Ruxolitinib for Immune Effector Cell Associated Hemophagocytic Lymphohistiocytosis-like Syndrome (RISE)

This is a pilot study to gather information about safety and efficacy of using ruxolitinib (RUX) to treat Immune Effector Cell Associated Hemophagocytic Lymphohistiocytosis-like Syndrome (IEC-HS) occurring after CAR-T therapy. In addition, correlative studies will be done to 1) estimate the optimal duration of RUX therapy, 2) to identify immunological biomarkers associated with response (3) To evaluate the dynamics of CAR T expansion following RUX treatment. Oral RUX will be administered twice daily, with dosing determined by the participant's baseline platelet count. Treatment will continue for up to 8 weeks unless significant adverse events occur or the treating physician concludes that the therapy is no longer providing clinical benefit. The study expects to accrue 16 evaluable patients diagnosed with IEC-HS over 2 years.

Inclusion Criteria: * Patients of age 18 or older * Diagnosis of for Immune Effector Cell Associated Hemophagocytic Lymphohistiocytosis-like Syndrome (IEC-HS) per ASTCT consensus criteria * Patients must have an elevated ferritin (\>2 × ULN) at time of infusion and/or have a ferritin count that is rapidly rising (per clinical assessment) and at least 2 of the following manifestations as described in the ASTCT consensus criteria: * Onset with resolving/resolved CRS or worsening inflammatory response after initial improvement with CRS-directed therapy * Hepatic transaminase elevation§ (\>5 × ULN (if baseline was normal) or \>5 × baseline if baseline was abnormal) * Hypofibrinogenemia (\