Immunomicelles: targeted pharmaceutical carriers for poorly soluble drugs

Abstract

To prepare immunomicelles, new targeted carriers for poorly soluble pharmaceuticals, a procedure has been developed to chemically attach mAbs to reactive groups incorporated into the corona of polymeric micelles made of polyethylene glycol-phosphatidylethanolamine conjugates. Micelle-attached antibodies retained their ability to specifically interact with their antigens. Immunomicelles with attached antitumor mAb 2C5 effectively recognized and bound various cancer cells in vitro and showed an increased accumulation in experimental tumors in mice when compared with nontargeted micelles. Intravenous administration of tumor-specific 2C5 immunomicelles loaded with a sparingly soluble anticancer agent, taxol, into experimental mice bearing Lewis lung carcinoma resulted in an increased accumulation of taxol in the tumor compared with free taxol or taxol in nontargeted micelles and in enhanced tumor growth inhibition. This family of pharmaceutical carriers can be used for the solubilization and enhanced delivery of poorly soluble drugs to various pathological sites in the body.

Figure 1

(A) Schematic structure of PEG–PE micelles containing a small addition of the pNP–PEG–PE component. (B) Coupling of amino group-containing ligands (antibodies) with pNP groups.

Figure 2

(Upper) Attachment of 2C5 antibodies to PEG–PE micelles via micelle-incorporated pNP–PEG–PE. (Lower) 2C5 attachment yield as a function of pNP–PEG–PE content in the micelle.

Figure 3

(Upper) Size distribution of “plain” PEG–PE/pNP–PEG–PE micelles (Left) and the same micelles after the attachment of 2C5 (Center) or 2G4 (Right). (Lower) Freeze–fracture electron images of plain PEG–PE/pNP–PEG–PE micelles (A) and 2C5 immunomicelles of the same composition (B).

Figure 4

(Upper) Binding of 2C5 immunomicelles to a monolayer of nucleosomes. (Lower) Binding of 2G4 immunomicelles to a monolayer of myosin.

Figure 5

Microscopy data on the binding of Rh-labeled 2C5 immunomicelles to EL4 T lymphoma cells (Top), LLC cells (Middle), and BT20 mammary adenocarcinoma cells (Bottom). (Left) Bright-field light microscopy. (Right) Fluorescent microscopy.

Figure 6

Blood clearance of plain micelles and 2C5 immunomicelles in mice.

Figure 7

(Upper) Accumulation of PEG–PE micelles in s.c. LLC tumor in mice at different time points. (Lower) Accumulation of free and micellar taxol in LLC tumor at the same time points.

Figure 8

Inhibition of LLC tumor growth in mice with different taxol preparations.