PRIMARY OBJECTIVES:~I. To evaluate the anti-myeloma activity of leflunomide, when given as a single agent, as assessed by freedom from progression at 2-years.~II. To evaluate the safety and tolerability of single agent leflunomide.~SECONDARY OBJECTIVES:~I. To summarize and assess toxicities by type, frequency, severity, attribution, time course and duration.~II. To estimate overall and progression-free survival probabilities. III. To estimate response rate and duration of response. IV. To describe the impact of treatment on quality of life, as assessed by the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) Score version (v)3.0.~EXPLORATORY OBJECTIVES:~I. To characterize the molecular evolution of the tumor cells. II. To evaluate whether specific genetic subtypes respond differently to leflunomide.~III. To evaluate the role of immune cells in the progression of smoldering multiple myeloma (SMM).~IV. To evaluate the role of leflunomide in modulating the immune system. V. To examine the relationship between immunological changes and disease progression.~OUTLINE:~Patients receive leflunomide orally (PO) once daily (QD) on days 1-28. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity.~After completion of study treatment, patients are followed up yearly.
This phase II trial studies the effects of leflunomide in treating African-American and European-American patients with high-risk smoldering multiple myeloma. Leflunomide is used to decrease the body's immune response and may delay the symptoms of multiple myeloma in patients of African-American and European decent.