This is a pilot study of the DRibble vaccine in patients with advanced prostate cancer.

The primary objective of this pilot study is to assess the safety and tolerability of DRibble vaccine, cyclophosphamide, imiquimod, and Ceravix in castrate resistant prostate cancer.

This study will also assess:

• the immune profile of tumor biopsy specimens if sites amenable to biopsy are present
• humoral and cellular responses to cancer antigens after DRibble vaccination
• the response to a reporter antigen vaccine (Ceravix) after DRibble vaccination

An exploratory objective is to characterize the microbiome before and after study drugs administration and correlate prostate cancer responses.

Inclusion Criteria:

• Subjects have measurable or evaluable metastatic castrate resistant adenocarcinoma of the prostate with progression after chemotherapy, combined androgen blockade and/or peripheral androgen or androgen receptor suppression. Either histologic or serum marker diagnosis is acceptable.
• Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1
• Ability to give informed consent and comply with the protocol.
• Prior therapy with investigational agents must have been completed at least 3 weeks prior to study enrollment.
• Patients must have normal organ and marrow function as determined by routine blood tests

Exclusion Criteria:

• Active autoimmune disease except vitiligo or hypothyroidism.
• Active other malignancy.
• Known HIV positive and/or Hepatitis B or C positive.
• Other medical or psychiatric conditions that in the opinion of the Principal Investigator would preclude safe participation in protocol.