Viral spike antigen clearance and augmented recovery in children with post-COVID multisystem inflammatory syndrome treated with larazotide

Multisystem inflammatory syndrome (MIS) is a severe disease that occurs weeks to months after acute infection with SARS-CoV-2, often occurring in children (MISC). Symptoms include high fever, rash, nausea, diarrhea, and abdominal pain. Children with MISC can develop cardiovascular injury including ventricular failure, coronary artery aneurysms, or shock. Current treatment strategies for these postacute sequelae of COVID-19 primarily target the hyperinflammatory response. However, a potential role for viral spike protein translocated via zonulin-mediated trafficking from gastrointestinal reservoirs of SARS-CoV-2 into the circulation has been suggested. Here, we report results from a phase 2a randomized, double-blind, placebo-controlled clinical trial testing the zonulin antagonist larazotide in 12 children with MISC with a median age of 5.7 years. Children were enrolled during hospitalization for acute MISC and were treated with adjuvant larazotide therapy four times daily for 3 weeks. Patients were monitored for 24 weeks for safety follow-up. No larazotide-related adverse events were reported. The concentration of SARS-CoV-2 spike protein antigen in blood samples correlated with inflammatory markers, including interferon-γ (IFN-γ) ( P = 0.004) and interleukin-6 (IL-6) ( P < 0.0001), and with gastrointestinal symptoms as assessed by the PedsQL GI symptom score ( P = 0.003). Children treated with larazotide displayed faster resolution of gastrointestinal symptoms, faster clearance of spike antigen, and a faster return to usual activities. Our findings suggest that larazotide treatment may be safe in children and may improve resolution of symptoms when used as an adjuvant therapy for MISC.