Lenalidomide and pomalidomide directly inhibit osteoclasts through the inhibition of αVβ3-integrin and cathepsin K expression and indirectly by decreasing in myeloma cells, protein expression levels of RANKL (but not OPG) conducting to a decrease in RANKL/OPG ratio and by limiting APRIL, BAFF and MIP-1α [131, 132]. This evidence concerns the gene CTSK and plasma cell myeloma.