Doxil®--the first FDA-approved nano-drug: lessons learned.

Background: Perfluorooctanoic acid (PFOA) is a synthetic chemical ubiquitous in the serum of U.S. residents. It causes liver, testicular, and pancreatic tumors in rats. Human studies are sparse.Obj...

Perfluorooctanoic Acid (PFOA) Exposures and Incident Cancers among Adults Living Near a Chemical Plant

The effects of vesicle size, lipid composition, and drug-to-lipid ratio on the biological activity of liposomal doxorubicin in mice have been investigated using a versatile procedure for encapsulating doxorubicin inside liposomes. In this procedure, vesicles exhibiting transmembrane pH gradients (acidic inside) were employed to achieve drug trapping efficiencies in excess of 98%. Drug-to-lipid ratios as high as 0.3:1 (wt:wt) could be obtained in a manner that is relatively independent of lipid composition and vesicle size. Egg phosphatidylcholine (EPC)/cholesterol (55:45; mol/mol) vesicles sized through filters with a 200-nm pore size and loaded employing transmembrane pH gradients to achieve a doxorubicin-to-lipid ratio of 0.3:1 (wt/wt) increased the LD50 of free drug by approximately twofold. Removing cholesterol or decreasing the drug-to-lipid ratio in EPC/cholesterol preparations led to significant decreases in the LD50 of liposomal doxorubicin whereas, the LD50 increased 4- to 6-fold when distearoylphosphatidylcholine was substituted for EPC. The results suggest that the stability of liposomally entrapped doxorubicin in the circulation is an important factor in the toxicity of this drug in liposomal form. In contrast, the antitumor activity of liposomal doxorubicin is not influenced dramatically by alterations in lipid composition. Liposomal doxorubicin preparations of EPC, EPC/cholesterol (55:45; mol:mol), EPC/egg phosphatidylglycerol (EPG)/cholesterol (27.5:27.5:45; mol:mol), and distearoylphosphatidylcholine/cholesterol (55:45; mol:mol) all demonstrated similar efficacy to that of free drug when given at doses of 20 mg/kg and below. Higher dose levels of the less toxic formulations could be administered, leading to enhanced increases in life span (ILS) values. Variations in vesicle size, however, strongly influenced the antitumor activity of liposomal doxorubicin. At a dose of 20 mg/kg, large EPC/cholesterol systems are significantly less effective than free drug (with ILS values of 65% and 145%, respectively). In contrast, small systems sized through filters with a 100-nm pore size are more effective than free drug, resulting in an ILS of 375% and a 30% long term (greater than 60 days) survival rate when administered at a dose of 20 mg/kg. Similar size-dependent effects are observed for distearoylphosphatidylcholine/cholesterol systems.

https://cancerres.aacrjournals.org/content/canres/49/21/5922.full.pdf

Influence of Vesicle Size, Lipid Composition, and Drug-to-Lipid Ratio on the Biological Activity of Liposomal Doxorubicin in Mice

Uptake of adriamycin into large unilamellar vesicles in response to a pH gradient.

The anthracyclines are a group of antibiotics that are among the most potent chemotherapeutic agents. They are highly effective against a broad spectrum of malignancies, including lymphoma, gastric cancer, small cell lung cancer, sarcoma, and breast cancer. Unfortunately, these agents also exhibit a well-recognized cumulative-dose related cardiotoxic profi le that limits the extent to which they can be used safely. In clinical practice, most clinicians limit the cumulative dose of doxorubicin (the most widely used agent in this group) to 400-450 mg/m 2 , but considerable cardiac damage is now known to occur at cumulative dosages considerably below this level. Regimens using newer combinations of agents, the most widely studied of which is the monoclonal antibody trastuzumab, are known to augment the cardiotoxicity of anthracyclines. The application of nanotechnology to medicine involves the use of devices that will interact with the body at the molecular level. These methods can lead to target and tissue specifi c clinical application, often with minimal or reduced side effects. Liposomal preparations incorporate such technology, thereby altering some important characteristics of the parent compound and facilitating concentration at the tumor site. In the case of liposomal doxorubicin, cardiotoxicity is reduced signifi cantly. This review summarizes the important information on the liposomal preparation of anthracyclines.

Anthracycline-induced cardiotoxicity and the cardiac-sparing effect of liposomal formulation.

Doxorubicin possesses high affinity for binding to cardiolipin. We have utilized these properties in preparing stable liposomes of doxorubicin and cardiolipin with a net positive charge. Doxorubicin liposomes were formed by using 11.2 mumol of drug, 5.6 mumol of cardiolipin, 28.5 mumol of phosphatidylcholine, 19.5 mumol of cholesterol, and 11.1 mumol of stearylamine. These liposomes were sonicated for 90 min at 37 degrees followed by extensive dialysis against buffer. The pharmacological, toxicological, and therapeutic effects of doxorubicin entrapped in cardiolipin liposomes were compared with those of free doxorubicin in mice. At a dose of 4 mg/kg i.v., the peak cardiac concentration was achieved in 30 min following free doxorubicin administration, the value being 8.1 micrograms/g. The peak cardiac concentration with doxorubicin in cardiolipin liposomes was obtained at 5 min with a value of 2.8 micrograms/g of tissue. The cardiac concentration X time values for free doxorubicin for the 24-hr period of observation were 55.1 micrograms X hr/g, whereas it was only 7.8 micrograms X hr/g with the drug entrapped in cardiolipin liposomes. Compared to free drug, the liposomal entrapped doxorubicin significantly reduced the histopathological lesions in cardiac tissue of mice at a dose of 15 mg/kg as determined by electron microscopy. The nadir of peripheral white blood cell counts in mice with free drug, 6 mg/kg, was observed on Day 3 which was 50% of control, whereas with liposomal encapsulated drug it was reduced only 23% on Day 7. Doxorubicin in cardiolipin liposomes demonstrated enhanced chemotherapeutic potential against murine ascitic P388 leukemia with a 144% increased life span compared to 55% increased life span with free drug at a dose of 7.5 mg/kg on Days 1, 3, and 7. We conclude that doxorubicin liposomes developed in these studies possess improved therapeutic action as demonstrated by their ability to reduce the toxicity of the drug substantially.

https://cancerres.aacrjournals.org/content/canres/45/2/796.full.pdf

Geoffrey White

Papers

Pharmacological, toxicological, and therapeutic evaluation in mice of doxorubicin entrapped in cardiolipin liposomes.