Study of SB939 in Subjects With Myelofibrosis

The Study Drug:

SB939 is designed to change the DNA (genetic material) of cancer cells. This may keep the
cells from growing and cause them to die.

This is the first study in which SB939 is given to patients with myelofibrosis.

Study Drug Administration:

If you are found to be eligible to take part in this study, you will take SB939 by mouth 3
times a week for the first 3 weeks of every 4-week cycle. In some cases, the study doctor
may decide your dose can be raised sometime after Cycle 1.

SB939 can be taken at any time of day, with or without food. You should take SB939 at about
the same time each day. Do not open, break, or chew the capsules.

If you have any side effects, the doctor may change the amount or how often you take SB939.

You will fill out a study drug diary to keep track of your SB939 doses. You should bring
the diary and all used and unused bottles of study drug with you to every study visit.

Study Visits:

At every study visit, you will be asked about any side effects you have had and any drugs
you may be taking.

On Day 1 of Cycle 1 (+/- 3 days):

- You will have a physical exam, including measurement of your vital signs.

- You will be asked about any blood transfusions you have had and drugs you have taken
since the last visit.

- Your performance status will be recorded.

- Blood (about 4 teaspoons) will be drawn for routine tests.

- You will have an ECG.

On Day 15 of Cycle 1 (+/- 3 days):

- You will have a physical exam, including measurement of your vital signs.

- Blood (about 4 teaspoons) will be drawn for routine tests.

- You will have an ECG.

On Day 1 of Cycles 2 and 3 (+/- 3 days):

- You will have a physical exam, including measurement of your vital signs.

- You will be asked about any blood transfusions you have had since the last visit.

- Your performance status will be recorded.

- Blood (about 4 teaspoons) will be drawn for routine tests.

- You will have an ECG.

On Day 1 of Cycles 4 and beyond (+/- 3 days), or every 3 cycles starting on Day 1 of Cycle 6
(+/- 3 days) if the doctor decides your schedule can change (if you have not had serious
side effects):

- You will have a physical exam, including measurement of your vital signs.

- You will be asked about any blood transfusions you have had and drugs you have taken
since the last visit.

- Your performance status will be recorded.

- Blood (about 4 teaspoons) will be drawn for routine tests.

- You will have a bone marrow biopsy and aspiration to check the status of the disease,
if the doctor thinks it is needed.

If your study visit schedule is changed to every 3 cycles (Day 1 of Cycles 6, 9, and so on),
blood (about 4 teaspoons) will be drawn for routine tests every 28 days (+/- 3 days). These
tests will be done at your local doctor's office. Every 28 days (+/- 3 days), the study
staff will also call you to ask how you are doing and if you have had any side effects.

You may have additional bone marrow biopsies and aspirations and ECGs any time the doctor
thinks it is needed. The study visits may also occur more often than described above, if
the doctor thinks it is needed.

Length of Study:

You may continue taking the study drug for as long as the doctor thinks it is in your best
interest. You will no longer be able to take the study drug if the disease gets worse, if
intolerable side effects occur, or if you need radiation therapy, surgery, or other
chemotherapy.

Your participation on the study will be over once you have completed the end-of-treatment
visit and follow-up.

End-of-Treatment Visit:

After you stop taking the study drug for any reason, the following tests and procedures will
be performed:

- You will have a physical exam, including measurement of your vital signs.

- You will be asked about any blood transfusions you have had and drugs you have taken
since the last visit.

- Your performance status will be recorded.

- Blood (about 4 teaspoons) will be drawn for routine tests.

- You will have a bone marrow biopsy and aspiration to check the status of the disease,
if the doctor thinks it is needed.

Follow-up:

- The study staff will call you 30 days after your last dose of the study drug (+/- 3
days).

- You will be asked how you are doing and if you have had any side effects.

If you have any side effects within 30 days after you stop taking the study drug, you may
have extra tests and procedures. For example, blood (about 2 teaspoons) may be drawn for
routine tests. If you are still having side effects, the study staff will continue calling
you to ask how you are doing until the side effects get better. The schedule for how often
you are called will depend on the side effects.

This is an investigational study. SB939 is not FDA approved or commercially available. It
is currently being used for research purposes only.

Up to 41 patients will take part in this study. All will be enrolled at M. D. Anderson.