Pharmacokinetics and pharmacodynamics of irinotecan and its metabolites from plasma and saliva data in patients with metastatic digestive cancer receiving Folfiri regimen

Evaluation of UGT1A1 and CYP3A Genotyping and Single-Point Irinotecan and Metabolite Concentrations as Predictors of the Occurrence of Adverse Events in Cancer Treatment

PURPOSE

The variability on irinotecan (IRI) pharmacokinetics and toxicity has been attributed mostly to genetic variations in the UGT1A1 gene, responsible for conjugation of the active metabolite SN-38. Also, CYP3A mediates the formation of inactive oxidative metabolites of IRI. The association between the occurrence of severe adverse events, pharmacokinetics parameters, and UGT1A1 and CYP3A4 predicted phenotypes was evaluated, as the evaluation of [SN-38]/IRI dose ratio as predictor of severe adverse events.

METHODS

Forty-one patients undergoing IRI therapy were enrolled in the study. Blood samples were collected 15 min after the end of drug the infusion, for IRI, SN-38, SN-38G, bilirubin concentrations measurements, and UGT1A1 and CYP3A genotype estimation. Data on adverse event was reported.

RESULTS

Fifteen patients (36.5%) developed grade 3/4 adverse events. A total of 9.8% (n = 4) of the patients had UGT1A1 reduced activity phenotype, and 48.7% (n = 20) had UGT1A1 and 63.4% (n = 26) CYP3A intermediary phenotypes. Severe neutropenia and diarrhea were more prevalent in patients with reduced UGT1A1 in comparison with functional metabolism (50% and 75% versus 0% and 13%, respectively). SN-38 levels and its concentrations adjusted by IRI dose were significantly correlated to toxicity (rs = 0.31 (p = 0.05) and rs = 0.425 (p < 0.01)). The [SN-38]/IRI dose ratio had a ROC curve of 0.823 (95% CI 0.69-0.956) to detect any severe adverse event and 0.833 (95% CI 0.694-0.973) to detect severe diarrhea. The cut-off of 0.075 ng mL-1 mg-1 had 100% sensitivity and 65.7% specificity to predict severe diarrhea.

CONCLUSION

Our data confirmed the relevance of the pre-emptive genotypic information of UGT1A1. The [SN-38]/IRI ratio, measured 15 min after the end of the IRI infusion, was a strong predictor of severe toxicity and could be applied to minimize the burden of patients after IRI administration.

Pharmacokinetic and Pharmacogenetic Markers of Irinotecan Toxicity

BACKGROUND

Irinotecan (IRI) is a widely used chemotherapeutic drug, mostly used for first-line treatment of colorectal and pancreatic cancer. IRI doses are usually established based on patient's body surface area, an approach associated with large inter-individual variability in drug exposure and high incidence of severe toxicity. Toxic and therapeutic effects of IRI are also due to its active metabolite SN-38, reported to be up to 100 times more cytotoxic than IRI. SN-38 is detoxified by the formation of SN-38 glucuronide, through UGT1A1. Genetic polymorphisms in the UGT1A1 gene are associated to higher exposures to SN-38 and severe toxicity. Pharmacokinetic models to describe IRI and SN-38 kinetic profiles are available, with few studies exploring pharmacokinetic and pharmacogenetic-based dose individualization. The aim of this manuscript is to review the available evidence supporting pharmacogenetic and pharmacokinetic dose individualization of IRI in order to reduce the occurrence of severe toxicity during cancer treatment.

METHODS

The PubMed database was searched, considering papers published in the period from 1995-2017, using the keywords irinotecan, pharmacogenetics, metabolic genotyping, dose individualization, therapeutic drug monitoring, pharmacokinetics and pharmacodynamics, either alone or in combination, with original papers being selected based on the presence of relevant data.

CONCLUSION

The findings of this review confirm the importance of considering individual patient characteristics to select IRI doses. Currently, the most straightforward approach for IRI dose individualization is UGT1A1 genotyping. However, this strategy is sub-optimal due to several other genetic and environmental contributions to the variable pharmacokinetics of IRI and its active metabolite. The use of dried blood spot sampling could allow the clinical application of limited sampling and population pharmacokinetic models for IRI doses individualization.

Population pharmacokinetics of PEGylated liposomal CPT-11 (IHL-305) in patients with advanced solid tumors

PURPOSE

To investigate pharmacokinetics (PK) of encapsulated CPT-11, released CPT-11 and the active metabolite SN-38 following administration of IHL-305 and to identify factors that may influence IHL-305 PK.

METHODS

Plasma samples from 39 patients with solid tumors were collected in a phase I study. IHL-305 was administered as a 1 h IV infusion with doses ranging from 3.5 to 210 mg/m(2). Plasma concentrations of encapsulated CPT-11, released CPT-11 and SN-38 were used to develop a population PK model using NONMEM®.

RESULTS

PK of encapsulated CPT-11 was described by 1-compartment model with nonlinear clearance and PK of released CPT-11 was described by a 1-compartment model with linear clearance for all patients. PK of the active metabolite SN-38 was described by a 2-compartment model with linear clearance for all patients. Covariate analysis revealed that gender was a significant covariate for volume of distribution of encapsulated CPT-11. Vencap in male patients is 1.5-fold higher compared with female patients.

CONCLUSIONS

The developed population PK modeling approach is useful to predict PK exposures of encapsulated and released drug and can be applied to the more than 300 other nanoparticle formulations of anticancer agents that are currently in development. The effect of gender on PK of IHL-305 needs to be further evaluated.

[Recent developments of pharmacogenomics in the treatment of colorectal cancers]

Colorectal cancer (CCR), which is one of the most common causes of cancer, has benefited from the major advances in the understanding of the intracellular signaling pathways implicated in the initiation, growing and local and metastasis dissemination of tumor, which have occurred during the 20 past years. The pharmacogenomics approach, especially the determination of the genetic polymorphisms, tries to find prognosis and predictive biomarkers permitting to identify patients who could benefit from a particular treatment or those exhibiting higher risks of toxicity. Among the numerous biomarkers, which have been studied, few are currently in use in clinical practice. The phenotyping of DPD and UGT1A1 activities, and to a lesser extent, its genotyping, appears as the most useful tool in terms of prediction of toxicities induced by two major drugs: 5-FU and irinotecan. For oxaliplatin, the determination of the polymorphisms of reparases and detoxification systems such as GSTpi seems interesting, but its exact place should be more defined. It is in the field of targeted therapies that the pharmacogenomics approach seems to be the more relevant. KRAS mutation is a dramatic example of single nucleotide polymorphism, which is able to identify a priori patients that could receive or not an anti-EGFR monoclonal antibody such as cetuximab or panitumumab. It is obvious that pre-clinical identification of molecular biomarkers predictive of the sensitivity of the drug targets, which subsequently implicate the selection of patients and the rational evaluation of responses, will be the cornerstone of any clinical trials concerning targeted therapies. Besides the determination of drug target polymorphisms, it is also important to consider those related to the distribution and metabolism. In this area, the determination of enzymatic activities should recover its place besides the genomic profiling.

Pharmacokinetic analysis of irinotecan plus bevacizumab in patients with advanced solid tumors

PURPOSE

The purpose of this study was to evaluate the effect of bevacizumab on the pharmacokinetics (PK) of irinotecan and its active metabolite. Exploratory analyses of the impact of variability in uridine diphosphate glucuronosyltransferase 1A (UGT1A) genes on irinotecan metabolism and toxicity were conducted.

METHODS

This was an open-labeled, fixed-sequence study of bevacizumab with FOLFIRI (irinotecan, leucovorin, and infusional 5-fluorouracil). Pharmacokinetic assessments were conducted in cycles 1 and 3.

RESULTS

Forty-five subjects were enrolled. No difference in dose-normalized AUC(0-last) for irinotecan and SN-38 between irinotecan administered alone or in combination with bevacizumab was identified. Leukopenia was associated with higher exposure to both irinotecan and SN-38. UGT1A1 polymorphisms were associated with variability in irinotecan PK. Gastrointestinal toxicity was associated with UGT1A6 genotype. No other associations between UGT1A genotypes and toxicity were detected.

CONCLUSION

Bevacizumab does not affect irinotecan PK when administered concurrently. A variety of pharmacogenetic relationships may influence the pharmacokinetics of irinotecan and its toxicity.

Enterohepatic recirculation model of irinotecan (CPT-11) and metabolite pharmacokinetics in patients with glioma

BACKGROUND

Enterohepatic recirculation of irinotecan and one of its metabolites, SN-38, has been observed in pharmacokinetic data sets from previous studies. A mathematical model that can incorporate this phenomenon was developed to describe the pharmacokinetics of irinotecan and its metabolites.

PATIENTS AND METHODS

A total of 32 patients with recurrent malignant glioma were treated with weekly intravenous administration of irinotecan at a dose of 125 mg/m(2). Plasma concentrations of irinotecan and its three major metabolites were determined. Pharmacokinetic models were developed and tested for simultaneous fit of parent drug and metabolites, including a recirculation component.

RESULTS

Rebound in the plasma concentration suggestive of enterohepatic recirculation at approximately 0.5-1 h post-infusion was observed in most irinotecan plasma concentration profiles, and in some plasma profiles of the SN-38 metabolite. A multi-compartment model containing a recirculation chain was developed to describe this process. The recirculation model was optimal in 22 of the 32 patients compared to the traditional model without the recirculation component.

CONCLUSION

A recirculation chain incorporated in a multi-compartment pharmacokinetic model of irinotecan and its metabolites appears to improve characterization of this drug's disposition in patients with glioma.

Irinotecan-based chemotherapy in a metastatic colorectal cancer patient under haemodialysis for chronic renal dysfunction: two cases considered

The pharmacokinetics of irinotecan and its metabolites has been widely studied. No pharmacokinetic data, however, are available in haemodialysis patients. We report two clinical cases of severe toxicity, one of which was fatal, in two haemodialysis patients treated with irinotecan for a metastatic colorectal cancer. In case no. 1, M.S., aged 71 years, was treated with first-line FOLFIRI chemotherapy (irinotecan 180 mg/m) for local recurrence with liver metastases of a colon cancer treated with an LV5FU2 protocol as an adjuvant therapy 3 years previously. After the first cycle of irinotecan, the patient presented grade 4 diarrhoea on day 9, then a febrile grade 4 neutropenia on day 14 leading to his death on day 18. In case no. 2, M.D., aged 57 years, was treated successively by radiochemotherapy with an LV5FU2 regimen, then with four cycles of FOLFIRI (irinotecan at 125 mg/m) and finally with the cetuximab/irinotecan combination using the conventional dosage. Febrile neutropenia was observed on day 10 of the first irinotecan infusion with a dose of 180 mg/m and on day 8 of the second infusion with a lower dose of 120 mg/m. The patient's general condition progressively deteriorated with the advancement of the neoplastic disease, which led ultimately to his death. In this patient, plasma concentrations of irinotecan and its metabolite, SN-38, were measured during the course of the first FOLFIRI cycle on day 2 and on day 4, before and after dialysis sessions. The observed results suggest that, although irinotecan is partially dialysable, SN-38 is not. In conclusion, dose recommendations have to be defined in haemodialysis patients with renal dysfunction owing to the potential toxicity of irinotecan in these patients. Special care should be taken in liver metastasis cases owing to the nondialysability of SN-38.

Medicinal Cannabis Does Not Influence the Clinical Pharmacokinetics of Irinotecan and Docetaxel

OBJECTIVE

To date, data regarding the potential of cannabinoids to modulate cytochrome P450 isozyme 3A (CYP3A) activity are contradictory. Recently, a standardized medicinal cannabis product was introduced in The Netherlands. We anticipated an increased use of medicinal cannabis concurrent with anticancer drugs, and undertook a drug-interaction study to evaluate the effect of concomitant medicinal cannabis on the pharmacokinetics of irinotecan and docetaxel, both subject to CYP3A-mediated biotransformation.

PATIENTS AND METHODS

Twenty-four cancer patients were treated with i.v. irinotecan (600 mg, n = 12) or docetaxel (180 mg, n = 12), followed 3 weeks later by the same drugs concomitant with medicinal cannabis (200 ml herbal tea, 1 g/l) for 15 consecutive days, starting 12 days before the second treatment. Blood samples were obtained up to 55 hours after dosing and analyzed for irinotecan and its metabolites (SN-38, SN-38G), respectively, or docetaxel. Pharmacokinetic analyses were performed during both treatments. Results are reported as the mean ratio (95% confidence interval [CI]) of the observed pharmacokinetic parameters with and without concomitant medicinal cannabis.

RESULTS

Medicinal cannabis administration did not significantly influence exposure to and clearance of irinotecan (1.04; CI, 0.96-1.11 and 0.97; CI, 0.90-1.05, respectively) or docetaxel (1.11; CI, 0.94-1.28 and 0.95; CI, 0.82-1.08, respectively).

CONCLUSION

Coadministration of medicinal cannabis, as herbal tea, in cancer patients treated with irinotecan or docetaxel does not significantly influence the plasma pharmacokinetics of these drugs. The evaluated variety of medicinal cannabis can be administered concomitantly with both anticancer agents without dose adjustments.

Multicentre phase II study using increasing doses of irinotecan combined with a simplified LV5FU2 regimen in metastatic colorectal cancer

PURPOSE

Irinotecan at 180 mg/m2 combined with an infusional 5-fluorouracil/leucovorin (5-FU/LV) regimen (FOLFIRI) is a standard first line therapy for metastatic colorectal cancer (mCRC). This phase II study aimed to assess whether increasing the irinotecan dose in the first line FOLFIRI regimen would benefit mCRC patients.

PATIENTS AND METHODS

Patients received FOLFIRI every 2 weeks for up to six cycles, comprising a 5-FU/LV regimen combined with irinotecan at 180 mg/m2 (cycle 1), increasing to 220 mg/m2 (cycle 2) and 260 mg/m2 (cycle 3 and subsequent cycles) dependent on toxicity. Efficacy and safety were determined in the intention to treat (ITT) population and in patients able to receive irinotecan at 260 mg/m2 for at least four cycles [high-dose (HD) population].

RESULTS

Fifty-four eligible patients were included. Among them, 44 (81.5%) formed the HD population. The ITT objective response rate was 48% (90%CI: 36-60) with 25/26 of the responses in the HD population. The disease control rate was 76% (90%CI: 65-85) and median overall survival was 20.4 months (90%CI: 6.4-27.1). The main grade 3/4 toxicities (ITT/HD populations) were neutropenia (61%/59%), and diarrhoea (18%/11%), respectively.

CONCLUSIONS

This study confirms the feasibility of increasing the standard dose of the irinotecan component of FOLFIRI to 260 mg/m2, for more than 80% of patients but does not support a clear advantage of this strategy on unselected mCRC patients.