Design and Synthesis of MBP-Fc-Bifunctional Peptide Inhibitor to Improve <i>In Vivo</i> Half-Life and Efficacy

Multiple Sclerosis (MS) is an autoimmune disease in which the myelin sheath surrounding neurons is degenerate, resulting in physical and cognitive impairment in patients. While current treatments have shown efficacy in reducing symptoms and treating MS, they have also been found to suppress the general immune system. Thus, treated patients are susceptible to opportunistic infections. Bifunctional peptide inhibitors (BPIs) have been designed to selectively target T cells against myelin sheath proteins to promote a tolerogenic response. BPIs are composed of a signal-2 blocking peptide called the LFA-1 alpha blocker left (LABL) peptide and the myelin-derived antigenic peptide linked by a peptide chain. While effective, BPIs have short half-lives and require higher doses to have a therapeutic effect, which could lead to adverse side effects. To mitigate these shortcomings, the BPIs were modified to Fc-BPI by using the Fc region of human IgG1 as a linker between LABL and antigenic peptides. Here, we successfully synthesized MBP-Fc-BPI containing a myelin basic protein (MBP) peptide. The MBP-Fc-BPI has longer half-lives <i>in vitro</i> and <i>in vivo</i> compared to the parent MBP-BPI peptide. The MBP-Fc-BPI had a similar secondary structure and physical stability as the precursor LABL-Fc-ST, indicating that the addition of the MBP antigenic peptide did not alter the conformation of MBP-Fc-BPI. MBP-Fc-BPI significantly suppressed the EAE disease symptoms compared to PBS. MBP-Fc-BPI was more effective in suppressing the EAE than MBP-BPI and LABL-Fc-ST.