Brentuximab Vedotin in Treating Patients With Advanced Systemic Mastocytosis or Mast Cell Leukemia

Brentuximab vedotin is an antibody with a covalently attached toxin. The antibody portion targets the protein CD30 on the surface of cells, and the toxin acts against those cells. PRIMARY OBJECTIVES: I. To evaluate the response rate to SGN-35 (brentuximab vedotin) in patients with tumor necrosis factor receptor superfamily, member 8 (CD30+) advanced systemic mastocytosis (SM) (ASM or mast cell leukemia \[MCL\] with or without an associated hematological clonal non-mast cell lineage disease \[AHNMD\]). SECONDARY OBJECTIVES: I. To evaluate the tolerability and safety profile of SGN-35 in patients with SM. II. To evaluate expression of CD30 on neoplastic mast cells before and during therapy with SGN-35. III. To evaluate changes in mastocytosis related symptom scores and quality of life (QOL) using a modified Myeloproliferative Neoplasm Symptom Assessment Form (MPNSAF). IV. To evaluate the duration of response (DoR) and time to response (TTR). V. To evaluate progression-free survival (PFS). OUTLINE: Patients receive brentuximab vedotin intravenously (IV) over 30 minutes on day 1. Treatment repeats every 21 days for 8 courses in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 6 weeks for 1 year and then every 12 weeks thereafter.