A Study of Oral Ixazomib Maintenance Therapy in Participants With Newly Diagnosed Multiple Myeloma (NDMM) Not Treated With Stem Cell Transplantation (SCT)

The drug being tested in this study is called ixazomib citrate. Ixazomib citrate is being tested to slow progressive disease (PD) and improve overall survival in people who have NDMM who have had a major positive response to initial therapy and have not undergone SCT. This study will look at the effect of ixazomib citrate has on the length of time that participants are free of PD and their overall survival. The study will enrol approximately 700 participants. Participants will be randomly assigned (by chance, like flipping a coin) in 3:2 ratio to Ixazomib or matching placebo groups-which will remain undisclosed to the participant and study doctor during the study (unless there is an urgent medical need): * Ixazomib citrate initiates at 3 mg which will be escalated to 4 mg with cycle 5 day 1 * Placebo (dummy inactive pill) - this is a capsule that looks like the study drug but has no active ingredient All participants will be asked to take one capsule on Days 1, 8 and 15 of each 28-day cycle. The treatment period will be approximately 24 months (equivalent to 26 cycles) or until patients experience PD or unacceptable toxicities, whichever occurs first. This multi-center trial will be conducted worldwide. The overall time to participate in this study is approximately 78 to 106 months. Participants will make 28 visits to the clinic during the treatment period and will continue to make follow-up visits every 4 weeks until the next line of therapy begins. Participants will also be contacted by telephone every 12 weeks after last treatment visit for a follow-up assessment.