Pharmacokinetics and posterior segment biodistribution of ESBA105, an anti-TNF-alpha single-chain antibody, upon topical administration to the rabbit eye.

PURPOSE: The purpose of this study was to characterize local distribution and systemic absorption of the tumor necrosis factor (TNF)-alpha inhibitory single-chain antibody fragment (scFv) ESBA105 following topical administration to the eye in vivo. METHODS: Rabbits received ESBA105 as topical eye drops in two dosing regimens. First, pharmacokinetics after the topical route of administration was compared to the intravenous (i.v.) route by means of applying the identical cumulative daily dose of ESBA105. In a second study rabbits received five eye drops daily for six consecutive days in a lower frequency topical dosing regimen. Kinetics and biodistribution of ESBA105 in ocular tissues and fluids as well as in sera were determined in all animals. RESULTS: After topical administration to the eye, ESBA105 quickly reaches therapeutic concentrations in all ocular compartments. Systemic exposure after topical administration is 25,000-fold lower than exposure after i.v. injection of the identical cumulative daily dose. ESBA105 levels in vitreous humor and neuroretina are significantly higher on topical administration than after i.v. injection. Absolute and relative intraocular biodistribution of ESBA105 is different with topical and systemic delivery routes. Compared to its terminal half-life in circulation (7 hours), the vitreal half-life of ESBA105 is significantly enhanced (16-24 hours). CONCLUSIONS: On topical administration, ESBA105 is efficiently absorbed and distributed to all compartments of the eye, whereby systemic drug exposure is very low. Based on its unique intraocular biodistribution and pharmacokinetics and the absolute intraocular levels reached, topical ESBA105 appears highly attractive for treatment of various ophthalmological disorders.

Can MMTV exploit TLR4?

The recognition of microbial pathogens based on their molecular patterns is essential for host defense. Recently, Toll-like receptors have been shown not only to recognize viruses as well as bacteria and fungi, but also to trigger an efficient immune response. A recent publication proposed that the retrovirus mouse mammary tumor virus exploits the pattern-recognition receptor Toll-like receptor 4 to achieve more efficient infection.

Direct analysis of peptide binding to cell-associated MHC class I molecules.

Exogenously added synthetic peptides can mimic endogenously produced antigenic peptides recognized on target cells by MHC class I-restricted cytolytic T lymphocytes. While it is assumed that exogenous peptides associate with class I molecules on the target cell surface, direct binding of peptides to cell-associated class I molecules has been difficult to demonstrate. Using a newly developed binding assay based on photoaffinity labeling, we have investigated the interaction of two antigenic peptides, known to be recognized in the context of H-2Kd or H-2Db, respectively, with 20 distinct class I alleles on living cells. None of the class I alleles tested, with the exception of H-2Kd or H-2Db, bound either of the peptides, thus demonstrating the exquisite specificity of peptide binding to class I molecules. Moreover, peptide binding to cell-associated H-2Kd was drastically reduced when metabolic energy, de novo protein synthesis or protein egress from the endoplasmic reticulum was inhibited. It is thus likely that exogenously added peptides do not associate with the bulk of class I molecules expressed at the cell surface, but rather bind to short-lived molecules devoid of endogenous peptides.