Inclusion Criteria:

1. Must have a histologic diagnosis of adenocarcinoma of the prostate Stage D2 that is
unresponsive or refractory to hormone therapy. Must have metastatic prostate cancer
with a rising PSA, and deemed to be hormone refractory.

2. All subjects must have pre-study PSA within 28 days prior to registration

3. Subjects who have measurable disease must have had X-rays, scans or physical
examinations used for tumor measurement completed within 28 days prior to
registration. Subjects must have non-measurable disease assessed within 28 days (for
PSA level) or 42 days (for imaging studies) prior to registration.

4. Subjects with bone metastases, as documented by X-ray, bone scan, MRI, or biopsy.

5. All subjects must have had a CT scan of the abdomen and pelvis within 28 days prior
to registration.

6. Subjects must have been surgically or medically castrated. If the method of
castration was LHRH (Luteinizing Hormone-Releasing Hormone) agonists, then the
subject must be willing to continue the use of LHRH agonists.

7. If the subject has been treated with non-steroidal anti-androgens or other hormonal
treatment these agents must have been stopped at least 28 days prior to enrollment
for flutamide or ketoconazole, and at least 42 days prior to enrollment for
bicalutamide or nilutamide; and the subjects must have demonstrated progression of
disease since the agents were suspended.

8. Prior radiation therapy is allowed. At least 21 days must have elapsed since the
completion of radiation therapy, and the subject must have recovered from the side
effects of the radiation

9. 9. Due to the unknown side effects of imatinib, men of reproductive potential must
agree to use an effective contraceptive method.

10. Subjects must have recovered from major infections and/or surgical procedures and, in
the opinion of the investigator, not have significant active concurrent other medical
illness precluding protocol treatment.

11. ECOG performance status of 0-1

12. ANC ≥ 1,500/mL and a platelet count of ³ 100,000/mL. These tests must be obtained
within 7 days prior to registration.

13. Serum bilirubin ≤ 1.3, SGOT and SGPT ≤ 2 x institutional upper limit of normal, and
a serum creatinine ≤ 1.8 mg/dl. These tests must be obtained within 7 days prior to
registration. Testosterone level may be done 28 days prior to study entry.
Testosterone level should be below 50 ng/dL.

Exclusion Criteria:

1. No prior chemotherapy for hormone-refractory disease is allowed. At least three
weeks must have elapsed since the completion of any non-cytotoxic investigational
therapy, and the patient must have recovered from the side effects of the therapy.

2. No other cytotoxics, biological response modifiers, radiation therapy, corticosteroid
or hormonal concomitant therapy (other than continuing LHRH treatment) may be given
during protocol treatment. Bisphosphonates may be given during protocol treatment.
No unconventional therapy may be given during protocol treatment.

3. Subjects must NOT have Grade III/IV cardiac problems as defined by the New York Heart
Association Criteria.

4. Subjects with known chronic liver disease are NOT eligible

5. Must NOT have a known diagnosis of human immunodeficiency virus (HIV) infection.

6. Subjects must NOT have known brain metastases.

7. No prior malignancy is allowed except for the following: adequately treated basal
cell or squamous cell skin cancer, in situ carcinoma of any site, adequately treated
Stage I or II cancer from which the patient is currently in complete remission, or
any other cancer from which the patient has been disease-free for 5 years.