Sirolimus in Previously Treated Idiopathic Multicentric Castleman Disease

Human herpesvirus(HHV)-8-negative, idiopathic multicentric Castleman disease (iMCD) is a rare hematologic illness. Current therapeutic options are limited and provide benefit for only a subset of patients. Blockade of IL-6 signaling with siltuximab or tocilizumab abrogates symptoms and improves lymphadenopathy in a portion of patients. However, 66% of patients in the siltuximab Phase II clinical trial did not meet response criteria, and recent studies found that IL-6 is not significantly elevated in many iMCD patients. Recent research has suggested a key role for the phosphoinositide 3-kinase(PI3K)/Akt/mechanistic target of rapamycin (mTOR) pathway in iMCD pathogenesis and off-label administration of sirolimus, an mTOR inhibitor, has shown clinical activity. Based on these experiences, we plan to evaluate the efficacy of sirolimus as a therapy for iMCD patients who are either unable to tolerate anti-IL-6 blockade therapy (siltuximab or tocilizumab), or who fail, relapse, or are refractory to such treatment. This study is a Phase II open label study of daily administration of sirolimus in up to 24 evaluable male or female adults. Participants with iMCD who have failed previous therapy will take daily oral sirolimus for 12 months. Information that is collected as per standard of care will be used to review efficacy, in addition to samples collected specifically for research.