Inclusion Criteria:

1. Diagnosis of primary myelofibrosis, essential thrombocythemia related myelofibrosis,
or polycythemia vera related myelofibrosis requiring therapy, including:

1. those previously treated and relapsed or refractory

2. or newly diagnosed, with intermediate or high risk according to Lille Scoring
system (adverse prognostic factors are: Hb < 10 g/dl, WBC < 4 or > 30 x 109/L;
risk group: 0 = low, 1 = intermediate, 2 = high)

3. or with symptomatic splenomegaly (must be >=10 cm below the left costal margin
in the mid-clavicular line).

2. The subject must not be considered as a candidate to receive allogeneic hematopoietic
stem cell transplant at the time of being enrolled into the study.

3. The subject has a detectable JAK2 V617F mutation.

4. Signed informed consent: Patients must have signed consents for both the Lestaurtinib
protocol and for the mandatory biomarker MDP-RC 107 protocol to be eligible to
participate.

5. Patients must have been off any PMF-directed therapy for 4 weeks prior to entering
this study and have recovered from the toxic effects (grade 0-1) of that therapy.
Treatment with erythropoietin is permitted.

6. Serum bilirubin levels less than or equal to 2 times the upper limit of the normal
range for the laboratory (ULN). Higher levels are acceptable if these can be
attributed by treating physician to active hemolysis or ineffective erythropoiesis
due to myelofibrosis.

7. Serum glutamic-pyruvic transaminase (SGPT) (alanine aminotransferase [ALT]) levels
less than or equal to 2 x ULN.

8. Serum creatinine levels less than or equal to 1.5 x ULN.

9. Women of childbearing potential must have a negative serum or urine pregnancy test
prior to Lestaurtinib treatment and should be advised to avoid becoming pregnant.
Men must be advised to not father a child while receiving treatment with
Lestaurtinib. Both women of childbearing potential and men must practice effective
methods of contraception (those generally accepted as standard of care measures).
Women of child bearing potential are women who are not menopausal for 12 months or
who have not undergone previous surgical sterilization. If the subject is a woman of
childbearing potential, she must use a medically acceptable form of contraception
during the study period and for 30 days thereafter. If the subject is a man he must
be surgically sterile or must use a medically approved method of contraception for
the duration of the study and for 60 days following the last dose of CEP-701.

10. Age > 18 years.

Exclusion Criteria:

1. Nursing and pregnant females. Should a woman become pregnant or suspect she is
pregnant while participating in this study, she should inform her treating physician
immediately.

2. New York Heart Association (NYHA) Grade II or greater congestive heart failure.

3. Unstable angina.

4. Major surgical procedure, open biopsy, or significant traumatic injury within 28
days, or anticipation of the need for major surgical procedure during the course of
the study.

5. Biopsy or other minor surgical procedure, excluding placement of a vascular access
device or bone marrow biopsy, within 7 days prior to study enrollment.

6. Ongoing serious, non-healing wound, ulcer, or bone fracture.

7. Known hypersensitivity to any component of Lestaurtinib.

8. The subject has received a donor stem cell transplant in the past and has detectable
full or partial donor chimerism.

9. The subject requires treatment with a CYP3A4 inhibitor, including azole antifungals
(topicals are permitted); protease inhibitors; nefazodone; cyclosporine;
erythromycin; clarithromycin; and troleandomycin.