Study to Evaluate Optimized Retreatment and Prolonged Therapy With Bortezomib

Inclusion Criteria:

* Have received a bortezomib containing regimen in one of the previous line(s) of therapy and have shown at least PR to the previous bortezomib therapy.
* Have relapsed / progressed multiple myeloma following 1 or 2 previous lines of therapy as defined in the protocol.
* Have measurable secretory multiple myeloma: measurable disease for secretory multiple myeloma is defined by at least one of the following measurements: serum M protein greater than or equal to 1 g/dL (≥10g/L\], urine M-protein of ≥200 mg/24 hours.
* Have an ECOG performance status of ≤2.
* Have a life expectancy estimated at screening of ≥6 months.

Exclusion Criteria:

* Has received more than 2 previous lines of therapy for multiple myeloma or has received no previous bortezomib-containing regimen.
* Has been refractory to bortezomib, defined as either having progressed during bortezomib therapy or relapsed/progressed within 6 months after the last dose of bortezomib.
* Has oligosecretory or nonsecretory multiple myeloma.
* Has a history of a myocardial infarction within 6 months of enrollment or has New York Heart Association (NYHA) Class III or IV heart failure, uncontrolled angina, severe uncontrolled ventricular arrhythmias, or electrocardiographic evidence of acute ischemia or active conduction system abnormalities.
* Has peripheral neuropathy or neuropathic pain of grade 2 or greater intensity, as defined by the National Cancer Institute Common Terminology Criteria of Adverse Events (NCI CTCAE), version 4.0.