An inhibitor of cereblon (IC50 = ~3 μM for the human recombinant CRBN-DDB1 complex); inhibits autoubiquitination of CRBN in HEK293T cells expressing CRBN; inhibits proliferation of U266 myeloma cells at 0.1-10 μM; reduces tumor growth in a H929 R10-1 lenalidomide-resistant mouse xenograft model at 3 mg/kg per day when used in combination with dexamethasone