Melendez Hebib, V.; Earls, B.; Stoll, B.; Vonderohe, C.; Guthrie, G.; Haiser, H. J.; Paton, M.; Balani, S.; Hesse, M.; Burrin, D.

Necrotizing enterocolitis (NEC) is a disease in preterm infants associated with an increased abundance of Enterobacteriaceae. FimH, a mannose-binding adhesin on Enterobacteriaceae type 1 fimbriae, mediates mucosal attachment and TLR4-dependent inflammatory cascades. We evaluated the safety, pharmacokinetics, and efficacy of an oral FimH inhibitor (Sibofimloc) to reduce Enterobacteriaceae colonization and prevent NEC in preterm piglets. We performed a 9-d dose-escalation safety study (10, 25, 50 mg/kg BID) assessing absorption and tolerability and a 10-d randomized efficacy study. Piglets in the efficacy study received an infant formula diet with or without oral sibofimloc (40 mg/kg BID), or donor human milk (DHM) as a healthy control. NEC incidence, tissue histopathology, and gut microbiota composition via metagenomic whole-genome sequencing (WGS) were evaluated. Systemic exposure data reveal that sibofimloc was dose-dependently absorbed, while plasma levels decreased from postnatal day 2 to day 8, indicating reduced drug absorption with maturation of the intestinal barrier. Treatment with sibofimloc did not reduce NEC incidence (100% in sibofimloc in formula controls) or severity, whereas DHM-fed piglets experienced 0% NEC. Sibofimloc-treated animals exhibited significantly reduced crypt depths, demonstrating heightened mucosal injury and impaired regenerative capacity. WGS revealed that sibofimloc-treated animals maintained a gut luminal microbiota composition similar to untreated formula controls, dominated by Clostridium perfringens (C. perfringens). Selective targeting of FimH-expressing Enterobacteriaceae was insufficient to prevent NEC or alter the gut microbiota in this preterm piglet model, underscoring the complexity of NEC-associated microbial communities and suggesting that additional microbial targets and other colonization mechanisms may contribute to disease development.