Favorable coronary outcomes following IL-6 blockade with tocilizumab in IVIG-resistant kawasaki disease: a case series.

Objective: To evaluate the efficacy and coronary outcomes of tocilizumab (TCZ) in patients with intravenous immunoglobulin (IVIG)-resistant Kawasaki disease (KD), and to place these findings against the conflicting available evidence. Methods: We retrospectively analyzed four patients with IVIG-resistant KD who received TCZ as rescue therapy. Clinical, laboratory, and echocardiographic data (coronary artery Z-scores) were collected before and after treatment. Results: All patients received a second dose of IVIG before TCZ administration, however, symptoms did not improve. Following TCZ administration (median 15.5 days from onset), all patients achieved normothermia within 24 hours, accompanied by rapid normalization of inflammatory markers. Notably, no new coronary artery lesions (CALs) were identified after treatment. Additionally, in the two patients with pre-existing CALs, complete resolution of coronary dilation was observed during follow-up. No drug-related adverse events occurred. Conclusion: In this series, late administration of TCZ during the subacute phase was associated with a rapid anti-inflammatory response and favorable coronary remodeling, including aneurysm regression. This outcome contrasts with previous reports of coronary dilation following earlier intervention. Critically, these observations lead us to propose a "phase-dependent efficacy" hypothesis: the timing of IL-6 blockade relative to disease stage may be a critical determinant of coronary outcomes. This hypothesis underscores the need to consider the disease phase when evaluating IL-6 blockade for refractory KD.