A Phase 2 Study Of PRM-151 In Subjects With Myelofibrosis

Stage 2 of this study is ongoing. Stage 2 is a randomized, double-blind Phase 2 study to
determine the efficacy and safety of three different doses of PRM-151 in subjects with PMF
and post ET/PV MF. Subjects will be randomized to one of three doses: 0.3 mg/kg, 3.0 mg/kg or
10 mg/kg of PRM-151. This is the second stage of an adaptive design study as defined in FDA
Draft Guidance for Industry: Adaptive Design Clinical Trials for Drugs and Biologics,
February 2010. Modifications to dose levels, schedule, and regimen have been made in Stage 2
based on data from Stage 1.

Stage 1 of this study has completed. Stage 1 was an open-label, Simon two stage, Phase 2
study to determine the efficacy and safety of two different dose schedules of PRM-151 in
subjects with PMF and post ET/PV MF. There were two treatment cohorts, each assigned to one
of two dose schedules of PRM-151. Subjects were assigned to a weekly or every four week
dosing schedule by the investigator.

Inclusion Criteria:

1. Subjects must be ≥18 years of age at the time of signing the Informed Consent Form
(ICF);

2. Subjects must voluntarily sign an ICF;

3. Subjects must have a pathologically confirmed diagnosis of PMF as per the WHO
diagnostic criteria or post ET/PV MF;

4. At least Grade 2 marrow fibrosis according to the WHO Grading of Bone Marrow Fibrosis;

5. Intermediate-1, intermediate -2, or high risk disease according to the IWG -MRT
Dynamic International Prognostic Scoring System

6. A bone marrow biopsy must be performed within four weeks prior to Cycle 1 Day 1
treatment to establish the baseline fibrosis score;

7. Subjects must not be candidates for ruxolitinib based on EITHER:

1. Platelet count < 50 x 10e9/L, OR

2. Hgb < 100 g/L, have received ≥ 2 units PRBC in the 12 weeks prior to study entry,
and be intolerant of or had inadequate response to ruxolitinib;

8. Subjects must have an Eastern Cooperative Oncology Group (ECOG) Performance Status of
0-2. (Appendix F);

9. Life expectancy of at least twelve months;

10. At least four weeks must have elapsed between the last dose of any MF- directed drug
treatments for myelofibrosis (including investigational therapies) and study
enrollment;

11. Recovery to ≤ Grade 1 or baseline of any toxicities due to prior systemic treatments,
excluding alopecia;

12. Women of child bearing potential (WCBP), defined as a sexually mature woman not
surgically sterilized or not post-menopausal for at least 24 consecutive months if ≤55
years or 12 months if >55 years, must have a negative serum pregnancy test within four
weeks prior to the first dose of study drug and must agree to use adequate methods of
birth control throughout the study. Adequate methods of contraception are outlined in
the protocol.

13. Ability to adhere to the study visit schedule and all protocol requirements;

14. Must have adequate organ function as demonstrated by the following:

- ALT (SGPT) and/or AST (SGOT) ≤ 3x upper limit of normal (ULN), or ≤ 4 x ULN (if
upon judgment of the treating physician, it is believed to be due to
extramedullary hematopoiesis [EMH] related to MF);

- Direct bilirubin ≤ 1.5 x ULN; or ≤ 2x ULN (if upon judgment of the treating
physician, it is believed to be due to EMH related to MF);

- Serum creatinine ≤ 2.5 mg/dL x ULN.

Exclusion Criteria:

1. White blood cell count > 25 x 10e9/L or > 10% peripheral blood blasts;

2. Other invasive malignancies within the last 3 years, except non- melanoma skin cancer
and localized cured prostate and cervical cancer;

3. History of stroke, unstable angina, myocardial infarction, or ventricular arrhythmia
requiring medication or mechanical control within the last 6 months;

4. Presence of active serious infection;

5. Any serious, unstable medical or psychiatric condition that would prevent, (as judged
by the Investigator) the subject from signing the informed consent form or any
condition, including the presence of laboratory abnormalities, which places the
subject at unacceptable risk if he/she were to participate in the study or confounds
the ability to interpret data from the study;

6. Known history of human immunodeficiency virus (HIV), or known active hepatitis A, B,
or C infection;

7. Organ transplant recipients other than bone marrow transplant;

8. Women who are pregnant or lactating.