Antithymocyte Globulin and Sirolimus in Treating Patients With Relapsed Multiple Myeloma

DISEASE CHARACTERISTICS: Previously diagnosed multiple myeloma (MM) based on standard criteria Soft tissue (not bone only) plasmacytomas allowed Measurable disease, meeting both of the following criteria: Monoclonal population of plasma cell in the bone marrow Quantifiable serum and/or urine monoclonal protein (i.e., generally, but not exclusively, IgG > 1 g/dL, IgA > 0.5 g/dL, or urine light-chain excretion ≥ 200 mg/24 hours) Steroid-refractory disease, defined as less than a minimum response to prior high-dose glucocorticoid therapy Minimal response requires all of the following criteria: 25-49% reduction in the level of serum monoclonal paraprotein maintained for ≥ 6 weeks 50-89% reduction in 24-hour urinary light-chain excretion, but still > 200 mg/24 hours, maintained for ≥ 6 weeks 25-49% reduction in the size of soft tissue plasmacytomas (clinically or by CT scan or MRI) No increase in size or number of lytic bone lesions High-dose glucocorticoid therapy defined as 480 mg dexamethasone (or equivalent) alone or as part of a vincristine, doxorubicin, and dexamethasone regimen Must have undergone autologous transplantation OR received ≥ 2 conventional lines of therapy Currently requiring therapy for progressive disease, as indicated by any of the following criteria: 25% increase in paraprotein Development of new or progression of pre-existing lytic bone lesions or soft tissue plasmacytomas Hypercalcemia not attributable to any other cause Relapse from complete remission No nonsecretory MM PATIENT CHARACTERISTICS: Zubrod performance status 0-2 3-4 allowed if, in the opinion of the investigator, secondary to MM-related bone pain Life expectancy ≥ 3 months Creatinine ≤ 1.5 times upper limit of normal (ULN) AST and ALT ≤ 2.5 times ULN Bilirubin ≤ 1.5 times ULN Calcium < 14 mg/dL Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception HIV negative Hepatitis B surface antigen and hepatitis C antibody negative No known history of allergy to rabbit proteins No history of cardiac amyloidosis No poorly controlled hypertension, diabetes mellitus, coronary artery disease, or other serious medical or psychiatric illness No myocardial infarction within the past 6 weeks No New York Heart Association class III or IV heart failure No uncontrolled angina No severe uncontrolled ventricular arrhythmias No evidence of acute ischemia or active conduction system abnormality by electrocardiogram No active systemic infection requiring treatment unless adequately controlled with appropriate antimicrobial therapy (e.g., treated central line infection) No acute viral illness No pathologic fractures or symptomatic hyperviscosity No other prior malignancy except adequately treated basal cell or squamous cell skin cancer, cervical cancer in situ, or any other cancer with a disease-free status for ≥ 3 years PRIOR CONCURRENT THERAPY: See Disease Characteristics At least 8 weeks since prior immunotherapy or antibody therapy At least 4 weeks since prior major surgery (except for kyphoplasty) At least 3 weeks since prior conventional chemotherapy or radiotherapy for MM At least 3 weeks since prior bortezomib, thalidomide, or clarithromycin for MM No prior anti-thymocyte globulin No concurrent radiotherapy No other concurrent antineoplastic therapy with known activity against MM, including clarithromycin No other concurrent investigational agents