Study of Natalizumab in Relapsed/Refractory Multiple Myeloma No Longer Recruiting Participants. Purpose Preclinical data support the evaluation of natalizumab in oncology as a single agent or in combination with standard anti-cancer therapies. Therefore, natalizumab is being developed for the treatment of patients with relapsed or refractory multiple myeloma. Study Type: Interventional Study Design:  Treatment, Randomized, Open Label, Single Group Assignment, Safety/Efficacy Study Official Title: A Phase 1/2, Two-Arm, Dose-Finding Study of Natalizumab for the Treatment of Subjects With Relapsed or Refractory Multiple Myeloma Further study details as provided by Biogen Idec: Primary Outcome Measures: To evaluate the safety profile of 2 dose levels of natalizumab in subjects with relapsed or refractory multiple myeloma To evaluate the anti-tumor activity of 2 dose levels of natalizumab in this study population    Estimated Enrollment:   42 Study Start Date:   May 2008 Estimated Study Completion Date:   April 2012 Estimated Primary Completion Date:   June 2010 (Final data collection date for primary outcome measure)   Arms Assigned Interventions 300 mg Treatment Arm: Experimental Drug: Natalizumab 300 mg Intravenous (IV) infusions of natalizumab once every 28 days for 6 months. 450 mg Treatment Arm: Experimental Drug: Natalizumab 450 mg Intravenous (IV) infusions of natalizumab once every 28 days for 6 months. Eligibility Ages Eligible for Study:   18 Years and older Genders Eligible for Study:   Both Accepts Healthy Volunteers:   No Criteria Inclusion Criteria: Age >/=18 years at the time of informed consent Relapsed or refractory multiple myeloma that was treated with or was considered inappropriate for treatment with bortezomib and an IMiD drug (including an analogue). ECOG Performance Status </=2. Corrected calcium <10.6 mg/dL Exclusion Criteria: Candidates for stem cell transplantation willing to undergo transplantation. (Subjects who are candidates for stem cell transplantation, but are not willing to undergo transplant will be eligible for the study.) Autologous stem cell transplantation <3 months post transplant. Prior allogeneic stem cell transplantation. Non secretory myeloma. Plasma cell leukemia (>2000/uL circulating plasma cells by standard cell counting differential), hyperleukocytosis (white blood cells >100,000/uL, clinical evidence of hyperviscosity syndrome, POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes syndrome), or primary systemic amyloidosis. Subjects who cannot undergo a brain MRI study. Clinically significant (as determined by the Investigator) 12 lead electrocardiogram (ECG) abnormalities, including QTc prolongnation (>450 ms in males; >470 ms in females). Please refer to: www.biogenideconcology.com Please refer to the clinicaltrials.gov website for further details on the study: http://clinicaltrials.gov/ct2/show/NCT00675428?term=101-my-201&rank=1 To contact Biogen, click here.