Hybrid Immunotherapy for Hemophagocytic LymphoHistiocytosis

An Open Label Phase II Pilot Study of Hybrid ImmunoTherapy(ATG/Dexamethasone/Etoposide) for Hemophagocytic LymphoHistiocytosis:HIT-HLH

Despite good progress during the last decade, hemophagocytic lymphohistiocytosis (HLH) remains difficult to treat. Two different treatment regimens have been used successfully. The first one, a treatment regimen based on two drugs called etoposide and dexamethasone, has been used worldwide. The second regimen, based on two drugs called Anti-thymocyte globulin (ATG) and prednisone, has been used mostly at one hospital in Paris, for over 15 years. With either regimen, about three quarters of treated children survive the most difficult time, the first two months after diagnosis. These two different regimens appear to work somewhat differently, and we suspect that combining them may give better results than either regimen alone. We are conducting this clinical trial to test the combination of ATG, dexamethasone, and etoposide for the treatment of HLH. The purpose of this research study is to find out what effects (good and bad) this drug combination has on you and your HLH.

Hemophagocytic lymphohistiocytosis (HLH) is a rare immunological disorder first recognized almost 70 years ago.(1) Genetic and animal studies have indicated that the familial form of HLH is clearly due to a deficiency of cytotoxic killing. Patients with HLH present with a potentially fatal syndrome of 'hyperimmunity.' These patients have severe inflammation, associated with cytopenias and variably severe bone marrow, liver, or CNS damage. Tissue damage and mortality appear to be due to hypercytokinemia related to persistent immune hyperactivation. An animal model of HLH and correlative human studies all suggest that excessive and abnormal activation of T cells drives the pathophysiology of this disorder, and that suppressing this excessive activation is critical for successful therapy of HLH. It is believed a combination of the two proven induction regimens for hemophagocytic lymphohistiocytosis (HLH) (anti-thymocyte globulin (ATG)- and etoposide-based) will result in response rates and overall survival rates at eight weeks which are comparable or better than the current standard of care (induction therapy per the HLH-94 protocol).

ATG, rabbit: intravenous, 5 mg/kg/dose, 5 consecutive days Dexamethasone: intravenous, 20mg/m2/day x7days, 10mg/m2/day x7days, 5mg/m2/day x14days, 2.5mg/m2/day x14days, 1.25mg/m2/day x14days Etoposide: intravenous, 150 mg/m2 weekly, starting 7 days after first dose of Thymoglobulin Methotrexate and hydrocortisone: intrathecal to patients with central nervous system involvement, age< 1 yr: 6/8mg (MTX/HC), 1-2 yrs: 8/10mg, 2-3 yrs: 10/12mg, >3 yrs: 12/15 mg, on day 7, 14, 21 and 42

ATG, rabbit (Thymoglobulin, Genzyme) will be dosed at 5 mg/kg/dose, given IV on 5 consecutive days (titrated over 4 to 8 hours).

Etoposide will be dosed at 150mg/m2, given IV. The first dose will be given 7 days (+/- 2 days) after the first dose of ATG, and be given weekly for a total of 7 doses.

Intrathecal Methotrexate and hydrocortisone will be administered to CNS+ patients (CNS+ patients are those patients which have any of the following: elevated CSF (cerebral spinal fluid) protein or white count, seizures, focal or global neurologic deficit, MRI abnormalities consistent with CNS involvement by HLH.) in the following doses: age< 1 yr: 6/8mg (MTX/HC), 1-2 yrs: 8/10mg, 2-3 yrs: 10/12mg, >3 yrs: 12/15 mg. It will be administered (+/- 3 days) on day 7, 14, 21 and 42.

Intrathecal Methotrexate and hydrocortisone will be administered to CNS+ patients (CNS+ patients are those patients which have any of the following: elevated CSF (cerebral spinal fluid) protein or white count, seizures, focal or global neurologic deficit, MRI abnormalities consistent with CNS involvement by HLH.) in the following doses: age< 1 yr: 6/8mg (MTX/HC), 1-2 yrs: 8/10mg, 2-3 yrs: 10/12mg, >3 yrs: 12/15 mg. It will be administered (+/- 3 days) on day 7, 14, 21 and 42.

will be started with the ATG. It will be divided BID, given IV for at least 1 week before switching to PO. Dosing: 20mg/m2/day x7days, 10mg/m2/day x7days, 5mg/m2/day x14days, 2.5mg/m2/day x14days, 1.25mg/m2/day x14days.

To determine the overall survival of patients with hemophagocytic lymphohistiocytosis at 8 weeks after an ATG/etoposide-based induction regimen and to determine the feasibility of this approach in the context of a multicenter clinical trial.

To determine overall survival prior to the initiation of BMT (bone marrow transplant) preparative regimen (or day 180, if BMT preparative regimen not yet begun)

To determine the frequency of disease reactivation prior to initiation of BMT preparative regimen (or day 180, if BMT preparative regimen not yet begun)

To determine overall survival to day +100 after BMT, for patients who have undergone BMT within 6 months of study entry

Inclusion Criteria: diagnosis of hemophagocytic lymphohistiocytosis Patients <18 years of age The patient must have active disease at the time of enrollment Patient's legal guardians must sign an Institutional Review Board approved consent form indicating their awareness of the investigational nature and the risks of this study. Eligible subjects must be enrolled with the protocol coordinating center Exclusion Criteria: Recent treatment, within 3 months, with another therapeutic regimen for HLH Known active malignancy Known rheumatologic diagnosis which may be the underlying cause of HLH Pregnancy (as determined by serum or urine test) or active breast feeding Failure to provide signed informed consent