Inclusion Criteria:

- Diagnosis of multiple myeloma.

- Status of refractory to or relapsed from at least one prior bortezomib-containing
regimen.

- Progressive disease.

- Age >= 18 years.

- Karnofsky performance status >= 60%

- Acceptable liver function:

- Bilirubin =< 1.5 x ULN (upper limit of normal)

- Aspartate transaminase (AST) and alanine transaminase (ALT) =< 3 x ULN

- Acceptable hematologic status:

- Absolute Neutrophil Count (ANC) >= 1.5 x 109/L

- Platelet count >= 100 x 109/L

- Hemoglobin >= 9 g/dL

- Coagulation status PT-INR/PTT =< 1.5 x ULN or in the therapeutic range if on
anticoagulation therapy. (PT-INR/PTT= prothrombin - international normalized
ratio / prothrombin time)

- Serum potassium within normal range.

- Estimated life expectancy greater than 3 months.

- Signed, written IRB (institutional Review Board)-approved informed consent.

Exclusion Criteria:

- Non-secretory multiple myeloma or symptomatic amyloidosis.

- Hypersensitivity to bortezomib, boron, or mannitol.

- Less than 4 weeks since prior chemotherapy, radiotherapy, endocrine therapy, or
immunotherapy, except if disease is rapidly progressing.

- Less than 4 weeks since prior use of other investigational agents.

- Serious concomitant systemic disorders (e.g. active infection).

- Significant cardiovascular disease.

- Marked baseline prolongation of QT/QTc (corrected QT interval)interval.

- Central nervous system disorders requiring neuroleptics / anti-convulsants.

- Peripheral sensory neuropathy of ≥ Grade 2

- Renal insufficiency defined as a creatinine clearance of < 30 ml/min.

- Non-willingness to use effective contraceptive methods for patients of child-bearing
age / potential.

- Pregnant or breast-feeding women.

- Known HIV positivity.

- Prior treatment with belinostat (PXD101), or any other HDAC (histone deacetylase)
inhibitor.

- Altered mental status which precludes an understanding of the Informed Consent
Document.