This is a Phase I, open-label, multi-dose trial to define the MTD and tolerability of a regimen including lenalidomide, dexamethasone, and intravenous SGN-40 in patients with relapsed multiple myeloma.

Inclusion Criteria:

• Diagnosis of multiple myeloma.
• Received at least one prior systemic therapy other than single-agent corticosteroids.
• Measurable disease of monoclonal protein greater than or equal to 0.5 gram/dL in plasma or 0.5 gram/24 hr urine collection, or greater than 10 mg/dL free light chain (FLC) in serum as determined by serum FLC assay and provided the serum FLC ratio is abnormal.

Exclusion Criteria:

• Received an allogenic stem cell transplant.
• Previous intolerance of lenalidomide or dexamethasone.
• Primary invasive malignancy (other than multiple myeloma) within the last 3 years.