Open-Label Extension Study of Ubenimex in Patients With Pulmonary Arterial Hypertension (WHO Group 1)

Inclusion Criteria:

- Patients must have completed Study EIG-UBX-001 through Week 24.

- In the opinion of the Principal Investigator, has been generally compliant with study
requirements during Study EIG-UBX-001.

- Agrees to use a medically acceptable method of contraception throughout the entire
study period.

- Willing and able to comply with scheduled visits, treatment plans, and laboratory
tests and other study procedures.

Exclusion Criteria:

- Is pregnant or lactating.

- Concurrent regular use of another leukotriene pathway inhibitor.

- Any reason that, in the opinion of the investigator, precludes the patient from
participating in the study.

1. Any condition that is unstable or that could jeopardize the safety of the patient
and his/her compliance in the study

2. A serious uncontrolled medical disorder/condition that in the opinion of the
investigator would impair the ability of the patient to receive protocol therapy

- An ongoing, drug-related, serious adverse event (SAE).

- Significant/chronic renal insufficiency.

- Transaminases (alanine transaminase, aspartate transaminase) levels >3 × upper limit
of normal (ULN) and/or bilirubin level >2 × ULN.

- Absolute neutrophil count <1500 mm3.

- Hemoglobin concentration <9 g/dL at Screening.