Real-time pharmacokinetics guiding clinical decisions

P-glycoprotein antibody-conjugated paclitaxel liposomes targeted for multidrug-resistant lung cancer

Aims: To overcome the resistance of lung cancer to paclitaxel. Methods: P-glycoprotein antibody-conjugated paclitaxel PEG-coated immunoliposomes (Pab-PTX-L) were prepared, and a series of quality evaluations, in vitro cell evaluation and assessment of their in vivo antitumor effect in mice were conducted. Results: The results showed that Pab-PTX-L was nano-sized with high encapsulation efficiency of paclitaxel. For the paclitaxel-resistant lung cancer A549/T cells, the cellular uptake and cell viability inhibition and apoptosis of Pab-PTX-L-treated cells were higher than those of the control groups. More importantly, Pab-PTX-L showed a good targeting and antitumor effect on tumor tissue in mouse experiments. Conclusion: This study will provide a new insight on enhanced paclitaxel delivery into paclitaxel-resistant cancer cells.

Recent Clinical Developments of Nanomediated Drug Delivery Systems of Taxanes for the Treatment of Cancer

Conventional taxanes are used as cornerstone of the chemotherapeutical treatment for a variety of malignancies. Nevertheless, a large proportion of patients do not benefit from their treatment while they do suffer from severe adverse events related to the solvent or to the active compound. Cremophor EL and polysorbate 80 free formulations, conjugates, oral formulations and different types of drug delivery systems are some examples of the several attempts to improve the treatment with taxanes. In this review article, we discuss recent clinical developments of nanomediated drug delivery systems of taxanes for the treatment of cancer. Targeting mechanisms of drug delivery systems and characteristics of the most commonly used taxane-containing drug delivery systems in the clinical setting will be discussed in this review.

Nanoparticle delivery systems to combat drug resistance in ovarian cancer

Due to the lack of early symptoms and difficulty of accurate diagnosis, ovarian cancer is the most lethal gynecological cancer faced by women. First-line therapy includes a combination of tumor resection surgery and chemotherapy regimen. However, treatment becomes more complex upon recurrence due to development of drug resistance. Drug resistance has been linked to many mechanisms, including efflux transporters, apoptosis dysregulation, autophagy, cancer stem cells, epigenetics, and the epithelial-mesenchymal transition. Thus, developing and choosing effective therapies is exceptionally complex. There is a need for increased specificity and efficacy in therapies for drug-resistant ovarian cancer, and research in targeted nanoparticle delivery systems aims to fulfill this challenge. Although recent research has focused on targeted nanoparticle-based therapies, few of these therapies have been clinically translated. In this review, non-viral nanoparticle delivery systems developed to overcome drug-resistance in ovarian cancer were analyzed, including their structural components, surface modifications, and drug-resistance targeted mechanisms.

Nab-paclitaxel for breast cancer: a new formulation with an improved safety profile and greater efficacy

Taxanes, paclitaxel and docetaxel, are among the most effective agents used to treat breast cancer. Nab-paclitaxel (ABI-007, Abraxane) is paclitaxel encapsulated in albumin. This differs from the more conventional formulation which uses cremophor to increase the solubility of paclitaxel (CrEL-paclitaxel). In a randomized trial that formed the basis of its regulatory approval in the USA, 3-weekly nab-paclitaxel induced a higher response rate and longer time to progression than CrEL-paclitaxel in patients with metastatic breast cancer. Except for grade 3 sensory neuropathy, nab-paclitaxel was also safer. An interim analysis from a more recent randomized Phase II trial suggests that weekly nab-paclitaxel is more effective and safer than either 3-weekly nab-paclitaxel or 3-weekly docetaxel. The superior efficacy of nab-paclitaxel is presumably due to the improved safety profile, which allows for the administration of higher doses, a greater proportion of which actually reaches the tumor. Observations on the development of nab-paclitaxel have important implications for our understanding of dose response in the use of cytotoxic drugs to treat all forms of cancer. Although it is not yet clear whether nab-paclitaxel can be routinely substituted for CrEL-paclitaxel or docetaxel in breast cancer treatment regimens, it seems highly likely that this will occur within the next 5 years.

Liposomal paclitaxel formulations

Over the past three decades, taxanes represent one of the most important new classes of drugs approved in oncology. Paclitaxel (PTX), the prototype of this class, is an anti-cancer drug approved for the treatment of breast and ovarian cancer. However, notwithstanding a suitable premedication, present-day chemotherapy employing a commercial preparation of PTX (Taxol®) is associated with serious side effects and hypersensitivity reactions. Liposomes represent advanced and versatile delivery systems for drugs. Generally, both in vivo mice tumor models and human clinical trials demonstrated that liposomal PTX formulations significantly increase a maximum tolerated dose (MTD) of PTX which outperform that for Taxol®. Liposomal PTX formulations are in various stages of clinical trials. LEP-ETU (NeoPharm) and EndoTAG®-1 (Medigene) have reached the phase II of the clinical trials; Lipusu® (Luye Pharma Group) has already been commercialized. Present achievements in the preparation of various liposomal formulations of PTX, the development of targeted liposomal PTX systems and the progress in clinical testing of liposomal PTX are discussed in this review summarizing about 30 years of liposomal PTX development.

A critical review of lipid-based nanoparticles for taxane delivery

Nano-based delivery systems have attracted a great deal of attention in the past two decades as a strategy to overcome the low therapeutic index of conventional anticancer drugs and delivery barriers in solid tumors. Myriads of preclinical studies have been focused on developing nano-based formulations to effectively deliver taxanes, one of the most important and most prescribed anticancer drug types in the clinic. Given the hydrophobic property of taxanes, lipid-based NPs, serve as a viable alternative delivery system. This critical review will provide an overview and perspective of the advancement of lipid-based nanoparticles for taxane delivery. Currently available formulations of taxanes and their drawbacks as well as criteria for idea taxane delivery system will be discussed.

Moving molecular targeted drug therapy towards personalized medicine: issues related to clinical trial design

With the event of new Molecular targets, clinical trial design requirements to perform these trials are changing. This paper discusses some of the considerations that need to be taken into account when designing a trial, including those trials that assess combinations of targets.

A model of competing saturable kinetic processes with application to the pharmacokinetics of the anticancer drug paclitaxel

A saturable multi-compartment pharmacokinetic model for the anti-cancer drug paclitaxel is proposed based on a meta-analysis of pharmacokinetic data published over the last two decades. We present and classify the results of time series for the drug concentration in the body to uncover the underlying power laws. Two dominant fractional power law exponents were found to characterize the tails of paclitaxel concentration-time curves. Short infusion times led to a power exponent of -1.57 ± 0.14, while long infusion times resulted in tails with roughly twice the exponent. Curves following intermediate infusion times were characterized by two power laws. An initial segment with the larger slope was followed by a long-time tail characterized by the smaller exponent. The area under the curve and the maximum concentration exhibited a power law dependence on dose, both with compatible fractional power exponents. Computer simulations using the proposed model revealed that a two-compartment model with both saturable distribution and elimination can reproduce both the single and crossover power laws. Also, the nonlinear dose-dependence is correlated with the empirical power law tails. The longer the infusion time the better the drug delivery to the tumor compartment is a clinical recommendation we propose.

Naposomes: a new class of peptide-derivatized, target-selective multimodal nanoparticles for imaging and therapeutic applications

Modified supramolecular aggregates for selective delivery of contrast agents and/or drugs are examined with a focus on a new class of peptide-derivatized nanoparticles: naposomes. These nanoparticles are based on the co-aggregation of two different amphiphilic monomers that give aggregates of different shapes and sizes (micelles, vesicles and liposomes) with diameters ranging between 10 and 300 nm. Structural properties and in vitro and in vivo behaviors are discussed. For the high relaxitivity values (12–19 mM-1s-1) and to detect for the presence of a surface-exposed peptide, the new peptide-derived supramolecular aggregates are very promising candidates as target-selective MRI contrast agents. The efficiency of surface-exposed peptides in homing these nanovectors to a specific target introduces promising new opportunities for the development of diagnostic and therapeutic agents with high specificity toward the biological target and reduced toxic side effects on nontarget organs.

Paclitaxel poliglumex and carboplatin as first-line therapy in ovarian, peritoneal or fallopian tube cancer: a phase I and feasibility trial of the Gynecologic Oncology Group

PURPOSE

To estimate the maximum tolerated dose (MTD) of paclitaxel poliglumex (PPX) in combination with carboplatin in patients with chemotherapy-naive ovarian, primary peritoneal or fallopian tube cancer, and to assess the feasibility of administering multiple cycles of this regimen.

METHODS

The first 11 patients were treated in a standard 3 + 3 dose-seeking design, with carboplatin held constant at area under the curve (AUC) of 6 and PPX at 225, 175 or 135 mg/m(2). Pharmacokinetics of PPX and carboplatin were evaluated during this dose-seeking component of the trial. MTD was defined by acute dose-limiting toxicities (DLT) in the first cycle. Twenty additional evaluable patients were treated at the estimated MTD to assess the feasibility of this regimen over >or=4cycles.

RESULTS

PPX at 225 mg/m(2) resulted in DLT in 2/3 patients, and was de-escalated first to 175 mg/m(2) and then to 135 mg/m(2). PPX slowly hydrolyzed to paclitaxel and did not alter the pharmacokinetics of carboplatin. DLT within the first 4-cycles were observed in 3 patients (15%) treated at the MTD: neutropenia > 2weeks (2), febrile neutropenia (1). Nineteen patients (95%) experienced grade 4 neutropenia. Sixteen patients (80%) had at least one episode of grade 3 thrombocytopenia. Three patients (15%) had grade 2 and one had grade 3 peripheral neuropathy. Complete response by CA-125 was 75%.

CONCLUSIONS

The recommended dose of PPX of 135 mg/m(2) with carboplatin (AUC = 6) in newly diagnosed ovarian cancer was feasible for multiple cycles, but hematologic toxicity was greater compared with standard carboplatin and 3-hour paclitaxel.

Phase I and Pharmacokinetic Study of AI-850, A Novel Microparticle Hydrophobic Drug Delivery System for Paclitaxel

PURPOSE

AI-850, paclitaxel in a novel polyoxyethylated castor oil-free hydrophobic microparticle delivery system, is being developed based on its favorable preclinical safety and antitumor activity profiles. The objectives of the study were to assess the feasibility and safety of administering AI-850 as a <30-min i.v. infusion without premedication every 3 weeks, determine the maximum tolerated dose and the phase II recommended dose of AI-850, study the pharmacokinetics of paclitaxel in this new formulation, and seek evidence of anticancer activity.

EXPERIMENTAL DESIGN

This was an open-label phase I dose escalation study of AI-850 in patients with advanced solid malignancies. AI-850 doses were escalated according to a modified Fibonacci scheme. Clinical and laboratory toxicity was monitored, and paclitaxel plasma concentrations were measured by liquid chromatography-tandem mass spectrometry.

RESULTS

Twenty-two patients received 56 courses of AI-850 at five dose cohorts ranging from 36 to 250 mg/m(2). Grade 4 neutropenia, either exceeding 5 days or complicated by fever, was dose limiting in two of six patients at 250 mg/m(2) AI-850. Three patients experienced grade 2 to 4 infusion-related adverse reactions. Toxicities, including fatigue, alopecia, nausea and vomiting, neuropathy, anorexia, and myalgia, were mild to moderate, reversible, and not dose related. Pharmacokinetics of free and total paclitaxel showed biexponential plasma decay and dose proportionality for maximum plasma paclitaxel concentration and area under the concentration versus time curve. Antitumor activity was documented in two patients with endometrial and tongue carcinomas.

CONCLUSIONS

The administration of AI-850 as a brief infusion once every 3 weeks was feasible at doses up to 205 mg/m(2). The potential of AI-850 as an alternative to other approved paclitaxel formulations requires further clinical evaluation.

A phase I and pharmacokinetic study of paclitaxel poliglumex (XYOTAX), investigating both 3-weekly and 2-weekly schedules

PURPOSE

To determine the safety, maximum tolerated dose, pharmacokinetics, and toxicities associated with administration of paclitaxel poliglumex (PPX, XYOTAX, Cell Therapeutics, Inc., Bresso, Italy) given on either 3-weekly or 2-weekly schedule.

EXPERIMENTAL DESIGN

Nineteen patients were investigated on the 3-weekly phase Ia study and 11 patients on the 2-weekly phase Ib study. Dose escalation starting with 100% increments and one patient per dose level was modulated in accordance with the observed toxicities. Conjugated and unconjugated paclitaxel were measured in plasma.

RESULTS

Dose-limiting toxicity of neutropenia was encountered at 266 mg/m(2) (paclitaxel equivalents) in phase Ia and the maximum tolerated dose was 233 mg/m(2). Neuropathy was dose-limiting in phase Ib with a maximum tolerated dose of 177 mg/m(2). Pharmacokinetic investigations indicated a prolonged half-life of >100 hours for conjugated taxanes. Plasma concentrations of unconjugated paclitaxel were similar to those following administration of an equivalent dose of Taxol. Two partial responses were observed, one in a patient with mesothelioma at 177 mg/m(2) in phase Ia and one in a patient with gastric carcinoma at 175 mg/m(2) in phase Ib.

CONCLUSION

PPX is a water-soluble paclitaxel-polymer conjugate with a prolonged half-life and limited volume of distribution. Dose-limiting toxicities were neutropenia and neuropathy. PPX showed activity in this patient population.

Liposomal encapsulated anti-cancer drugs

Among several drug delivery systems, liposomal encapsulated anti-cancer agents represent an advanced and versatile technology. Several formulations of liposomal anthracyclines are approved, e.g. for the treatment of metastatic breast cancer (pegylated and non-pegylated liposomal doxorubicin) or AIDS-related Kaposi's sarcoma (pegylated liposomal doxorubicin and liposomal daunorubicin). Meanwhile, virtually all anti-cancer drugs have been encapsulated in liposomes using different technologies. This review will summarize preclinical and clinical data of approved and exemplary emerging liposomal anti-cancer agents.

Intravenous Hydrophobic Drug Delivery: A Porous Particle Formulation of Paclitaxel (AI-850)

PURPOSE

To develop a rapidly dissolving porous particle formulation of paclitaxel without Cremophor EL that is appropriate for quick intravenous administration.

METHODS

A rapidly dissolving porous particle formulation of paclitaxel (AI-850) was created using spray drying. AI-850 was compared to Taxol following intravenous administration in a rat pharmacokinetic study, a rat tissue distribution study, and a human xenograft mammary tumor (MDA-MB-435) model in nude mice.

RESULTS

The volume of distribution and clearance for paclitaxel following intravenous bolus administration of AI-850 were 7-fold and 4-fold greater, respectively, than following intravenous bolus administration of Taxol. There were no significant differences between AI-850 and Taxol in tissue concentrations and tissue area under the curve (AUC) for the tissues examined. Nude mice implanted with mammary tumors showed improved tolerance of AI-850, enabling higher administrable does of paclitaxel, which resulted in improved efficacy as compared to Taxol administered at its maximum tolerated dose (MTD).

CONCLUSIONS

The pharmacokinetic data indicate that paclitaxel in AI-850 has more rapid partitioning from the bloodstream into the tissue compartments than paclitaxel in Taxol. AI-850, administered as an intravenous injection, has been shown to have improved tolerance in rats and mice and improved efficacy in a tumor model in mice when compared to Taxol.

Development and characterization of a novel Cremophor® EL free liposome-based paclitaxel (LEP-ETU) formulation

Taxol is a marketed product for the treatment of ovarian, breast, non-small cell lung cancer and AIDS-related Kaposi's Sarcoma. It is thus far one of the most effective anticancer drugs available on the market. However, paclitaxel is only sparingly soluble in water and therefore, intravenous administration depends on the use of the non-ionic surfactant Cremophor EL (polyethoxylated castor oil) to achieve a clinically relevant concentrated solution. Unfortunately, Cremophor EL increases toxicity and leads to hypersensitivity reactions in certain individuals. We have developed a well characterized novel lyophilized liposome-based paclitaxel (LEP-ETU) formulation that is sterile, stable and easy-to-use. The mean particle size of the liposomes is about 150 nm before and after lyophilization, and the drug entrapment efficiency is greater than 90%. Stability data indicated that the lyophilized LEP-ETU was physically and chemically stable for at least 12 months at 2-8 and 25 degrees C. Moreover, the formulation can be diluted to about 0.25mg/ml without drug precipitation or change in particle size. In vitro drug release study in phosphate-buffered saline (PBS, pH 7.4) showed that less than 6% of the entrapped paclitaxel was released after 120 h, indicating that the drug is highly stable in an entrapped form at physiologic temperature.