New research has uncovered a precision medicine test using blood proteins to identify a novel patient subgroup of idiopathic multicentric Castleman disease (iMCD), a rare blood disorder, who are more likely to respond to siltuximab, the only FDA approved treatment for the disease. The international study was led by researchers at Penn Medicine and the Castleman Disease Collaborative Network (CDCN).

Prior research suggests that half of patients do not respond to the monoclonal antibody treatment, siltuximab. For those patients, rapid administration of other treatments is needed to prevent deterioration, so understanding who is likely to benefit is critical. This study also revealed that an existing drug approach, Janus kinase (JAK) inhibitors, which are already approved for treating certain cancers and rheumatoid arthritis, are a promising alternative treatment option for patients who do not respond to siltuximab. The study, which is the largest to date for iMCD, is published in Blood Advances.

“This discovery has the potential to improve precision medicine for iMCD—the concept that the right patient is given the right drug at the right time. Knowing which patients are likely to benefit from which drugs is a key piece of this puzzle,” says David Fajgenbaum, an assistant professor of translational medicine and human genetics, Director of the Center for Cytokine Storm Treatment & Laboratory at the Perelman School of Medicine, co-founder of the CDCN, and associate director of patient impact at the Penn Orphan Disease Center, and the study’s senior author. Fajgenbaum is also an iMCD patient.

—Sophie Kluthe