Quantitative Prediction of the Effect of CYP3A Inhibitors and Inducers on Venetoclax Pharmacokinetics Using a Physiologically Based Pharmacokinetic Model

Individualized medication of venetoclax based on therapeutic drug monitoring in Chinese acute myeloid leukemia patients using an HPLC method

OBJECTIVE

The aim of this study was to establish a simple and sensitive high-performance liquid chromatography method for therapeutic drug monitoring of venetoclax (VEN) and optimize regimens.

METHODS

The analysis required the extraction of a 50 μl plasma sample and the precipitation of proteins using acetonitrile extraction. The chromatographic method employed a mobile phase of acetonitrile: 0.5% KH 2 PO 4 (pH 3.5) (60/40, v/v) on a Diamond C 18 (4.6 mm × 250 mm, 5 μm) column at a flow rate of 1.0 ml/min. The quantitative method was validated based on standards described in 'Bioanalytical Method Validation: Guidance for Industry' published by the US Food and Drug Administration (FDA).

RESULTS

The calibration curve was linear ( R2  = 0.9998) over the range of 75-4800 ng/ml, with limits of quantification of 25 ng/ml. The coefficients of intraday and interday validation, specificity, recovery, and stability all met the criteria of FDA guidance. The method was successfully applied to analyze VEN concentrations in 30 cases of acute myeloid leukemia patients. The peak concentration ( Cmax ) was 1881.19 ± 756.61 ng/ml, while the trough concentration ( Cmin ) was 1212.69 ± 767.92 ng/ml in acute myeloid leukemia patients.

CONCLUSION

Our study establishes a simple, precise, and sensitive high-performance liquid chromatography method for monitoring VEN and confirms its applicability for therapeutic drug monitoring of VEN in hematological cancers.

Precision medicine for multiple myeloma: The case for translocation (11;14)

The t(11;14) translocation is among the most prevalent cytogenetic abnormalities in multiple myeloma (MM), distinguished by its unique features and biology that have been thoroughly explored for decades. What further sets this MM subtype apart is its oscillating prognostic significance, from initially being considered a favorable alteration to intermediate risk and potential future reclassification as favorable risk. Despite not being inherently a high-risk alteration indicative of an aggressive phenotype, it appears that t(11;14)-MM is less responsive to novel agents like proteasome inhibitors and immunomodulatory drugs which have otherwise transformed the disease's treatment landscape, perhaps partially explained by its reduced propensity for immunoglobulin production and oligosecretory nature. However, its distinct reliance on Bcl-2 has heightened its sensitivity to venetoclax. Further subclassification based on morphological and genomic characteristics could enhance our prediction models of treatment responses and enable more tailored therapeutic strategies for patients. This review aims to encapsulate the existing research evidence in this area.

Venetoclax combined with decitabine induced tumor lysis syndrome in a young patient with acute myeloid leukemia: a case report and literature review

Venetoclax, in combination with hypomethylation agents (HMAs), is a novel treatment for leukemia patients with low chemotherapy tolerance. However, it has been reported to be a risk of causing tumor lysis syndrome (TLS) in chronic lymphocytic leukemia (CLL) and elderly acute myeloid leukemia (AML) patients. Here we report a rare case of a young adult AML patient who induced TLS after receiving a combination therapy of venetoclax with decitabine (DEC). A 36-year-old male patient presented with an unexplained fever and was diagnosed with AML-M5a. The patient was first treated with a combination of antibiotics, including voriconazole 300 mg Q12h. After the infection was relieved, he was treated with 100 mg venetoclax in combination with 75 mg/m 2 DEC. However, 12 h after the first treatment, he developed diarrhea, fatigue and other symptoms, and the laboratory results were consistent with the laboratory TLS. The patient stopped chemotherapy immediately, and TLS gradually improved after receiving rehydration, diuresis, dialysis and other treatments. Finally, the patient achieved complete remission. Based on the experience of this case and related studies, we recommend the prevention of TLS should not be limited to elderly patients taking venetoclax, and it is equally important in young patients. And reduce the dosage of venetoclax when using azole antifungal drugs.

Population Pharmacokinetic Models of Venetoclax in Hematologic Malignancies: A Systematic Review

Several population pharmacokinetic (PPK) models of B cell lymphoma-2 (BCL-2) venetoclax (VEN) have been developed and published to characterize the influencing factors of pharmacokinetics in hematologic malignancies. This review described PPK models of VEN examining the magnitude and types of covariate effects in PK parameters, as well as identified areas that require further investigation in order to facilitate their use. Currently, there are six analyses on PPK models of VEN summarized in this review. Most analyses described the pharmacokinetics of VEN with a two-compartment model and all covariates are categorical. The median estimated apparent clearance (CL/F) was 446 L/Day and apparent volume of distribution of the central compartment (V2/F) was 114.5 L. The median IIV of CL/F reported was 39.5% and V2/F was 46.7%. Most commonly, CYP3A inhibitors, OATP1B3 inhibitors and rituximab co-administration were found to be significant covariates on CL/F. In addition, sex and population were influential covariates on V2/F. A detailed description of the characteristics of PPK models of VEN is provided in this review, as well as the effects of covariates on the PK parameters. For future development of the VEN PPK model, CYP3A inhibitors, rituximab co-administration, OATP1B1 transporter inhibitors, sex, population, and food might be considered. Further research and comprehensive investigations should be undertaken to explore reference ranges for therapeutic drug monitoring, define the potential role of patients with cerebrospinal fluid complications, and assess new or potential covariates. These endeavors will facilitate the development of personalized VEN therapy.

Venetoclax Clinical Pharmacokinetics After Administration of Crushed, Ground or Whole Tablets

PURPOSE

Venetoclax is a potent, orally bioavailable BCL-2 inhibitor used in the treatment of some hematological malignancies. Crushing tablets may be necessary to help with the administration of venetoclax to patients with swallowing difficulties or patients requiring nasogastric tube feeding. The study was conducted to assess the bioavailability of crushed and finely ground venetoclax tablets relative to whole tablets.

METHODS

An open-label, randomized, 3-way, crossover study in 15 healthy adult females was conducted. Venetoclax tablets were administered orally in a crushed, ground or intact form on Day 1 of each period with water following a high-fat breakfast. Pharmacokinetic samples were collected up to 72 hours postdosing.

FINDINGS

The crushed and ground tablets met the bioequivalence criteria (0.80-1.25) relative to the intact tablets with respect to area under the concentration-time curve to time of the last measurable concentration (AUCt) and to infinite time (AUCinf) but exhibited a slightly lower maximum plasma concentration (Cmax). This was not considered clinically significant as only venetoclax overall exposure (AUC) has been shown to correlate with clinical efficacy. There was no change in the physical appearance and the evaluated physicochemical properties of crushed and ground venetoclax tablets after 72 hours of storage at 25°C/60% relative humidity.

IMPLICATIONS

Crushing or grinding venetoclax tablets before administration could be considered as a viable alternative method of administration for patients who have difficulty swallowing whole venetoclax tablets or patients requiring nasogastric tube feeding.

CLINICALTRIALS

GOV IDENTIFIERS

NCT05909553, registered June 12, 2023.

Clinical pharmacokinetics and pharmacodynamics of venetoclax, a selective B-cell lymphoma-2 inhibitor

Venetoclax, a highly potent BCL-2 inhibitor, is indicated for treatment of some hematologic malignancies as monotherapy, and/or in combination with other agents. Venetoclax pharmacokinetics has been extensively characterized in patients and healthy participants. After oral dosing, the median time to reach maximum plasma concentration ranged from 5 to 8 h and harmonic mean half-life ranged from 14 to 18 h. Food increases venetoclax bioavailability by 3-5-fold and venetoclax should be administered with food to ensure adequate and consistent bioavailability. Venetoclax is eliminated via cytochrome P450 (CYP)3A metabolism, and a negligible amount of unchanged drug is excreted in urine. Strong CYP3A/P-glycoprotein inhibitors increased venetoclax exposures (AUC) by 1.44- to 6.90-fold while a significant decrease (71%) has been observed when dosed with strong CYP3 inducers. Venetoclax does not inhibit or induce CYP enzymes or transporters. Venetoclax pharmacokinetics is not appreciably altered by age, weight, sex, but the exposure is up to twofold higher in participants from Asian countries. Mild-to-severe renal impairment or end-stage renal disease do not alter venetoclax exposures, and venetoclax is not cleared by dialysis. Although mild-to-moderate hepatic impairment does not affect venetoclax exposures, twofold higher exposure was observed in subjects with severe hepatic impairment. Venetoclax exposure is comparable across patients with different hematologic malignancies and healthy participants. Overall, venetoclax exposure is only affected by food and CYP3A modulators and is only higher in Asian subjects and subjects with severe hepatic impairment. Venetoclax exposure-response relationships are malignancy-dependent and can be different between monotherapy and combination therapy.

Venetoclax-Related Neutropenia in Leukemic Patients: A Comprehensive Review of the Underlying Causes, Risk Factors, and Management

Venetoclax is a Bcl-2 homology domain 3 (BH3) mimetic currently approved for the treatment of chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML) that has proven to be highly effective in reinstating apoptosis in leukemic cells through the highly selective inhibition of the anti-apoptotic protein B-cell lymphoma-2 (Bcl-2). Clinically, venetoclax has provided lasting remissions through the inhibition of CLL and AML blasts. However, this activity has often come at the cost of grade III/IV neutropenia due to hematopoietic cells' dependence on Bcl-2 for survival. As life-threatening infections are an important complication in these patients, an effective management of neutropenia is indispensable to maximize patient outcomes. While there is general consensus over dose reduction and scheduling modifications to minimize the risk of neutropenia, the impact of these modifications on survival is uncertain. Moreover, guidelines do not yet adequately account for patient-specific and disease-specific risk factors that may predict toxicity, or the role combination treatment plays in exacerbating neutropenia. The objective of this review is to discuss the venetoclax-induced mechanism of hematological toxicity, the potential predictive risk factors that affect patient vulnerability to neutropenia, and the current consensus on practices for management of neutropenia.

Plasma Venetoclax Concentrations in Patients with Acute Myeloid Leukemia Treated with CYP3A4 Inhibitors

Venetoclax (VEN) is used in patients with acute myeloid leukemia (AML) and is primarily metabolized by CYP3A4, a major drug-metabolizing enzyme. Patients with AML simultaneously administered VEN and CYP3A4 inhibitors require a more appropriate management of drug-drug interactions (DDIs). Here, we report two cases of patients with AML (54-year-old man and 22-year-old woman) administrated VEN and CYP3A4 inhibitors, such as posaconazole, cyclosporine, or danazol. In the first case, we evaluated the appropriateness of timing for adjusting VEN dosage subsequent to the cessation of posaconazole. Consequently, modifying the VEN dosage in conjunction with the cessation of Posaconazole simultaneously may result in elevated plasma VEN levels. In the second case, plasma VEN concentrations were markedly elevated when co-administered with several CYP3A4 inhibitors. Additionally, in vitro assays were conducted for reverse translational studies to analyze CYP3A4 inhibition. CYP3A4 inhibition by combinatorial administration of cyclosporine A and danazol was demonstrated in vitro, which potentially explains the increasing plasma VEN concentrations observed in clinical settings. Although the acquisition of therapeutic effects is a major priority for patients, frequent therapeutic drug monitoring and dosage adjustments considering DDIs would be important factors in chemotherapy.

Venetoclax dose adjustment due to drug-drug interactions: a case report and literature review

The primary aim of the study is to discuss the potential interactions between venetoclax and common drugs used in department of hematology and the corresponding effects on the efficacy and safety of venetoclax treatment. Here, we report an acute myeloid leukemia patient treated with venetoclax and posaconazole, and the dose of venetoclax was adjusted due to drug interactions. Clinical pharmacists actively participated in treatment of this patient to provide pharmacy care to assist clinicians to identify the venetoclax-induced liver function impairment and give timely management. The case reported here is hoped to provide reference for clinical venetoclax treatment in patients with such disease. Clinical pharmacists should actively participate in clinical treatment, actively screen potential drug interactions, strengthen cooperation and communication with doctors, provide patients with high-quality pharmaceutical services, and establish clinical pharmacists' status in the multidisciplinary treatment of tumor.

LC-MS/MS methods for determination of venetoclax in human plasma and cerebrospinal fluid

We developed and validated sensitive MS/MS methods for the determination of venetoclax, an oral selective B-cell lymphoma-2 inhibitor, in human plasma and cerebrospinal fluid (CSF). Acetonitrile was used as protein precipitant. The mobile phase was 10 mM ammonium formate consisting of 0.1% formic acid and acetonitrile (40:60, v/v). The analytes were separated on an ACQUITY UPLC HSS T3 column (2.1 × 50 mm, 1.8 μm) in 5 min. An API 4000 mass spectrometer was selected to quantify venetoclax and internal standard using m/z 868.3 → 636.3 and 876.3 → 644.3 under multiple response monitoring mode. In plasma, the calibration curve exhibited good linearity ranging from 20.0 to 5000 ng/mL, whereas in the CSF, the linear range was 0.500-100 ng/mL. The matrix effect of venetoclax and internal standard (venetoclax-d8) was not obvious in both plasma and CSF. The inter- and intra-run accuracy was within ±11.9%, and the inter- and intra-run precision was below 13.6%. Both methods had no carryover, and the recovery was close to 100%. The validated methods were employed to quantify the concentrations of venetoclax in the plasma and CSF of patients diagnosed with chronic lymphocytic leukemia or acute myelogenous leukemia.

Low dose venetoclax plus itraconazole outpatient induction in newly diagnosed acute myeloid leukemia: A phase 2 study

Data concerning venetoclax and azacitidine (Ven/Aza) as first-line therapy for newly diagnosed acute myeloid leukemia (ND-AML) in candidates for intensive chemotherapy are limited, and outpatient induction regimens in ND-AML have been poorly explored. The enzyme CYP3A4 metabolizes Venetoclax. Conversely, itraconazole is a strong CYP3A4 inhibitor; thus, it produces a 75 % reduction in the dose and cost of venetoclax. This phase 2 trial assessed the feasibility, safety, and efficacy of outpatient induction with venetoclax 100 mg daily from days 1-21, itraconazole 100 mg twice daily from days 1-21, and azacytidine 100 mg subcutaneously, once daily from days 1-7. Fifteen adults with ND-AML were enrolled. The median age was 53 (range 25-73) and twelve (80 %) were considered candidates for intensive chemotherapy. Nine (60 %) subjects started treatment as outpatients,. The first treatment cycle completion in the outpatient setting was achieved in 77.7 %. Early 14-day, 30-day, and 60-day mortality rates were 6.7 %, 13.3 %, and 13.3 %, respectively. Composite CR/CRi after the first and second treatment cycles were 53.9 % and 85.7 %, respectively. Common adverse events included hematological and gastrointestinal toxicities. Outpatient induction with low-dose venetoclax plus itraconazole is feasible, safe, and has acceptable preliminary efficacy in ND-AML patients. This trial was registered in www.clinicaltrials.gov as #NCT05048615.

Application of physiologically based pharmacokinetics modeling in the research of small-molecule targeted anti-cancer drugs

INTRODUCTION

Physiologically based pharmacokinetics (PBPK) models are increasingly used in the drug research and development, especially in anti-cancer drugs. Between 2001 and 2020, a total of 89 small-molecule targeted antitumor drugs were approved in China and the United States, some of which already included PBPK modeling in their application or approval packages. This article intended to review the prevalence and application of PBPK model in these drugs.

METHOD

Article search was performed in the PubMed to collect English research articles on small-molecule targeted anti-cancer drugs using PBPK modeling. The selected articles were classified into nine categorizes according to the application areas and further analyzed.

RESULT

From 2001 to 2020, more than 60% of small-molecule targeted anti-cancer drugs (54/89) were studied using PBPK model with a wide range of application. Ninety research articles were included, of which 48 involved enzyme-mediated drug-drug interaction (DDI). Of these retrieved articles, Simcyp, GastroPlus, and PK-Sim were the most widely model building platforms, which account for 63.8%, 15.2%, and 8.6%, respectively.

CONCLUSION

PBPK modeling is commonly and widely used to research small-molecule targeted anti-cancer drugs.

Assessment of Drug-Drug Interaction Risk Between Intravenous Fentanyl and the Glecaprevir/Pibrentasvir Combination Regimen in Hepatitis C Patients Using Physiologically Based Pharmacokinetic Modeling and Simulations

INTRODUCTION

An unsafe injection practice is one of the major contributors to new hepatitis C virus (HCV) infections; thus, people who inject drugs are a key population to prioritize to achieve HCV elimination. The introduction of highly effective and well-tolerated pangenotypic direct-acting antivirals, including glecaprevir/pibrentasvir (GLE/PIB), has revolutionized the HCV treatment landscape. Glecaprevir is a weak cytochrome P450 3A4 (CYP3A4) inhibitor, so there is the potential for drug-drug interactions (DDIs) with some opioids metabolized by CYP3A4, such as fentanyl. This study estimated the impact of GLE/PIB on the pharmacokinetics of intravenous fentanyl by building a physiologically based pharmacokinetic (PBPK) model.

METHODS

A PBPK model was developed for intravenous fentanyl by incorporating published information on fentanyl metabolism, distribution, and elimination in healthy individuals. Three clinical DDI studies were used to verify DDIs within the fentanyl PBPK model. This model was integrated with a previously developed GLE/PIB PBPK model. After model validation, DDI simulations were conducted by coadministering GLE 300 mg + PIB 120 mg with a single dose of intravenous fentanyl (0.5 µg/kg).

RESULTS

The predicted maximum plasma concentration ratio between GLE/PIB + fentanyl and fentanyl alone was 1.00, and the predicted area under the curve ratio was 1.04, suggesting an increase of only 4% in fentanyl exposure.

CONCLUSION

The administration of a therapeutic dose of GLE/PIB has very little effect on the pharmacokinetics of intravenous fentanyl. This negligible increase would not be expected to increase the risk of fentanyl overdose beyond the inherent risks related to the amount and purity of the fentanyl received during recreational use.

Impact of Multiple Concomitant CYP3A Inhibitors on Venetoclax Pharmacokinetics: A PBPK and Population PK-Informed Analysis

Venetoclax is an approved, orally bioavailable, B-cell lymphoma type 2 (BCL-2) inhibitor that is primarily metabolized by cytochrome P450 3A (CYP3A). Polypharmacy is common in patients undergoing treatment for hematological malignancies such as acute myeloid leukemia or chronic lymphocytic leukemia, and although venetoclax exposure has been well characterized with 1 concomitant CYP3A inhibitor, complex drug-drug interactions (DDIs) involving more than 1 inhibitor have not been systematically evaluated. Here, we aimed to describe the potential impact of multiple concomitant CYP3A inhibitors on venetoclax pharmacokinetics (PK) using physiologically based pharmacokinetic (PBPK) and population PK modeling. The modeling approaches were informed by clinical data in the presence of single or multiple CYP3A inhibitors, and the effects of 1 or more inhibitors were systematically considered within these modeling frameworks. The PBPK modeling approach was independently validated against clinical data involving more than 1 CYP3A inhibitor along with CYP3A substrates other than venetoclax. Both approaches indicated that combining a strong CYP3A inhibitor with another competitive CYP3A inhibitor does not seem to result in any additional increase in venetoclax exposure, beyond what would be expected with a strong inhibitor alone. This suggests that the current dose reductions recommended for venetoclax would be appropriate even when 2 or more CYP3A inhibitors are taken concomitantly. However, the results indicate that the involvement of time-dependent inhibition might lead to additional inhibitory effects over and above the effect of a single strong CYP3A inhibitor. Thus, the clinical management of such interactions must consider the underlying mechanism of the interactions.

Retrospective, real‐life study of venetoclax plus azacitidine or low‐dose cytarabine in French patients with acute myeloid leukemia ineligible for intensive chemotherapy

BACKGROUND

Recently, the combination of venetoclax plus a hypomethylating agent (HMA; azacitidine ordecitabine) or low-dose cytarabine (LDAC) showed promise in Phase III trials in previously untreated AML. In France at the time of this study, venetoclax was not yet approved for AML and there were therefore no formal usage recommendations. Here we report the first study in a French cohort that assessed venetoclax in combination with existing treatments for AML under real-life conditions.

METHOD

This retrospective, real-life study collected data on venetoclax use and management in a French cohort with acute myeloid leukemia (AML) ineligible for intensive chemotherapy.

RESULT

Of 118 patients, 81 were in second line/beyond (71.6% also hypomethylating agent [HMA]; 23.5% lowdose cytarabine [LDAC]) and 37 in first line. For venetoclax initiation, 57.3% underwent ramp up and 74.6% were hospitalized. Median venetoclax duration was 2.5 months (range 0.03-16.2). With all treatment lines and regimens, most common grade 3/4 adverse events were hematologic (overall 96.4% of patients) and infections (57.1%). Dosage adjustments for drug interactions and safety varied between centers. In second-line/beyond, median progression-free survival was 4.0 months (95% confidence interval [CI] 2.7-12.8) with venetoclax-HMA and 3.4 months (1.3-8.9) with venetoclax-LDAC; overall response rate was 51.9% and 41.2%, respectively. Thus, we showed that venetoclax-based treatment yields promising findings in patients with AML, but to address treatment complexity, practice harmonization is needed.

The successful combination of grapefruit juice and venetoclax in an unfit acute myeloid leukemia patient with adverse risk: A case report

Venetoclax combined with hypomethylating agents such as azacitidine and decitabine is the standard regime for the elderly patient with acute myeloid leukemia (AML) unfit for intensive induction therapy. However, many patients struggle with finances and forgo treatments due to the high costs of venetoclax. In this study, we performed the regime with azacitidine, low-dose venetoclax, and grapefruit juice on an unfit AML patient with TP53 mutation. The peak venetoclax concentration (Cmax) and side effects on the patient were also monitored. The patient achieved complete remission with the venetoclax Cmax within the effective concentration range (1,000–3,000 ng/ml) and maintained durable remission until recently. Febrile neutropenia, thrombocytopenia, and pneumonia appeared during the first cycle and were recovered by stimulating agents and antibiotic treatment. This improvement combination approach by drug-food interaction may enlighten other similarly patients with AML, especially those in low-middle income countries.

Development of Physiology Based Pharmacokinetic Model to Predict the Drug Interactions of Voriconazole and Venetoclax

PURPOSE

Venetoclax (VEN), an anti-tumor drug that is a substrate of cytochrome P450 3A enzyme (CYP3A4), is used to treat leukemia. Voriconazole (VCZ) is an antifungal medication that inhibits CYP3A4. The goal of this study is to predict the effect of VCZ on VEN exposure.

METHOD

Two physiological based pharmacokinetics (PBPK) models were developed for VCZ and VEN using the bottom-up and top-down method. VCZ model was also developed to describe the effect of CYP2C19 polymorphism on its pharmacokinetics (PK). The reversible inhibition constant (Ki) of VCZ for CYP3A4 was calibrated using drug-drug interaction (DDI) data of midazolam and VCZ. The clinical verified VCZ and VEN model were used to predict the DDI of VCZ and VEN at clinical dosing scenario.

RESULT

VCZ model predicted VCZ exposure in the subjects of different CYP2C19 genotype and DDI related fold changes of sensitive CYP3A substrate with acceptable prediction error. VEN model can capture PK of VEN with acceptable prediction error. The DDI PBPK model predicted that VCZ increased the exposure of VEN by 4.5-9.6 fold. The increase in VEN exposure by VCZ was influenced by subject's CYP2C19 genotype. According to the therapeutic window, VEN dose should be reduced to 100 mg when co-administered with VCZ.

CONCLUSION

The PBPK model developed here could support individual dose adjustment of VEN and DDI risk assessment. Predictions using the robust PBPK model confirmed that the 100 mg dose adjustment is still applicable in the presence of VCZ with high inter-individual viability.

Pharmacokinetics and Exposure-Response Analysis of Venetoclax + Obinutuzumab in Chronic Lymphocytic Leukemia: Phase 1b Study and Phase 3 CLL14 Trial

INTRODUCTION

This study aims to investigate pharmacokinetics (PK) and exposure-response parameters of the 400 mg once-daily venetoclax dose regimen in combination with obinutuzumab, which was approved for the first-line (1L) treatment of chronic lymphocytic leukemia (CLL) based on data from the phase 3 CLL14 study and the phase 1b dose-finding GP28331 study.

METHODS

Parameter estimates and uncertainty, which were estimated by a previously developed population PK (popPK) model, were used as informative priors for this analysis. They were re-estimated, and then used to evaluate additional covariate effects, describe venetoclax PK when administered with obinutuzumab, and provide empirical Bayes estimates of PK parameters and exposure. Exposure-progression-free survival (PFS) and exposure-safety relationships were assessed using data from CLL14, with steady-state nominal venetoclax exposure (C_{meanSS,nominal}) as the predictor variable. Exposure-safety analyses were conducted using logistic regression for selected treatment-emergent grade ≥ 3 adverse events (AEs) and serious AEs (SAEs). Dose intensities were summarized by tertiles of C_{meanSS,nominal}.

RESULTS

PK data from 274 patients (CLL14, n = 194; GP28331, n = 80) were included. The final model provided good fit of the observed data. Obinutuzumab co-administration, history of prior treatments, and disease severity at baseline had no appreciable influence on venetoclax steady-state exposure. No significant correlations were observed between venetoclax exposure and PFS, or between venetoclax exposure and the probability of treatment-emergent grade ≥ 3 neutropenia, grade ≥ 3 thrombocytopenia, grade ≥ 3 infections, and SAEs. Median dose intensities for venetoclax and obinutuzumab remained similar across venetoclax exposure tertiles.

CONCLUSION

PopPK and exposure-efficacy, exposure-safety, and exposure-tolerability analyses support the 400 mg once-daily venetoclax dose plus obinutuzumab for 1L treatment in patients with CLL.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifiers NCT02242942 and NCT02339181.

How do we manage t(11;14) plasma cell disorders with venetoclax?

The oral BCL-2 inhibitor venetoclax has demonstrated promising efficacy in patients with t(11;14) plasma cell disorders, both as a single-agent and in combination. However, there was an increased mortality signal in the randomized BELLINI trial that was primarily driven by non-t(11;14) patients. Based on current evidence, venetoclax is included as an option for relapsed/refractory t(11;14) plasma cell dyscrasias in NCCN guidelines and is being widely used in clinical practice. In this review, we aim to critically appraise the current literature and perform case-based illustration of our approach to management of t(11;14) plasma cell disorders with venetoclax.

Quantification of Venetoclax for Therapeutic Drug Monitoring in Chinese Acute Myeloid Leukemia Patients by a Validated UPLC-MS/MS Method

Venetoclax has emerged as a breakthrough for treatment of leukemia with a wide interindividual variability in pharmacokinetics. Herein, a rapid, sensitive, and reliable UPLC-MS/MS method for quantification of venetoclax in plasma was developed and validated. The method was operated in the multiple-reaction monitoring (MRM) mode to detect venetoclax at m/z transition 868.5 > 321.0 and IS at 875.5 > 321.0, respectively. Protein precipitation prior to injection into the LC-MS/MS and the analyte was separated on an ACQUITY UPLC BEH C18 column by gradient elution with acetonitrile and 0.1% formic acid in water. Linear calibration curves were obtained in the range of 25−8000 ng/mL. The specificity, recovery, matrix effect, and stability also met the acceptance criteria of FDA guidance. The method was successfully applied to analyze plasma in acute myeloid leukemia (AML) patients. The peak plasma concentration (Cmax) of venetoclax in Chinese AML patient was 2966.0 ± 1595.0 ng/mL while the trough concentration (Cmin) was 1018.0 ± 729.4 ng/mL. Additionally, Cmax and Cmin showed a positive correlation with AST levels. Furthermore, Cmax was significantly higher in the older patients. The present method can be applied for TDM of venetoclax in treatment of hematological cancers.

Predicting the Drug-Drug Interaction Mediated by CYP3A4 Inhibition: Method Development and Performance Evaluation

The prediction of drug-drug interactions (DDIs) plays critical roles for the estimation of DDI risk caused by inhibition of CYP3A4. The aim of this paper is to develop a physiologically based pharmacokinetic (PBPK)-DDI model for prediction of the DDI co-administrated with ketoconazole in humans and evaluate the predictive performance of the model. The pharmacokinetic and biopharmaceutical properties of 35 approved drugs, as victims, were collected for the development of a PBPK model, which were linked to the PBPK model of ketoconazole for the DDI prediction. The PBPK model of victims and ketoconazole were validated by matching actual in vivo pharmacokinetic data. The predicted results of DDI were compared with actual data to evaluate the predictive performance. The percentage of predicted ratio of AUC (AUCR), C_max (C_maxR), and T_max (T_maxR) was 75%, 69%, and 91%, respectively, which were within the twofold threshold (range, 0.5-2.0×) of the observed values. Only 3% of the predicted AUCRs are obviously underestimated. After integration of the reported fraction of metabolism (f_m) into the PBPK-DDI model for limited four cases, the model-predicted AUCRs were improved from the twofold range of the observed AUCRs to the 90% confidence interval. The developed method could reasonably predict drug-drug interaction with a low risk of underestimation. The present accuracy of the prediction was improved compared with that of static mechanistic models. The evaluation of predictive performance increases the confidence using the model to evaluate the risk of DDIs co-administrated with ketoconazole before the in vivo DDI study.

Analysis of physicochemical properties of protein-protein interaction modulators suggests stronger alignment with the "rule of five"

Despite the important roles played by protein-protein interactions (PPIs) in disease, they have been long considered as 'undruggable'. However, recent advances have suggested that PPIs are druggable but may not follow conventional rules of 'drug ability'. Here we explore which physicochemical parameters are essential for a PPI modulator to be a clinical drug by analysing the physicochemical properties of small-molecule PPI modulators in the market, in clinical trials, and published. Our analysis reveals that those compounds currently on the market have a larger range of values for most of the physicochemical parameters, whereas those in clinical trials fit much more stringently to standard drug-like parameters. This observation was particularly true for molecular weight, clog P and topological polar surface area, where aside from a few outliers, most of the compounds in clinical trials fit within standard drug-like parameters. This implies that the newer PPI modulators are more drug-like than those currently on the market, suggesting that designing new PPI-specific screening libraries should remain within standard drug-like parameters in order to obtain a clinical candidate. Taken together, our analysis has important implications for designing future drug discovery campaigns aimed at targeting PPIs.

When to change treatment of acute invasive aspergillosis: an expert viewpoint

Invasive aspergillosis (IA) is an acute infection affecting patients who are immunocompromised, as a result of receiving chemotherapy for malignancy, or immunosuppressant agents for transplantation or autoimmune disease. Whilst criteria exist to define the probability of infection for clinical trials, there is little evidence in the literature or clinical guidelines on when to change antifungal treatment in patients who are receiving prophylaxis or treatment for IA. To try and address this significant gap, an advisory board of experts was convened to develop criteria for the management of IA for use in designing clinical trials, which could also be used in clinical practice. For primary treatment failure, a change in antifungal therapy should be made: (i) when mycological susceptibility testing identifies an organism from a confirmed site of infection, which is resistant to the antifungal given for primary therapy, or a resistance mutation is identified by molecular testing; (ii) at, or after, 8 days of primary antifungal treatment if there is increasing serum galactomannan, or galactomannan positivity in serum, or bronchoalveolar lavage fluid when the antigen was previously undetectable, or there is sudden clinical deterioration, or a new clearly distinct site of infection is detected; and (iii) at, or after, 15 days of primary antifungal treatment if the patient is clinically stable but with ≥2 serum galactomannan measurements persistently elevated compared with baseline or increasing, or if the original lesions on CT or other imaging, show progression by >25% in size in the context of no apparent change in immune status.

A microdosing framework for absolute bioavailability assessment of poorly soluble drugs: A case study on cold-labeled venetoclax, from chemistry to the clinic

This work presents an end‐to‐end approach for assessing the absolute bioavailability of highly hydrophobic, poorly water‐soluble compounds that exhibit high nonspecific binding using venetoclax as a model drug. The approach utilizes a stable labeled i.v. microdose and requires fewer resources compared with traditional approaches that use radioactive ¹⁴C‐labeled compounds. The stable labeled venetoclax and internal standard were synthesized, then an i.v. formulation was developed. In the clinical study, female subjects received a single oral dose of venetoclax 100 mg followed by a 100‐µg i.v. dose of cold‐labeled ¹³C‐venetoclax at the oral time of maximum concentration (T_max). The i.v. microdose was prepared as an extemporaneous, sterile compounded solution on the dosing day by pharmacists at the clinical site. Several measures were taken to ensure the sterility and safety of the i.v. preparation. A sensitive liquid chromatography‐tandem mass spectrometry method was developed to allow the detection of plasma levels from the i.v. microdose. Plasma samples were collected through 72 h, and pharmacokinetic parameters were estimated using noncompartmental methods. Postdosing sample analysis demonstrated the consistency of the preparations and allowed the precise calculation of the pharmacokinetic parameters based on the actual injected dose. The absolute bioavailability of venetoclax was estimated at 5.4% under fasting conditions. Venetoclax extraction ratio was estimated to be 0.06 suggesting that the fraction transferred from the enterocytes into the liver is limiting venetoclax bioavailability. The proposed framework can be applied to other highly hydrophobic, poorly water‐soluble compounds that exhibit high nonspecific binding to support the understanding of their absorption and disposition mechanisms and guide formulation development.

Assessment of Vedolizumab Disease-Drug-Drug Interaction Potential in Patients With Inflammatory Bowel Diseases

Disease-drug-drug interactions (DDDIs) have been identified in some inflammatory diseases in which elevated proinflammatory cytokines can downregulate the expression of cytochrome P450 (CYP) enzymes, potentially increasing systemic exposure to drugs metabolized by CYPs. Following anti-inflammatory treatments, CYP expression may return to normal, resulting in reduced drug exposure and diminished clinical efficacy. Vedolizumab has a well-established positive benefit-risk profile in patients with ulcerative colitis (UC) or Crohn's disease (CD) and has no known systemic immunosuppressive activity. A stepwise assessment was conducted to evaluate the DDDI potential of vedolizumab to impact exposure to drugs metabolized by CYP3A through cytokine modulation. First, a review of published data revealed that patients with UC or CD have elevated cytokine concentrations relative to healthy subjects; however, these concentrations remained below those reported to impact CYP expression. Exposure to drugs metabolized via CYP3A also appeared comparable between patients and healthy subjects. Second, serum samples from patients with UC or CD who received vedolizumab for 52 weeks were analyzed and compared with healthy subjects. Cytokine concentrations and the 4β-hydroxycholesterol-to-cholesterol ratio, an endogenous CYP3A4 biomarker, were comparable between healthy subjects and patients both before and during vedolizumab treatment. Finally, a medical review of postmarketing DDDI cases related to vedolizumab from the past 6 years was conducted and did not show evidence of any true DDDIs. Our study demonstrated the lack of clinically meaningful effects of disease or vedolizumab treatment on the exposure to drugs metabolized via CYP3A through cytokine modulation in patients with UC or CD.

Mechanistic physiology-based pharmacokinetic modeling to elucidate vincristine-induced peripheral neuropathy following treatment with novel kinase inhibitors

Purpose

Limited information is available regarding the drug–drug interaction (DDI) potential of molecular targeted agents and rituximab plus cyclophosphamide, doxorubicin (hydroxydaunorubicin), vincristine (Oncovin), and prednisone (R-CHOP) therapy. The addition of the Bruton tyrosine kinase (BTK) inhibitor ibrutinib to R-CHOP therapy results in increased toxicity versus R-CHOP alone, including higher incidence of peripheral neuropathy. Vincristine is a substrate of P-glycoprotein (P-gp, ABCB1); drugs that inhibit P-gp could potentially cause increased toxicity when co-administered with vincristine through DDI. While the combination of the BTK inhibitor acalabrutinib and R-CHOP is being explored clinically, the DDI potential between these therapies is unknown.

Methods

A human mechanistic physiology-based pharmacokinetic (PBPK) model of vincristine following intravenous dosing was developed to predict potential DDI interactions with combination therapy. In vitro absorption, distribution, metabolism, and excretion and in vivo clinical PK parameters informed PBPK model development, which was verified by comparing simulated vincristine concentrations with observed clinical data.

Results

While simulations suggested no DDI between vincristine and ibrutinib or acalabrutinib in plasma, simulated vincristine exposure in muscle tissue was increased in the presence of ibrutinib but not acalabrutinib. Extrapolation of the vincristine mechanistic PBPK model to other P-gp substrates further suggested DDI risk when ibrutinib (area under the concentration–time curve [AUC] ratio: 1.8), but not acalabrutinib (AUC ratio: 0.92), was given orally with venetoclax or digoxin.

Conclusion

Overall, these data suggest low DDI risk between acalabrutinib and P-gp substrates with negligible increase in the potential risk of vincristine-induced peripheral neuropathy when acalabrutinib is added to R-CHOP therapy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-021-04302-5.

PBPK modeling to predict drug-drug interactions of ivosidenib as a perpetrator in cancer patients and qualification of the Simcyp platform for CYP3A4 induction

Ivosidenib is a potent, targeted, orally active, small-molecule inhibitor of mutant isocitrate dehydrogenase 1 (IDH1) that has been approved in the United States for the treatment of adults with newly diagnosed acute myeloid leukemia (AML) who are greater than or equal to 75 years of age or ineligible for intensive chemotherapy, and those with relapsed or refractory AML, with a susceptible IDH1 mutation. Ivosidenib is an inducer of the CYP2B6, CYP2C8, CYP2C9, and CYP3A4 and an inhibitor of P-glycoprotein (P-gp), organic anion transporting polypeptide-1B1/1B3 (OATP1B1/1B3), and organic anion transporter-3 (OAT3) in vitro. A physiologically-based pharmacokinetic (PK) model was developed to predict drug-drug interactions (DDIs) of ivosidenib in patients with AML. The in vivo CYP3A4 induction effect of ivosidenib was quantified using 4β-hydroxycholesterol and was subsequently verified with the PK data from an ivosidenib and venetoclax combination study. The verified model was prospectively applied to assess the effect of multiple doses of ivosidenib on a sensitive CYP3A4 substrate, midazolam. The simulated midazolam geometric mean area under the curve (AUC) and maximum plasma concentration (C_max ) ratios were 0.18 and 0.27, respectively, suggesting ivosidenib is a strong inducer. The model was also used to predict the DDIs of ivosidenib with CYP2B6, CYP2C8, CYP2C9, P-gp, OATP1B1/1B3, and OAT3 substrates. The AUC ratios following multiple doses of ivosidenib and a single dose of CYP2B6 (bupropion), CYP2C8 (repaglinide), CYP2C9 (warfarin), P-gp (digoxin), OATP1B1/1B3 (rosuvastatin), and OAT3 (methotrexate) substrates were 0.90, 0.52, 0.84, 1.01, 1.02, and 1.27, respectively. Finally, in accordance with regulatory guidelines, the Simcyp modeling platform was qualified to predict CYP3A4 induction using known inducers and sensitive substrates.

Venetoclax for the treatment of elderly or chemotherapy-ineligible patients with acute myeloid leukemia: a step in the right direction or a game changer?

INTRODUCTION

Acute myeloid leukemia (AML) is an aggressive malignancy with poor prognosis and high rates of relapse, especially in elderly patients who are ineligible to receive intensive chemotherapy. Venetoclax, an oral BCL-2 inhibitor, is approved by the Food and Drug Administration in combination with hypomethylating agents or low-dose cytarabine in newly-diagnosed AML patients who are ineligible to receive intensive chemotherapy. Confirmatory phase III VIALE-A and VIALE-C trials showed a composite complete remission rate of 66.4% and 48%, respectively. Thus, further validating venetoclax as an attractive therapeutic option in the AML treatment landscape.

AREAS COVERED

A review of venetoclax in AML, focusing on preclinical and clinical data, toxicity profile, and mechanisms of resistance; and its strengths and weaknesses in regards to its current and future role in AML treatment is discussed. To find relevant studies, authors searched PubMed/Medline and ClinicalTrials.gov.

EXPERT OPINION

The introduction of venetoclax-based combination therapies has greatly expanded the therapeutic options for elderly and chemotherapy-ineligible AML patients. Additional studies with extended follow-up are necessary to address remaining open questions such as (I) durability of responses, (II) head-to-head comparisons with intensive chemotherapy in selected patients (e.g. TP53 mutations), and (III) novel triplet combinations using an HMA-venetoclax backbone.

Dose adjustment of venetoclax when co-administered with posaconazole: clinical drug-drug interaction predictions using a PBPK approach

PURPOSE

Venetoclax, a targeted anticancer agent approved for the treatment of chronic lymphocytic leukemia and acute myeloid leukemia, is a substrate of cytochrome P450 (CYP) 3A enzyme (CYP3A4). Posaconazole, commonly used to prevent invasive fungal infections in neutropenic patients with hematological malignancies, potently inhibits CYP3A4. The purpose of this evaluation was to predict venetoclax exposures following co-administration of posaconazole at doses not previously studied clinically.

METHODS

Two physiologically based pharmacokinetic (PBPK) models were developed for posaconazole based on published parameters, one for an oral suspension and another for delayed released tablets. Parameter optimization, guided by sensitivity analyses, was conducted such that the models could replicate clinical exposures of posaconazole and drug-drug interactions with sensitive CYP3A substrates including venetoclax. The clinically verified posaconazole PBPK models were then utilized to predict DDI with a previously published venetoclax PBPK model at clinically relevant dosing scenarios.

RESULTS

The posaconazole PBPK models predicted posaconazole exposure and DDI related fold changes with acceptable prediction errors for both posaconazole formulations. The model predicted exposures of venetoclax, when co-administered with a 300 mg QD dose of delayed release tablets of posaconazole, were in concordance with observed data. Increasing the posaconazole dose to 500 mg QD increased venetoclax exposures by about 12% relative to 300 mg QD, which were still within the venetoclax safe exposure range.

CONCLUSIONS

The posaconazole PBPK models were developed and clinically verified. Predictions using the robust PBPK model confirmed the venetoclax label recommendation of 70 mg in the presence of posaconazole at doses up to 500 mg QD.

Venetoclax-Based Combinations in Acute Myeloid Leukemia: Current Evidence and Future Directions

The past decade has witnessed major advances in our understanding of molecular biology, which led to breakthrough novel therapies, importantly including the B-cell lymphoma-2 (BCL-2) inhibitor venetoclax. Notably, venetoclax-based combinations have improved outcomes, including both remission rates and overall survival, of older patients with acute myeloid leukemia (AML) deemed "unfit" for intensive chemotherapy due to age or comorbidities. This has translated into a rapid and widespread use of venetoclax-based combinations in both academic and community-based settings. Other venetoclax-based combinations are being investigated in AML with the ultimate goal of improving cure rates across many subgroups; frontline and relapsed/refractory, in combination with intensive chemotherapy, in the post-transplant setting, or as maintenance strategy. In this article, we summarize the current available data on venetoclax-based combinations. We also highlight areas of unmet medical need, and we offer practical clinical pearls for management of patients receiving such therapy.

Bayesian Population Model of the Pharmacokinetics of Venetoclax in Combination with Rituximab in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia: Results from the Phase III MURANO Study

BACKGROUND

Venetoclax is a selective B-cell lymphoma-2 (BCL-2) inhibitor approved for use as monotherapy or with rituximab in patients with chronic lymphocytic leukemia (CLL). The objectives of the current analysis of observed data from adult patients randomized to venetoclax-rituximab in the phase III MURANO study were to characterize venetoclax pharmacokinetics (PKs) using a Bayesian approach, evaluate whether a previously developed population PK model for venetoclax can describe the PKs of venetoclax when administered with rituximab, and to determine post hoc estimates of PK parameters for the exposure-response analysis.

METHODS

Parameter estimates and uncertainty estimated by a population PK model were used as priors. Additional covariate effects (CLL risk status, geographic region, and 17p deletion [del(17p)] status) were added to the model. The updated model was used to describe venetoclax PKs after repeated dosing in combination with rituximab, and to determine post hoc estimates of PK parameters for exposure-response analysis.

RESULTS

The PK analysis included 600 quantifiable venetoclax PK samples from 182 patients in the MURANO study. Model evaluation using standard diagnostic plots, visual predictive checks, and normalized prediction distribution error plots indicated no model deficiencies. There was no significant relationship between venetoclax apparent clearance (CL/F) and bodyweight, age, sex, mild and moderate hepatic and renal impairment, or coadministration of weak cytochrome P450 3A inhibitors. The chromosomal abnormality del(17p) and CLL risk status had no apparent effect on the PKs of venetoclax. A minimal increase in venetoclax CL/F (approximately 7%) was observed after coadministration with rituximab. CL/F was 30% lower in patients from Central and Eastern Europe (n = 60) or Asia (n = 4) compared with other regions (95% confidence interval [CI] 21-39%). Apparent central volume of distribution was 30% lower (95% CI 22-38%) in females (n = 56) compared with males (n = 126). No clinically significant impact of region or sex was observed on key safety and efficacy outcomes.

CONCLUSIONS

The Bayesian model successfully characterized venetoclax PKs over time and confirmed key covariates affecting PKs in the MURANO study. The model was deemed appropriate for further use in simulations and for generating individual patient PK parameters for subsequent exposure-response evaluation.

Pharmacokinetics of the BCL-2 Inhibitor Venetoclax in Subjects with Hepatic Impairment

INTRODUCTION

Venetoclax is a selective B cell lymphoma-2 inhibitor. It is approved for treatment of chronic lymphocytic leukemia and is being investigated for other hematological malignancies. Venetoclax is predominantly eliminated by the liver; therefore, there is a need to investigate the effect of hepatic insufficiency on venetoclax pharmacokinetics.

METHODS

A phase I study was carried out in 24 women with normal hepatic function or mild, moderate, or severe hepatic impairment (based on Child-Pugh scores), who received a single 50 mg dose of venetoclax with a low-fat meal. Blood samples were collected up to 120 h after venetoclax administration. Pharmacokinetic parameters were estimated using non-compartmental methods.

RESULTS

Venetoclax maximum observed plasma concentration (C_max) and area under the plasma concentration-time curve (AUC) in subjects with mild or moderate hepatic impairment were similar to subjects with normal hepatic function. Mean venetoclax AUC in subjects with severe hepatic impairment was 2.3- to 2.7-fold higher than in subjects with normal hepatic function. The half-life of venetoclax in subjects with severe hepatic impairment was approximately two-fold longer than in subjects with normal hepatic function and subjects with mild or moderate hepatic impairment. Unbound fractions of venetoclax in subjects with mild, moderate, and severe hepatic impairment were similar to the subjects with normal hepatic function. No significant adverse safety events were reported.

CONCLUSIONS

No venetoclax dosage adjustment is required in subjects with mild or moderate hepatic impairment. In subjects with severe hepatic impairment, a 50% dose reduction of venetoclax is recommended to account for higher exposures and the longer half-life.

Quantitative Assessment of Elagolix Enzyme-Transporter Interplay and Drug-Drug Interactions Using Physiologically Based Pharmacokinetic Modeling

INTRODUCTION

Elagolix is approved for the management of moderate-to-severe pain associated with endometriosis. The aim of this analysis was to develop a physiologically based pharmacokinetic (PBPK) model that describes the enzyme-transporter interplay involved in the disposition of elagolix and to predict the magnitude of drug-drug interaction (DDI) potential of elagolix as an inhibitor of P-glycoprotein (P-gp) and inducer of cytochrome P450 (CYP) 3A4.

METHODS

A PBPK model (SimCYP® version 15.0.86.0) was developed using elagolix data from in vitro, clinical PK and DDI studies. Data from DDI studies were used to quantify contributions of the uptake transporter organic anion transporting polypeptide (OATP) 1B1 and CYP3A4 in the disposition of elagolix, and to quantitatively assess the perpetrator potential of elagolix as a CYP3A4 inducer and P-gp inhibitor.

RESULTS

After accounting for the interplay between elagolix metabolism by CYP3A4 and uptake by OATP1B1, the model-predicted PK parameters of elagolix along with the DDI AUC∞ and Cmax ratios, were within 1.5-fold of the observed data. Based on model simulations, elagolix 200 mg administered twice daily is a moderate inducer of CYP3A4 (approximately 56% reduction in midazolam AUC∞). Simulations of elagolix 150 mg administered once daily with digoxin predicted an increase in digoxin Cmax and AUC∞ by 68% and 19%, respectively.

CONCLUSIONS

A PBPK model of elagolix was developed, verified, and applied to characterize the disposition interplay between CYP3A4 and OATP1B1, and to predict the DDI potential of elagolix as a perpetrator under dosing conditions that were not tested clinically. PBPK model-based predictions were used to support labeling language for DDI recommendations of elagolix.

How I manage CLL with venetoclax-based treatments

Targeted therapies for chronic lymphocytic leukemia (CLL) include venetoclax, the oral inhibitor of B-cell lymphoma-2, and inhibitors of kinases in the B-cell receptor signaling pathway, like Bruton tyrosine kinase and phosphatidylinositol 3 kinase. Randomized clinical trials clearly demonstrated improved progression-free survival with targeted therapy over chemoimmunotherapy in first-line and treatment of relapsed/refractory CLL. Comparative trials of venetoclax-based vs other targeted therapies have not been conducted. Differentiating features and considerations with targeted therapies include goals of treatment and therapeutic approach as well as side effect and toxicity profiles. With targeted therapy options for first-line and relapsed CLL, it is ever more important to develop sound rationale and strategy for selecting first-line and treatment of relapsed disease and for long-term management of the disease, including therapeutic sequencing. Fixed-duration therapy with a treatment-free remission is a particularly appealing prospect, since it avoids continuous exposure to treatment and potential for toxicity. We discuss rationale and practical application of venetoclax in first-line and treatment of relapsed and refractory CLL. Venetoclax is highly active at achieving deep remission for most treated patients with CLL, including those with high-risk disease such as del(17p) CLL.

Semimechanistic Modeling to Guide Venetoclax Coadministration with Ritonavir and Digoxin

Venetoclax is a cytochrome P450, family 3, subfamily A (CYP3A) substrate and was shown to inhibit P-gp efflux transporters in vitro. To quantify the impact of CYP3A inhibition by ritonavir on venetoclax disposition and P-gp inhibition by venetoclax on digoxin pharmacokinetics, two semimechanistic drug-drug interaction (DDI) models of venetoclax were developed using clinical data from healthy volunteers who received subtherapeutic doses of venetoclax with ritonavir 50-100 mg or digoxin 0.5 mg. These models were then used to assess the magnitude of interaction at therapeutic venetoclax doses and to explore various clinical dosing strategies that maintain venetoclax and digoxin concentrations within their respective therapeutic windows. Simulations demonstrated that venetoclax dose reductions of at least 75% are needed when venetoclax is coadministered with ritonavir and administering digoxin at least 2 hours before venetoclax would minimize DDI. Semimechanistic modeling leveraging clinical data is a plausible approach to predict DDI and propose dose adjustments, and administration time of interacting drugs.

The efficacy and safety of venetoclax therapy in elderly patients with relapsed, refractory chronic lymphocytic leukaemia

Elderly chronic lymphocytic leukaemia (CLL) patients treated outside of trials have notably greater toxicity with the Bruton's tyrosine kinase inhibitor ibrutinib compared to younger patients. It is not known whether the same holds true for the B-cell lymphoma 2 inhibitor venetoclax. We provide a comprehensive analysis of key safety measures and efficacy in 342 patients comparing age categories ≥75 and <75 years treated in the relapsed, refractory non-trial setting. We demonstrate that venetoclax has equivalent efficacy and safety in relapsed/refractory CLL patients who are elderly, the majority of whom are previous ibrutinib-exposed and therefore may otherwise have few clear therapeutic options.

Tumour lysis syndrome in patients with chronic lymphocytic leukaemia treated with BCL-2 inhibitors: risk factors, prophylaxis, and treatment recommendations

Tumour lysis syndrome is a complication of chemotherapy for haematological malignancies; in particular, aggressive leukaemias and lymphomas. For haematological malignancies, targeted therapies, such as small molecule inhibitors and monoclonal antibodies, have a high anti-tumour activity, are well tolerated, and have a low incidence of associated tumour lysis syndrome. The BCL-2 inhibitor venetoclax has a high anti-tumour activity in chronic lymphocytic leukaemia, achieving deep remissions by potently inducing apoptosis and increasing the risk for tumour lysis syndrome. In this Viewpoint, we discuss the pathophysiology, risk factors, monitoring, changes in laboratory parameters, and clinical manifestations of tumour lysis syndrome, and the prophylaxis and treatments available for this complication. Prophylaxis and treatment strategies have been implemented as standard of care in patients receiving venetoclax to minimise the risk of both laboratory and clinical manifestations of tumour lysis syndrome.

Model-Informed Dosing of Venetoclax in Healthy Subjects: An Exposure-Response Analysis

Venetoclax is an approved drug for the treatment of some hematological malignancies. Venetoclax can cause reduction in B-lymphocyte counts as an on-target effect. The purpose of this analysis is to quantify the relationship between venetoclax exposure and B-lymphocyte levels to inform dosing of venetoclax in healthy subjects. Data were pooled from 10 studies in healthy subjects with venetoclax doses ranging from 10 mg to 400 mg and food ranging from fasting to high-fat meals. Venetoclax pharmacokinetics (PK) was characterized in 203 subjects using a population approach, as implemented in NONMEM version 7.3 (Icon Development Solutions, Ellicott City, MD, USA). A semimechanistic pharmacodynamic (PD) model with a linear drug effect was fit to the B-lymphocyte data to determine the exposure-response relationship. The population PK and PD model described the observed data adequately. The 200 and 400 mg doses were shown to reduce the B-lymphocyte levels by 24% (15-35%) and 38% (25-54%), respectively. B-lymphocytes recovered to normal levels within an average of 48 (21-64) days and 59 (30-66) days, respectively, with 200 and 400 mg doses. Venetoclax can be safely administered in healthy subjects. The PK-PD model characterized the relationship between venetoclax exposure and reduction in B-lymphocytes and will help design future venetoclax studies in healthy subjects.

Optimizing venetoclax dose in combination with low intensive therapies in elderly patients with newly diagnosed acute myeloid leukemia: An exposure-response analysis

The objective of this research was to characterize the venetoclax exposure-efficacy and exposure-safety relationships and determine its optimal dose in elderly patients with newly diagnosed acute myeloid leukemia (AML) receiving venetoclax in combination with low intensity therapies (hypomethylating agent [HMA; azacitidine or decitabine] or low-dose cytarabine [LDAC]). A total of 212 patients from the HMA study and 92 patients from the LDAC study were included in the exposure-safety analyses. Those who received at least one dose of venetoclax and had at least one measurable response (201 and 83 in the HMA and LDAC studies, respectively) were included in the exposure-efficacy analyses. The probability of response based on International Working Group (IWG) for AML response criteria, adverse events of grade 3 or worse neutropenia or infection or a serious adverse event was modeled using logistic regression analyses to characterize the venetoclax exposure-response relationships. In combination with an HMA, increasing concentrations of venetoclax, up to those associated with a less than or equal to 400-mg once daily (QD) dose, were associated with a higher probability of response, with a trend for flat or decreasing probabilities of response thereafter. In combination with LDAC, increasing concentrations of venetoclax were associated with higher probabilities of response, with no plateau observed. Increasing concentrations of venetoclax were not associated with increasing probability of any safety event except for a slight increase in grade 3 or worse infections with HMAs; however, tolerability issues were observed at doses of greater than or equal to 800 mg QD in each study. Exposure-response analyses support the use of venetoclax 400 mg QD in combination with an HMA and 600 mg QD in combination with LDAC (ie, the next highest dose evaluated below 800 mg in each combination) to safely maximize the probability of response in elderly patients with newly diagnosed AML.

Physiologically Based Pharmacokinetic Modeling Suggests Limited Drug-Drug Interaction for Fesoterodine When Coadministered With Mirabegron

5-Hydroxymethyl tolterodine (5-HMT; the active fesoterodine metabolite) is metabolized via the cytochrome P450 (CYP) 2D6 and CYP3A pathways. Mirabegron is a moderate CYP2D6 inhibitor and weak CYP3A inhibitor. Potential drug-drug interactions (DDIs) following coadministration of these 2 overactive bladder treatments were estimated using physiologically based pharmacokinetic models, developed and verified by comparing predicted and observed pharmacokinetic profiles from clinical studies. Models predicted and verified mirabegron and desipramine (CYP2D6 substrate) and 5-HMT and ketoconazole (strong CYP3A inhibitor) DDIs. Mirabegron model-predicted mean steady-state AUC and C_max were within 11% of clinical observations. The predicted versus observed geometric mean ratio (GMR) of AUC_inf for CYP2D6 substrates desipramine and metoprolol coadministered with mirabegron 100 or 160 mg once daily were 3.47 versus 3.41 and 2.97 versus 3.29, respectively, indicating that the mirabegron model can be used to predict clinical CYP2D6 inhibition. 5-HMT fractional clearance by CYP3A and CYP2D6 was verified from clinical DDI studies with a potent CYP3A4 inhibitor (ketoconazole) and inducer (rifampicin) in CYP2D6 extensive and poor metabolizers and with a moderate CYP3A inhibitor (fluconazole) in healthy volunteers. 5-HMT AUC_inf and C_max GMRs for fesoterodine DDIs were all predicted within 1.26-fold of clinical observation, providing verification for the fesoterodine substrate model. The predicted changes in 5-HMT AUC_inf and C_max ratios for 8 mg fesoterodine when coadministered with 50 mg mirabegron were 1.22-fold and 1.17-fold, respectively, relative to 8 mg fesoterodine given alone. This modest increase in 5-HMT exposures by approximately 20% is considered clinically insignificant and would not require fesoterodine dose adjustment when coadministered with mirabegron within approved daily-dose ranges.

Hypomethylating agents in combination with venetoclax for acute myeloid leukemia: Update on clinical trial data and practical considerations for use

One of the most promising developments in therapy for acute myeloid leukemia (AML) in recent years has been the combination of hypomethylating agents (HMA, either decitabine or 5-azacytidine) with the Bcl-2 inhibitor venetoclax (VEN). Although both classes of drugs have single-agent activity in AML, the combination has resulted in high rates of complete remission (CR) both in the frontline and relapsed settings suggesting synergy between these two agents. Recent data have suggested that CR + CR with incomplete count recovery rate may exceed 70% for frontline VEN-HMA. Moreover, this activity has been observed across various genetic subtypes of AML including those known to have very poor response to conventional chemotherapy. Although VEN has only recently obtained FDA approval for treatment of AML, there has been increasing on and off-label use of this combination given its striking efficacy and excellent toxicity profile. In this article, we summarize the current available data on this combination and offer practical guidelines for management of patients receiving VEN-HMA. Our recommendations are based on protocol guidelines, published data from clinical trials as well as from analysis of real world evidence from patients treated with this combination.

Effect of Azithromycin on Venetoclax Pharmacokinetics in Healthy Volunteers: Implications for Dosing Venetoclax with P-gp Inhibitors

INTRODUCTION

Venetoclax, a substrate of cytochrome P450 (CYP) 3A and P-glycoprotein (P-gp), is approved for the treatment of patients with chronic lymphocytic leukemia who have received at least one prior therapy. This study evaluated the effect of azithromycin, a commonly used antibiotic in cancer patients and a P-gp inhibitor, on the pharmacokinetics of venetoclax.

METHODS

In this single-center, open-label, nonfasting, two-period study, 12 healthy female subjects received a single 100 mg dose of venetoclax on day 1 of period 1 and day 3 of period 2. Subjects received azithromycin 500 mg on day 1 and 250 mg once daily on days 2 through 5. Serial blood samples for the determination of venetoclax concentrations were collected after dosing in both periods. Safety was evaluated throughout the study.

RESULTS

Following coadministration of venetoclax with multiple doses of azithromycin, venetoclax maximum concentration and area under the curve to infinite time were 25% and 35% lower, respectively, compared to venetoclax administered alone. Venetoclax half-life and time to maximum concentration remained relatively unchanged when administered with azithromycin. Venetoclax was well tolerated with no serious adverse events reported.

CONCLUSIONS

The modest changes in venetoclax exposures when given with azithromycin indicate that no dose adjustment would be needed when venetoclax is coadministered with azithromycin or other drugs with P-gp inhibitory potential. Azithromycin represents an alternative to other antimicrobial agents with higher potential to alter venetoclax pharmacokinetics such as clarithromycin, erythromycin, and ciprofloxacin.

FUNDING

AbbVie in collaboration with Genentech/Roche.

Utility of physiologically based pharmacokinetic (PBPK) modeling in oncology drug development and its accuracy: a systematic review

PURPOSE

Physiologically based pharmacokinetic (PBPK) modeling, a mathematical modeling approach which uses a pharmacokinetic model to mimick human physiology to predict drug concentration-time profiles, has been used for the discover and development of drugs in various fields, including oncology, since 2000. There have been a few general review articles on the utilization of PBPK in the development of oncology drugs, but these do not include an evaluation of model prediction accuracy. We therefore conducted a systematic review to define the accuracy of PBPK model prediction and its utility throughout all the developmental phases of oncology drugs.

METHODS

A systematic search was performed in the PubMed, PubMed Central and Cochrane Library databases from 1980 to February 2017 for articles (1) written in English, (2) focused on oncology or antineoplastic or anticancer drugs, tumor or cancer or anticancer drugs listed in the U.S. National Institutes of Health and (3) involving a PBPK model. The absolute-average-folding-errors (AAFEs) of the area under the curve (AUC) between predicted and observed values in each article were calculated to assess model prediction accuracy.

RESULTS

Of the 2341 articles initially identified by our search of the databases, 40 were included in the review analysis. These articles reported on six types of studies, i.e. in vivo (n = 4), first-in-human (n = 5), phase II/III clinical trials (n = 9), organ impairment (n = 3), pediatrics (n = 4) and drug-drug interactions (n = 15). AAFEs of the predicted AUC for all groups of studies were within 1.3-fold of each other despite variations in experimental methodologies.

CONCLUSION

PBPK modeling is a potential tool which can be effectively applied throughout all phases of oncology drug development. The number of experimental animals and human participants enrolled in the studies can be reduced using PBPK modeling and PBPK-population-PK modeling. The limited number of publications of unsuccessful model application to date may contribute to bias toward the usefulness of modeling.

Guiding dose adjustment of amlodipine after co-administration with ritonavir containing regimens using a physiologically-based pharmacokinetic/pharmacodynamic model

Amlodipine, a commonly prescribed anti-hypertensive drug, shows increased systemic exposure with cytochrome P450 (CYP) 3A inhibitors. Ritonavir (RTV) is a potent mechanism-based and reversible CYP3A inhibitor and moderate inducer that is used as a pharmacokinetic enhancer in several antiviral treatment regimens. Drug-drug interaction (DDI) between RTV and amlodipine is due to mixed inhibition and induction of CYP3A4, which is challenging to predict without a mechanistic model that accounts for the complexity of both mechanisms occurring simultaneously. A novel physiologically-based pharmacokinetic (PBPK) model was developed for amlodipine, and the model was verified using published clinical PK and DDI data. The verified amlodipine PBPK model was linked to a pharmacodynamics model that describes changes in systolic blood pressure (SBP) during and after co-administration with RTV. The magnitude and time course of RTV effects on amlodipine plasma exposures and SBP were evaluated, to provide guidance on dose adjustment of amlodipine during and after co-administration with RTV-containing regimens. Model simulations suggested that the increase in amlodipine's plasma exposure by RTV diminishes by approximately 80% within 5 days after the last dose of RTV. PBPK simulations suggested that resuming a full dose of amlodipine [5 mg once daily (QD)] immediately after RTV's last dose would decrease daily average SBP by a maximum of 3.3 mmHg, while continuing with the reduced dose (2.5 mg QD) for 5 days after the last dose of RTV would increase daily average SBP by a maximum of 5.8 mmHg. Based on these results, either approach of resuming amlodipine's full dose could be appropriate when combined with appropriate clinical monitoring.

Impact of ritonavir dose and schedule on CYP3A inhibition and venetoclax clinical pharmacokinetics

PURPOSE

Venetoclax is a selective BCL-2 inhibitor indicated for the treatment of patients with chronic lymphocytic leukemia (CLL). It is predominately metabolized by cytochrome P450 (CYP) 3A. The study objective was to determine the effect of different dosage regimens of ritonavir, a strong CYP3A inhibitor, on the pharmacokinetics of venetoclax in 20 healthy subjects.

METHODS

In cohorts 1 and 2, subjects received single 10 mg doses of venetoclax in periods 1 and 2 and a single 50- or 100-mg dose of ritonavir in period 2. In cohort 3, subjects received 10-mg venetoclax doses on day 1 of period 1 and days 1 and 11 of period 2, and 50 mg ritonavir daily on days 1 to 14 of period 2.

RESULTS

Single doses of 50 and 100 mg ritonavir increased the venetoclax maximum concentration (C_max) 2.3- to 2.4-fold compared to venetoclax alone and the area under the curve (AUC) 6.1- and 8.1-fold, respectively. Daily 50 mg ritonavir resulted in a 2.4- and 7.9-fold increase in venetoclax C_max and AUC, respectively. Administration of 50 mg ritonavir daily saturated CYP3A inhibition and completely inhibited the formation of the major venetoclax metabolite M27. Time-dependent CYP3A inhibition with daily 50 mg ritonavir was offset by ritonavir CYP3A induction, resulting in a limited net increase in CYP3A inhibition with multiple doses.

CONCLUSION

After completion of the dose ramp-up, venetoclax dose reductions of at least 75% are recommended when administered concomitantly with strong CYP3A inhibitors to maintain venetoclax exposures within the established therapeutic window for CLL treatment.