™™| 09/06/10 | |||
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Technology name:
Technology description: We have developed a discovery system for tissue targeting molecules. Using M13, a filamentous bacteriophage, we are able to identify short peptides with tissue specific targeting properties. These peptides may be used to deliver a variety of substances to the targeted tissue, including pharmaceuticals and gene therapy vectors. Since the targeting molecules consist of short peptide sequences, they may be readily produced at commercially feasible scales via synthetic or recombinant thechnology. Their biologic nature allows them to be directly incorporated into biological vector systems, such as those used in gene therapy, by simply adding the appropriate DNA code to that of the therapeutic vector construct. Methodology: For most applications, a "library" of phage containing a mixture of all possible sequences for a 7 amino acid peptide, is injected into an animal i.v. and allowed to circulate for one hour or less. This time period allows the bacteriophage particles in the circulation to passively diffuse through pores in the walls of blood vessels in the spaces surrounding the cells in a given tissue. If the peptide carried by the bacteriophage binds to a cell in "targeted" tissue, it is retained in that tissue and is no lnager free to diffuse. Thus, over the course of an hour, the concentrations of bacteriophage carrying peptides that have an affinity for the cells of the tissue in question is increased, and these bacteriophage are over-represented (compared to background or untargeted bacteriophage) in the bacteriophage harvested from that tissue. After several rounds of in vivo screening in this manner, the bacteriophage are collected and sequenced, with the result that one or more clones appear at significantly higher numbers than expected. Other clones with similar sequences are also seen, allowing one to establish a "consensus" sequence for the "targeting" peptide. Results: To date, we have identified peptides with enhanced binding to skeletal muscle, cardiac muscle, central nervous system tissues, and mammary adenocarcinoma. These peptides have been demonstrated to escape the vasculature, cross the extracellular matrix, bind to parenchymal tissue, and in some cases, the peptides have been demonstrated to internalize in the target tissue. The peptides have resulted in more than 25 fold enhancement in binding to specific tissues, which, when combined with the reduction in delivery to untargeted tissue of up to 5 fold, results in relative delivery efficiencies of greater 100 fold. The peptides, while selected mainly in the mouse, have been shown to bind to specific proteins from the target tissue in other mammals, both by PAGE and a sensitive microbalance system. We expect that these peptides, or closely related derivatives will be extremely active in targeting human tissues. | |||