Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed adenocarcinoma of the prostate

- Metastatic disease

- Progressive disease after prior antiandrogen therapy, as evidenced by at least 1 of
the following parameters:

- New osseous lesions on bone scan

- Greater than 25% increase in the sum of the products of the longest
perpendicular diameters of the lesions OR the appearance of new lesions on MRI
or CT scan

- Rising prostate-specific antigen (PSA) despite adequate medical or surgical
castration therapy

- Consecutive increase in PSA, determined by two separate measurements taken
at least 1 week apart and confirmed by a third, and if necessary, a fourth
measurement

- PSA must be ≥ 5 ng/mL and ≥ 25% above the previous nadir

- Measurable or evaluable disease

- Serum testosterone ≤ 50 ng/dL

- No confluent lesions involving axial and appendicular skeleton on bone scan
("superscan")

PATIENT CHARACTERISTICS:

Age

- Over 18

Performance status

- Karnofsky 70-100%

Life expectancy

- At least 6 months

Hematopoietic

- Absolute neutrophil count ≥ 2,000/mm^3

- Hematocrit ≥ 30%

- Hemoglobin ≥ 10 g/dL

- Platelet count ≥ 150,000/mm^3

- No serious hematologic illness that would preclude study participation

Hepatic

- AST ≤ 2 times upper limit of normal (ULN)

- Bilirubin ≤ 1.5 times ULN

- PTT normal

- PT normal OR

- INR normal

- No serious hepatic illness that would preclude study participation

Renal

- Creatinine ≤ 2.5 mg/dL

- Calcium ≤ 11 mg/dL

- No serious renal illness that would preclude study participation

Cardiovascular

- No New York Heart Association class III or IV heart disease

- No active angina pectoris

- No prior deep vein thrombophlebitis within the past 3 months

- No other serious cardiac illness that would preclude study participation

Pulmonary

- No pulmonary embolus within the past 3 months

- No other serious respiratory illness that would preclude study participation

Other

- Fertile patients must use effective contraception

- HIV negative

- No serious CNS illness that would preclude study participation

- No active serious infection not controlled by antibiotics

- No other serious illness that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

- More than 2 weeks since prior red blood cell or platelet transfusions

- More than 2 weeks since prior hematopoietic growth factors

- No prior monoclonal antibody therapy except ProstaScint®

- No other concurrent monoclonal antibody-based therapy

- No concurrent medication to support platelet count (e.g., oprelvekin)

Chemotherapy

- More than 4 weeks since prior cytotoxic chemotherapy

Endocrine therapy

- See Disease Characteristics

- Concurrent luteinizing hormone-releasing hormone (LHRH) analog allowed provided 1 of
the following is true:

- Treatment is maintained during study participation

- Treatment is terminated at least 10 weeks (for 1-month depot preparations), 24
weeks (for 3-month depot preparations), or 32 weeks (for 4-month depot
preparations) prior to study entry

- More than 4 weeks since prior corticosteroids

- More than 4 weeks since prior adrenal hormone inhibitors

- Concurrent low-dose prednisone (≤ 5mg/day) for adrenal insufficiency allowed

- No concurrent finasteride

Radiotherapy

- More than 4 weeks since prior radiotherapy

- No prior radiotherapy to > 25% of skeleton

- No prior strontium chloride Sr 89 or samarium Sm 153 lexidronam
pentasodium-containing compounds (e.g., Metastron® or Quadramet®)

Surgery

- Not specified

Other

- More than 4 weeks since prior PC-SPES

- More than 4 weeks since prior investigational therapy (medications or devices)

- At least 1 week since prior aspirin and/or nonsteroidal anti-inflammatory agents
possessing antiplatelet activity

- At least 1 week since prior antiplatelet medication, including the following:

- Abciximab

- Cilostazol

- Clopidogrel

- Dipyridamole

- Ticlopidine

- No concurrent anticoagulant medications (for platelet count < 50,000/mm^3), including
the following:

- Dalteparin

- Danaparoid

- Enoxaparin

- Heparin

- Warfarin

- No other concurrent investigational therapy