DISEASE CHARACTERISTICS:

• Histologically confirmed multiple myeloma

• Relapsed or relapsed/refractory disease

  • Failed ≥ 1 prior therapy for multiple myeloma

• CD56-positive disease by immunohistochemistry or flow cytometry, as defined by 1 of the following:

  • Staining intensity is ≥ 1 (weak) and the uniformity of staining is ≥ focal (i.e., present on < 25% of myeloma cells) in the bone marrow aspirate or core bone marrow biopsy (using immunohistochemistry)
  • At least 5% CD56-positive myeloma cells on flow cytometry of the marrow aspirate using dual staining for CD138 and CD56 (using flow cytometry)

PATIENT CHARACTERISTICS:

• ECOG (Zubrod) performance status 0-2
• Life expectancy ≥ 12 weeks
• Platelet count ≥ 75,000/mm^3
• Absolute neutrophil count > 1,000/mm^3
• Hemoglobin ≥ 8.5 g/dL
• AST and ALT ≤ 3 times upper limit of normal (ULN)
• Bilirubin ≤ 1.5 times ULN
• Creatinine ≤ 2 mg/dL
• Left ventricular ejection fraction ≥ lower limit of normal on MUGA
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No peripheral neuropathy ≥ grade 3 or painful grade 2 neuropathy

• No significant cardiac disease, including any of the following:

  • Myocardial infarction within the past 6 months
  • Unstable angina
  • Uncontrolled congestive heart failure
  • Uncontrolled hypertension (i.e., recurrent or persistent increases in systolic blood pressure ≥ 180 mm Hg or diastolic blood pressure ≥ 110 mm Hg)
  • Uncontrolled cardiac arrhythmias
  • Cardiac toxicity ≥ grade 3 after prior chemotherapy
• No history of multiple sclerosis or other demyelinating disease
• No hemorrhagic or ischemic stroke within the past 6 months
• No Eaton-Lambert syndrome (para-neoplastic syndrome)
• No CNS injury with residual neurological deficit (other than peripheral neuropathy ≤ grade 2)
• No other malignancy within the past 3 years except adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, in situ breast cancer, or in situ prostate cancer
• No clinically relevant active infection, including active hepatitis B or C infection or HIV infection
• No other condition or disease, including laboratory abnormalities, that, in the opinion of the investigator, may preclude study treatment

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin C)
• At least 4 weeks since prior radiotherapy
• At least 4 weeks since prior major surgery (except placement of a vascular access device or tumor biopsies)
• More than 4 weeks since prior investigational agents
• At least 2 weeks since prior antineoplastic therapy with biological agents
• No prior monoclonal antibody therapy
• No other concurrent investigational agents

• No concurrent corticosteroids (except as indicated for other medical conditions [< 10 mg prednisone or equivalent]; as pre-medication for administration of certain medications or blood products [≤ 100 mg hydrocortisone]; or for treatment of infusion reactions)

  • Concurrent topical steroids allowed
• No other concurrent antineoplastic treatment (e.g., chemotherapy, radiotherapy, or biological agents)
• Concurrent bisphosphonates allowed provided patient began bisphosphonates before study entry and is maintained on a stable dose during study treatment