Identification of Enzymes Oxidizing the Tyrosine Kinase Inhibitor Cabozantinib: Cabozantinib Is Predominantly Oxidized by CYP3A4 and Its Oxidation Is Stimulated by cyt b5 Activity

[Precision Medicine for Patients with Renal Cell Carcinoma Based on Drug-metabolizing Enzyme Expression Levels]

Notable advances have recently been achieved in drug therapies for renal cell carcinoma (RCC). Several tyrosine kinase inhibitors (TKIs) and immune checkpoint inhibitors (ICIs) have been approved for metastatic RCC (mRCC). The current first-line treatment for mRCC involves combination therapies using TKIs and ICIs. However, there is no consensus on which TKI+ICI therapy is best or how to select the appropriate therapy for individual patients with RCC. The kidney expresses various metabolic enzymes, including CYP and uridine diphosphate glucose (UDP)-glucuronosyltransferase (UGT). Although information on CYP and UGT expression in the kidney is limited compared to our understanding of liver expression, the main CYP and UGT subtypes expressed at high levels in the kidney are estimated to be CYP2B6, CYP3A5, CYP4A11, CYP4F2, UGT1A6, UGT1A9, and UGT2B7. In RCC, the expression profiles and levels of these enzymes are somewhat altered compared with normal kidney. The main known subtypes of CYP and UGT in RCC are CYP1B1, CYP3A5, CYP4A11, UGT1A6, UGT1A9, UGT1A10, and UGT2B7. High CYP expression has been reported in several cancers, possibly conferring resistance to anti-cancer drugs including TKIs, due to extensive drug metabolism. Additionally, CYP and UGT expression levels may possibly affect cancer prognosis by metabolizing endogenous substrates, regardless of their role in anti-cancer drug metabolism. In this review, I discuss CYP and UGT expression level profiles in RCC based on previously published papers, including ours, and examine possible relationships between these enzyme expression profiles and treatment outcomes for patients with RCC.

Cabozantinib Induces Isolated Hyperbilirubinemia in Renal Cell Carcinoma Patients carrying the UGT1A1*28 Polymorphism

BACKGROUND

Genetic variants of UGT1A1, involved in glucuronidation and clearance of bilirubin, are associated with reduced bilirubin metabolization and drug-induced isolated hyperbilirubinemia. We studied the impact of the UGT1A1*28 polymorphism on drug-induced isolated hyperbilirubinemia in metastatic renal cell carcinoma patients treated with pazopanib, cabozantinib, and axitinib.

METHODS

We genotyped the UGT1A1*28 TA6/TA6-TA6/TA7-TA7/TA7 polymorphism and correlated with median baseline, on-treatment and peak bilirubin levels during therapy, incidence of grade-1- or -2 (G1/2)-hyperbilirubinemia and time-to-G1-hyperbilirubinemia.

RESULTS

Of the 66 patients treated with pazopanib, 29 received axitinib and 28 cabozantinib upon progression. Median baseline bilirubin was higher in TA7/TA7-carriers versus TA6/TA6+TA6/TA7-carriers at start of pazopanib (P < .0001), cabozantinib (P < .0001), and axitinib (P = .007). During pazopanib therapy, median bilirubin increased 1.4-fold in TA7/TA7+TA6/TA7-carriers but not in TA6/TA6-carriers. On cabozantinib, bilirubin increased 1.5-fold in TA7/TA7-carriers but not in TA6/TA6+TA6/TA7-carriers. Axitinib did not increase bilirubin in any genotype. Peak bilirubin in TA7/TA7- versus TA6/TA6+TA6/TA7-carriers was higher on pazopanib (P < .0001) or cabozantinib (P < .0001). With pazopanib, G1-hyperbilirubinemia occurred in 57% of TA7/TA7- and 12% of TA6/TA6+TA6/TA7-carriers (P = .0009) and G2-hyperbilirubinemia in 36% and 6% of the patients, respectively (P = .004). On cabozantinib, G1-hyperbilirubinemia occurred in 100% of TA7/TA7- and 5% of TA6/TA6+TA6/TA7-carriers (P < .0001) and G2-hyperbilirubinemia in 33% and 0% of the patients, respectively (P = .04). On axitinib, no correlation between the genotypes and G1/2-hyperbilirubinemia was observed.

CONCLUSION

We validate the previously described impact of the UGT1A1*28 polymorphism on isolated bilirubin increase on pazopanib. We report for the first time that cabozantinib also interferes with UGT1A1 and causes isolated bilirubin increase.

Phase I Trial of the Multi-kinase Inhibitor Cabozantinib, a CYP3A4 Substrate, plus CYP3A4-Interacting Antiretroviral Therapy in People Living with HIV and Cancer (AMC-087)

PURPOSE

To evaluate the safety, pharmacokinetics, and pharmacodynamic effects of cabozantinib, a CYP3A4 substrate, in people living with human immunodeficiency virus and cancer receiving antiretrovirals (ARV).

PATIENTS AND METHODS

Patients received a reduced dose of cabozantinib (20 mg orally daily) with strong CYP3A4 inhibitors (ARV ritonavir or non-ARV cobicistat, stratum A), or a standard 60 mg dose with ARVs that are CYP3A4 inducers (efavirenz or etravirine, stratum B) or noninteracting ARVs (stratum C). Initial dose escalation in stratum A and stratum B was performed on the basis of tolerability.

RESULTS

36 patients received cabozantinib plus ARVs, including 20 in stratum A, 9 in B, and 7 in C. The recommended initial cabozantinib doses for stratum A, B, and C were 20, 60, and 60 mg, respectively. Doses of 40 or 60 mg plus CYP3A4 inhibitors in stratum A and 100 mg plus CYP3A4 inducers in stratum B were associated with excessive toxicity, whereas 60 mg with noninteracting ARVs was not. The steady state minimal concentrations were lower at 20 mg in stratum A or 60 mg in stratum B compared with 60 mg in stratum C, while total exposure was only lower in 60 mg in stratum B compared with 60 mg in stratum C. Activity was observed in Kaposi sarcoma and an AXL-amplified sarcoma.

CONCLUSIONS

Cabozantinib as a single agent should be initiated at 20 mg daily and 60 mg daily when taken concurrently with ARVs that are strong CYP3A4 inhibitors and inducers, respectively, with consideration for subsequent escalation per current cabozantinib guidelines. See related commentary by Eisenmann and Sparreboom, p. 4999.

Real-world experience of cabozantinib in Asian patients with advanced renal cell carcinoma following treatment with VEGFR tyrosine kinase inhibitors and/or immune-checkpoint inhibitors

Background

There is a lack of real-world data on the use of cabozantinib in Asian patients with metastatic renal cell carcinoma.

Methods

We conducted a retrospective study to investigate the toxicity and efficacy of cabozantinib in this patient population who progressed on tyrosine kinase inhibitors and/or immune-checkpoint inhibitors from six oncology centres in Hong Kong. The primary endpoint was the incidence of serious adverse events (AEs) attributed to cabozantinib. Secondary safety endpoints included dose reductions and AE-led treatment terminations. Secondary effectiveness endpoints included overall survival, progression-free survival, and objective response rate.

Results

A total of 24 patients were included. Half received cabozantinib as a third-line or later-line treatment, whilst 50% received prior immune-checkpoint inhibitors, primarily nivolumab. Overall, 13 (54.2%) patients reported at least one cabozantinib-related AE of grades 3-4. The most commonly reported AEs were hand-foot skin reactions (9; 37.5%) and anaemia (4; 16.7%). Fifteen (65.2%) patients required dose reductions. Three patients discontinued treatment because of AEs. The median progression-free survival and overall survival were 10.3 months and 13.2 months, respectively; 6 (25%) patients achieved partial responses, and 8 (33.3%) achieved stable disease.

Conclusion

Cabozantinib was generally well tolerated and efficacious in Asian patients with metastatic renal cell carcinoma who were heavily pretreated.

Pilot Study on the Impact of Polymorphisms Linked to Multi-Kinase Inhibitor Metabolism on Lenvatinib Side Effects in Patients with Advanced Thyroid Cancer

Multi-kinase inhibitors (MKIs) represent the best therapeutic option in advanced thyroid cancer patients. The therapeutic efficacy and toxicity of MKIs are very heterogeneous and are difficult to predict before starting treatment. Moreover, due to the development of severe adverse events, it is necessary to interrupt the therapy some patients. Using a pharmacogenetic approach, we evaluated polymorphisms in genes coding for proteins involved with the absorption and elimination of the drug in 18 advanced thyroid cancer patients treated with lenvatinib, and correlated the genetic background with (1) diarrhea, nausea, vomiting and epigastric pain; (2) oral mucositis and xerostomia; (3) hypertension and proteinuria; (4) asthenia; (5) anorexia and weight loss; (6) hand foot syndrome. Analyzed variants belong to cytochrome P450 (CYP3A4 rs2242480 and rs2687116 and CYP3A5 rs776746) genes and to ATP-binding cassette transporters (ABCB1 rs1045642, rs2032582 and rs2235048 and ABCG2 rs2231142). Our results suggest that the GG genotype for rs2242480 in CYP3A4 and CC genotype in rs776746 for CYP3A5 were both associated with the presence of hypertension. Being heterozygous for SNPs in the ABCB1 gene (rs1045642 and 2235048) implicated a higher grade of weight loss. The ABCG2 rs2231142 statistically correlated with a higher extent of mucositis and xerostomia (CC genotype). Heterozygous and rare homozygous genotypes for rs2242480 in CYP3A4 and for rs776746 for CYP3A5 were found to be statistically linked to a worse outcome. Evaluating the genetic profile before starting lenvatinib treatment may help to predict the occurrence and grade of some side effects, and may contribute to improving patient management.

A high throughput method for Monitoring of Sorafenib, regorafenib, cabozantinib and their metabolites with UPLC-MS/MS in rat plasma

As multi-targeted tyrosine kinase inhibitors, sorafenib, regorafenib and cabozantinib are widely used in hepatocellular carcinoma (HCC) for systemic therapies with anti-proliferative and anti-angiogenic effects. Nevertheless, adverse effects or insufficient efficacy appear frequently due to the plasma concentration with individual variability of these drugs. To ensure the curative effect and safety by therapeutic drug monitoring (TDM), this study developed a high throughput method to quantify sorafenib, regorafenib, cabozantinib and their active metabolites in plasma simultaneously. The chromatographic separation analysis achievement was performed on a Waters-ACQUITY UPLC BEH C18 column by UPLC-MS/MS system using a gradient elution of solvent A (acetonitrile) and solvent B (water with 0.1% formic acid) in 3.0 min. This method presented satisfactory results of specificity, precision (the intra-day coefficient of variation was between 2.5% and 6.6%, and the inter-day coefficient of variation was between 4.0% and 11.1%) and accuracy (within ±15% for intra-day and inter-day), as well as the stability under certain conditions, the matrix effect in plasma, and extraction recovery (75.6%–94.4%). The linearity of each analyte in the proper concentration scope indicated excellent. This study strictly complied with the performance rules of assay validation in biological medium proposed by FDA and was successfully applied to the pharmacokinetic study in rats. Thus, it would be an advantageous option to research the relationship between concentration-efficacy and concentration-toxic in HCC patients who were supposed to take these medications.

The impact of individual human cytochrome P450 enzymes on oxidative metabolism of anticancer drug lenvatinib

Lenvatinib, a small molecule tyrosine kinase inhibitor (TKI), exhibits good inhibitory effect in several types of carcinomas. Specifically, it is the most effective TKI used for treatment of thyroid cancer. To extend pharmacokinetics data on this anticancer agent, we aimed to identify the metabolites of lenvatinib formed during in vitro incubation of lenvatinib with human hepatic microsomes or recombinant cytochromes P450 (CYPs) by using high performance liquid chromatography and mass spectrometry. The role of CYPs in the oxidation of lenvatinib was initially investigated in hepatic microsomes using specific CYP inhibitors. CYP-catalytic activities in each microsomal sample were correlated with the amounts of lenvatinib metabolites formed by these samples. Further, human recombinant CYPs were employed in the metabolic studies. Based on our data, lenvatinib is metabolized to O-desmethyl lenvatinib, N-descyclopropyl lenvatinib and lenvatinib N-oxide. In the presence of cytochrome b₅, recombinant CYP3A4 was the most efficient to form these metabolites. In addition, CYP1A1 significantly contributes to the lenvatinib metabolism. It was even more efficient in forming of O-desmethyl lenvatinib than CYP3A4 in the absence of cytochrome b₅. The present study indicates that further research focused on drug-drug interactions, in particular on CYP3A4 and CYP1A1 modulators, is needed. This will pave new avenues towards TKIs-mediated personalized therapy.