Phase I and pharmacokinetic study of BMS-184476, a taxane with greater potency and solubility than paclitaxel

Identification of new 3-phenyl-1H-indole-2-carbohydrazide derivatives and their structure-activity relationships as potent tubulin inhibitors and anticancer agents: A combined in silico, in vitro and synthetic study

Virtual screening of commercially available molecular entities by using CDRUG, structure-based virtual screening, and similarity identified eight new derivatives of 3-phenyl-1H-indole-2-carbohydrazide with anti-proliferative activities. The molecules were tested experimentally for inhibition of tubulin polymerisation, which revealed furan-3-ylmethylene-3-phenyl-1H-indole-2-carbohydrazide (27a) as the most potent candidate. Molecule 27a was able to induce G2/M phase arrest in A549 cell line, similar to other tubulin inhibitors. Synthetic modifications of 27a were focussed on small substitutions on the furan ring, halogenation at R₁ position and alteration of furyl connectivity. Derivatives 27b, 27d and 27i exhibited the strongest tubulin inhibition activities and were comparable to 27a. Bromine substitution at R₁ position showed most prominent anticancer activities; derivatives 27b-27d displayed the strongest activities against HuCCA-1 cell line and were more potent than doxorubicin and the parent molecule 27a with IC₅₀ values <0.5 μM. Notably, 27b with a 5-methoxy substitution on furan displayed the strongest activity against HepG2 cell line (IC₅₀ = 0.34 µM), while 27d displayed stronger activity against A549 cell line (IC₅₀ = 0.43 µM) compared to doxorubicin and 27a. Fluorine substitutions at the R₁ position tended to show more modest anti-tubulin and anticancer activities, and change of 2-furyl to 3-furyl was tolerable. The new derivatives, thiophenyl 26, displayed the strongest activity against A549 cell line (IC₅₀ = 0.19 µM), while 1-phenylethylidene 21b and 21c exhibited more modest anticancer activities with unclear mechanisms of action; 26 and 21c demonstrated G2/M phase arrest, but showed weak tubulin inhibitory properties. Molecular docking suggests the series inhibit tubulin at the colchicine site, in agreement with the experimental findings. The calculated molecular descriptors indicated that the molecules obey Lipinski's rule which suggests the molecules are drug-like structures.

Is there a role of nab-paclitaxel in the treatment of advanced non-small cell lung cancer? The data suggest yes

Nab-paclitaxel is a novel therapeutic agent, which was approved in combination with carboplatin in the first-line treatment of advanced non-small cell lung cancer (NSCLC) regardless of histologic subtype in the United States of America by the Food and Drug Administration in 2012 and by the European Commission in 2015. This approval was based on the results of a phase III clinical trial showing superior response rates compared with solvent-based paclitaxel in combination with carboplatin. This review will focus on the early development and clinical data to date supporting the use of nab-paclitaxel in advanced NSCLC. The clinical question central to this review is whether nab-paclitaxel has a place in the current therapeutic landscape of advanced NSCLC.

Update on taxane development: new analogs and new formulations

The taxanes (paclitaxel and docetaxel) represent an important class of antineoplastic agents that interfere with microtubule function leading to altered mitosis and cellular death. Paclitaxel (Taxol(®)) was originally extracted from a yew tree (Taxus spp., Taxaceae) a small slow-growing evergreen, coniferous tree. Due to the initial scarcity of paclitaxel, docetaxel (Taxotere(®)) a semisynthetic analog of paclitaxel produced from the needles of European yew tree, Taxus baccata was developed. Docetaxel differs from paclitaxel in two positions in its chemical structure and this small alteration makes it more water soluble. Today, paclitaxel and docetaxel are widely prescribed antineoplastic agents for a broad range of malignancies including lung cancer, breast cancer, prostate cancer, Kaposi's sarcoma, squamous cell carcinoma of the head and neck, gastric cancer, esophageal cancer, bladder cancer, and other carcinomas. Although very active clinically, paclitaxel and docetaxel have several clinical problems including poor drug solubility, serious dose-limiting toxicities such as myelosuppression, peripheral sensory neuropathy, allergic reactions, and eventual development of drug resistance. A number of these side effects have been associated with the solvents used for dilution of these antineoplastic agents: Cremophor EL for paclitaxel and polysorbate 80 for docetaxel. In addition, reports have linked these solvents to the alterations in paclitaxel and docetaxel pharmacokinetic profiles. In this review, we provide preclinical and clinical data on several novel taxanes formulations and analogs which are currently US Food and Drug Administration (FDA)-approved or in clinical development in various solid tumor malignancies. Of the new taxanes nab-paclitaxel and cabazitaxel have enjoyed clinical success and are FDA-approved; while many of the other compounds described in this review are unlikely to be further developed for clinical use in daily practice. Furthermore, the successful clinical emergence of novel nontaxane microtubule-targeting chemotherapy agents such as epothilones and eribulin is liable to further restrict the development of novel taxanes.

Evolutionary modeling of combination treatment strategies to overcome resistance to tyrosine kinase inhibitors in non-small cell lung cancer

Many initially successful anticancer therapies lose effectiveness over time, and eventually, cancer cells acquire resistance to the therapy. Acquired resistance remains a major obstacle to improving remission rates and achieving prolonged disease-free survival. Consequently, novel approaches to overcome or prevent resistance are of significant clinical importance. There has been considerable interest in treating non-small cell lung cancer (NSCLC) with combinations of EGFR-targeted therapeutics (e.g., erlotinib) and cytotoxic therapeutics (e.g., paclitaxel); however, acquired resistance to erlotinib, driven by a variety of mechanisms, remains an obstacle to treatment success. In about 50% of cases, resistance is due to a T790M point mutation in EGFR, and T790M-containing cells ultimately dominate the tumor composition and lead to tumor regrowth. We employed a combined experimental and mathematical modeling-based approach to identify treatment strategies that impede the outgrowth of primary T790M-mediated resistance in NSCLC populations. Our mathematical model predicts the population dynamics of mixtures of sensitive and resistant cells, thereby describing how the tumor composition, initial fraction of resistant cells, and degree of selective pressure influence the time until progression of disease. Model development relied upon quantitative experimental measurements of cell proliferation and death using a novel microscopy approach. Using this approach, we systematically explored the space of combination treatment strategies and demonstrated that optimally timed sequential strategies yielded large improvements in survival outcome relative to monotherapies at the same concentrations. Our investigations revealed regions of the treatment space in which low-dose sequential combination strategies, after preclinical validation, may lead to a tumor reduction and improved survival outcome for patients with T790M-mediated resistance.

What is the role of novel taxanes in non-small-cell lung cancer?

The taxanes are among the most active cytotoxic agents in oncology and are widely used in adjuvant and advanced treatment settings in multiple tumor types. Paclitaxel and docetaxel are standard therapies in advanced non-small-cell lung cancer (NSCLC) and are increasingly used in earlier treatment settings. The taxanes are generally well tolerated but can be associated with severe, irreversible (and rarely life-threatening) toxicity. Premedication and special infusion sets are necessary to reduce the risk of hypersensitivity reactions. Newer taxanes are in development designed to improve the therapeutic index and ease of administration. Several agents have completed phase I/II clinical trials and are in phase III testing. Many other novel taxanes are at earlier stages of development and appear promising as single agents and in combination regimens. Safer and more effective taxanes could replace paclitaxel and docetaxel as standard treatments in NSCLC.

A phase I and pharmacokinetic study of temsirolimus (CCI-779) administered intravenously daily for 5 days every 2 weeks to patients with advanced cancer

PURPOSE

Patients with advanced cancer received temsirolimus (Torisel, CCI-779), a novel inhibitor of mammalian target of rapamycin, i.v. once daily for 5 days every 2 weeks to determine the maximum tolerated dose, toxicity profile, pharmacokinetics, and preliminary antitumor efficacy.

EXPERIMENTAL DESIGN

Doses were escalated in successive cohorts of patients using a conventional phase I clinical trial design. Samples of whole blood and plasma were collected to determine the pharmacokinetics of temsirolimus and sirolimus, its principal metabolite.

RESULTS

Sixty-three patients were treated with temsirolimus (0.75-24 mg/m(2)/d). The most common drug-related toxicities were asthenia, mucositis, nausea, and cutaneous toxicity. The maximum tolerated dose was 15 mg/m(2)/d for patients with extensive prior treatment because, in the 19 mg/m(2)/d cohort, two patients had dose-limiting toxicities (one with grade 3 vomiting, diarrhea, and asthenia and one with elevated transaminases) and three patients required dose reductions. For minimally pretreated patients, in the 24 mg/m(2)/d cohort, one patient developed a dose-limiting toxicity of grade 3 stomatitis and two patients required dose reductions, establishing 19 mg/m(2)/d as the maximum acceptable dose. Immunologic studies did not show any consistent trend toward immunosuppression. Temsirolimus exposure increased with dose in a less than proportional manner. Terminal half-life was 13 to 25 hours. Sirolimus-to-temsirolimus exposure ratios were 0.6 to 1.8. A patient with non-small cell lung cancer achieved a confirmed partial response, which lasted for 12.7 months. Three patients had unconfirmed partial responses; two patients had stable disease for >/=24 weeks.

CONCLUSION

Temsirolimus was generally well tolerated on this intermittent schedule. Encouraging preliminary antitumor activity was observed.

Novel formulations of taxanes: a review. Old wine in a new bottle?

Over the past two decades, the taxanes have played a significant role in the treatment of various malignancies. However, the poor solubility of these compounds necessitates the inclusion of surfactant vehicles in their commercial formulations. Cremophor EL and polysorbate 80 have long comprised the standard solvent system for paclitaxel and docetaxel, respectively. A number of pharmacologic and biologic effects related to both of these drug formulations have been described, including clinically relevant acute hypersensitivity reactions and peripheral neuropathy. In addition, these solvents affect the disposition of intravenously administered solubilized drugs and leach plasticizers from polyvinylchloride infusion sets. A number of strategies to develop formulations of surfactant-free taxanes have been developed. They include albumin nanoparticles, polyglutamates, taxane analogs and prodrugs, emulsions, and lipsomes. An overview of these novel formulations of taxanes, their mechanisms of action, pharmacokinetics, dose and administration, adverse effects, and clinical efficacy will be discussed.

Review: tubulin function, action of antitubulin drugs, and new drug development

Anticancer agents that interfere with microtubulin function are in widespread use in man and have a broad spectrum of activity against both hematological malignancies and solid tumors. The mechanisms of actions of these agents have been better defined during the past decade, indicating that there are distinct binding sites for these agents and that they interfere with microtubulin dynamics (growth and shortening of tubules) at low concentrations and only evoke microtubulin aggregation or dissociation at high concentrations. Tubulin has been recently described in the nucleus of cells and in mitochondria. Downstream events from tubulin binding are believed to be critical events for the generation of apoptosis in the malignant cell. The effects of vinca alkaloids and taxanes are distinct, suggesting that the interference with the tubulin cap by high-affinity binding of effective agents is not the only mechanism of cytotoxic effect, and the low-affinity binding of drug, which distorts microtubulin function, may also be important. The epothilones share some of the binding characteristics of the taxanes and are in clinical trials because of cytoxic activity in taxane resistant cells. Tubulin has additional target sites for anticancer drugs including interference with the binding and function of microtubule associated proteins and interference with motor proteins which are essential for the transport of substances within the cell. Because many of these microtubule associated proteins have an ATP binding site, both computer-aided design and combinatorial chemistry techniques can be used to make agents to interfere with their function analogous to imatinib mesylate (Gleevec). Agents that interfere with the motor protein kinesin are entering clinical trials.

Phase I Pharmacokinetic and Pharmacodynamic Study of 17-Allylamino, 17-Demethoxygeldanamycin in Patients With Advanced Malignancies

Purpose

To study the toxicity and pharmacokinetic-pharmacodynamic profile of 17-allylamino, 17- demethoxygeldanamycin (17-AAG) and to recommend a dose for phase II trials.

Patients and Methods

This was a phase I study examining a once-weekly dosing schedule of 17-AAG. Thirty patients with advanced malignancies were treated.

Results

The highest dose level reached was 450 mg/m2/week. The dose-limiting toxicities (DLTs) encountered were grade 3 diarrhea in three patients (one at 320 mg/m2/week and two at 450 mg/m2/week) and grade 3 to 4 hepatotoxicity (AST/ALT) in one patient at 450 mg/m2/week. Two of nine DLTs were at the highest dose level. Two patients with metastatic melanoma had stable disease and were treated for 15 and 41 months, respectively. The dose versus area under the curve-relationship for 17-AAG was linear (r2 = .71) over the dose range 10 to 450 mg/m2/week, with peak plasma concentrations of 8,998 μg/L (standard deviation, 2,881) at the highest dose level. After the demonstration of pharmacodynamic changes in peripheral blood leukocytes, pre- and 24 hours post-treatment, tumor biopsies were performed and demonstrated target inhibition (c-RAF-1 inhibition in four of six patients, CDK4 depletion in eight of nine patients and HSP70 induction in eight of nine patients) at the dose levels 320 and 450 mg/m2/week. It was not possible to reproducibly demonstrate these changes in biopsies taken 5 days after treatment.

Conclusion

It has been possible to demonstrate that 17-AAG exhibits a tolerable toxicity profile with therapeutic plasma concentrations and target inhibition for 24 hours after treatment and some indications of clinical activity at the dose level 450 mg/m2/week. We recommend this dose for phase II clinical trials.

Phase II trial of the novel taxane BMS-184476 as second-line in non-small-cell lung cancer

BACKGROUND

The purpose of this study was to evaluate the tolerability and efficacy of BMS-184476, an analog of paclitaxel, in patients with advanced non-small-cell lung cancer (NSCLC) progressing or relapsing following at least one prior chemotherapy regimen.

PATIENTS AND METHODS

Fifty-six previously treated advanced NSCLC patients received BMS-184476 at a dose of 60 mg/m(2) administered intravenously over 1 h every 21 days.

RESULTS

The median number of cycles delivered per patient was five (range one to 17). Dose reduction was required in only 3.8% of cycles. Grade 4 neutropenia occurred in 19.6% of patients, but no grade 4 thrombocytopenia or anemia was reported. Febrile neutropenia was observed in only two (3.6%) patients and there were no life-threatening events. Grade 3/4 peripheral sensory-motor neuropathy was reported in 9% of patients. Other non-hematological toxicities, such as nausea and vomiting, myalgia and arthralgia, diarrhea, and mucositis, were uncommon. Partial responses were observed in eight (14.3%) patients and stable disease in 33 (58.9%). Median progression-free survival was 3.7 months [95% confidence interval (CI) 2.7-5.4] and median overall survival was 10 months (95% CI 6-13.4).

CONCLUSIONS

BMS-184476 was well tolerated at the dose of 60 mg/m(2) and showed evidence of antitumor activity in previously treated NSCLC.

Phase I trial of the novel taxane BMS-184476 administered in combination with carboplatin every 21 days

The aim of the study was to determine the maximum-tolerated dose and dose-limiting toxicities for BMS-184476, in combination with carboplatin, in patients with advanced solid tumours and to describe any preliminary antitumour activity associated with this regimen. Patients received combination therapy with BMS-184476 given intravenously over 1 h followed by carboplatin administered over 30 min on day 1 of a 21-day cycle. In all, 28 patients received 146 cycles of BMS-184476 and carboplatin. Patients were enrolled at four dose levels: BMS-184476 (mg m(-2))/carboplatin (mg min ml(-1)): 40/5, 50/5, 50/6 and 60/6. Dose-limiting toxicity at 60/6 was neutropenia. Among 27 evaluable patients, 11 demonstrated stable disease for a median of 8.5 cycles. In 22 patients, the pharmacokinetics of BMS-184476 appeared independent of dose of BMS-184476. The mean+/-s.e.m. values for clearance (Cl), volume of distribution at steady state and apparent terminal half-life of BMS-184476 in the four dose groups during cycle 1 were 192+/-25 ml min m(-2), 377+/-69 l m(-2) and 33.7+/-5.9 h, respectively. An increase in the dose of carboplatin from 5 to 6 mg min ml(-1) may have decreased Cl of BMS-184476. BMS-184476 in combination with carboplatin was well tolerated at a dose of 50/6 and shows evidence of antitumour activity in a pretreated population.

Phase IB and pharmacological study of the novel taxane BMS-184476 in combination with doxorubicin

The aim of this study was to define the maximum tolerated dose (MTD) and the pharmacological profile of the paclitaxel analogue BMS-184476 given once every 3 weeks, or on days 1 and 8 every 3 weeks (d1&8), in combination with a fixed dose of 50 mg/m(2) of Doxorubicin (Doxo) administered on day 1 of a 21-day cycle. Adult patients with advanced solid malignancies received escalating doses of BMS-184476 infused over 1 h after bolus Doxo. Pharmacokinetics (PK) of BMS-184476, Doxo and metabolites were investigated. The effect of BMS-184476 on doxorubicinol formation was studied in the cytosol from human myocardium. The MTD of 3-weekly BMS-184476 was 30 mg/m(2). The MTD/recommended Phase II dose was 35 mg/m(2)/week (70 mg/m(2) per cycle) in the d1&8 schedule. The dose-limiting toxicity was neutropenia for both schedules. Other toxicities were loss of appetite, asthenia, and mild, cumulative peripheral neuropathy. The objective response rate in 17 previously untreated or minimally pretreated patients with breast cancer treated at 35 mg/m(2)/week of BMS-184476 was 59% (95% Confidence Interval (CI): 33-82%). Two of the 7 patients not responding to the study regimen later responded to Doxo and paclitaxel. Plasma disposition of BMS-184476 at 30, 35 and 40 mg/m(2) was linear without evidence of a PK interaction with Doxo. In studies with cytosol from human myocardium, the formation of cardiotoxic doxorubicinol was not enhanced by BMS-184476. Dosing of BMS-184476 for 2 consecutive weeks allowed the administration of larger doses of the taxane with a promising antitumour activity in patients with untreated or minimally pretreated breast cancer. The higher than expected myelotoxicity of the 3-weekly schedule is unexplained by the investigated interactions. Lack of enhanced doxorubicinol formation in human myocardium is consistent with the cardiac safety of the regimen.

Phase I Clinical and Pharmacokinetic Study of BMS-247550, a Novel Derivative of Epothilone B, in Solid Tumors

PURPOSE

The purpose of this study was to determine the maximum tolerated dose, toxicity, and pharmacokinetics of BMS-247550 administered as a 1-h i.v. infusion every 3 weeks.

EXPERIMENTAL DESIGN

Patients with advanced solid malignancies were premedicated and treated with escalating doses of BMS-247550. Blood sampling was performed to characterize the pharmacodynamics and pharmacokinetics of BMS-247550.

RESULTS

Twenty-five patients were treated at six dose levels ranging from 7.4 to 59.2 mg/m(2). At 50 mg/m(2), 4 of 9 patients (44.4%) had dose-limiting toxicity (neutropenia, abdominal pain/nausea). At 40 mg/m(2) (the recommended Phase II dose), 2 of 12 patients (16.7%) had dose-limiting neutropenia. Overall, the most common nonhematological toxicity was fatigue/generalized weakness (grade 3-4 seen in 9.0% of patients), followed by neurosensory deficits manifested as peripheral neuropathy and by gastrointestinal discomfort. At 40 mg/m(2), the incidence of grade 3 fatigue, abdominal pain, diarrhea, and neuropathy was 7.7%. Grade 1-2 neuropathy was observed in all patients enrolled and treated at 40 mg/m(2). Two patients with paclitaxel-refractory ovarian cancer, one patient with taxane-naïve breast cancer, and another patient with docetaxel-refractory breast cancer had objective partial responses (lasting 6.0, 5.3, 3.0, and 4.5 months, respectively). The mean pharmacokinetic parameter values during course 1 for clearance, volume of distribution, and apparent terminal elimination half-life at the 40 mg/m(2) (recommended Phase II dose) dose level were 21 liters/h/m(2), 826 liters/m(2), and 35 h (excluding one outlier of 516 h), respectively. Values during course 1 and course 2 were similar.

CONCLUSIONS

The recommended dose for Phase II evaluation of BMS-247550 is 40 mg/m(2), although more long-term observations are needed. BMS-247550 has advantages over taxanes in relation to drug resistance and warrants further study.

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.

Ovarian cancer: progress and continuing controversies in management

Ovarian cancer is the most lethal of the gynaecological cancers, affecting approximately 1 in 75 women in the developed world. In most cases (>75%), the disease is disseminated beyond the ovary at diagnosis. For patients with stage III-IV disease, many clinicians agree that standard treatment should comprise six cycles of paclitaxel-carboplatin. Randomised trials over the past 10 years have indicated the superiority of paclitaxel-based treatment and that carboplatin is equivalent to cisplatin, but better tolerated. A recent trial has suggested that docetaxel may be a better option than paclitaxel, with reduced neurotoxicity and comparable efficacy. Overall treatment results remain unsatisfactory, since the median survival for these patients is 2-3 years. Future progress may be made by addressing the following issues: Would sequential regimes be more effective? Intriguing results from two large randomised trials (ICON-3 and GOG-132) indicate that single agent platinum might well be incorporated into such regimes. Additionally, a range of other agents could be tested as part of first-line regimes, having demonstrated activity in relapsed patients; these include topotecan, gemcitabine and liposomal doxorubicin. Newer agents, such as cell signalling inhibitors have shown potential as single agents, but may be particularly effective in combination with current drugs. Real progress can be expected when a better understanding is achieved of the mechanisms underlying clinical drug resistance in ovarian cancer, and a close laboratory-clinical interaction is crucial.

Implementation and results of a test dose program with taxanes

PURPOSE

A pilot taxane test-dose policy was developed and implemented to determine whether the severity of patient hypersensitivity reaction and drug waste would be reduced.

PATIENTS AND METHODS

Data from 206 eligible cancer patients undergoing first-dose taxane chemotherapy were analyzed. The severity of hypersensitivity reactions before and after the implementation of taxane test dose was graded (scale 1-4) and analyzed for statistical differences between groups. Average drug wastage was calculated before and after program initiation.

RESULTS

Twenty-two of 206 patients (10.7%) experienced a hypersensitivity reaction. The mean hypersensitivity reaction severity for reacting patients who did not receive a test dose (N = 12) was 3.3, and for those who were given a test dose (N = 10), it was 1.5. Only one of five patients who experienced a hypersensitivity reaction that required hospitalization was from the test-dose group. The value of drug alone wasted before test-dose utilization was about $1794 per reacting patient, and the use of taxane test doses saved approximately $1784 per reacting individual. This represented more than a $178 savings for every patient receiving a taxane for the first time. These figures do not include resuscitation, hospital, and other subsequent other costs associated with morbidity.

CONCLUSIONS

Implementation of a taxane test-dose policy significantly reduced hypersensitivity reaction severity, drug wastage, and hospitalizations.

Commercial taxane formulations induce stomatocytosis and increase blood viscosity

1. Taxanes are antineoplastic drugs which have cardiovascular side effects of unknown mechanism. We investigated their influence on blood viscosity and erythrocyte morphology. 2. Whole blood was incubated in vitro with increasing concentrations of Taxol, Taxotere, paclitaxel (0-100 microM) and the vehicles Cremophor-EL and Tween 80 (0-5% vol) for 1 h at 37 degrees C. Plasma and whole blood viscosity (Haematocrit 45%) were measured and erythrocyte morphology was assessed on glutaraldehyde-fixed cells. The same investigations were performed in seven patients before and after a Taxol-infusion. 3. Taxol and Taxotere induced a dose- and time-dependent stomatocytic shape transformation of erythrocytes. Paclitaxel alone had no effect, but the vehicles cremophor-EL and Tween 80, used in Taxol and Taxotere, respectively, induced a comparable degree of stomatocytosis. This suggests a preferential intercalation of these substances into the inner hemileaflet of the membrane lipid bilayer. Associated with this shape change a dose-dependent increase in plasma and whole blood viscosity was observed. Neither shape nor viscosity changes were reversible upon removal of the agents. After the infusion of 130-300 mg Taxol in patients a slight shift towards stomatocytosis and an increase in whole blood viscosity at high shear rate from 5.09+/-0.30 to 5.44+/-0.38 mPa.s (P<0.05) were confirmed. 4. Commercial taxane drug formulations induce stomatocytosis and increase blood viscosity, which is due to their formulation vehicles. These findings may contribute to the understanding of the cardiovascular side effects of these drugs.