Inclusion Criteria:

1. Written informed consent

2. 18 years of age or older

3. Histologically confirmed, metastatic prostate cancer (positive bone scan and/or
measurable disease on CT scan and/or MRI of the abdomen and pelvis).

4. Progressive disease after androgen deprivation, as defined by Prostate Cancer Working
Group 2 and/or Response Evaluation Criteria in Solid Tumors criteria

5. Laboratory requirements:

- Absolute neutrophil count (ANC) ≥ 1500/μL

- Bilirubin < 1.5 x ULN

- Hemoglobin > 8 g/dL

- PSA > 2 ng/mL

- Platelets > 100,000/µL

- AST and ALT < 2.5 x ULN

- Creatinine clearance ≥ 60mL/min

- Testosterone < 50 ng/dL

6. Eastern Cooperative Oncology Group (ECOG) performance status 0 - 2 and life
expectancy > 12 weeks

7. Patients receiving any other hormonal therapy, including any dose of megestrol
acetate (Megace), Proscar (finasteride), any herbal product known to decrease PSA
levels (e.g. Saw Palmetto, PC-SPES), or agents such as abiraterone, TAK700, MDV3100
as well as any systemic corticosteroid use, must discontinue the agent for at least
four weeks prior to study treatment. Progressive disease as defined above must be
documented after discontinuation of any hormonal therapy (with the exception of a
LHRH agonist).

8. Prior radiation therapy must be completed > 4 weeks prior to enrollment and the
patient must have recovered from all toxicity. Prior radiopharmaceuticals (strontium,
samarium) must be completed ≥ 8 weeks prior to enrollment.

9. Because of the unknown potential risk to a gamete and/or developing embryo from these
investigational therapies, patients must agree to use adequate contraception (barrier
method for males) for the duration of study participation, and for three months after
discontinuing therapy.

Exclusion Criteria:

1. Prior chemotherapy for prostate cancer, with the exception of neo-adjuvant
chemotherapy, because of the potential effect of chemotherapy on the immune system.

2. Prior sipuleucel-T treatment or investigational immunotherapy.

3. Prostate cancer pain requiring regularly scheduled narcotics.

4. Current treatment with systemic steroid therapy (inhaled/topical steroids are
acceptable). Systemic corticosteroids must be discontinued for at least 4 weeks prior
to first treatment.

5. Clinically active autoimmune disease.

6. Diagnosis of prostate cancer with neuroendocrine differentiation

7. Known presence of central nervous system metastases, pleural effusions or ascites

8. Medical or psychiatric illness that would, in the opinion of the investigator,
preclude participation in the study or the ability of patients to provide informed
consent for themselves.

9. Cardiovascular disease that meets one of the following: congestive heart failure (New
York Heart Association Class III or IV), active angina pectoris, or recent myocardial
infarction (within the last 6 months).

10. Concurrent or prior malignancy except for the following:

- Adequately treated basal or squamous cell skin cancer

- Adequately treated stage I or II cancer from which the patient is currently in
complete remission

- Any other cancer from which the patient has been disease-free for 5 years

11. Known HIV or other history of immunodeficiency disorder.

12. Prisoners or subjects who are compulsorily detained (involuntarily incarcerated) for
treatment of either a psychiatric or medical (e.g. infectious) illness.

13. Any underlying medical or psychiatric condition, which in the opinion of the
investigator will make the administration of BPX-201 and AP1903 hazardous or obscure
the interpretation of AEs, such as a condition associated with frequent diarrhea.

14. Any non-oncology vaccine therapy used for prevention of infectious diseases for up to
1 month before BPX-201