Single-dose pharmacokinetics of ibrutinib in subjects with varying degrees of hepatic impairment*

Incorporation and Performance Verification of Hepatic Portal Blood Flow Shunting in Minimal and Full PBPK Models of Liver Cirrhosis

Patho-physiological changes in liver cirrhosis create portacaval shunts that allow blood flow to bypass the hepatic portal vein into the systemic circulation affecting drug pharmacokinetics (PKs). The objectives of this work were to implement a physiologically-based pharmacokinetic (PBPK) framework describing shunted blood flows in virtual patients with differing degrees of liver cirrhosis; and to assess the minimal and full PBPK model's performance using drugs with intermediate to high hepatic extraction. Single dose concentration-time profiles and PK parameters for oral ibrutinib, midazolam, propranolol, and buspirone were simulated in healthy volunteers (HVs) and subjects with cirrhosis (Child-Pugh severity score (CP-A, CP-B, or CP-C)). Model performance was verified by comparing predicted to observed fold-changes in PK parameters between HVs and cirrhotic subjects. The verified model was used to simulate the PK changes for simvastatin in patients with cirrhosis. The predicted area under the curve ratios (AUCCirr :AUCHV ) for ibrutinib were 3.38, 6.87, and 11.46 using the minimal PBPK model with shunt and 1.61, 2.58, and 4.33 without the shunt, these compared with observed values of 4.33, 8.14, and 9.04, respectively. For ibrutinib, propranolol, and buspirone, including a shunt in the PBPK model improved the prediction of the AUCCirr :AUCHV and maximum plasma concentration ratios (CmaxCirr :CmaxHV ). For midazolam, an intermediate extraction drug, the differences were less clear. Simulated simvastatin dose adjustments in cirrhosis suggested that 20 mg in CP-A and 10 mg in CP-B could be used clinically. A mechanistic model-informed understanding of the anatomic and pathophysiology of cirrhosis will facilitate improved dose prediction and adjustment in this vulnerable population.

Predicting changes in the pharmacokinetics of CYP3A-metabolized drugs in hepatic impairment and insights into factors driving these changes

Physiologically based pharmacokinetic models, populated with drug-metabolizing enzyme and transporter (DMET) abundance, can be used to predict the impact of hepatic impairment (HI) on the pharmacokinetics (PK) of drugs. To increase confidence in the predictive power of such models, they must be validated by comparing the predicted and observed PK of drugs in HI obtained by phenotyping (or probe drug) studies. Therefore, we first predicted the effect of all stages of HI (mild to severe) on the PK of drugs primarily metabolized by cytochrome P450 (CYP) 3A enzymes using the default HI module of Simcyp Version 21, populated with hepatic and intestinal CYP3A abundance data. Then, we validated the predictions using CYP3A probe drug phenotyping studies conducted in HI. Seven CYP3A substrates, metabolized primarily via CYP3A (fraction metabolized, 0.7-0.95), with low to high hepatic availability, were studied. For all stages of HI, the predicted PK parameters of drugs were within twofold of the observed data. This successful validation increases confidence in using the DMET abundance data in HI to predict the changes in the PK of drugs cleared by DMET for which phenotyping studies in HI are not available or cannot be conducted. In addition, using CYP3A drugs as an example, through simulations, we identified the salient PK factors that drive the major changes in exposure (area under the plasma concentration-time profile curve) to drugs in HI. This theoretical framework can be applied to any drug and DMET to quickly determine the likely magnitude of change in drug PK due to HI.

Evaluation of the Pharmacokinetics and Safety of a Single Dose of Acalabrutinib in Subjects With Hepatic Impairment

Acalabrutinib received approval for treatment of adult patients with mantle cell lymphoma who received at least one prior therapy and adult patients with chronic lymphocytic leukemia or small lymphocytic lymphoma. This study investigated the impact of hepatic impairment (HI) on acalabrutinib PK and safety at a single 50-mg dose in fasted subjects. This study was divided into two studies: study 1, an open-label, parallel-group study in Child-Pugh Class A or B subjects and healthy subjects, and study 2, an open-label, parallel-group study in Child-Pugh Class C subjects and healthy subjects. Baseline characteristics and safety profiles were similar across groups. Acalabrutinib exposure (area under the curve [AUC]) increased slightly (1.90- and 1.48-fold) in subjects with mild (Child-Pugh Class A) and moderate (Child-Pugh Class B) HI compared with healthy subjects. In severe HI (Child-Pugh Class C), acalabrutinib exposure (AUC and maximum concentration [C_max ]) increased approximately 5.0-fold and 3.6-fold, respectively. Results were consistent across total and unbound exposures. Severe HI did not impact total/unbound metabolite (ACP-5862) exposures; metabolite to parent ratio decreased to 0.6 - 0.8 (versus 3.1 - 3.6 in healthy subjects). In summary, single oral dose of 50 mg acalabrutinib was safe and well tolerated in subjects with mild, moderate and severe HI and in healthy control subjects. In subjects with severe HI, mean acalabrutinib exposure increased by up to 5-fold and should be avoided. Acalabrutinib does not require dose adjustment in patients with mild or moderate HI. This article is protected by copyright. All rights reserved.

Population Pharmacokinetics of Ibrutinib in Healthy Adults

BACKGROUND AND OBJECTIVES

Ibrutinib is an antineoplastic agent that reduces B-cell proliferation by inhibiting Bruton's tyrosine kinase. We describes population pharmacokinetics of ibrutinib in healthy adults, and explores potential patient characteristics associated with ibrutinib pharmacokinetics.

METHODS

A population pharmacokinetic modeling approach was applied to 39 healthy subjects. Modeling was performed using Monolix (v.2019R2). Serial blood samples to measure the plasma ibrutinib concentration were collected following the oral administration of 140 mg ibrutinib on two different occasions under fasting conditions. Demographic and clinical information were evaluated as possible predictors of ibrutinib pharmacokinetics during model development. Simulations (using mlxR: R package v.4.0.2) following the administration of therapeutic doses were performed to explore the clinical implications of identified covariates on ibrutinib steady-state concentrations.

RESULTS

A two-compartment model with zero order absorption best fit the data. Inter-individual and inter-occasion variability were quantified by the proposed model. We identified smoking status as a significant covariate associated with ibrutinib clearance. Smoking was found to increase ibrutinib clearance by approximately 60%, which resulted in a reduction in simulated steady-state concentrations by around 40%.

CONCLUSION

The model can be used to simulate clinical trials or various dosing scenarios. The proposed model can be used to optimize ibrutinib dosing based on the smoking status.

Pharmacokinetics under the COVID-19 storm

AIMS

The storm-like nature of the health crises caused by COVID-19 has led to unconventional clinical trial practices such as the relaxation of exclusion criteria. The question remains: how can we conduct diverse trials without exposing subgroups of populations to potentially harmful drug exposure levels? The aim of this study was to build a knowledge base of the effect of intrinsic/extrinsic factors on the disposition of several repurposed COVID-19 drugs.

METHODS

Physiologically based pharmacokinetic (PBPK) models were used to study the change in the pharmacokinetics (PK) of drugs repurposed for COVID-19 in geriatric patients, different race groups, organ impairment and drug-drug interactions (DDIs) risks. These models were also used to predict epithelial lining fluid (ELF) exposure, which is relevant for COVID-19 patients under elevated cytokine levels.

RESULTS

The simulated PK profiles suggest no dose adjustments are required based on age and race for COVID-19 drugs, but dose adjustments may be warranted for COVID-19 patients also exhibiting hepatic/renal impairment. PBPK model simulations suggest ELF exposure to attain a target concentration was adequate for most drugs, except for hydroxychloroquine, azithromycin, atazanavir and lopinavir/ritonavir.

CONCLUSION

We demonstrate that systematically collated data on absorption, distribution, metabolism and excretion, human PK parameters, DDIs and organ impairment can be used to verify simulated plasma and lung tissue exposure for drugs repurposed for COVID-19, justifying broader patient recruitment criteria. In addition, the PBPK model developed was used to study the effect of age and ethnicity on the PK of repurposed drugs, and to assess the correlation between lung exposure and relevant potency values from in vitro studies for SARS-CoV-2.

Sources of Interindividual Variability

The efficacy, safety, and tolerability of drugs are dependent on numerous factors that influence their disposition. A dose that is efficacious and safe for one individual may result in sub-therapeutic or toxic blood concentrations in others. A significant source of this variability in drug response is drug metabolism, where differences in presystemic and systemic biotransformation efficiency result in variable degrees of systemic exposure (e.g., AUC, C_max, and/or C_min) following administration of a fixed dose.Interindividual differences in drug biotransformation have been studied extensively. It is recognized that both intrinsic factors (e.g., genetics, age, sex, and disease states) and extrinsic factors (e.g., diet , chemical exposures from the environment, and the microbiome) play a significant role. For drug-metabolizing enzymes, genetic variation can result in the complete absence or enhanced expression of a functional enzyme. In addition, upregulation and downregulation of gene expression, in response to an altered cellular environment, can achieve the same range of metabolic function (phenotype), but often in a less predictable and time-dependent manner. Understanding the mechanistic basis for variability in drug disposition and response is essential if we are to move beyond the era of empirical, trial-and-error dose selection and into an age of personalized medicine that will improve outcomes in maintaining health and treating disease.

Therapeutic efficacy of lenvatinib in hepatocellular carcinoma patients with portal hypertension

AIM

Preserved liver function may be an important factor affecting therapeutic efficacy in hepatocellular carcinoma patients treated with lenvatinib, but not all patients can be treated while preserving liver function. This study evaluated the therapeutic efficacy of lenvatinib in patients with poor liver function with and without portal hypertension.

METHODS

This prospectively registered multicenter study analyzed 93 patients treated with lenvatinib. Progression-free survival was compared between patients with and without advanced portal hypertension according to baseline liver function. Advanced portal hypertension was defined as having both splenomegaly and any portosystemic collaterals.

RESULTS

A total of 37 patients (40.7%) had advanced portal hypertension. Progression-free survival did not differ between patients with and without advanced portal hypertension in the entire cohort (median 7.6 vs. 4.1 months, respectively; P = 0.148), but was significantly longer in patients with advanced portal hypertension than in those without advanced portal hypertension in the albumin-bilirubin grade 2 or 3 group (median 7.6 vs. 2.1 months, respectively; P = 0.016). In a multivariate analysis, the presence of advanced portal hypertension was identified as the only significant predictor associated with prolonged progression-free survival in the albumin-bilirubin grade 2 or 3 group.

CONCLUSIONS

Advanced portal hypertension was associated with the therapeutic efficacy of lenvatinib in controlling the progression of hepatocellular carcinoma in patients with poor liver function.

Dose recommendations for anticancer drugs in patients with renal or hepatic impairment

Renal or hepatic impairment is a common comorbidity for patients with cancer either because of the disease itself, toxicity of previous anticancer treatments, or because of other factors affecting organ function, such as increased age. Because renal and hepatic function are among the main determinants of drug exposure, the pharmacokinetic profile might be altered for patients with cancer who have renal or hepatic impairment, necessitating dose adjustments. Most anticancer drugs are dosed near their maximum tolerated dose and are characterised by a narrow therapeutic index. Consequently, selecting an adequate dose for patients who have either hepatic or renal impairment, or both, is challenging and definitive recommendations on dose adjustments are scarce. In this Review, we discuss the effect of renal and hepatic impairment on the pharmacokinetics of anticancer drugs. To guide clinicians in selecting appropriate dose adjustments, information from available drug labels and from the published literature were combined to provide a practical set of recommendations for dose adjustments of 160 anticancer drugs for patients with hepatic and renal impairment.

Ibrutinib dose modifications in the management of CLL

Background

Ibrutinib is a Bruton tyrosine kinase inhibitor approved for the treatment of chronic lymphocytic leukemia (CLL) in 2014. Ibrutinib is often used to treat patients who are younger than the patients originally included in theclinical trials have additional unfavorable prognostic factors and suffer from additional comorbidities excluded from the original phase III trials. Our objective was to examine current clinical practices and their impact in this expanded population of CLL patients who often require adjustments in the standard prescribed dose and schedule of therapy.

Materials and methods

An extensive review of the medical literature was conducted to establish the consensus on ibrutinib dose modifications in patients with CLL. Twenty-nine studies were reviewed including fourteen clinical trials and fifteen “real-world practice” studies.

Results

The average discontinuation rate was similar between clinical trials and “real-world practice” studies though the reasons for discontinuation differed. CLL progression was a more common reason for discontinuation in clinical trial studies while toxicity was a more common reason for discontinuation in “real-world practice” studies. Some studies have suggested worse outcomes in patients requiring dose reductions in ibrutinib while others have shown no change in treatment efficacy in patients requiring dose reductions due to concomitant CYP medications or increased immunosuppression post-transplant.

Conclusion

The impact of ibrutinib dose modifications on clinical outcome remains unclear. Patients on concomitant CYP3A inhibitors should be prescribed a lower dose than the standard 420 mg daily, in order to maintain comparable pharmacologic properties. Further research is required to establish definitive clinical practice guidelines.

Clinical Pharmacokinetic and Pharmacodynamic Considerations in Treating Non-Hodgkin Lymphoma

Non-Hodgkin lymphoma (NHL) includes a variety of closely related malignancies that originate from lymphoid precursors. The majority of NHLs are of B-cell lineage, for which traditional therapy involves chemotherapy in combination with the anti-CD20 monoclonal antibody rituximab. Ongoing research into the pathogenesis of NHL subtypes has given rise to the use of novel agents that target specific molecular pathways. While the incidence of NHL extends over a range of ages from pediatric to elderly settings, the majority of diagnoses occur over age 60 years. Increasing the use of concomitant medication coupled with declining organ function among this group of patients creates pharmacokinetic (PK) challenges in administering a number of agents involved in the treatment of NHL. In addition, since many of the new agents are administered orally, there are a number of added PK factors that must be taken into consideration with their prescribing and administration. This article will review the available literature on the PK and pharmacodynamic properties of agents commonly used in the treatment of NHL, and intends to provide information that can assist with properly using these drugs in this setting.

Simulating the Impact of Elevated Levels of Interleukin-6 on the Pharmacokinetics of Various CYP450 Substrates in Patients with Neuromyelitis Optica or Neuromyelitis Optica Spectrum Disorders in Different Ethnic Populations

A physiologically based pharmacokinetic (PBPK) model was used to simulate the impact of elevated levels of interleukin (IL)-6 on the exposure of several orally administered cytochrome P450 (CYP) probe substrates (caffeine, S-warfarin, omeprazole, dextromethorphan, midazolam, and simvastatin). The changes in exposure of these substrates in subjects with rheumatoid arthritis (and hence elevated IL-6 levels) compared with healthy subjects were predicted with a reasonable degree of accuracy. The PBPK model was then used to simulate the change in oral exposure of the probe substrates in North European Caucasian, Chinese, and Japanese population of patients with neuromyelitis optica (NMO) or NMO spectrum disorder with elevated plasma IL-6 levels (up to 100 pg/mL). Moderate interactions [mean AUC fold change, ≤ 2.08 (midazolam) or 2.36 (simvastatin)] was predicted for CYP3A4 probe substrates and weak interactions (mean AUC fold change, ≤ 1.29-1.97) were predicted for CYP2C19, CYP2C9, and CYP2D6 substrates. No notable interaction was predicted with CYP1A2. Although ethnic differences led to differences in simulated exposure for some of the probe substrates, there were no marked differences in the predicted magnitude of the change in exposure following IL-6-mediated suppression of CYPs. Decreased levels of serum albumin (as reported in NMO patients) had little impact on the magnitude of the simulated IL-6-mediated drug interactions. This PBPK modeling approach allowed us to leverage knowledge from different disease and ethnic populations to make predictions of cytokine-related DDIs in a rare disease population where actual clinical studies would otherwise be difficult to conduct.