Pyrimethamine to Treat Autoimmune Lymphoproliferative Syndrome

The Autoimmune Lymphoproliferative Syndrome (ALPS) is an inherited disease associated with a defect of lymphocyte apoptosis that leads to lymphoproliferation and autoimmunity. Although, there are treatments for many of its complications, there currently is no safe and effective therapy for this syndrome itself. Recently investigators in Europe serendipitously observed that some children with ALPS showed reductions in spleen and lymph node size while in pyrimethamine/sulfadoxine (Fansidar) for Pneumocystis carinii prophylaxis. Our own subsequent pilot clinical trial of Fansidar (Protocol #01-I-0132) was terminated after failure to recruit well-defined ALPS patients who lacked histories suspicious for allergies to sulfa drugs. Our own in vitro studies, however revealed that pyrimethamine and not sulfadoxine induces lymphocyte apoptosis and this observation has suggested to us that pyrimethamine may be beneficial alone, thus avoiding the added risks of allergy and hypersensitivity associated with the sulfa drugs. However, potential bone marrow toxicity that may result from an escalating dose schedule of pyrimethamine should respond to the addition of folinic acid (Leucovorin) to the regimen. We propose to conduct a pilot study on the safety and efficacy of the drug, pyrimethamine for the treatment of ALPS. Six to 8 individuals, with ALPS will be treated for up to 3 months, initially, with twice-weekly pyrimethamine (Daraprim) at escalating doses adjusted by weight, with the addition of folinic acid when needed to aid management of marrow toxicity. The effects of pyrimethamine treatment on lymph node and/or spleen size will be assessed by CT scan. The effect of treatment on other laboratory features of ALPS will also be assessed. Evaluating the effects of pyrimethamine on these clinical and laboratory parameters will allow us to determine if this drug demonstrates sufficient activity to warrant study in a larger randomized controlled trial.