Axitinib pharmacologic therapeutic monitoring reveals severe under-exposure despite titration in patients with metastatic renal cell carcinoma

Therapeutic Drug Monitoring for Tyrosine Kinase Inhibitors in Metastatic Renal Cell Carcinoma

Inter-individual variability in drug response pose significant challenges to treatment with tyrosine kinase inhibitors (TKIs) in patients with metastatic renal cell carcinoma (mRCC). TKIs meet traditional criteria for using therapeutic drug monitoring (TDM), but research is still limited. Understanding the role of TDM in individualizing treatment strategies could help optimize treatment. Here we review the state of knowledge of TDM for TKIs in mRCC treatment. A comprehensive literature review of original research studies focusing on TDM of TKIs in mRCC treatment, clinical in vivo studies reporting on pharmacokinetics-pharmacodynamics, therapeutic ranges, drug concentrations, dose adjustments, clinical outcomes, or other relevant aspects related to TDM. We reviewed studies involving human subjects published in peer-reviewed journals. A narrative synthesis approach was employed to summarize the findings. Key themes and trends related to TDM of TKIs in mRCC treatment were identified and synthesized to provide a comprehensive overview of the current state of knowledge. Our search yielded 25 articles. Most were observational. The most consistently reported association between plasma concentration and effect was pazopanib Ctrough >20 µg/mL, but this concentration was not significant across all studies. We found inconsistent evidence for sunitinib and cabozantinib. For axitinib, we found a clear exposure-response relationship, but research was too diverse to conclude on a therapeutic window to use for TDM. We found much heterogeneity between recommended time of measurement (minimum plasma concentration [Cmin], maximal plasma concentration [Cmax], area under the curve [AUC]) and large variation in plasma concentration associated with clinical outcomes, which makes it difficult to recommend specific concentration intervals based on 1 or more of these measurements. Results were more consistent with TKIs continuously administered. Further research is needed to elucidate the long-term impact of TDM to possibly establish standardized therapeutic intervals. Prospective studies are suggested. The application of TDM in TKI-combination therapy is warranted in future research.

Development and clinical application of a liquid chromatography-tandem mass spectrometry-based assay to quantify eight tyrosine kinase inhibitors in human plasma

Introduction

Tyrosine kinase inhibitors (TKIs) are widely used in tumor treatment. The detection of these medicines by liquid chromatography-tandem mass spectrometry (LC-MS/MS) can avoid the interference of structurally similar compounds.

Objectives

This study aimed to develop and validate a new LC-MS/MS assay for the quantification of eight tyrosine kinase inhibitors in human plasma and to preliminarily evaluate the clinical utility of the therapeutic drug monitoring method.

Methods

Plasma samples were prepared by simple protein precipitation and separated using an ultra-high-performance reversed phase column. Detection was achieved using a triple quadrupole mass spectrometer in the positive ionization mode. The assay was validated against standard guidelines. We reviewed and analyzed the results of 268 plasma samples obtained from patients administered imatinib and other TKIs collected from January 2020 to November 2021 at Zhongshan Hospital. The analytes were separated and quantified within 3.5 min.

Results

The newly developed method demonstrated linearity for the detected drug concentration in the range of 20 to 2000 ng/ml for gefitinib (r² = 0.991) and crizotinib (r² = 0.992), 50 to 5000 ng/ml for nilotinib (r² = 0.991) and imatinib (r² = 0.995), 1500-150,000 ng/ml for vemurafenib (r² = 0.998), 1000-100,000 ng/ml for pazopanib (r² = 0.993), 0.5-100 ng/ml for axitinib (r² = 0.992) and 5-500 ng/ml for sunitinib (r² = 0.991) and N-desethyl sunitinib (r² = 0.998). The lower limit of quantification (LLOQ) was 20 ng/ml for gefitinib and crizotinib, 50 ng/ml for nilotinib and imatinib, 1500 ng/ml for vemurafenib, 1000 ng/ml for pazopanib, 0.5, and 5 ng/ml for sunitinib and N-desethyl sunitinib, respectively. Specificity, precision, accuracy, and stability were tested, and met the requirements of the guidelines. At the same dose, there was no significant difference in plasma drug concentration between the original imatinib medicine and the generic medicine after patent expiration.

Conclusion

We developed a sensitive and reliable method for the quantification of eight TKIs.

Pyrazole-containing pharmaceuticals: target, pharmacological activity, and their SAR studies

Pyrazole is a five-membered heterocycle bearing two adjacent nitrogen atoms. Both pharmaceutical agents and natural products with pyrazole as a nucleus have exhibited a broad spectrum of biological activities. In the last few decades, more than 40 pyrazole-containing drugs have been approved by the FDA for the treatment of a broad range of clinical conditions including celecoxib (anti-inflammatory), CDPPB (antipsychotic), difenamizole (analgesic), etc. Owing to the unique physicochemical properties of the pyrazole core, pyrazole-containing drugs may exert better pharmacokinetics and pharmacological effects compared with drugs containing similar heterocyclic rings. The purpose of this paper is to provide an overview of all the existing drugs bearing a pyrazole nucleus that have been approved or in clinical trials, involving their pharmacological activities and SAR studies.

A Profile of Avelumab Plus Axitinib in the Treatment of Renal Cell Carcinoma

Until recently, the approved first-line treatment for metastatic RCC (mRCC) consisted of tyrosine kinase inhibitors (TKI) targeting the vascular endothelial growth factor receptors (VEGFR) monotherapy. The landscape of first-line treatment has been transformed in the last few years with the advent of immune checkpoint inhibitors (ICI) or VEGFR TKI plus ICI combinations. This article focuses on the profile of one of these ICI plus VEGFR TKI combination, avelumab plus axitinib. We detail the characteristics of each drug separately, and then we explore the rationale for their association, its efficacy and the resulting toxicity. Finally, we examine the factors associated with avelumab plus axitinib outcomes, and their impact on therapeutic strategy.

Absorption of the orally active multikinase inhibitor axitinib as a therapeutic index to guide dose titration in metastatic renal cell carcinoma

Purpose Axitinib is an orally active multikinase inhibitor currently used to treat patients with metastatic renal cell carcinoma (RCC). This study examined the pharmacokinetics of axitinib and the relationship between peak drug concentration (C_max) and clinical outcomes in real-world practice. Methods Twenty patients with metastatic RCC treated with axitinib monotherapy were enrolled. Post-dose (1-4 h) blood samples were obtained, and axitinib C_max in plasma was measured by liquid chromatography-tandem mass spectrometry. Efficacy endpoints were best overall response (per RECIST 1.1) and progression-free survival (PFS). The safety endpoint was the cumulative incidence of dose-limiting toxicities (DLTs). Results Large inter- and intra-individual variability in dose-adjusted C_max was observed (0.02-11.2 ng/mL/mg). Axitinib absorption was significantly influenced by glucuronidation activity (P = 0.040). C_max at steady state was significantly higher in responders than in non-responders (P = 0.013). The optimal C_max cutoff to predict a clinical response was 12.4 ng/mL. The median PFS was significantly longer in patients who achieved an average steady state C_max above the threshold than in those who did not (799 vs. 336 days; P = 0.047). The cumulative incidence of DLTs was significantly higher in patients with C_max ≥ 40.2 ng/mL than in other patients (sub-hazard ratio, 4.13; 95% confidence interval, 1.27-13.5; P = 0.019). Conclusions The potential therapeutic window of axitinib C_max in metastatic RCC was estimated at 12.4-40.2 ng/mL. Pharmacokinetically guided dose titration using therapeutic drug monitoring may improve the efficacy and safety of axitinib, warranting further investigation in a larger patient population.