance of genetic polymorphisms in liver transplantation outcomes

Although, liver transplantation serves as the only curative treatment for patients with end-stage liver diseases, it is burdened with complications, which affect survival rates. In addition to clinical risk factors, contribution of recipient and donor genetic prognostic markers has been extensively studied in order to reduce the burden and improve the outcomes. Determination of single nucleotide polymorphisms (SNPs) is one of the most important tools in development of personalized transplant approach. To provide a better insight in recent developments, we review the studies published in the last three years that investigated an association of recipient or donor SNPs with most common issues in liver transplantation: Acute cellular rejection, development of new-onset diabetes mellitus and non-alcoholic fatty liver disease, hepatocellular carcinoma recurrence, and tacrolimus concentration variability. Reviewed studies confirmed previously established SNP prognostic factors, such as PNPLA3 rs738409 for non-alcoholic fatty liver disease development, or the role of CYP3A5 rs776746 in tacrolimus concentration variability. They also identified several novel SNPs, with a reasonably strong association, which have the potential to become useful predictors of post-transplant complications. However, as the studies were typically conducted in one center on relatively low-to-moderate number of patients, verification of the results in other centers is warranted to resolve these limitations. Furthermore, of 29 reviewed studies, 28 used gene candidate approach and only one implemented a genome wide association approach. Genome wide association multicentric studies are needed to facilitate the development of personalized transplant medicine.

Influence of Germline Genetics on Tacrolimus Pharmacokinetics and Pharmacodynamics in Allogeneic Hematopoietic Stem Cell Transplant Patients

Tacrolimus exhibits high inter-patient pharmacokinetics (PK) variability, as well as a narrow therapeutic index, and therefore requires therapeutic drug monitoring. Germline mutations in cytochrome P450 isoforms 4 and 5 genes (CYP3A4/5) and the ATP-binding cassette B1 gene (ABCB1) may contribute to interindividual tacrolimus PK variability, which may impact clinical outcomes among allogeneic hematopoietic stem cell transplantation (HSCT) patients. In this study, 252 adult patients who received tacrolimus for acute graft versus host disease (aGVHD) prophylaxis after allogeneic HSCT were genotyped to evaluate if germline genetic variants associated with tacrolimus PK and pharmacodynamic (PD) variability. Significant associations were detected between germline variants in CYP3A4/5 and ABCB1 and PK endpoints (e.g., median steady-state tacrolimus concentrations and time to goal tacrolimus concentration). However, significant associations were not observed between CYP3A4/5 or ABCB1 germline variants and PD endpoints (e.g., aGVHD and treatment-emergent nephrotoxicity). Decreased age and CYP3A5*1/*1 genotype were independently associated with subtherapeutic tacrolimus trough concentrations while CYP3A5*1*3 or CYP3A5*3/*3 genotypes, myeloablative allogeneic HSCT conditioning regimen (MAC) and increased weight were independently associated with supratherapeutic tacrolimus trough concentrations. Future lines of prospective research inquiry are warranted to use both germline genetic and clinical data to develop precision dosing tools that will optimize both tacrolimus dosing and clinical outcomes among adult HSCT patients.

A novel random forest integrative approach based on endogenous CYP3A4 phenotype for predicting tacrolimus concentrations and dosages in Chinese renal transplant patients

WHAT IS KNOWN AND OBJECTIVE

Personalized treatment with tacrolimus has remained a challenge. The present study aimed to evaluate the potential of an integrative approach to predict individual tacrolimus concentrations and dosages based on endogenous CYP3A4 phenotype, CYP3A5 genotype and clinical variables.

METHODS

A random forest (RF) algorithm which incorporated an endogenous CYP3A4 phenotype (assessed by urinary ratio of 6β-hydroxycortisol and 6β-hydroxycortisone to cortisol and cortisone), CYP3A5*3 genotype and other clinical determinants of tacrolimus disposition was performed in 182 medically stable renal transplant recipients.

RESULTS AND DISCUSSION

The results suggested that endogenous CYP3A4 phenotype was the most important determinant of tacrolimus concentrations and dose requirements. RF models provided high goodness of fit (R² ) with .92 and .95 for the prediction of tacrolimus trough concentrations and dosages, respectively, as well as high predictability (Q² ) with 0.63 and 0.70, respectively. Significant correlations existed between experimental and predictive data.

WHAT IS NEW AND CONCLUSION

In summary, endogenous CYP3A4 phenotype is a critical biomarker for the determination of tacrolimus disposition. This predictive RF approach based on CYP3A4 biomarker with the combination of CYP3A5*3 genotype and other clinical variables can be used for predicting tacrolimus concentrations and dosages, which may serve as a useful tool in individualized tacrolimus dosing.

Reproductive toxicity of the hydroethanolic extract of the flowers ofAcmella oleraceaand spilanthol in zebrafish: In vivo and in silico evaluation

Hydroethanolic preparations of Acmella oleracea is used in the north of Brazil as a female aphrodisiac. Thus, the objective of this study was to evaluate the action of the hydroethanolic extract of Acmella oleracea (EHFAo) flowers (21.873 and 44.457 mg/kg) and spilanthol (3 mg/kg) administered orally on reproductive performance and effects on the embryonic development of zebrafish F1 generation. It was observed that in the groups in which males and females received EHFAo and spilanthol, the spawning was interrupted, whereas in the groups in which only the females were treated, spawning occurred during the 21 days. Thus, in the histopathological evaluation of the gonads, it was possible to observe that the percentage of mature cells in the spermatozoa and females was significantly reduced. Only the embryo groups in which parental generation was treated with EHFAo showed lethal and teratogenic effects. On the other hand, the parental groups treated with the spilanthol presented only the lethality. Spilanthol and some metabolites showed good oral availability and important toxicological properties. Thus, it is suggested that the treatment of parental generation of zebrafish with EHFAo and spilanthol caused severe changes in the gonads and on fertility. However, on the embryo, the most striking effects in the development were recorded in the groups in which the parental generation was treated with the EHFAo, while the spilanthol influenced the lethality of the embryos.

Interaction of cyclosporine with phenobarbital in cats: a preliminary study

Phenobarbital (PB) decreases the cyclosporine (CsA) blood level in humans. However, the interaction of PB with CsA has not been reported in cats. This study investigated the effects of multiple doses of PB on the pharmacokinetics of CsA in three healthy cats. The treatments included oral CsA 5 mg/kg alone and oral CsA 5 mg/kg plus PB 5 mg/kg for 4 weeks. Co-administration of PB with CsA resulted in significant decreases in the oral bioavailability of CsA though both the first pass and elimination phases. These preliminary results suggest that oral administration of multiple doses of PB increases the required CsA dosage in CsA-based immunosuppressive therapy in cats.

Drug interactions between direct-acting oral anticoagulants and calcineurin inhibitors during solid organ transplantation: considerations for therapy

Introduction: There is a high incidence of venous thromboembolism (VTE) in solid organ transplant recipients. The safety and efficacy of direct-acting oral anticoagulants (DOAC) have been well established in clinical practice for the prevention and treatment of VTE in broad populations. However, the management of VTE in the setting of solid organ transplantation remains a challenge to clinicians due to limited evidence of DOAC usage with calcineurin inhibitors. Areas covered: The current literature available on the pharmacokinetic-pharmacodynamic interaction between DOACs and calcineurin inhibitors is presented. A comprehensive review was undertaken using PubMed, Embase, drug product labeling, and drug product review conducted by the US Food and Drug Administration using Drugs@FDA. The potential for mitigation strategies and clinical management using extant knowledge is explored. Expert opinion: Immunosuppression therapy is necessary to prevent graft rejection by the host. The sparsity of data together with the lack of well-designed prospective studies of DOAC use in solid organ transplant recipients presents a unique challenge to clinicians in determining the clinical relevance of possible drug interactions. Existing evidence suggests that with attention to concomitant drug use and renal function, the co-administration of DOACs and calcineurin inhibitors is safe and effective.

Model extrapolation to a real-world dataset: evaluation of tacrolimus population pharmacokinetics and drug interaction in pediatric liver transplantation patients

1. Numerous tacrolimus population pharmacokinetic (PPK) models in pediatric liver transplantation patients have been established to define an optimal dose schedule. However, the applicability of extrapolating these PPK models to our clinical center remains unknown. The goals of the present study was to evaluate model external predictiveness and establish a new model applicable to traditional therapeutic drug monitoring data.2. Published PPK models were collected from the literature and assessed using our real-world dataset including 41 pediatric liver transplantation patients via the individual prediction error method. The establishment of a new model was characterized using non-linear mixed-effects modeling.3. Nine published pediatric liver transplantation PPK models were identified, three of which could be applied to our real-world dataset. However, these models were dissatisfactory in terms of individual prediction error and hence, inadequate for extrapolation. Finally, a new model applicable to our real-world dataset was established as follows: CL/F = 22.9 × (WT/70)^0.75 × (1 - WZ × 0.264) × (1 - FCZ × 0.338) × (1 + ASPI × 0.281) × (POD/41)^0.0486 L/h; V/F = 906 × (WT/70) L. Where WT, WZ, FCZ, ASPI and POD were weight, Wuzhi capsule, fluconazole, aspirin and post-transplantation day, respectively. In conclusion, published models were inadequate for application to our real-world dataset. The present study produced a new model applicable to our real-world study data.

A Minimal Physiologically-Based Pharmacokinetic Model for Tacrolimus in Living-Donor Liver Transplantation: Perspectives Related to Liver Regeneration and the cytochrome P450 3A5 (CYP3A5) Genotype

In adult patients after living‐donor liver transplantation, postoperative days and the cytochrome P450 3A5 (CYP3A5) genotype are known to affect tacrolimus pharmacokinetics. In this study, we constructed a physiologically‐based pharmacokinetic model adapted to the clinical data and evaluated the contribution of liver regeneration as well as hepatic and intestine CYP3A5 genotypes on tacrolimus pharmacokinetics. As a result, liver function recovered immediately and affected the total body clearance of tacrolimus only during a limited period after living‐donor liver transplantation. The clearance was about 1.35‐fold higher in the recipients who had a liver with the CYP3A5*1 allele than in those with the CYP3A5*3/*3 genotype, whereas bioavailability was ~0.7‐fold higher in the recipients who had intestines with the CYP3A5*1 allele than those with CYP3A5*3/*3. In conclusion, the constructed physiologically‐based pharmacokinetic model clarified that the oral clearance of tacrolimus was affected by the CYP3A5 genotypes in both the liver and intestine to the same extent.

A Single Dose of Baicalin Has No Clinically Significant Effect on the Pharmacokinetics of Cyclosporine A in Healthy Chinese Volunteers

Despite its narrow therapeutic window and large interindividual variability, cyclosporine A (CsA) is the first-line therapy following organ transplantation. Metabolized mainly by CYP3A and being a substrate of P-glycoprotein (P-gp), CsA is susceptible to drug–drug interactions. Baicalin (BG) is a drug used for adjuvant therapy of hepatitis in traditional Chinese medicine. Since its aglycone baicalein (B) inhibits CYP3A and P-gP, co-administration might affect CsA pharmacokinetics. This study investigated the effect of BG on CsA pharmacokinetics. In a two-period study, 16 healthy volunteers received a single 200 mg oral CsA dose alone (reference period) or in combination with 500 mg BG (test period). Pharmacokinetic evaluation of CsA was carried out using non-compartmental analysis (NCA) and population pharmacokinetics (popPK). Treatments were compared using the standard bioequivalence method. Based on NCA, 90% CIs of AUC and C_max test-to-reference ratios were within bioequivalence boundaries. In the popPK analysis, a two-compartment model (clearance/F 62.8 L/h, central and peripheral volume of distribution/F 254 L and 388 L) with transit compartments for absorption appropriately described CsA concentrations. No clinically relevant effect of 500 mg BG co-administration on CsA pharmacokinetics was identified and both treatments were well tolerated.

Glucagon-Like Peptide-1 Receptor Agonists and Strategies To Improve Their Efficiency

Type 2 diabetes mellitus (T2DM) is increasing in global prevalence and is associated with serious health problems (e.g., cardiovascular disease). Various treatment options are available for T2DM, including the incretin hormone glucagon-like peptide-1 (GLP-1). GLP-1 is a therapeutic peptide secreted from the intestines following food intake, which stimulates the secretion of insulin from the pancreas. The native GLP-1 has a very short plasma half-life, owning to renal clearance and degradation by the enzyme dipeptidyl peptidase-4. To overcome this issue, various GLP-1 agonists with increased resistance to proteolytic degradation and reduced renal clearance have been developed, with several currently marketed. Strategies, such as controlled release delivery systems, methods to reduce renal clearance (e.g., PEGylation and conjugation to antibodies), and methods to improve proteolytic stability (e.g., stapling, cyclization, and glycosylation) provide means to further improve the ability of GLP-1 analogs. These will be discussed in this literature review.

Effect of Multidrug-Resistant 1 (MDR1) and CYP3A4*1B Polymorphisms on Cyclosporine-Based Immunosuppressive Therapy in Renal Transplant Patients

Background

Immunosuppressive drugs such as cyclosporine A (CsA) are characterized by a narrow therapeutic range and high interindividual pharmacokinetic variations. Therefore, the effective monitoring of drug serum level is crucial for successful therapy. This variability can be caused by polymorphisms in genes encoding drug transporters and enzymes responsible for biotransformation. The aim of this study was to determine the relationship between CYP3A4*1B and MDR1 polymorphisms and dose requirements to achieve the target therapeutic range for CsA.

Material/Method

The study group consisted of 184 patients after kidney transplantation who were treated with immunosuppressive therapy. The MDR1 3435C>T and CYP3A4*1B polymorphisms were determined by the real-time PCR using the LightCycler^® 480 device (Roche Diagnostics).

Results

Patients with the CYP3A4*1/*1 genotype received the lowest mean dose of CsA compared to CYP3A4*1/*1B, and had a higher average drug concentration in the blood. In the case of MDR1 3435C>T polymorphism, we observed that patients with the CC genotype received lower doses of CsA than patients with the CT and TT genotypes. Average drug concentration in the blood was comparable to individuals with different MDR-1 genotypes. Analysis of dependence between both polymorphisms and concentration/dose ratio showed no statistically significant differences.

Conclusions

The characterization of CYP3A4*1B and 3435C>T MDR1 polymorphism cannot provide useful guidance for individualizing CsA dosages in renal transplant patients by indicating the optimal dose of these drugs without exposing patients to possible adverse effects associated mainly with nephrotoxicity.

Dasatinib significantly reduced in vivo exposure to cyclosporine in a rat model: The possible involvement of CYP3A induction

BACKGROUND

This study was designed to investigate the effects of dasatinib and nilotinib on the pharmacokinetics of cyclosporine in rats, as these drugs have been reported to be cytochrome P450 3A4 (CYP3A4) substrates.

METHODS

Control and test groups (n = 5) were treated with vehicle and dasatinib (4 mg/kg, and 16 mg/kg, oral) or nilotinib (94 mg/kg, oral), respectively, for 8 consecutive days. On day 8, all groups were administered cyclosporine (30 mg/kg) 1 h after the last dose of dasatinib or nilotinib. Blood was collected from the retro-orbital plexus in heparinized tubes at different time points (0, 0.5, 1, 1.5, 2, 3.5, 8, 12, and 24 h). The cyclosporine concentration in blood samples was determined by ultra-performance liquid chromatography-tandem mass spectrometry. The effects of dasatinib on CYP3A2 mRNA and protein expression levels were also investigated.

RESULTS

Dasatinib significantly reduced the maximum blood concentration (Cmax) of cyclosporine by 85.7%, and increased hepatic and intestinal CYP3A2 mRNA and protein expression levels by 2.4- and 1.25-fold, respectively, compared to those in the controls (p <  0.05). On the other hand, nilotinib had no significant effects on cyclosporine pharmacokinetic parameters.

CONCLUSIONS

Dasatinib significantly reduced cyclosporine exposure, which was most probably related to the induction of CYP3A-mediated cyclosporine metabolism.

Identification of genetic variants associated with tacrolimus metabolism in kidney transplant recipients by extreme phenotype sampling and next generation sequencing

An extreme phenotype sampling (EPS) model with targeted next-generation sequencing (NGS) identified genetic variants associated with tacrolimus (Tac) metabolism in subjects from the Deterioration of Kidney Allograft Function (DeKAF) Genomics cohort which included 1,442 European Americans (EA) and 345 African Americans (AA). This study included 48 subjects separated into 4 groups of 12 (AA high, AA low, EA high, EA low). Groups were selected by the extreme phenotype of dose-normalized Tac trough concentrations after adjusting for common genetic variants and clinical factors. NGS spanned >3 Mb of 28 genes and identified 18,661 genetic variants (3,961 previously unknown). A group of 125 deleterious variants, by SIFT analysis, were associated with Tac troughs in EAs (burden test, p=0.008), CYB5R2 was associated with Tac troughs in AAs (SKAT, p=0.00079). In CYB5R2, rs61733057 (increased allele frequency in AAs) was predicted to disrupt protein function by SIFT and PolyPhen2 analysis. The variants merit further validation.