Study of Oral Ixazomib in Adult Participants With Relapsed and/or Refractory (RR) Multiple Myeloma

Inclusion Criteria:

Each participant must meet all of the following inclusion criteria to be enrolled in the study:

* Multiple myeloma diagnosed according to the standard criteria.
* Participants with multiple myeloma who have relapsed following at least 2 lines of therapy.
* Participants must have measurable disease.
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.
* Female participants who are post menopausal, surgically sterile, or agree to practice 2 effective methods of contraception or abstain from heterosexual intercourse.
* Male participants who agree to practice effective barrier contraception or agree to abstain from heterosexual intercourse.
* Voluntary written consent.
* Suitable venous access for study-required blood sampling.

Exclusion Criteria:

Participants meeting any of the following exclusion criteria are not to be enrolled in the study:

* Peripheral neuropathy greater than or equal to (\>=) Grade 2.
* Female participants who are lactating or have a positive serum pregnancy test during the screening period.
* Major surgery within 14 days before the first dose of study drug.
* Infection requiring systemic antibiotic therapy or other serious infection within 14 days before the first dose of study treatment.
* Life-threatening illness unrelated to cancer.
* Diarrhea \> Grade 1, based on the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) categorization.
* Systemic antineoplastic or radiation therapy within 14 days of cytotoxic agents within 21 days before the first dose of study treatment.
* Treatment with any investigational products within 21 days before the first dose of study treatment.
* Treatment with any investigational proteasome inhibitor.
* Systemic treatment with prohibited medication.
* Ongoing therapy with corticosteroids greater than 10mg of prednisone or its equivalent per day. Inhaled and topical steroids are permitted.
* Central nervous system involvement.
* Evidence of current uncontrolled cardiovascular conditions, including cardiac arrhythmias, congestive heart failure, angina, or myocardial infarction within the past 6 months.
* Corrected QT interval (QTc) \> 470 milliseconds on a 12-lead electrocardiogram (ECG) obtained during the screening period.
* Known human immunodeficiency virus (HIV) positive, hepatitis B surface antigen-positive status, or known or suspected active hepatitis C infection.
* Any serious medical or psychiatric illness that could, in the investigator's opinion, potentially interfere with the completion of treatment according to the protocol.
* Known gastrointestinal (GI) disease or GI procedure that could interfere with the oral absorption of tolerance of ixazomib including difficulty swallowing.