The drug being tested in this study is called ixazomib citrate. Ixazomib citrate is being tested to slow disease progression and improve overall survival in people who have newly diagnosed multiple myeloma (NDMM) who have had a major positive response to initial therapy and have not undergone stem cell transplantation (SCT). This study will look at the effect of ixazomib citrate has on the length of time that participants are free of disease progression and their overall survival.