Open-label Extension Study of Seralutinib in Adult Subjects With PAH (PROSERA-EXT)

Inclusion Criteria:

1. Subjects must have completed a qualifying last visit in a prior seralutinib PAHstudy on investigational product (IP) and in accordance with the protocol.

2. Evidence of an informed consent document, signed and dated by the subject,indicating that the subject has been informed of all pertinent aspects of the studyprior to initiation of any subject-mandated procedures.

3. Willingness and ability to comply with scheduled visits, treatment plan, laboratorytests, and other study procedures

4. Women of childbearing potential (WOCBP) must have a negative urine or serumpregnancy test at enrollment visit before first administration of InvestigationalProduct (IP) in this study.

5. WOCBP who are not abstinent and intend to be sexually active with a non-sterilizedmale partner must be willing to use a highly effective method of contraception fromconsent through 30 days following the last administration of IP.

6. Male subjects: Non-sterilized male subjects who are not abstinent and intend to besexually active with a female partner of childbearing potential must use a malecondom from consent through 90 days after the last dose of IP.

Exclusion Criteria:

1. Severe acute or chronic medical or laboratory abnormality that may increase the riskassociated with study participation or seralutinib administration, unless associatedwith an ongoing AE and discussed with the Sponsor's medical monitor (MM) (ordesignee).

2. Have any other condition or reason that, in the opinion of the Investigator, wouldprohibit the subject from participating in the study.