Drug interactions of paclitaxel and docetaxel and their relevance for the design of combination therapy

Drug-Drug interactions of docetaxel in patients with breast cancer based on insurance claims data

Despite an increase in the use of targeted anticancer drugs and immunotherapy, cytotoxic anticancer drugs such as docetaxel continue to play a clinically important role. The aim of this study was to evaluate drug-drug interactions between docetaxel and coadministered medicines in patients with breast cancer a claims database. The Health Insurance Review and Assessment Service (HIRA) database (2017 to 2019) was used in this study. We evaluated the risk of neutropenia (defined using receipt of granulocyte colony-stimulating factor (G-CSF) prescriptions) under docetaxel administration or the coadministration of docetaxel and an interacting anticancer drug (predefined based on approval information obtained from the Korean Ministry of Food and Drug Safety and the Lexicomp electronic database). The propensity score matching method was applied to balance covariates in the case (patients with G-CSF prescriptions) and control (patients without G-CSF prescriptions) groups. We identified 947 female patients with breast cancer prescribed with docetaxel and excluded 321 patients based on inclusion criteria. Of the remaining 626 patients, 280 were assigned to the case group and 346 to the control group. Predefined drugs were coadministered to 71 (11.3%) patients during the 7-day period before and after the administration of docetaxel. Adjusted odds ratios (ORs) calculated using the logistic regression model applied to the propensity score matching showed no significant difference between the administration of docetaxel alone and docetaxel coadministration (adjusted OR, 2.010; 95% confidence interval, 0.906, 4.459). In conclusion, we suggest that coadministration of docetaxel and a predefined interacting drug are not associated with G-CSF prescription.

Distinguishing Pharmacokinetics of Marketed Nanomedicine Formulations Using a Stable Isotope Tracer Assay

The pharmacokinetics of nanomedicines are complicated by the unique dispositional characteristics of the drug carrier. Most simplistically, the carrier could be a solubilizing platform that allows administration of a hydrophobic drug. Alternatively, the carrier could be stable and release the drug in a controlled manner, allowing for distribution of the carrier to influence distribution of the encapsulated drug. A third potential dispositional mechanism is carriers that are not stably complexed to the drug, but rather bind the drug in a dynamic equilibrium, similar to the binding of unbound drug to protein; since the nanocarrier has distributional and binding characteristics unlike plasma proteins, the equilibrium binding of drug to a nanocarrier can affect pharmacokinetics in unexpected ways, diverging from classical protein binding paradigms. The recently developed stable isotope tracer ultrafiltration assay (SITUA) for nanomedicine fractionation is uniquely suited for distinguishing and comparing these carrier/drug interactions. Here we present the the encapsulated, unencapsulated, and unbound drug fraction pharmacokinetic profiles in rats for marketed nanomedicines, representing examples of controlled release (doxorubicin liposomes, Doxil; and doxorubicin HCl liposome generic), equilibrium binding (paclitaxel cremophor micelle solution, Taxol generic), and solubilizing (paclitaxel albumin nanoparticle, Abraxane; and paclitaxel polylactic acid micelle, Genexol-PM) nanomedicine formulations. The utility of the SITUA method in differentiating these unique pharmacokinetic profiles and its potential for use in establishing generic nanomedicine bioequivalence are discussed.

Biocompatible hyperbranched polyglycerol modified β-cyclodextrin derivatives for docetaxel delivery

The development of biocompatible vector for hydrophobic drug delivery remains a longstanding issue in cancer therapy. We design and synthesis a drug delivery system based on HPG modified β-CD (β-CD-HPG) by conjugating HPG branches onto β-CD core and its structure was confirmed by NMR, FTIR, GPC and solubility. In vitro biocompatibility tests showed that HPG modification significantly improved red blood cells morphology alteration and hemolysis cause by β-CD and β-CD-HPG displayed cell safety apparently in a wide range of 0.01-1mg/mL. An anti-cancer drug, docetaxel, was effectively encapsulated into β-CD-HPG which was confirmed by DSC analysis. This copolymer could form nanoparticles with small size (<200nm) and exhibited better DTX loading capacity and controlled release kinetics without initial burst release behavior compared with β-CD. Furthermore, antitumor assay in vitro show that β-CD-HPG/DTX effectively inhibited proliferation of human breast adenocarcinoma cells. Therefore, β-CD-HPG/DTX exhibit great potential for cancer chemotherapy.

When Is It Important to Measure Unbound Drug in Evaluating Nanomedicine Pharmacokinetics?

Nanoformulations have become important tools for modifying drug disposition, be it from the perspective of enabling prolonged drug release, protecting the drug molecule from metabolism, or achieving targeted delivery. When examining the in vivo pharmacokinetic properties of these formulations, most investigations either focus on systemic concentrations of total (encapsulated plus unencapsulated) drug, or concentrations of encapsulated and unencapsulated drug. However, it is rare to find studies that differentiate between protein-bound and unbound (free) forms of the unencapsulated drug. In light of the unique attributes of these formulations, we cannot simply assume it appropriate to rely upon the protein-binding properties of the traditionally formulated or legacy drug when trying to define the pharmacokinetic or pharmacokinetic/pharmacodynamic characteristics of these nanoformulations. Therefore, this commentary explores reasons why it is important to consider not only unencapsulated drug, but also the portion of unencapsulated drug that is not bound to plasma proteins. Specifically, we highlight those situations when it may be necessary to include measurement of unencapsulated, unbound drug concentrations as part of the nanoformulation pharmacokinetic evaluation.

Developing Exposure/Response Models for Anticancer Drug Treatment: Special Considerations

Anticancer agents often have a narrow therapeutic index (TI), requiring precise dosing to ensure sufficient exposure for clinical activity while minimizing toxicity. These agents frequently have complex pharmacology, and combination therapy may cause schedule-specific effects and interactions. We review anticancer drug development, showing how integration of modeling and simulation throughout development can inform anticancer dose selection, potentially improving the late-phase success rate. This article has a companion article in Clinical Pharmacology & Therapeutics with practical examples.

Lapatinib in combination with paclitaxel for the treatment of patients with metastatic breast cancer whose tumors overexpress HER2

SUMMARY Metastatic breast cancer (MBC) is the leading cause of cancer death for women worldwide. Amplification of the HER2 gene has been observed in approximately 20–25% of human breast cancers, and is associated with aggressive disease and a poor prognosis, and reduced progression-free survival and overall survival. Inhibition of HER2 activity has been an effective strategy against HER2-positive breast cancers. In the first-line metastatic setting, the combination of trastuzumab with paclitaxel is well-tolerated, offering significant clinical benefit to patients with HER2-positive MBC. It has also been shown that lapatinib combined with paclitaxel offers a significant survival benefit over paclitaxel alone in first-line treatment of HER2-positive MBC, especially when trastuzumab is not available.

In vitro assessment of cytochrome P450 inhibition and induction potential of felotaxel (SHR110008)

The purpose of this study was to assess the potential inhibitory and inductive effects of felotaxel on cytochrome P450 isozymes in vitro. The inhibitory effects of felotaxel on various CYP isozymes were determined in human liver microsomes. In addition, the ability of felotaxel to induce CYP enzymes in cultured human hepatocytes was evaluated. Results showed that felotaxel did not inhibit CYP1A2-, CYP2C9-, CYP2C19-, CYP2E1-, CYP2D6-, CYP2B6-, CYP2C8-, and mediated activities in human liver microsomes up to a concentration of 100 μM, while the inhibition (<30% inhibition) of CYP3A4 activities was observed at 100 μM felotaxel. In vitro felotaxel did not induce CYP1A2, CYP2C19, or CYP3A4/5 activities in cultured human hepatocytes. In present study, felotaxel has been identified as a potent inhibitor of metabolic activity of CYP3A4. Therefore, clinically relevant pharmacokinetic drug-drug interactions are likely to occur between felotaxel and co-administered substrates of these CYP3A4 isozymes. These findings provided some useful information for safe and effective use of felotaxel in clinical practice.

Cellular mechanisms of resistance to anthracyclines and taxanes in cancer: intrinsic and acquired

Taxanes and anthracyclines are two of the most potent and broadly effective classes of chemotherapeutic agents. However, resistance to these agents is common and significantly limits their potential. As such, there is a great need to understand the mechanisms underlying de novo and acquired resistance to these agents. Beyond the resistance barrier lies even greater potential to significantly alter the natural course of human cancer. This review discusses what we currently understand about the mechanisms of resistance to taxanes and anthracyclines. Preclinical models suggest a role for ATP-binding cassette transporters, tubulin isoforms, microtubule-associated proteins, tubulin gene mutations, and mitotic checkpoint signaling proteins in resistance to taxanes. Preclinical models also suggest that drug transport proteins, antioxidant defenses, apoptotic signaling, and topoisomerase modulation may mediate anthracycline resistance. Many of these hypotheses remain untested in appropriately designed clinical studies, but limited clinical evidence will be reviewed. Epothilones represent a novel class of non-taxane microtubule stabilizing agents with distinct drug-resistance profiles. Potential mechanisms behind these differences and their potential role in the treatment of both taxane- and anthracycline-refractory patients are discussed.

Effects of naringin on the pharmacokinetics of intravenous paclitaxel in rats

It was reported that paclitaxel is an inhibitor of hepatic P-glycoprotein (P-gp) and hepatic microsomal cytochrome P450 (CYP) 3A1/2, and that naringin is an inhibitor of biliary P-gp and CYP3A1/2 in rats. The purpose of this study was to report the effects of oral naringin on the pharmacokinetics of intravenous paclitaxel in rats. Oral naringin (3.3 and 10 mg/kg) was pretreated 30 min before intravenous (3 mg/kg) administration of paclitaxel. After intravenous administration of paclitaxel, the AUC was significantly greater (40.8% and 49.1% for naringin doses of 3.3 and 10 mg/kg, respectively), and Cl was significantly slower (29.0% and 33.0% decrease, respectively) than controls. The significantly greater AUC could be due mainly to an inhibition of metabolism of paclitaxel via CYP3A1/2 by oral naringin. The inhibition of hepatic P-gp by oral naringin could also contribute to the significantly greater AUC of intravenous paclitaxel by oral naringin.

Pharmacological effects of formulation vehicles : implications for cancer chemotherapy

The non-ionic surfactants Cremophor EL (CrEL; polyoxyethyleneglycerol triricinoleate 35) and polysorbate 80 (Tween) 80; polyoxyethylene-sorbitan-20-monooleate) are widely used as drug formulation vehicles, including for the taxane anticancer agents paclitaxel and docetaxel. A wealth of recent experimental data has indicated that both solubilisers are biologically and pharmacologically active compounds, and their use as drug formulation vehicles has been implicated in clinically important adverse effects, including acute hypersensitivity reactions and peripheral neuropathy.CrEL and Tween 80 have also been demonstrated to influence the disposition of solubilised drugs that are administered intravenously. The overall resulting effect is a highly increased systemic drug exposure and a simultaneously decreased clearance, leading to alteration in the pharmacodynamic characteristics of the solubilised drug. Kinetic experiments revealed that this effect is primarily caused by reduced cellular uptake of the drug from large spherical micellar-like structures with a highly hydrophobic interior, which act as the principal carrier of circulating drug. Within the central blood compartment, this results in a profound alteration of drug accumulation in erythrocytes, thereby reducing the free drug fraction available for cellular partitioning and influencing drug distribution as well as elimination routes. The existence of CrEL and Tween 80 in blood as large polar micelles has also raised additional complexities in the case of combination chemotherapy regimens with taxanes, such that the disposition of several coadministered drugs, including anthracyclines and epipodophyllotoxins, is significantly altered. In contrast to the enhancing effects of Tween 80, addition of CrEL to the formulation of oral drug preparations seems to result in significantly diminished drug uptake and reduced circulating concentrations. The drawbacks presented by the presence of CrEL or Tween 80 in drug formulations have instigated extensive research to develop alternative delivery forms. Currently, several strategies are in progress to develop Tween 80- and CrEL-free formulations of docetaxel and paclitaxel, which are based on pharmaceutical (e.g. albumin nanoparticles, emulsions and liposomes), chemical (e.g. polyglutamates, analogues and prodrugs), or biological (e.g. oral drug administration) strategies. These continued investigations should eventually lead to more rational and selective chemotherapeutic treatment.

Cardiotoxic effects of anthracycline-taxane combinations

The association of doxorubicin (DOX) and paclitaxel (PTX) is very active in breast cancer. Unfortunately, PTX may potentiate the cardiotoxic effects of anthracyclines: it causes nonlinear disposition of DOX and its metabolites, leading to persistant of elevated plasma concentrations of the anthracyclines. However, this pharmacokinetic interference is not sufficient to explain the enhanced cardiotoxicity of the combination. Recent data suggest that PTX stimulates the conversion of DOX to cardiotoxic metabolites (namely doxorubicinol) inside cardiomyocytes. Docetaxel (DTX) does not have a major influence on DOX plasma concentration because it does not interfere with its elimination. Clinical data suggest that DTX may not enhance anthracycline cardiotoxicity, but patients seldom received a total anthracycline dose compatible with increased risk. Furthermore, there are experimental data indicating that DTX can also stimulate the metabolism of DOX to toxic species in human heart.

Weekly carboplatin and docetaxel for locally advanced primary and recurrent cervical cancer: a phase I study

OBJECTIVE

The aim of this study was to determine the dose-limiting toxicities (DLTs) and maximum tolerated doses (MTDs) of a docetaxel-carboplatin regimen in patients with locally advanced cervical cancer (LACC) or recurrent cervical cancer. The regimen was administered weekly, with a maximum of 12 courses.

PATIENTS AND METHODS

Twenty patients were treated with with a total of 145 cycles of weekly carboplatin and docetaxel. The starting dose of docetaxel was 25 mg/m(2) with increments of 5 mg/m(2) until a final dose of 35 mg/m(2) was reached. Dose-escalation of docetaxel was followed by carboplatin at AUC 2, AUC 2.5, and AUC 3, respectively. Defined dose-limiting toxicities were WHO grade (G) 3 hematotoxicity, G4 mucositis, and G2 neurotoxicity. The response status of the patients was assessed using the common ECOG response criteria.

RESULTS

Two of four patients developed a DLT at dose level 4. Nonhematological toxicity was generally mild, except for ubiquitous complete alopecia. The MTD was reached at docetaxel 35 mg/m(2) and carboplatin AUC 2 mg/mL.min. The overall response rate was 65% in the entire group of evaluable patients and 77% in patients with primary LACC, with two cases of pathological complete response.

CONCLUSION

This dose-dense regimen was well-tolerated and could be administered on an outpatient basis.

In vitro pharmacodynamics of CKD-602 in HT-29 cells

CKD-602 (7-[2-(N-isopropylamino)ethyl]-(20S)-camptothecin) is a recently-developed synthetic camptothecin analogue and currently under clinical development by Chong Kun Dang Pharm (Seoul, Korea). CKD-602 showed potent topoisomerase inhibitory activity in vitro and broad antitumor activity against various human tumor cells in vitro and in vivo in animal models. This study describes the pharmacodynamics of the immediate and delayed cytotoxicity induced by CKD-602 in a human colorectal adenocarcinoma cell line, HT-29, and its intracellular drug accumulation by HPLC. The present study was designed to address whether the higher activity of CKD-602 with prolonged exposure is due to delayed exhibition of cytotoxicity and/or an accumulation of antiproliferative effect on continuous drug exposure. The drug uptake study was performed to determine whether the delayed cytotoxicity is due to a slow drug accumulation in cells. CKD-602 produced a cytotoxicity that was exhibited immediately after treatment (immediate effect) and after treatment had been terminated (delayed effect). Both the immediate and delayed effects of CKD-602 showed a time dependent decrease in IC50 values. Drug uptake was biphasic and the second equilibrium level was obtained as early as at 24 hr, indicating that the cumulative and delayed antitumor effects of CKD-602 were not due to slow drug uptake. On the other hand, CKD-602 treatment was sufficient to induce delayed cytotoxicity after 4 hr, however, longer treatment (>24 hr) enhanced its cytotoxicity due to the intracellular accumulation of the drug, which requires 24 hr to reach maximum equilibrium concentration. In addition, Cn x T=h analysis (n=0.481) indicated that increased exposure times may contribute more to the overall antitumor activity of CKD-602 than drug concentration. Additional studies to determine the details of the intracellular uptake kinetics (e.g., concentration dependency and retention studies) are needed in order to identify the optimal treatment schedules for the successful clinical development of CKD-602.

Farnesyl transferase inhibitors as anticancer agents

Protein farnesylation catalysed by the enzyme farnesyl protein transferase involves the addition of a 15-carbon farnesyl group to conserved amino acid residues at the carboxyl terminus of certain proteins. Protein substrates of farnesyl transferase include several G-proteins, which are critical intermediates of cell signalling and cytoskeletal organisation such as Ras, Rho, PxF and lamins A and B. Activated Ras proteins trigger a cascade of phosphorylation events through sequential activation of the PI3 kinase/AKT pathway, which is critical for cell survival, and the Raf/Mek/Erk kinase pathway that has been implicated in cell proliferation. Ras mutations which encode for constitutively activated proteins are found in 30% of human cancers. Because farnesylation of Ras is required for its transforming and proliferative activity, the farnesyl protein transferase inhibitors were designed as anticancer agents to abrogate Ras function. However, current evidence suggests that the anticancer activity of the farnesyl transferase inhibitors may not be simply due to Ras inhibition. This review will discuss available clinical data on three of these agents that are currently undergoing clinical trials.

Docetaxel does not impair cardiac autonomic function in breast cancer patients previously treated with anthracyclines

The effects of docetaxel treatment on autonomic cardiac function was studied with 24-h ECG recordings in breast cancer patients pretreated with anthracyclines. Twenty-four women were evaluated before docetaxel treatment and after 3-4 courses of docetaxel 100 mg/m(2). The heart rate, cardiac extrasystoles and heart rate variability (HRV) in both the time and frequency domain were assessed from 24-h ECG recordings. The acute effects of docetaxel were calculated from 1-h recordings immediately prior to, during and after infusion. Long-term effects were evaluated from 24-h recordings performed before treatment and after 3-4 courses of docetaxel. There was no increase in the number of cardiac extrasystoles during docetaxel infusion. The number of ventricular extrasystoles decreased from 14 (23) to 7 (14) during and 5 (10) after the first infusion (p=0.02). The heart rate, HRV and extrasystoles were similar before and after 3-4 courses of docetaxel. The treatment did not abolish circadian variability of the heart rate. Docetaxel did not deteriorate autonomic cardiac function. In conclusion, our findings suggest that docetaxel does not have harmful cumulative effects on autonomic control of the heart and is therefore unlikely to be cardiotoxic.

Combination chemotherapy of the taxanes and antimetabolites: its use and limitations

In an effort to improve response rates of chemotherapy, taxanes have been combined with other cytotoxic agents such as antimetabolites. However, the use of some of these combinations in patients has been restricted by severe toxicity. The significance of the sequence of drug administration in combining methotrexate (MTX) and taxanes was recognised in in vitro studies, showing synergistic effects for the sequence of MTX followed by paclitaxel, and antagonism for exposure in the reverse order. A possible explanation might be an MTX-induced synchronisation of cells in the S phase of the cell cycle, after which cells are more susceptible for the cytotoxic action of taxanes. Clinical studies using this sequence were hampered by severe neutropenia and mucositis at relatively low doses of both drugs. As no pharmacokinetic interactions were observed, the excess of toxicity may have been due to sequence-dependent synergistic actions on bone marrow and mucosa. In contrast, and confusingly, in vitro studies on 5-fluorouracil (5-FU) and taxanes indicate that 5-FU preceeding or simultaneously given to paclitaxel impairs cytotoxicity as compared with paclitaxel monotherapy, while the reverse sequence results in additive or synergistic cytotoxicity. While almost all clinical studies have used the sequence of a taxane followed by 5-FU, various schedules appeared feasible and effective. The combination of a 5-FU analogue, capecitabine and taxanes was supported by in vitro data. A large phase III trial confirmed the feasibility and superior efficacy of this combination in breast cancer patients relapsing after an anthracycline. Conflicting results exist on the benefit of combining gemcitabine and taxanes in tumour cell lines. Although the accumulation of gemcitabine triphosphate (dFdCTP) in mononuclear cells was significantly higher with an increasing dose of paclitaxel, no pharmacokinetic interactions for both agents were noticed. A pharmacokinetic analysis of the gemcitabine-docetaxel combination therapy has not been published in detail. Despite numerous trials, so far no optimum schedule has been established. Regarding data on actually delivered dose intensities, a 2- or 3-weekly cycle seems favourable and feasible. However, possible severe pulmonary toxicity warrants cautious monitoring of patients treated with this combination. Different outcomes of preclinical and clinical studies reveal that combining two chemotherapeutic agents is not simply a matter of putting antitumour activities together. Drug interaction may result in synergism, not only of efficacy but also of toxic side-effects. Adding two drugs may also implicate antagonism in drug efficacy due to unwanted interference in cytotoxicity or pharmacokinetics. For agents acting at a specific phase of the cell cycle, the sequence of administration may determine the efficacy and toxicity of a combination therapy. Because of an observed discrepancy between in vitro data and clinical studies, we would like to emphasise the need for adequate dose-finding clinical trials together with pharmacokinetic data analysis before examining any new combination chemotherapy in more detail in phase II studies.