Localization of Therapeutic Fab-CHP Conjugates to Sites of Denatured Collagen for the Treatment of Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation in synovial joints and protease-induced cartilage degradation. Current biologic treatments for RA can effectively reduce symptoms, primarily by neutralizing the proinflammatory cytokine TNFα; however, continued, indiscriminate overinhibition of inflammatory factors can significantly weaken the host immune system, leading to opportunistic infections and interrupting treatment. We hypothesize that localizing anti-TNFα therapeutics to denatured collagen (dCol) present at arthritic joints, via conjugation with collagen-hybridizing peptides (CHPs), will reduce off-site antigen binding and maintain local immunosuppression. We isolated the antigen-binding fragment of the clinically approved anti-TNFα therapeutic infliximab (iFab) and prepared iFab-CHP conjugates via lysine-based conjugation with an SMCC linker. After successful conjugation, confirmed by LC-MS, the binding affinity of iFab-CHP was characterized by ELISA-like assays, which showed comparable antigen binding relative to infliximab, comparable dCol binding relative to CHP, and the hybrid ability to bind both dCol and TNFα simultaneously. We further demonstrated localization of Fab-CHP to areas of high dCol in vivo and promising therapeutic efficacy, assessed by histological staining (Safranin-O and H&E), in a pilot mouse study.