Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed multiple myeloma

- Relapsed or relapsed/refractory disease

- Failed ≥ 1 prior therapy for multiple myeloma

- Once the MTD is defined, only patients who have received at least 1 but equal or
less than 6 prior chemotherapy regimens will be enrolled at this dose level

- CD56-positive disease confirmed by immunohistochemistry or 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

- Amylase and lipase within normal limits

- Creatinine ≤ 2 mg/dL

- Left ventricular ejection fraction ≥ lower limit of normal on MUGA or ECHO

- 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

- No known recent biochemical or clinical evidence of pancreatitis or extensive
metastatic disease involving the pancreas

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 hypersensitivity to 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