Project Summary/Abstract Thalidomide (Thal) and its derivatives, Lenalidomide (Len) and Pomalidomide (POM), are immune modulatory drugs (IMiDs) used in the treatment of multiple myeloma (MM) and few other hematological malignancies. Although they represent the backbone treatment for both newly diagnosed and relapse/refractory MM patients, their clinical use remains mostly empirical because of lack of suitable in vivo model systems to study their complex mechanisms of action. Murine cells are intrinsically resistant to IMiDs because of different amino acid sequence in the IMiD binding domain of cereblon (CRBN). By building upon our extensively validated Vk*MYC transgenic mouse model of MM, we have generated a novel transgenic mouse, Vk*MYChCRBN, expressing the full human CRBN (hCRBN) gene under the control of its endogenous regulatory elements, rendering it IMiD sensitive. As previously done for the Vk*MYC model, we will extensively characterize the new Vk*MYChCRBN model and will use it to understand the IMiD effects on the tumor and the immune system with the ultimate goal to inform clinical practice.