Phase I and pharmacokinetic trial of carboplatin and albumin-bound paclitaxel, ABI-007 (Abraxane) on three treatment schedules in patients with solid tumors

Taxol biosynthesis: Identification and characterization of two acetyl CoA:taxoid-O-acetyl transferases that divert pathway flux away from Taxol production

Two cDNAs encoding taxoid-O-acetyl transferases (TAX 9 and TAX 14) were obtained from a previously isolated family of Taxus acyl/aroyl transferase cDNA clones. The recombinant enzymes catalyze the acetylation of taxadien-5alpha,13alpha-diacetoxy-9alpha,10beta-diol to generate taxadien-5alpha,10beta,13alpha-tri-acetoxy-9alpha-ol and taxadien-5alpha,9alpha,13alpha-triacetoxy-10beta-ol, respectively, both of which then serve as substrates for a final acetylation step to yield taxusin, a prominent side-route metabolite of Taxus. Neither enzyme acetylate the 5alpha- or the 13alpha-hydroxyls of taxoid polyols, indicating that prior acylations is required for efficient peracetylation to taxusin. Both enzymes were kinetically characterized, and the regioselectivity of acetylation was shown to vary with pH. Sequence comparison with other taxoid acyl transferases confirmed that primary structure of this enzyme type reveals little about function in taxoid metabolism. Unlike previously identified acetyl transferases involved in Taxol production, these two enzymes appear to act exclusively on partially acetylated taxoid polyols to divert the Taxol pathway to side-route metabolites.

Microtubule active agents: beyond the taxane frontier

Microtubules are essential to cell transport, signaling, and mitosis. An increasing range of anticancer drugs interferes with the normal formation and function of microtubules. Vinca alkaloids act as microtubule destabilizers and the taxanes act as microtubule stabilizers. Taxanes are widely used cytotoxic agents that are active in a range of solid tumor malignancies and are routinely used in a variety of settings. Significant limitations with the taxanes exist, including acquired and intrinsic tumor resistance through the expression of multidrug resistance proteins such as P-glycoprotein, risk of hypersensitivity reactions, dose-limiting hematopoietic toxicity, and cumulative neurotoxicity. Hence, there is a need to develop novel agents that act on the microtubules. Epothilones are macrolide antibiotics that bind near the taxane-binding site on microtubules and have been extensively studied in recent and ongoing clinical trials. A variety of other agents that act on the microtubules at different sites with a variety of structures are at varying stages of development.

Phase I trial of nanoparticle albumin-bound paclitaxel in combination with gemcitabine in patients with thoracic malignancies

BACKGROUND

Nab-paclitaxel has a different toxicity profile than solvent-based paclitaxel including a lower rate of severe neutropenia. This trial was designed to determine the maximum tolerated dose and dose limiting toxicities (DLT) of nab-paclitaxel in combination with gemcitabine.

METHODS

Patients were required to have a performance status of 0 to 1, < or = three prior cytotoxic chemotherapy regimens, and preserved renal, hepatic, and bone marrow function. Patients received gemcitabine 1000 mg/m on days 1, 8 in all cohorts, and nab-paclitaxel at doses of 260, 300, 340 mg/m every 21 days depending on the treatment cohort (1 cycle = 21 days). DLT were assessed after the first cycle, and doses were escalated in cohorts of 3 to 6 patients.

RESULTS

Eighteen patients were consented and 15 patients are evaluable [median age 62 years (range, 35-75); median number of prior treatments 3 (range, 1-4); tumor types: non-small cell lung cancer (NSCLC) (n = 8), small cell lung cancer (SCLC) (n = 6), and esophageal cancer (n = 1)]. At a nab-paclitaxel dose of 300 mg/m, 1 of 6 pts experienced a DLT (omission of day 8 gemcitabine due to absolute neutrophil count < 500), and at an nab-paclitaxel dose of 340 mg/m 2 of 3 patients experienced a DLT (1 pt grade 3 rash and pruritus; 1 pt grade 3 fatigue and anorexia). Responses were observed in NSCLC and SCLC.

CONCLUSIONS

The maximum tolerated dose of nab-paclitaxel is 300 mg/m in combination with gemcitabine 1000 mg/m on days 1, 8 every 21 days. This combination demonstrated activity in previously treated NSCLC and SCLC patients.

Polymeric nanoparticles for cancer therapy

Cancer is an ever-increasing menace that needs to be curbed soon. Though chemotherapy is successful to some extent, the main drawbacks of chemotherapy is the limited accessibility of drugs to the tumor tissues requiring high doses, their intolerable toxicity, development of multiple drug resistance and their non-specific targeting. Nanoparticles (NPs), an evolution of nanotechnology, have the potential to successfully address these problems related to drug delivery and retention and are considered potential candidates to carry drugs to the desired site of therapeutic action. In this review, we give an overview of the use of clinically applicable NPs mainly for cancer therapy. We also focus on the different types of nanoscale polymer carriers used for the delivery of chemotherapeutic agents and the mechanisms that facilitate their targeted delivery to tumor cells.

Protein nanoparticles as drug carriers in clinical medicine

Solvent-based delivery vehicles for chemotherapy agents have been instrumental in providing a means for hydrophobic agents to be administered intravenously. These solvents, however, have been associated with serious and dose-limiting toxicities. Solvent-based formulations of taxanes, a highly active class of cytotoxic agents, are associated with hypersensitivity reactions, neutropenia, and neuropathy. Nanoparticle technology utilizing the human protein albumin exploits natural pathways to selectively deliver larger amounts of drug to tumors while avoiding some of the toxicities of solvent-based formulations. 130 nM albumin-bound (nab) paclitaxel (nab-paclitaxel; Abraxane) was recently approved for use in patients with metastatic breast cancer who have failed combination therapy. In a randomized, phase III study in metastatic breast cancer, nab-paclitaxel was found to have improved efficacy and safety compared with conventional, solvent-based paclitaxel. Preliminary data also suggest roles for nab-paclitaxel as a single agent and in combination therapy for first-line treatment of metastatic breast cancer as well as in other solid tumors, including non-small-cell lung cancer, ovarian cancer, and malignant melanoma. The nab technology promises to have broad utility in cancer therapy, and clinical trials are underway using nab formulations of other water-insoluble anticancer agents such as docetaxel and rapamycin.

Suspensions for intravenous (IV) injection: a review of development, preclinical and clinical aspects

There has been growing interest in nanoparticles as an approach to formulate poorly soluble drugs. Besides enhanced dissolution rates, and thereby, improved bioavailability, nanoparticles can also provide targeting capabilities when injected intravenously. The latter property has led to increased research and development activities for intravenous suspensions. The first intravenously administered nanoparticulate product, Abraxane (a reformulation of paclitaxel), was approved by the FDA in 2006. Additional clinical trials have been conducted or are ongoing for multiple other indications such as oncology, infective diseases, and restenosis. This article reviews various challenges associated with developing intravenous nanosuspension dosage forms. In addition, various formulation considerations specific to intravenous nanosuspensions as well as reported findings from various clinical studies have been discussed.

Downregulation of Plk1 expression by receptor-mediated uptake of antisense oligonucleotide-loaded nanoparticles

Human serum albumin (HSA) nanoparticles represent a promising tool for targeted drug delivery to tumor cells. The coupling of the antibody trastuzumab to nanoparticles uses the capability of human epidermal growth factor receptor 2 (HER2)-positive cells to incorporate agents linked to HER2. In our present study, we developed targeted nanoparticles loaded with antisense oligonucleotides (ASOs) against polo-like kinase 1 (Plk1). We evaluated the receptor-mediated uptake into HER2-positive and -negative breast cancer and murine cell lines. We performed quantitative real-time PCR and Western blot analyses to monitor the impact on Plk1 expression in HER2-positive breast cancer cells. Antibody-conjugated nanoparticles showed a specific targeting to HER2-overexpressing cells with cellular uptake by receptor-mediated endocytosis and a release into HER2-positive BT-474 cells. We observed a significant reduction of Plk1 mRNA and protein expression and increased activation of Caspase 3/7. Thus, this is the first report about ASO-loaded HSA nanoparticles, where an impact on gene expression could be observed. The data provide the basis for the further development of carrier systems for Plk1-specific ASOs to reduce off-target effects evoked by systemically administered ASOs and to achieve a better penetration into primary and metastatic target cells. Treatment of tumors using trastuzumab-conjugated ASO-loaded HSA nanoparticles could be a promising approach to reach this goal.