Inflammation-retentive hyaluronic acid-mesalamine conjugate for enhanced oral therapy in ulcerative colitis

Mesalamine (5-aminosalicylic acid; MES) is a cost-effective, first-line therapy for mild to moderate ulcerative colitis, but oral administration often results in rapid gastrointestinal (GI) absorption, limiting drug delivery to inflamed areas. To improve targeting and reduce systemic exposure, we developed an inflammation-retentive hyaluronic acid-mesalamine conjugate (HA-MES) via a water-based carbodiimide-mediated condensation reaction. ¹H NMR, FTIR, and UV spectroscopy confirmed the successful synthesis of HA-MES, with 10.9 % ± 1.7 % of the repeating disaccharide units of HA conjugated to MES. Orally administered HA-MES showed prolonged retention in colitic colon tissue for up to 24 h, with reduced retention in healthy tissues and significantly lower systemic exposure compared to MES alone or a physical HA and MES mixture (HA + MES). In a murine model of acute colitis, HA-MES demonstrated superior therapeutic efficacy by reducing myeloperoxidase (MPO) and pro-inflammatory cytokines (TNF-α and IL-1β), while increasing anti-inflammatory cytokine IL-10 and enhancing expression of tight junction protein zonula occludens-1 (ZO-1), and goblet cell regeneration, thereby promoting mucosal barrier restoration. These results suggest that HA-MES forms a stable reservoir at inflamed sites, enhancing local drug availability and therapeutic outcomes, presenting a promising oral treatment option for ulcerative colitis compared to MES alone or HA + MES.