Patient Inclusion Criteria

1.Subject must be willing and able to give written informed consent by signing an IRB approved Informed Consent Form prior to undergoing any study-specific procedures.
2.Subject must have had a diagnosis of ITP for at least 3 months and no known etiology for thrombocytopenia.
3.Subject's platelet count averages < 30,000/µL (and none > 35,000 unless as a result of rescue therapy) from at least 3 qualifying counts within the preceding 3 months. At least 2 of the qualifying counts must have been taken during the screening period.
4.Must have previously received at least 1 typical regimen for the treatment of ITP.
5.Male or female at least 18 years of age.
6.Performance status on Karnofsky performance status scale (KPS) > 70
7.Subject's concurrent treatment for ITP may consist of either glucocorticoids (< 20 mg prednisone equivalent per day), or azathioprine or danazol. The dose of the concurrent medication must have been stable for 14 days prior to baseline and must be expected to remain stable throughout the study. No other concurrent medications for ITP are permitted.
8.Subject's other therapeutic agents for ITP have been discontinued in accordance with the washout periods
9.Female subject must be either post-menopausal for at least 1 year or surgically sterile; or if female of child-bearing potential, must not be pregnant or lactating and must agree to use an acceptable method of birth control throughout the duration of the trial and for 30 days following the last dose. Acceptable methods of birth control are defined as: hormonal contraception (pill, injection or implant) used consistently for at least 30 days prior to screening, an intrauterine device (IUD), a double-barrier method (ie, condom and spermicide, or condom and diaphragm), or complete abstinence.
10.In the Investigator's opinion, the subject has the ability to understand the nature of the study and any hazards of participation and to communicate satisfactorily with the Investigator.

Patient Exclusion Criteria

1.Subject with ITP associated with lymphoma, chronic lymphocytic leukemia, viral infection, autoimmune disorders, thyroid disease, human immunodeficiency virus, or hepatitis or induced or alloimmune thrombocytopenia, or thrombocytopenia associated with myeloid dysplasia.
2.Subject with autoimmune hemolytic anemia.
3.Subject has a history of or active, clinically significant, respiratory, gastrointestinal (pancreatitis), renal, hepatic, neurological, psychiatric, musculoskeletal, genitourinary, dermatological, or other disorders that, in the Investigator's opinion, could affect the conduct of the study or the absorption, metabolism or excretion of the study drug.
4.Subject has had any major cardiovascular event within the 6 months prior to randomization, including but not limited to; myocardial infarction, unstable angina, cerebrovascular accident, pulmonary embolism, or New York Heart Association Class III or IV heart failure.
5.Subject has uncontrolled or poorly controlled hypertension, defined as systolic blood pressure ≥ 140 mm Hg, or diastolic blood pressure ≥ 90 mm Hg, whether or not the subject is receiving anti-hypertensive treatment. Subjects may be rescreened if the blood pressure is successfully and promptly controlled (within 30 days) using conventional anti-hypertensive therapy to achieve optimal blood pressure control (< 140/90 mmHg).
6.Subject has a history of coagulopathy including prothrombotic conditions such as Factor V Leiden, APC resistance, AT-III deficiency and lupus anticoagulant, or arterial or deep venous thrombosis within 6 months prior to randomization.
7.In subjects with deep venous thrombosis greater than 6 months prior to randomization, anticoagulants must have been discontinued for at least 30 days and subsequent D dimer must be within normal limits for the site's local laboratory.
8.Subject has a bleeding assessment score of Grade 2 at any site by the ITP Bleeding Scale (IBLS).
9.Subject has 1 or more of the following laboratory abnormalities: leukocyte count < 2,500/µL, neutrophil count of < 1,500/µL, lymphocyte count < 750/µL, Hgb < 10 g/L without ongoing transfusion support, or transaminase levels (ALT, AST) > 1.5x ULN, total bilirubin > 2.0 mg/dL, or estimated glomerular filtration rate (eGFR) < 30 mL/min at the time of screening and/or baseline (Day 1).
10.Subject has a significant infection, or an acute infection such as influenza, or is known to have an active inflammatory process at the time of screening and/or baseline (Day 1).
11.Subject has acute gastrointestinal symptoms at the time of screening and/or baseline (eg, nausea, vomiting, diarrhea, abdominal pain).
12.Subject has increased the dose of, or added, prescription drugs within the 2 weeks prior to Day 1, unless agent is agreed to be not clinically relevant by both the Investigator and Sponsor.
13.Subject has had positive results for HIV, HBV, or HCV by standard serologic tests.
14.Subject has received any blood or blood products within the 2 weeks prior to randomization. (IVIg or anti-rho (D) immunoglobulin (anti-D) are allowed if used for rescue therapy, unless platelet count is > 30,000/µL at the time of randomization.)
15.Subject is currently enrolled in an investigational drug or device study or has used an investigational drug or device within 30 days or 5 half-lives (whichever is longer) of Day 1.
16.Subject has a history of alcohol or substance abuse that, in the judgment of the Investigator, may impair or risk the subject's full participation in the study.
17.Subject has a known allergy and/or sensitivity to the test article or its components.