Inclusion Criteria:

   1. Must sign an Informed Consent Form (ICF)

   2. Males ≥ 18 years of age

   3. Able to adhere to the study visit schedule and requirements of the protocol

   4. Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 2

   5. Life expectancy of ≥ 12 weeks

   6. Willingness to participate in Patient-Reported Outcomes assessments

   7. Serum testosterone levels < 50 ng/dL

   8. Confirmed metastatic adenocarcinoma of the prostate that is unresponsive or refractory
   to hormonal therapy

   9. Have documented disease progression while receiving or following hormonal therapy as
   determined by increasing Serum Prostate Specific Antigen (PSA) level, Radiological
   Progression, or ≥2 new bone lesions

10. Subjects must agree to receive counseling related to pregnancy precautions,
   teratogenic and other risks of lenalidomide

11. Refrain from donating blood or semen as defined by protocol

Exclusion Criteria:

   1. A history of clinically significant disease that places subject at an unacceptable
   risk for study entry

   2. Prior Therapy with thalidomide, lenalidomide or pomalidomide

   3. Prior chemotherapy for prostate cancer

   4. Use of any other experimental drug or therapy within 28 days prior to randomization

   5. Prior radiation to ≥ 30% of bone marrow or any radiation therapy within 28 days prior
   to randomization

   6. Prior use of Strontium-89 at any time or Samarium-153 within 56 days prior to
   randomization

   7. Surgery within 28 days prior to randomization

   8. Concurrent anti-androgen therapy

   9. Abnormal serum chemistry or hematology laboratory values

10. Significant active cardiac disease within the previous 6 months:

11. Thrombotic or thromboembolic events within the past 6 months:

12. History of peripheral neuropathy of ≥grade 2

13. History of severe hypersensitivity reaction to drugs formulated with polysorbate 80

14. Paraplegia

15. History of Central nervous system (CNS) or brain metastases

16. History of malignancies other than prostate cancer within the past 5 years, with the
   exception of treated basal cell/squamous cell carcinoma of the skin

17. Concurrent use of alternative cancer therapies