Individualized dosing of oral targeted therapies in oncology is crucial in the era of precision medicine

Determining the optimal use of approved drugs in oncology

Optimising the use of approved drugs requires evidence from post-approval trials that investigate variations of their use. Determining optimal drug use goes beyond the dominant, academic effort to conduct trials to identify effective lower doses of new drugs. Other important therapeutic approaches that use either less, similar, or more drug than the standard dose need testing in clinical trials, to get the most out of these drugs. Trial objectives on survival outcomes vary greatly; some aim for superiority, others for equivalent exposure or non-inferiority. This Personal View aims to inform academic trialists in how to conceive and prioritise questions aimed at determining the optimal use of drugs, taking into account the perspectives of patients, clinicians, and trial funders, to maximise the chances of successful delivery and impact for patients globally.

Exposure-Response Relationships for Toceranib in Dogs with Solid Tumors: A Pilot Study

The existence of considerable interpatient variability in pharmacokinetic exposure necessitates dose adjustment to avoid potential adverse events and suboptimal efficacy in targeted therapy. Exposure-response relationships for toceranib phosphate (TOC), the most commonly used tyrosine kinase inhibitor in veterinary oncology, remain unclear. Correlations between TOC exposure and efficacy and safety were evaluated in dogs with solid tumors in our study. Plasma TOC was analyzed at 6 and 48 h post-administration. For the 10 dogs in the exposure-response analysis, the mean interpatient variabilities in dose-normalized peak (Cmax) and trough (Cmin) concentrations were 29% and 61%, respectively. Dose-normalized Cmax did not differ among weeks 1, 4, and 12 (p = 0.414), suggesting that steady-state plasma levels can be achieved within 1 week. Pharmacokinetic exposure at steady state was not significantly associated with efficacy (week 1 Cmax, p = 0.941; average Cmax, p = 0.548). Cmax was positively but nonsignificantly associated with the risk of adverse events (week 1 Cmax, p = 0.190; average Cmax, p = 0.109). These findings suggest the value of pharmacokinetic monitoring in optimizing TOC dosage and reducing its adverse effects in dogs with solid tumors. Clinicians should consider plasma TOC when managing TOC treatment in small-animal practice.

Clinical pharmacology-how it shapes the drug development journey

Every drug development is a complex and long journey. Clinical pharmacology is an essential discipline in modern drug development. With its applications, computational modelling, and simulation techniques, it can significantly contribute to the efficiency in drug development today. In this perspective, we highlight why pharmacokinetics and pharmacodynamics are important, what developers need to consider in their clinical development programme, how modelling influences the development process, and discuss recent trends such as artificial intelligence and machine learning that have the potential to reshape future drug development.

Palbociclib exposure in relation to efficacy and toxicity in patients with advanced breast cancer

BACKGROUND

Data on exposure-response or exposure-toxicity relationships of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) are limited and inconclusive. We aimed to investigate whether there is an association between palbociclib exposure and progression-free survival (PFS), adverse events (AEs) and dose reductions.

MATERIALS AND METHODS

Data were retrieved from the prospective, multicentre SONIA trial in which patients with advanced estrogen receptor-positive, human epidermal growth factor receptor 2-negative breast cancer were randomised to receive CDK4/6i treatment in first versus second line. Blood for pharmacokinetics (PK) was taken at day 15 of cycles 1 and 2 during CDK4/6i treatment. Individual trough concentrations and plasma area under the curves of palbociclib were constructed using a population PK model. Associations with palbociclib exposure were tested using Cox regression for PFS and chi-square tests for AEs or dose reductions.

RESULTS

PK data were available for 344 patients. No association between palbociclib exposure and PFS was found. Although patients with higher palbociclib exposure had more dose reductions during their entire CDK4/6i treatment course, this was not reflected by a higher incidence of grade 3-4 AEs in the first 3 months.

CONCLUSION

The absence of an association between palbociclib exposure and PFS and the presence of the association between palbociclib exposure and dose reductions suggest that dose reductions may safely be carried out in case of palbociclib-related toxicity.

Real-world pharmacokinetics of trametinib in pediatric low-grade glioma

PURPOSE

Trametinib, a MEK1/2 inhibitor, has emerged as a promising treatment for pediatric patients with low-grade gliomas (LGG). However, trametinib exhibits significant inter-individual pharmacokinetic (PK) variability, and studies in adults demonstrated an exposure-efficacy relationship. This study aimed to evaluate the PK profile of trametinib in pediatric routine care and explore potential exposure-outcome relationships.

METHODS

We analyzed PK data from 65 blood samples from 19 children receiving trametinib, either as single agent or in combination with dabrafenib. A trough concentration (Cmin) range of 8-15 ng/mL was considered, based on average exposure reported in the largest pediatric study.

RESULTS

The mean Cmin was 8.82 ng/ml, with 64.6% of samples falling within the predefined target range, while 35.4% were below it. Regarding tolerance, 84.2% of patients experienced treatment-related toxicities, predominantly skin and subcutaneous tissue disorders. Efficacy data were limited.

CONCLUSION

These findings underscore the necessity of therapeutic drug monitoring in pediatric patients to optimize treatment efficacy and minimize toxicity, highlighting trametinib's potential for personalized dosing strategies in this population.

Clinical Application of Volumetric Absorptive Microsampling for Therapeutic Drug Monitoring of Oral Targeted Anticancer Drugs

BACKGROUND

Therapeutic Drug Monitoring optimizes oral anticancer drug treatment by measuring plasma levels. Volumetric absorptive microsampling (VAMS) allows home sampling with a minimal blood sample. However, methods for converting whole blood into plasma are required to interpret these results. This study aimed to establish conversion methods for abiraterone, alectinib, cabozantinib, imatinib, olaparib, sunitinib, and their metabolites, while assessing the differences between venous and capillary blood. The feasibility of home sampling was also evaluated.

METHODS

Plasma and VAMS samples, both from venipuncture-collected whole blood tubes and from a finger prick, were collected from each patient. The VAMS samples were deemed comparable if their concentrations were within ±20% of each other for ≥2/3rd of the patients. The Passing-Bablok regression and conversion factor methods were tested for the plasma and VAMS finger prick samples. The estimated plasma concentrations using both methods were required to be within ±20% of the measured plasma concentrations for ≥2/3rd of the pairs.

RESULTS

Overall, 153 patients were enrolled in this study. Conversion methods were applied to the VAMS samples, and the acceptance criteria were met for alectinib-M4, cabozantinib, imatinib, N-desmethyl imatinib, olaparib, sunitinib, and N-desethyl sunitinib but not for abiraterone, D4A, or alectinib. The capillary and venous VAMS concentrations were similar, except for that of D4A. Patients were positive toward home sampling.

CONCLUSIONS

The established VAMS conversion methods for 7 out of 10 oral targeted anticancer drugs or metabolites met the acceptance criteria. Future studies need to validate the conversion methods with an independent cohort and integrate home sampling via VAMS to provide patients with an alternative to venipuncture at the outpatient clinic.

Drug exposure and measurable residual disease in chronic lymphocytic leukemia: a systematic review

For fixed-duration therapies against chronic lymphocytic leukemia (CLL), undetectable measurable residual disease (MRD) predicts overall and progression-free survival more accurately than complete remission. For indefinite therapies, MRD status can direct discontinuation of treatment. We systematically reviewed the relationship between antineoplastic drug exposures and undetectable MRD in CLL. Seventeen trials from MEDLINE and EMBASE met the inclusion criteria; four of which evaluated drug exposures in relation to MRD status. Undetectable MRD was associated with higher trough concentrations of ofatumumab and alemtuzumab, as well as increased maximum concentration and area under the plasma concentration curve (AUC) of ibrutinib. One study found an association between high rituximab AUC and undetectable MRD until adjusting for tumor burden. The limited studies, lack of exposure measurements of concomitant drugs, and high heterogeneity in designs limit the results' generalizability. Further research is needed to explore the exposure-MRD relationship and the possibility for therapeutic drug monitoring in CLL.

LC-MS/MS method for quantification of 23 TKIs in Plasma: Assessing the relationship between anlotinib trough concentration and toxicities

OBJECTIVES

To develop a simple, rapid, and sensitive LC-MS/MS method for quantifying 23 tyrosine kinase inhibitors (TKIs) in plasma samples, and evaluate the relationship between the trough concentration of anlotinib(ANL) and its toxicities.

METHODS

The method was developed in Agilent 1290-6460 UHPLC-MS/MS system. This study prospectively enrolled 55 cancer patients undergoing ANL treatment. Plasma samples were collected at steady-state trough concentration and subsequently analyzed using the method. Patients were recorded for the occurrence of toxicities. Statistical analysis was performed to assess the association of the toxicities with ANL exposure level and patients' characteristics.

RESULTS

The LC-MS/MS method was developed and validated for all items required by pharmacopoeia. The results revealed a positive association between the trough concentration of ANL and the incidence of toxicities. The exposure level 17.655 ng/mL (AUC 0.82, p = 0.010) was identified as a predictive threshold value for grade ≥ 3 overall toxicities. In addition, lower platelet count (PLT count < 179 × 109 g/L) was significantly associated with higher occurrence of grade ≥ 3 toxicities (AUC 0.75, p = 0.049). A logistic model incorporating these two factors demonstrated improved diagnostic capacity for predicting ≥ 3 overall toxicities (AUC = 0.90, p = 0.001).

CONCLUSIONS

This study successfully developed and validated a simple, rapid, and sensitive LC-MS/MS method for quantifying 23 TKIs in plasma samples. Besides, this study found that both Ctrough of ANL and PLT count as independent predictors for ANL-induced ≥ 3 overall toxicities. Moreover, a logistic model including these two factors presents better prediction capacity for ≥ 3 overall toxicities.

Microfluidic Nanoparticle Separation for Precision Medicine

A deeper understanding of disease heterogeneity highlights the urgent need for precision medicine. Microfluidics, with its unique advantages, such as high adjustability, diverse material selection, low cost, high processing efficiency, and minimal sample requirements, presents an ideal platform for precision medicine applications. As nanoparticles, both of biological origin and for therapeutic purposes, become increasingly important in precision medicine, microfluidic nanoparticle separation proves particularly advantageous for handling valuable samples in personalized medicine. This technology not only enhances detection, diagnosis, monitoring, and treatment accuracy, but also reduces invasiveness in medical procedures. This review summarizes the fundamentals of microfluidic nanoparticle separation techniques for precision medicine, starting with an examination of nanoparticle properties essential for separation and the core principles that guide various microfluidic methods. It then explores passive, active, and hybrid separation techniques, detailing their principles, structures, and applications. Furthermore, the review highlights their contributions to advancements in liquid biopsy and nanomedicine. Finally, it addresses existing challenges and envisions future development spurred by emerging technologies such as advanced materials science, 3D printing, and artificial intelligence. These interdisciplinary collaborations are anticipated to propel the platformization of microfluidic separation techniques, significantly expanding their potential in precision medicine.

Plasma concentrations of venetoclax and Pharmacogenetics correlated with drug efficacy in treatment naive leukemia patients: a retrospective study

Venetoclax (VEN) was the only Bcl-2 inhibitor approved yet and showed large differences in clinical efficacy. The aim of the study was to explore the relationships between the plasma concentration and efficacy of VEN, and identify potential influencing factors. A retrospective cohort study was conducted and a total of 76 trough (C0h) and 91 6 h post-dose plasma concentration (C6h) blood concentrations of VEN were collected in 54 patients. C6h/D concentration of VEN was found to be significantly correlated with treatment efficacy (p = 0.006) in leukemia patients with good or intermediate prognosis stratification. A ROC curve was then established and the cut-off value was calculated as 0.2868 μg/ml (AUC = 0.7097, p = 0.1081). Besides, patients co-administered with triazoles or carrying CYP3A5 rs776746 AA/AG genotypes were prone to induce higher VEN plasma concentration regardless of whether VEN dosage was reduced or not. Through LASSO-logistic regression and nomogram analysis, chemotherapy regimens and neutrophil percentages were identified as the critical elements that may predict drug response. Above all, in addition to identify prognostic stratification, AML patients taken with VEN were suggested to test plasma concentration routinely so as to achieve desired efficacy, especially when co-administered with triazoles or carried with CYP3A5 rs776746 AA/AG.

Comprehensive Advanced Physicochemical Characterization and In Vitro Human Cell Culture Assessment of BMS-202: A Novel Inhibitor of Programmed Cell Death Ligand

Background/Objectives: BMS-202, is a potent small molecule with demonstrated antitumor activity. The study aimed to comprehensively characterize the physical and chemical properties of BMS-202 and evaluate its suitability for topical formulation, focusing on uniformity, stability and safety profiles. Methods: A range of analytical techniques were employed to characterize BMS-202. Scanning Electron Microscopy (SEM) was used to assess morphology, Differential Scanning Calorimetry (DSC) provided insights of thermal behavior, and Hot-Stage Microscopy (HSM) corroborated these thermal behaviors. Molecular fingerprinting was conducted using Raman spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy, with chemical uniformity of the batch further validated by mapping through FTIR and Raman microscopies. The residual water content was measured using Karl Fisher Coulometric titration, and vapor sorption isotherms examined moisture uptake across varying relative humidity levels. In vitro safety assessments involved testing with skin epithelial cell lines, such as HaCaT and NHEK, and Transepithelial Electrical Resistance (TEER) to evaluate barrier integrity. Results: SEM revealed a distinctive needle-like morphology, while DSC indicated a sharp melting point at 110.90 ± 0.54 ℃ with a high enthalpy of 84.41 ± 0.38 J/g. HSM confirmed the crystalline-to-amorphous transition at the melting point. Raman and FTIR spectroscopy, alongside chemical imaging, confirmed chemical uniformity as well as validated the batch consistency. A residual water content of 2.76 ± 1.37 % (w/w) and minimal moisture uptake across relative humidity levels demonstrated its low hygroscopicity and suitability for topical formulations. Cytotoxicity testing showed dose-dependent reduction in skin epithelial cell viability at high concentrations (100 µM and 500 µM), with lower doses (0.1 µM to 10 µM) demonstrating acceptable safety. TEER studies indicated that BMS-202 does not disrupt the HaCaT cell barrier function. Conclusions: The findings from this study establish that BMS-202 has promising physicochemical and in vitro characteristics at therapeutic concentrations for topical applications, providing a foundation for future formulation development focused on skin-related cancers or localized immune modulation.

Quantification of Letrozole, Palbociclib, Ribociclib, Abemaciclib, and Metabolites in Volumetric Dried Blood Spots: Development and Validation of an LC-MS/MS Method for Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) may be beneficial for cyclin-dependent kinase 4/6 inhibitors (CDK4/6is), such as palbociclib, ribociclib, and abemaciclib, due to established exposure-toxicity relationships and the potential for monitoring treatment adherence. Developing a method for quantifying CDK4/6is, abemaciclib metabolites (M2, M20), and letrozole in dried blood spots (DBS) could be useful to enhance the feasibility of TDM. Thus, an optimized LC-MS/MS method was developed using the HemaXis DB10 device for volumetric (10 µL) DBS collection. Chromatographic separation was achieved using a reversed-phase XBridge BEH C18 column. Detection was performed with a triple quadrupole mass spectrometer, utilizing ESI source switching between negative and positive ionization modes and multiple reaction monitoring acquisition. Analytical validation followed FDA, EMA, and IATDMCT guidelines, demonstrating high selectivity, adequate sensitivity (LLOQ S/N ≥ 30), and linearity (r ≥ 0.997). Accuracy and precision met acceptance criteria (between-run: accuracy 95-106%, CV ≤ 10.6%). Haematocrit independence was confirmed (22-55%),with high recovery rates (81-93%) and minimal matrix effects (ME 0.9-1.1%). The stability of analytes under home-sampling conditions was also verified. Clinical validation supports DBS-based TDM as feasible, with conversion models developed for estimating plasma concentrations (the reference for TDM target values) of letrozole, abemaciclib, and its metabolites. Preliminary data for palbociclib and ribociclib are also presented.

Therapeutic drug monitoring in anticancer agents: perspectives of Australian medical oncologists

BACKGROUND

In the development of anticancer agents for solid tumours, body surface area continues to be used to personalise dosing despite minimal evidence for its use over other dosing strategies. With the development of tyrosine kinase inhibitors and other oral targeted anticancer agents, dosing using therapeutic drug monitoring (TDM) is now utilised in many health systems but has had limited uptake in Australia.

AIM

To determine attitudes and barriers to the implementation of TDM among Australian oncologists.

METHODS

A comprehensive questionnaire was developed by the Dutch Pharmacology Oncology Group from semistructured interviews of stakeholders. Seventy-nine questions across seven domains were developed with three free-text responses. This was rationalised to 17 questions with three free-text responses for Australian medical oncologists who identified limited experience with TDM.

RESULTS

Fifty-seven responses were received, with 49 clinicians (86%) identifying limited experience of performing TDM in daily practice. Clinicians were positive (62-91% agree/strongly agree across seven questions) about the advantages of TDM. There was a mixed response for cost-effectiveness and scientific evidence being a barrier to implementation, but strong agreement that prospective studies were needed (75% agreed or strongly agreed); that national treatment guidelines would enable practice (80%) and that a 'pharmacology of oncolytics' education programme would be useful (96%) to provide knowledge for dose individualisation.

CONCLUSION

Despite the limited experience of TDM in oncology in Australia, medical oncologists appear positive about the potential benefit to their patients. We have identified three barriers to implementation that could be targeted for increased adoption of TDM in oncology in Australia.

Reasons for non-feasibility of therapeutic drug monitoring of oral targeted therapies in oncology - an analysis of the closed cohorts of a multicentre prospective study

BACKGROUND

Therapeutic drug monitoring (TDM) - performing dose adjustments based on measured drug levels and established pharmacokinetic (PK) targets - could optimise treatment with drugs that show large interpatient variability in exposure. We evaluated the feasibility of TDM for multiple oral targeted therapies. Here we report on drugs for which routine TDM is not feasible.

METHODS

We evaluated drug cohorts from the Dutch Pharmacology Oncology Group - TDM study. Based on PK levels taken at pre-specified time points, PK-guided interventions were performed. Feasibility of TDM was evaluated, and based on the success and practicability of TDM, cohorts could be closed.

RESULTS

For 10 out of 24 cohorts TDM was not feasible and inclusion was closed. A high incidence of adverse events resulted in closing the cabozantinib, dabrafenib/trametinib, everolimus, regorafenib and vismodegib cohort. The enzalutamide and erlotinib cohorts were closed because almost all PK levels were above target. Other, non-pharmacological reasons led to closing the palbociclib, olaparib and tamoxifen cohort.

CONCLUSIONS

Although TDM could help personalising treatment for many drugs, the above-mentioned reasons can influence its feasibility, usefulness and clinical applicability. Therefore, routine TDM is not advised for cabozantinib, dabrafenib/trametinib, enzalutamide, erlotinib, everolimus, regorafenib and vismodegib. Nonetheless, TDM remains valuable for individual clinical decisions.

A Score to Predict the Clinical Usefulness of Therapeutic Drug Monitoring: Application to Oral Molecular Targeted Therapies in Cancer

Therapeutic drug monitoring (TDM) involves measuring and interpreting drug concentrations in biological fluids to adjust drug dosages. In onco-hematology, TDM guidelines for oral molecular targeted therapies (oMTTs) are varied. This study evaluates a quantitative approach with a score to predict the clinical usefulness of TDM for oMTTs. We identified key parameters for an oMTT's suitability for TDM from standard TDM recommendations. We gathered oMTT pharmacological data, which covered exposure variability (considering pharmacokinetic (PK) impact of food and proton pump inhibitors), technical intricacy (PK linearity and active metabolites), efficacy (exposure-response relationship), and safety (maximum tolerated dose, and exposure-safety relationship). To assess the validity and the relevance of the score and define relevant thresholds, we evaluated molecules with prospective validation or strong recommendations for TDM, both in oncology and in other fields. By September 1, 2021, the US Food and Drug Administration (FDA) approved 67 oMTTs for onco-hematological indications. Scores ranged from 15 (acalabrutinib) to 80 (sunitinib) with an average of 48.3 and a standard deviation of 15.6. Top scorers included sunitinib, sorafenib, cabozantinib, nilotinib, and abemaciclib. Based on scores, drugs were categorized into low (< 40), intermediate (≥ 40 and < 60), and high (≥ 60) relevance for TDM. Notably, negative controls generally scored around or under 40, whereas positive controls had a high score across different indications. In this work, we propose a quantitative and reproducible score to compare the potential usefulness of TDM for oMTTs. Future guidelines should prioritize the TDM for molecules with the highest score.

Pharmacology of Tyrosine Kinase Inhibitors: Implications for Patients with Kidney Diseases

Tyrosine kinase inhibitors (TKI) have introduced a significant advancement in cancer management. These compounds are administered orally, and their absorption holds a pivotal role in determining their variable efficacy. They exhibit extensive distribution within the body, binding strongly to both plasma and tissue proteins. Often reliant on efflux and influx transporters, TKI undergo primary metabolism by intestinal and hepatic cytochrome P450 enzymes, with nonkidney clearance being predominant. Owing to their limited therapeutic window, many TKI display considerable intraindividual and interindividual variability. This review offers a comprehensive analysis of the clinical pharmacokinetics of TKI, detailing their interactions with drug transporters and metabolic enzymes, while discussing potential clinical implications. The prevalence of kidney conditions, such as AKI and CKD, among patients with cancer is explored in their effect on TKI pharmacokinetics. Finally, the potential nephrotoxicity associated with TKI is also examined.

Therapeutic Drug Monitoring of Pazopanib in Renal Cell Carcinoma and Soft Tissue Sarcoma: A Systematic Review

BACKGROUND

Pazopanib, an anti-angiogenic multitarget tyrosine kinase inhibitor, has been approved for the treatment of metastatic renal cell carcinoma and soft tissue sarcoma. However, its recommended dose does not always produce consistent outcomes, with some patients experiencing adverse effects or toxicity. This variability is due to differences in the systemic exposure to pazopanib. This review aimed to establish whether sufficient evidence exists for the routine or selective therapeutic drug monitoring of pazopanib in adult patients with approved indications.

METHODS

A systematic search of the PubMed and Web of Science databases using search terms related to pazopanib and therapeutic drug monitoring yielded 186 and 275 articles, respectively. Ten articles associated with treatment outcomes or toxicity due to drug exposure were selected for review.

RESULTS

The included studies were evaluated to determine the significance of the relationship between drug exposure/Ctrough and treatment outcomes and between drug exposure and toxicity. A relationship between exposure and treatment outcomes was observed in 5 studies, whereas the trend was nonsignificant in 4 studies. A relationship between exposure and toxicity was observed in 6 studies, whereas 2 studies did not find a significant relationship; significance was not reported in 3 studies.

CONCLUSIONS

Sufficient evidence supports the therapeutic drug monitoring of pazopanib in adult patients to improve its efficacy and/or safety in the approved indications.

Pharmacokinetic Consideration of Venetoclax in Acute Myeloid Leukemia Patients: A Potential Candidate for TDM? A Short Communication

BACKGROUND

Venetoclax (VNX)-based regimens have demonstrated significantly favorable outcomes in patients with acute myeloid leukemia (AML) and are now becoming the standard treatment. Tyrosine kinase inhibitors are administered at a fixed dose, irrespective of body surface area or weight. For such orally targeted therapies, real-world data have highlighted a larger pharmacokinetic (PK) interindividual variability (IIV) than expected. Even if VNX PKs have been well characterized and described in the literature, only 1 clinical trial-based PK study has been conducted in patients with AML. This study aimed to evaluate the PK of VNX in AML patients.

MATERIAL AND METHODS

We retrospectively analyzed all patients treated with a combination of VNX-azacitidine between January and July 2022 at our center, using at least 1 available VNX blood sample. Based on a previously published population PK model, individual PK parameters were estimated to evaluate the exposure and IIV.

RESULTS

and Discussion. Twenty patients received VNX in combination with azacitidine, according to the PK data. A total of 93 plasma concentrations were collected. The dose of VNX was 400 mg, except in 7 patients who received concomitant posaconazole (VNX 70 mg). The patients' weight ranged from 49 kg to 108 kg (mean = 78 kg). Mean individual clearance was 13.5 ± 9.4 L/h with mean individual daily area under the concentration-time curves of 35.8 mg.h/L with significant IIV (coefficient of variation = 41.1%). Ten patients were still alive (8 in complete response), but all experienced at least 1 hematological toxicity of grade ≥ 3.

CONCLUSIONS

Based on the observed large PK variability in the data from our real-world AML patients, the risk of drug interactions and the recommended fixed-dosage regimen of VNX therapeutic drug monitoring may be useful.

Appropriate dose of regorafenib based on body weight of colorectal cancer patients: a retrospective cohort study

PURPOSE

Previous randomized studies have shown a survival benefit of using regorafenib but a high rate of adverse events in unresectable colorectal cancer patients. To reduce these adverse events and improve the tolerability, we examined the appropriate dose of regorafenib based on body weight.

METHODS

We used a nationwide claims database in Japan and examined the efficacy and safety of regorafenib for patients with metastatic colorectal cancer between groups divided by body weight (60 kg) and median average dose (120 mg) between 2013 and 2018. We also assessed overall survival (OS) and adverse events between these groups.

RESULTS

We identified 2530 Japanese patients (heavy weight/high dose: 513, light weight/low dose: 921, heavy weight/low dose: 452, and light weight/high dose: 644). There was no significant difference in the adverse events and OS after inverse probability treatment weighting (IPTW) adjustment between heavy weight/high dose group and light weight/low dose group (hazard ratio, HR=0.97). Among the light-weight patients, higher average dose was associated with shorter OS (IPTW adjusted HR=1.21, 95% CI 1.05 - 1.39, Table 3) while among the heavy-weight patients, there was no significant difference in OS between high and low dose groups (IPTW adjusted HR=1.14, 95% CI 0.95 - 1.37).

CONCLUSION

The findings suggest that a low dose of regorafenib for light-weight patients may be as safe and effective as high doses for heavy-weight patients. Further studies should be conducted to identify an appropriate dose based on each patient's physique and condition.

Therapeutic Drug Monitoring of Kinase Inhibitors in Oncology

Although kinase inhibitors (KI) frequently portray large interpatient variability, a 'one size fits all' regimen is still often used. In the meantime, relationships between exposure-response and exposure-toxicity have been established for several KIs, so this regimen could lead to unnecessary toxicity and suboptimal efficacy. Dose adjustments based on measured systemic pharmacokinetic levels-i.e., therapeutic drug monitoring (TDM)-could therefore improve treatment efficacy and reduce the incidence of toxicities. Therefore, the aim of this comprehensive review is to give an overview of the available evidence for TDM for the 77 FDA/EMA kinase inhibitors currently approved (as of July 1st, 2023) used in hematology and oncology. We elaborate on exposure-response and exposure-toxicity relationships for these kinase inhibitors and provide practical recommendations for TDM and discuss corresponding pharmacokinetic targets when possible.

Pharmacokinetics of Four Tyrosine Kinase Inhibitors in Adult and Paediatric Chronic Myeloid Leukaemia Patients

Tyrosine kinase inhibitors work by blocking the tyrosine kinases responsible for the dysregulation of intracellular signalling pathways in tumour cells. This study looked at the impact of age and sex on the levels of imatinib, dasatinib, nilotinib, and ponatinib in plasma and cerebrospinal fluid samples of patients with chronic myeloid leukaemia. Imatinib and dasatinib were used to treat the majority of the enrolled patients, and most of them were paediatrics. A total of 82.4% of the patients were men; however, sex-related differences in the drugs' pharmacokinetics were not found. Age and imatinib plasma concentration were found to be inversely correlated. The dasatinib concentrations in plasma were found to be substantially lower than those found in cerebrospinal fluid, particularly in paediatrics. Analysing the obtained data, we can state that therapeutic drug monitoring is a useful method for adjusting a patient's treatment schedule that depends on drug concentrations in biological fluids. The use of therapeutic drug monitoring in conjunction with tyrosine kinase inhibitors for the treatment of chronic myeloid leukaemia is supported by a number of sources of evidence. As a result, as the research develops, the tyrosine kinase inhibitor therapeutic drug monitoring classification needs to be refined in terms of factors like sex and age.

Click Chemistry Selectively Activates an Auristatin Protodrug with either Intratumoral or Systemic Tumor-Targeting Agents

The Click Activated Protodrugs Against Cancer (CAPAC) platform enables the activation of powerful cancer drugs at tumors. CAPAC utilizes a click chemistry reaction between tetrazine and trans-cyclooctene. The reaction between activator, linked to a tumor-targeting agent, and protodrug leads to the targeted activation of the drug. Here, tumor targeting is achieved by intratumoral injection of a tetrazine-modified hyaluronate (SQL70) or by infusion of a tetrazine-modified HER2-targeting antigen-binding fragment (SQT01). Monomethyl auristatin E (a cytotoxin hindered in its clinical use by severe toxicity) was modified with a trans-cyclooctene to form the protodrug SQP22, which reduced its cytotoxicity in vitro and in vivo. Treatment of SQP22 paired with SQL70 demonstrated antitumor effects in Karpas 299 and RENCA murine tumor models, establishing the requirement of click chemistry for protodrug activation. SQP22 paired with SQT01 induced antitumor effects in the HER2-positive NCI-N87 xenograft model, showing that tumor-targeted activation could be accomplished via systemic dosing. Observed toxicities were limited, with transient myelosuppression and moderate body weight loss detected. This study highlights the capabilities of the CAPAC platform by demonstrating the activity of SQP22 with two differentiated targeting approaches and underscores the power of click chemistry to precisely control the activation of drugs at tumors.

First reported double drug-drug interaction in a cancer renal patient under everolimus treatment: therapeutic drug monitoring and review of literature

Everolimus is an inhibitor of mammalian target of rapamycin (mTOR) used in both transplantation and cancer treatment (breast, renal and neuroendocrine). In transplantation, therapeutic drug monitoring (TDM) is recommended due to the potential drug-drug interactions with chronic medications, which can affect everolimus pharmacokinetics. In cancer treatment, everolimus is used at higher doses than in transplantation and without a systematic drug monitoring.We present a case report of a 72-year-old woman with epilepsy history to whom everolimus 10 mg QD was prescribed as third line of treatment for renal cell carcinoma (RCC). The potential drug interactions between everolimus and the patient's chronic medications, carbamazepine and phenytoin, are significant as both are known as strong inducers CYP3A4 metabolism, potentially leading to underexposure to everolimus.TDM of everolimus was recommended by the pharmacist. The literature suggests that a minimum plasma concentration (Cminss) of everolimus over 10 ng/ml is associated with better response to treatment and progression-free survival (PFS). The patient's everolimus dose had to be increased until 10 mg BID, and regular monitoring of everolimus levels showed an increase in Cminss from 3.7 ng/ml to 10.8 ng/ml.This case highlights the importance of checking for potential drug interactions and monitoring everolimus levels in patients on chronic medication, especially those with several inducers or inhibitors of CYP3A4 metabolism. TDM can help to ensure that patients are treated with their optimal dose, which can improve the effectiveness of the treatment or minimize the risk of toxicities.

Framework for Implementing Individualised Dosing of Anti-Cancer Drugs in Routine Care: Overcoming the Logistical Challenges

Precision medicine in oncology involves identifying the 'right drug', at the 'right dose', for the right person. Currently, many orally administered anti-cancer drugs, particularly kinase inhibitors (KIs), are prescribed at a standard fixed dose. Identifying the right dose remains one of the biggest challenges to optimal patient care. Recently the Precision Dosing Group established the Accurate Dosing of Anti-cancer Patient-centred Therapies (ADAPT) Program to address individualised dosing; thus, use existing anti-cancer drugs more safely and efficiently. In this paper, we outline our framework, based on the Medical Research Council (MRC) framework, with a simple 6-step process and strategies which have led to the successful implementation of the ADAPT program in South Australia. Implementation strategies in our 6-step process involve: (1) Evaluate the evidence and identify the cancer drugs: Literature review, shadowing other experts, establishing academic partnerships, adaptability/flexibility; (2) Establishment of analytical equipment for drug assays for clinical purposes: assessment for readiness, accreditation, feasibility, obtaining formal commitments, quality assurance to all stakeholders; (3) Clinical preparation and education: educational material, conducted educational meetings, involve opinion leaders, use of mass media, promote network weaving, conduct ongoing training; (4) Blood collection, sample preparation and analyses: goods received procedures, critical control points (transport time); (5) Interpret and release results with recommendations: facilitate the relay of clinical data to providers; (6) Clinical application: providing ongoing consultation, identify early adopters, identify, and prepare champions. These strategies were selected from the 73 implementation strategies outlined in the Expert Recommendations for Implementing Change (ERIC) study. The ADAPT program currently provides routine plasma concentrations for patients on several orally administered drugs in South Australia and is currently in its evaluation phase soon to be published. Our newly established framework could provide great potential and opportunities to advance individualised dosing of oral anti-cancer drugs in routine clinical care.

Dose Optimization in Oncology Drug Development: The Emerging Role of Pharmacogenomics, Pharmacokinetics, and Pharmacodynamics

Drugs' safety and effectiveness are evaluated in randomized, dose-ranging trials in most therapeutic areas. However, this is only sometimes feasible in oncology, and dose-ranging studies are mainly limited to Phase 1 clinical trials. Moreover, although new treatment modalities (e.g., small molecule targeted therapies, biologics, and antibody-drug conjugates) present different characteristics compared to cytotoxic agents (e.g., target saturation limits, wider therapeutic index, fewer off-target side effects), in most cases, the design of Phase 1 studies and the dose selection is still based on the Maximum Tolerated Dose (MTD) approach used for the development of cytotoxic agents. Therefore, the dose was not optimized in some cases and was modified post-marketing (e.g., ceritinib, dasatinib, niraparib, ponatinib, cabazitaxel, and gemtuzumab-ozogamicin). The FDA recognized the drawbacks of this approach and, in 2021, launched Project Optimus, which provides the framework and guidance for dose optimization during the clinical development stages of anticancer agents. Since dose optimization is crucial in clinical development, especially of targeted therapies, it is necessary to identify the role of pharmacological tools such as pharmacogenomics, therapeutic drug monitoring, and pharmacodynamics, which could be integrated into all phases of drug development and support dose optimization, as well as the chances of positive clinical outcomes.

High throughput LC/ESI-MS/MS method for simultaneous analysis of 20 oral molecular-targeted anticancer drugs and the active metabolite of sunitinib in human plasma

Many types of oral molecular-targeted anticancer drugs are clinically used in cancer genomic medicine. Combinations of multiple molecular-targeted anticancer drugs are also being investigated, expecting to prolong the survival of patients with cancer. Therapeutic drug monitoring of oral molecular-targeted drugs is important to ensure efficacy and safety. A liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has been used for simultaneous determination of these drugs in human plasma. However, the sensitivity of mass spectrometers and differences in the therapeutic range of drugs have rendered the development of simultaneous LC/ESI-MS/MS methods difficult. In this study, a simultaneous quantitative method for 20 oral molecular-targeted anticancer drugs and the active metabolite of sunitinib was developed based on the results of linear range shifts of the calibration curves using four ion abundance adjustment techniques (collision energy defects, in-source collision-induced dissociation, secondary product ion selected reaction monitoring, and isotopologue selected reaction monitoring). The saturation of the detector for the seven analytes was resolved by incorporating optimal ion abundance adjustment techniques. Furthermore, the reproducibility of this method was confirmed in validation tests, and plasma from patients was measured by this method to demonstrate its usefulness in actual clinical practice. This analytical method is expected to make a substantial contribution to the promotion of personalized medicine in the future.

LC-MS/MS Method for the Quantification of PARP Inhibitors Olaparib, Rucaparib and Niraparib in Human Plasma and Dried Blood Spot: Development, Validation and Clinical Validation for Therapeutic Drug Monitoring

Poly (ADP-ribose) polymerase inhibitors (PARPis) are becoming increasingly meaningful in oncology, and their therapeutic drug monitoring (TDM) might be beneficial for patients. Several bioanalytical methods have been reported for PARPis quantification in human plasma, but advantages might be obtained using dried blood spot (DBS) as a sampling technique. Our aim was to develop and validate a liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for olaparib, rucaparib, and niraparib quantification in both human plasma and DBS matrices. Additionally, we aimed to assess the correlation between the drug concentrations measured in these two matrices. DBS from patients was obtained using Hemaxis DB10 for volumetric sampling. Analytes were separated on a Cortecs-T3 column and detected with electrospray ionization (ESI)-MS in positive ionization mode. Validation was performed according to the latest regulatory guidelines, in the range (ng/mL) 140-7000 for olaparib, 100-5000 for rucaparib, and 60-3000 for niraparib, within the hematocrit (Hct) range 29-45%. The Passing-Bablok and Bland-Altman statistical analyses revealed a strong correlation between plasma and DBS for olaparib and niraparib. However, due to the limited amount of data, it was challenging to establish a robust regression analysis for rucaparib. To ensure a more reliable assessment, additional samples are required. The DBS-to-plasma ratio was used as a conversion factor (CF) without considering any patient-related hematological parameters. These results provide a solid basis for the feasibility of PARPis TDM using both plasma and DBS matrices.

Recyclable detection of gefitinib in clinical sample mediated by multifunctional Ag-anchored g-C3N4/MoS2 composite substrate

Surface-enhanced Raman scattering (SERS) technology enables to satisfy the increasing demand of clinical drug monitoring due to the superiority of fingerprint recognition, real-time response, and nondestructive collection. Here, a novel graphitic carbon nitride (g-C₃N₄)/ molybdenum disulfide (MoS₂)/Ag composite substrate with a 3D surface structure was successfully developed for the recyclable detection of gefitinib in serum. Attributed to the uniform and dense "hotspots" on the shrubby active surfaces in conjunction with the potential synergistic chemical enhancement of g-C₃N₄/MoS₂ heterosystem, a remarkable SERS sensitivity with an attractive enhancement factor value of 3.3 × 10⁷ was demonstrated. Meanwhile, a type-II heterojunction between g-C₃N₄ and MoS₂ enabled more efficient diffusion of photogenerated e^--h⁺ pairs assisted by the localized surface plasmon resonance of Ag NPs, which contributed to the reliable recyclable detection of gefitinib. The ultra-low limit of detection at 10^-5 mg/mL and high recycling rates of gefitinib beyond 90% in serum were successfully realized. The results demonstrated the as-prepared SERS substrate has tremendous potential to be untilized for in-situ drug diagnostics.

A strategy for low-cost portable monitoring of plasma drug concentrations using a sustainable boron-doped-diamond chip

On-site monitoring of plasma drug concentrations is required for effective therapies. Recently developed handy biosensors are not yet popular owing to insufficient evaluation of accuracy on clinical samples and the necessity of complicated costly fabrication processes. Here, we approached these bottlenecks via a strategy involving engineeringly unmodified boron-doped diamond (BDD), a sustainable electrochemical material. A sensing system based on a ∼1 cm² BDD chip, when analysing rat plasma spiked with a molecular-targeting anticancer drug, pazopanib, detected clinically relevant concentrations. The response was stable in 60 sequential measurements on the same chip. In a clinical study, data obtained with a BDD chip were consistent with liquid chromatography-mass spectrometry results. Finally, the portable system with a palm-sized sensor containing the chip analysed ∼40 μL of whole blood from dosed rats within ∼10 min. This approach with the 'reusable' sensor may improve point-of-monitoring systems and personalised medicine while reducing medical costs.

Pharmacokinetic approach in therapeutic monitoring of antineoplastic drugs and the impact on pharmacoeconomics: A systematic review

OBJECTIVES

Therapeutic drug monitoring aims to quantify the concentration of a drug in a biological matrix. In oncology, the therapeutic arsenal is vast and therapeutic drug monitoring optimizes treatment and reduces costs. This review will analyze the financial impact of therapeutic monitoring of anticancer drugs in healthcare institutions.

METHODS

Keywords were selected using Decs (MeSH). Through the Pubmed, Scopus, and Virtual Health Library (VHL) databases, 74 articles were found, of which 4 meet the inclusion criteria. Methodological quality and risk of bias were assessed according to the Research Triangle Institute Item Bank (RTI-Item Bank) scale.

KEY FINDINGS

Therapeutic drug monitoring is an important tool for dose reduction or dose increase due to toxicity and lack of response, respectively. The main barriers are associated costs and lack of cost-benefit data. An alternative is to use population pharmacokinetic models, measured plasma concentration(s) and relevant patient characteristics, estimated individual pharmacokinetic parameters, and predicted drug concentrations at any point in the dosing range.

CONCLUSIONS

Therapeutic drug monitoring is understood as a technology that adds costs to payers. Future studies should generate clinical evidence of population pharmacokinetics from therapeutic drug monitoring studies.

A liquid chromatography-tandem mass spectrometry method for simultaneous quantification of thirty-nine tyrosine kinase inhibitors in human plasma

Currently, the use of targeted drugs such as tyrosine kinase inhibitors (TKIs) plays an important role in clinical therapy. As the number of approved TKIs continues to increase, existing analysis methods will not be able to meet the growing needs, and will hamper the development of therapeutic drug monitoring (TDM) of TKIs. Based on LC-MS/MS technology, this study tends to develop and validate a multi-component analysis method for simultaneous determination of the concentrations of 39 TKIs in plasma. Spiked plasma was blended with isotope labelled internal standards, and injected into the LC-MS/MS system after protein precipitation by acetonitrile. Chromatographic separation was achieved using an ODS-4 column with gradient elution of formic acid/water (1:1000; v/v) and acetonitrile. Analytes detection was conducted in positive ionisation mode using MRM. The total run time was 8 min. The method validation was conducted by assessing the following parameters: selectivity, linearity and the lower limit of qualification, accuracy and precision, stability, matrix effect and recovery. The concentrations of 39 TKIs showed good linearity within the range of their respective standard curves in plasma, the accuracy of all quality control samples ranged from 85.9% to 114.1%, and the precision was lower than 13.3%. The extraction recovery ranged from 92.6% to 114.7%, and the matrix effect of plasma was lower than 11.3%. This new method was successfully developed, can be used for the determination of drug concentrations in multiple patients with different kinds of TKIs, and will therefore be suitable for TDM of 39 TKIs.

Bioanalytical Methods for Poly(ADP-Ribose) Polymerase Inhibitor Quantification: A Review for Therapeutic Drug Monitoring

BACKGROUND

Therapeutic drug monitoring (TDM) of poly(ADP-ribose) polymerase inhibitors (PARPis) is an exploratory practice aimed at improving the quality of treatment through personalized therapy. Currently, there are 4 European Medicines Agency-approved and US Food and Drug Administration-approved PARPis available clinically whose quantification requires validated analytical methods: olaparib, niraparib, rucaparib, and talazoparib. The purpose of this literature review was to highlight the pharmacological features of PARPis that could support their TDM practice and provide a detailed discussion of the available liquid chromatography coupled with tandem mass spectrometry methods for their quantification.

METHODS

Using several Medical Subject Heading terms, the literature was searched using several research engines, including SciFinder, Web of Science, Google Scholar, and PubMed, to find articles published before August 2022.

RESULTS

Exposure-efficacy and exposure-safety profiles, drug-drug interactions, and hepatic/renal impairment of PARPis provide the potential rationale to monitor their concentrations through TDM. Several bioanalytical methods for their quantification have been reported and compared, and a great deal of heterogeneity has been found among methods, regarding both their analytical and regulatory aspects.

CONCLUSIONS

In addition to reducing toxicity and increasing the efficacy of PARPis therapy, TDM could be beneficial to thoroughly investigate the exposure-response relationships of PARPis and to establish pharmacokinetic thresholds for clinical decisions. Based on the comparison of published bioanalytical methods, their transferability and validation both play a key role in method selection. For future use in clinical TDM, we anticipate that bioanalytical methods should address every analytical need more thoroughly and should be validated with standardized guidelines.

Therapeutic Drug Monitoring of Protein Kinase Inhibitors in the Treatment of Non-small Cell Lung Cancer

Targeted therapy with protein kinase inhibitors (PKIs) represents one of the important treatment options for non-small cell lung cancer (NSCLC). It has contributed to improve patients' survival and quality of life significantly. These anticancer drugs are administrated orally in flat-fixed doses despite the well-known large interpatient pharmacokinetic variability and the possible need for dose individualization. To optimize and individualize dosing of PKIs, and thereby increasing the effectiveness and safety of the treatment, therapeutic drug monitoring (TDM) is the most frequently mentioned method. Unlike other areas of medicine, TDM has been rather exceptional in oncological practise since there is a little evidence or no data for concentration-effect relationships of PKIs. Therefore, the aim of this review is to summarize the pharmacokinetic characteristics of PKIs and provide the evidence supporting the use of TDM for personalised treatment of patients with NSCLC.

Therapeutic drug monitoring for cytotoxic anticancer drugs: Principles and evidence-based practices

Cytotoxic drugs are highly efficacious and also have low therapeutic index. A great degree of caution needs to be exercised in their usage. To optimize the efficacy these drugs need to be given at maximum tolerated dose which leads to significant amount of toxicity to the patient. The fine balance between efficacy and safety is the key to the success of cytotoxic chemotherapeutics. However, it is possibly more rewarding to obtain that balance for this class drugs as the frequency of drug related toxicities are higher compared to the other therapeutic class and are potentially life threatening and may cause prolonged morbidity. Significant efforts have been invested in last three to four decades in therapeutic drug monitoring (TDM) research to understand the relationship between the drug concentration and the response achieved for therapeutic efficacy as well as drug toxicity for cytotoxic drugs. TDM evolved over this period and the evidence gathered favored its routine use for certain drugs. Since, TDM is an expensive endeavor both from economic and logistic point of view, to justify its use it is necessary to demonstrate that the implementation leads to perceivable improvement in the patient outcomes. It is indeed challenging to prove the utility of TDM in randomized controlled trials and at times may be nearly impossible to generate such data in view of the obvious findings and concern of compromising patient safety. Therefore, good quality data from well-designed observational study do add immense value to the scientific knowledge base, when they are examined in totality, despite the heterogeneity amongst them. This article compiles the summary of the evidence and the best practices for TDM for the three cytotoxic drug, busulfan, 5-FU and methotrexate. Traditional use of TDM or drug concentration data for dose modification has been witnessing a sea change and model informed precision dosing is the future of cytotoxic drug therapeutic management.

Therapeutic drug monitoring-based precision dosing of oral targeted therapies in oncology: a prospective multicenter study

BACKGROUND

Oral targeted therapies show a high pharmacokinetic (PK) interpatient variability. Even though exposure has been positively correlated with efficacy for many of these drugs, these are still dosed using a one-size-fits-all approach. Consequently, individuals have a high probability to be either underexposed or overexposed, potentially leading to suboptimal outcomes. Therapeutic drug monitoring, which is personalized dosing based on measured systemic drug concentrations, could address these problems.

PATIENTS AND METHODS

Patients were enrolled in this prospective multicenter study (www.trialregister.nl; NL6695) if they started treatment with one of the 24 participating oral targeted therapies. Primary outcome was to halve the proportion of underexposed patients, compared with historical data. PK sampling was carried out after 4, 8 and 12 weeks, and every 12 weeks thereafter. In case of Cmin below the predefined target and manageable toxicity, a pharmacokinetically guided intervention was proposed (i.e. checking compliance and drug-drug interactions, concomitant intake with food, splitting intake moments or dose increments).

RESULTS

In total, 600 patients were included of whom 426 patients are assessable for the primary outcome and 552 patients had ≥1 PK sample(s) available and were therefore assessable for the overall analyses. Pharmacokinetically guided dosing reduced the proportion of underexposed patients at the third PK measurement by 39.0% (95% confidence interval 28.0% to 49.0%) compared with historical data. At the third PK measurement, 110 out of 426 patients (25.8%) had a low exposure. In total, 294 patients (53.3%) had ≥1 PK sample(s) below the preset target at a certain time point during treatment. In 166 of these patients (56.5%), pharmacokinetically guided interventions were carried out, which were successful in 113 out of 152 assessable patients (74.3%).

CONCLUSIONS

Pharmacokinetically guided dose optimization of oral targeted therapies was feasible in clinical practice and reduced the proportion of underexposed patients considerably.

Development and Validation of an LC-MS/MS Method to Quantify Gilteritinib and Its Clinical Application in Patients With FLT3 Mutation-Positive Acute Myelogenous Leukemia

BACKGROUND

Gilteritinib, a novel oral tyrosine kinase inhibitor, is used to treat acute myeloid leukemia (AML) with FMS-like tyrosine kinase-3 (FLT3) mutations. Therapeutic drug monitoring (TDM) of gilteritinib is important for improving clinical outcomes and ensuring safety. Therefore, this study aimed to develop a simplified method for quantifying gilteritinib in human plasma using liquid chromatography-tandem mass spectrometry.

METHODS

Liquid chromatography was performed by using an Acquity BEH C18 column (50 mm × 2.1 mm, 1.7 μm) and a gradient elution with 0.1% formic acid in water (A) and acetonitrile (B). Detection was performed by using a Shimadzu tandem mass spectrometer through multiple reaction monitoring in the positive-ion mode.

RESULTS

The developed method enabled quantification of gilteritinib in 4 minutes and was validated by evaluating selectivity, calibration curve (10-1000 ng/mL, r 2 > 0.99), a lower limit of quantification (LLOQ), accuracy (overall bias -4.2% to 1.9%), precision (intraday CV ≤ 7.9%; interday CV ≤ 13.6%), carryover, recovery, matrix effect, dilution integrity, and stability according to the US Food and Drug Administration (FDA) guidelines. This method was successfully applied to the TDM of gilteritinib trough concentrations in 3 patients with AML.

CONCLUSIONS

The developed method fulfilled the FDA guideline criteria and can easily be implemented to facilitate TDM in patients receiving gilteritinib in a clinical setting.

Feasibility of therapeutic drug monitoring of sorafenib in patients with liver or thyroid cancer

INTRODUCTION

Sorafenib is a tyrosine-kinase inhibitor approved for the treatment of renal cell carcinoma, hepatocellular carcinoma, thyroid carcinoma, and desmoid fibromatosis. As high inter-individual variability exists in exposure, there is a scientific rationale to pursue therapeutic drug monitoring (TDM). We investigated the feasibility of TDM in patients on sorafenib and tried to identify sub-groups in whom pharmacokinetically (PK) guided-dosing might be of added value.

METHODS

We included patients who started on sorafenib (between October 2017 and June 2020) at the recommended dose of 400 mg BID or with a step-up dosing schedule. Plasma trough levels (C_trough) were measured at pre-specified time-points. Increasing the dose was advised if C_trough was below the target of 3750 ng/mL and toxicity was manageable.

RESULTS

A total of 150 samples from 36 patients were collected. Thirty patients (83 %) had a C_trough below the prespecified target concentration at a certain time point during treatment. Toxicity from sorafenib hampered dosing according to target C_trough in almost half of the patients. In 11 patients, dosing was adjusted based on C_trough. In three patients, this resulted in an adequate C_trough without additional toxicity four weeks after the dose increase. In the remaining eight patients, dose adjustment based on C_trough did not result in a C_trough above the target or caused excessive toxicity.

CONCLUSIONS

TDM for sorafenib is not of added value in daily clinical practice. In most cases, toxicity restricts the possibility of dose escalations.

Therapeutic Drug Monitoring of Tyrosine Kinase Inhibitors Using Dried Blood Microsamples

Therapeutic drug monitoring (TDM) of tyrosine kinase inhibitors (TKIs) is not yet performed routinely in the standard care of oncology patients, although it offers a high potential to improve treatment outcome and minimize toxicity. TKIs are perfect candidates for TDM as they show a relatively small therapeutic window, a wide inter-patient variability in pharmacokinetics and a correlation between drug concentration and effect. Moreover, most of the available TKIs are susceptible to various drug-drug interactions and medication adherence can be checked by performing TDM. Plasma, obtained via traditional venous blood sampling, is the standard matrix for TDM of TKIs. However, the use of plasma poses some challenges related to sampling and stability. The use of dried blood microsamples can overcome these limitations. Collection of samples via finger-prick is minimally invasive and considered convenient and simple, enabling sampling by the patients themselves in their home-setting. The collection of small sample volumes is especially relevant for use in pediatric populations or in pharmacokinetic studies. Additionally, working with dried matrices improves compound stability, resulting in convenient and cost-effective transport and storage of the samples. In this review we focus on the different dried blood microsample-based methods that were used for the quantification of TKIs. Despite the many advantages associated with dried blood microsampling, quantitative analyses are also associated with some specific difficulties. Different methodological aspects of microsampling-based methods are discussed and applied to TDM of TKIs. We focus on sample preparation, analytics, internal standards, dilution of samples, external quality controls, dried blood spot specific validation parameters, stability and blood-to-plasma conversion methods. The various impacts of deviating hematocrit values on quantitative results are discussed in a separate section as this is a key issue and undoubtedly the most widely discussed issue in the analysis of dried blood microsamples. Lastly, the applicability and feasibility of performing TDM using microsamples in a real-life home-sampling context is discussed.

Therapeutic Drug Monitoring as a Tool for Therapy Optimization

The use of pharmacotherapy for improving healthcare in society is increasing. A vast majority of patients have either received subtherapeutic treatment (which could result from low pharmacokinetic) or experienced adverse effects due to the toxic levels of the drug. The medicines used to treat chronic conditions, such as epilepsy; cardiovascular diseases; and oncological, neurological, and psychiatric disorders, require routine monitoring. New targeted therapies suggest an individualized treatment that can slowly move practitioners away from the concept of a one-size-fits-all-fixed-dosing approach. Therapeutic drug use can be monitored based on pharmacokinetic, pharmacodynamic, and pharmacometric methods. Based on the experiences of therapeutic drug monitoring of various agents across the globe, we can look ahead to the possible developments of therapeutic drug monitoring in India.

Ritonavir-Boosted Exposure of Kinase Inhibitors: an Open Label, Cross-over Pharmacokinetic Proof-of-Concept Trial with Erlotinib

Background

Although kinase inhibitors (KIs) are generally effective, their use has a large impact on the current health care budget. Dosing strategies to reduce treatment costs are warranted. Boosting pharmacokinetic exposure of KIs metabolized by cytochrome P450 (CYP)3A4 with ritonavir might result in lower doses needed and subsequently reduces treatment costs. This study is a proof-of-concept study to evaluate if the dose of erlotinib can be reduced by co-administration with ritonavir.

Methods

In this open-label, cross-over study, we compared the pharmacokinetics of monotherapy erlotinib 150 mg once daily (QD) (control arm) with erlotinib 75 mg QD plus ritonavir 200 mg QD (intervention arm). Complete pharmacokinetic profiles at steady-state were taken up to 24 h after erlotinib intake for both dosing strategies.

Results

Nine patients were evaluable in this study. For the control arm, the systemic exposure over 24 h, maximum plasma concentration and minimal plasma concentration of erlotinib were 29.3 μg*h/mL (coefficient of variation (CV):58%), 1.84 μg/mL (CV:60%) and 1.00 μg/mL (CV:62%), respectively, compared with 28.9 μg*h/mL (CV:116%, p = 0.545), 1.68 μg/mL (CV:68%, p = 0.500) and 1.06 μg/mL (CV:165%, p = 0.150) for the intervention arm. Exposure to the metabolites of erlotinib (OSI-413 and OSI-420) was statistically significant lower following erlotinib plus ritonavir dosing. Similar results regarding safety in both dosing strategies were observed, no grade 3 or higher adverse event was reported.

Conclusions

Pharmacokinetic exposure at a dose of 75 mg erlotinib when combined with the strong CYP3A4 inhibitor ritonavir is similar to 150 mg erlotinib. Ritonavir-boosting is a promising strategy to reduce erlotinib treatment costs and provides a rationale for other expensive therapies metabolized by CYP3A4.

Adaptive dosing of sunitinib in a metastatic renal cell carcinoma patient: when in silico modeling helps to go quicker to the point

PURPOSE

Adaptive dosing strategy with oral targeted therapies in oncology is mostly based upon clinical signs. Using pharmacokinetics (PK) models to customize dosing could help saving time, i.e., by predicting clinical outcome through early monitoring of drug levels.

CASE REPORT

We present the case of a metastatic renal cell carcinoma patient treated with standard Sunitinib dosing (i.e., 50 mg QD). Clinical signs suggested lack of efficacy. Therapeutic Drug Monitoring (TDM) confirmed that exposure was below the expected target exposure. PK modeling suggested that dosing could be increased safely to 75 mg QD. Sunitinib dosing was instead changed empirically to 62.5 mg only, increasing drug exposure to the lower part of the therapeutic window. Resolution of bone pains plus Stable Disease were observed. Even though further modeling suggested to increase Sunitinib dosing to 75 mg again, the intermediate dosing was maintained for the subsequent cycles to preserve the safety. Unfortunately, severe pains plus degradation of the general state were reported and imaging showed Progressive Disease. The patient was finally switched to alternative therapy, without being treated at the 75 mg level of Suntitinib.

CONCLUSIONS AND DISCUSSION

This case suggests that model-based adaptive dosing could have allowed to reach quicker the best dosing with Sunitinib, thus possibly ensuring a better management of this patient. Model-informed dosing should be used instead of empirical search for the most appropriate dosing to ensure a good benefit/risk ratio with Sunitinib, especially in the context of such aggressive disease.

Severe tyrosine-kinase inhibitor induced liver injury in metastatic renal cell carcinoma patients: two case reports assessed for causality using the updated RUCAM and review of the literature

Background

Sunitinib and pazopanib are both oral small molecule multityrosine kinase inhibitors (MTKI) used in the treatment of renal cell carcinoma (RCC). Hepatotoxicity or “liver injury” is the most important adverse effect of pazopanib administration, but little is known about the underlying mechanism. Liver injury may also occur in patients treated with sunitinib, but severe toxicity is extremely rare. Herein we report two new cases of severe liver injury induced by MTKI. Both cases are unique and exceptional. We assessed both cases for drug-induced liver injury (DILI) using the updated score Roussel Uclaf causality assessment method (RUCAM). The literature on potential pathogenic mechanisms and precautionary measures is reviewed.

Case presentation

A case of a metastatic RCC (mRCC) patient treated with pazopanib who had manifestation of severe liver injury is presented. These manifestations consisted of grade 4 alanine aminotransferase (ALT) increase and grade 4 hyperbilirubinemia. Alternate causes of acute or chronic liver disease were excluded. The patient gradually recovered from the liver injury and refused any further therapy for mRCC. The patient was diagnosed with acute myeloid leukemia (AML) two years later and eventually succumbed to the disease. The second case describes a mRCC patient treated with sunitinib for 3,5 years and fatal liver failure after 2 weeks of clarithromycin co-medication for acute bronchitis.

Conclusions

Liver injury has been commonly observed in TKI-treated patients with unpredictable course. Management requires regular routine liver enzyme-monitoring and the collaboration of medical oncologist and hepatologist. There is an unmet medical need for a risk stratification and definition of predictive biomarkers to identify potential genetic polymorphisms or other factors associated with TKI-induced liver injury. Any potential unrecommended concomitant therapy has to be avoided.

Therapeutic Drug Monitoring of Protein Kinase Inhibitors in Breast Cancer Patients

Protein kinase inhibitors (PKIs) represent up-to-date therapeutic approach in breast cancer treatment. Although cancer is a rapidly progressive disease, many substances, including PKIs, are usually used at fixed doses without regard to each patient's individuality. Therapeutic drug monitoring (TDM) is a tool that allows individualization of therapy based on drug plasma levels. For TDM conduct, exposure-response relationships of drug substances are required. The pharmacokinetic data and exposure-response evidence supporting the use of TDM for 6 PKIs used in breast cancer treatment, one of the most common female tumour diseases, are discussed in this review.

Precision Dosing of Targeted Therapies Is Ready for Prime Time

Fixed dosing of oral targeted therapies is inadequate in the era of precision medicine. Personalized dosing, based on pharmacokinetic (PK) exposure, known as therapeutic drug monitoring (TDM), is rational and supported by increasing evidence. The purpose of this perspective is to discuss whether randomized studies are needed to confirm the clinical value of precision dosing in oncology. PK-based dose adjustments are routinely made for many drugs and are recommended by health authorities, for example, for patients with renal impairment or for drug-drug interaction management strategies. Personalized dosing simply extrapolates this paradigm from selected patient populations to each individual patient with suboptimal exposure, irrespective of the underlying cause. If it has been demonstrated that exposure is related to a relevant clinical outcome, such as efficacy or toxicity, and that exposure can be optimized by PK-guided dosing, it could be logically assumed that PK-guided dosing would result in better treatment outcomes without the need for randomized confirmatory trials. We propose a path forward to demonstrate the clinical relevance of individualized dosing of molecularly-targeted anticancer drugs.

Developing a Nationwide Infrastructure for Therapeutic Drug Monitoring of Targeted Oral Anticancer Drugs: The ON-TARGET Study Protocol

Simple Summary

Relationships between drug concentrations in blood and efficacy and/or toxicity have been reported for up to 80% of oral anticancer drugs (OADs). Most OADs exhibit highly variable drug concentrations at the approved dose. This may result in a significant proportion of patients with suboptimal drug concentrations. Therapeutic Drug Monitoring (TDM), which is dose optimization based on measured drug concentrations, can be used to personalize drug dosing with the overall goal to improve the benefit-risk ratio of anticancer drug treatment. The ON-TARGET study aims to investigate the feasibility of TDM in patients receiving either axitinib or cabozantinib for the treatment of renal-cell carcinoma with the main objective to improve severe tyrosine kinase inhibitor associated toxicity. Additionally, the feasibility of volumetric absorptive microsampling (VAMS), a novel minimally invasive and easy to handle blood sampling technique, for TDM sample collection is investigated.

Abstract

Exposure-efficacy and/or exposure-toxicity relationships have been identified for up to 80% of oral anticancer drugs (OADs). Usually, OADs are administered at fixed doses despite their high interindividual pharmacokinetic variability resulting in large differences in drug exposure. Consequently, a substantial proportion of patients receive a suboptimal dose. Therapeutic Drug Monitoring (TDM), i.e., dosing based on measured drug concentrations, may be used to improve treatment outcomes. The prospective, multicenter, non-interventional ON-TARGET study (DRKS00025325) aims to investigate the potential of routine TDM to reduce adverse drug reactions in renal cell carcinoma patients receiving axitinib or cabozantinib. Furthermore, the feasibility of using volumetric absorptive microsampling (VAMS), a minimally invasive and easy to handle blood sampling technique, for sample collection is examined. During routine visits, blood samples are collected and sent to bioanalytical laboratories. Venous and VAMS blood samples are collected in the first study phase to facilitate home-based capillary blood sampling in the second study phase. Within one week, the drug plasma concentrations are measured, interpreted, and reported back to the physician. Patients report their drug intake and toxicity using PRO-CTCAE-based questionnaires in dedicated diaries. Ultimately, the ON-TARGET study aims to develop a nationwide infrastructure for TDM for oral anticancer drugs.

Optimized Dosing: The Next Step in Precision Medicine in Non-Small-Cell Lung Cancer

In oncology, and especially in the treatment of non-small-cell lung cancer (NSCLC), dose optimization is often a neglected part of precision medicine. Many drugs are still being administered in "one dose fits all" regimens or based on parameters that are often only minor determinants for systemic exposure. These dosing approaches often introduce additional pharmacokinetic variability and do not add to treatment outcomes. Fortunately, pharmacological knowledge is increasing, providing valuable information regarding the potential of, for example, therapeutic drug monitoring. This article focuses on the evidence for the most promising and easily implemented optimized dosing approaches for the small-molecule inhibitors, chemotherapeutic agents, and monoclonal antibodies as treatment options currently approved for NSCLC. Despite limitations such as investigations having been conducted in oncological diseases other than NSCLC or the retrospective origin of many analyses, an alternative dosing regimen could be beneficial for treatment outcomes, prescriber convenience, or financial burden on healthcare systems. This review of the literature provides recommendations on the implementation of dose optimization and advice regarding promising strategies that deserve further research in NSCLC.

Therapeutic drug monitoring in oncology: International Association of Therapeutic Drug Monitoring and Clinical Toxicology consensus guidelines for imatinib therapy

Although therapeutic drug monitoring (TDM) is an important tool in guiding drug dosing for other areas of medicine including infectious diseases, cardiology, psychiatry and transplant medicine, it has not gained wide acceptance in oncology. For imatinib and other tyrosine kinase inhibitors, a flat dosing approach is utilised for management of oral chemotherapy. There are many published studies examining the correlation of blood concentrations with clinical effects of imatinib. The International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT) determined that there was a need to examine the published literature regarding utility of TDM in imatinib therapy and to develop consensus guidelines for TDM based on the available data. This article summarises the scientific evidence regarding TDM of imatinib, as well as the consensus guidelines developed by the IATDMCT.