siltuximab + best supportive care

**Siltuximab + best supportive care** is a combination therapy comprising siltuximab, a chimeric monoclonal antibody that selectively binds to and neutralizes interleukin-6 (IL-6), administered alongside best supportive care measures. Siltuximab blocks IL-6, a cytokine central to the pathogenesis of multicentric Castleman disease (MCD), resulting in tumor shrinkage and symptomatic improvement. Best supportive care includes all other non-curative treatments to mitigate disease symptoms and complications. This regimen is approved for the treatment of adult patients with symptomatic idiopathic multicentric Castleman disease (iMCD) who are HIV- and HHV-8-negative.