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