Recombinant rat complement regulatory proteins as therapeutic agents in inflammatory disease

摘要

The complement system has become a therapeutic target due to its involvement in a number of inflammatory conditions. Soluble recombinant forms of the membrane- associated regulators (CReg) have been created as therapeutics. However, these reagents are limited by their short half-lives in vivo and their tendency to systemically inhibit complement. To extend their circulating half-lives Fc fusion proteins have been generated while targeting reagents to sites of inflammation or inhibiting specific parts of complement, such as the terminal pathway, has been used to overcome systemic complement inhibition. Many of the reagents generated to date are based upon human proteins and are therefore immunogenic in rats, preventing their testing in rat models of chronic disease. To enable the testing of anti-complement therapeutics in rat models of chronic disease, various CReg-Fc containing a rat Fc and different portions of rat Crry were generated in this study. Functional analysis of the generated reagents was carried out to identify two different Crry-Fc. One would retain full activity while the other would address the issues of systemic complement inhibition by having negligible activity in the circulation, due to steric hindrance imparted on the Crry by the Fc, but could be cleaved at inflammatory sites to unleash an active regulator. A Crry-Fc that retained full activity was identified and tested in vivo. This reagent had a long circulating half- life, low immunogenicity and markedly reduced disease severity in a rat model of myasthenia gravis. Attempts to generate a Crry-Fc that had negligible activity in the circulation but could be cleaved at inflammatory sites to unleash anti-complement activity were unsuccessful. The generation of the active Crry-Fc reagent paves the way to testing anti-complement therapeutics in rat models of chronic disease.