Inclusion Criteria:

1. Subjects must have completed a prior seralutinib PAH study on investigational product (IP) and in accordance with the protocol.
2. Evidence of an informed consent document, signed and dated by the subject or his/her legal representative, indicating that the subject has been informed of all pertinent aspects of the study prior to initiation of any subject-mandated procedures.
3. Willingness and ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures
4. Women of childbearing potential (WOCBP) must have a negative pregnancy test at Screening and on Day 1 before first administration of Investigational Product (IP).
5. WOCBP who are not abstinent and intend to be sexually active with a non-sterilized male partner must be willing to use a highly effective method of contraception from consent through 30 days following the last administration of IP.
6. Male subjects: Non-sterilized male subjects who are not abstinent and intend to be sexually active with a female partner of childbearing potential must use a male condom 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 risk associated with study participation or seralutinib administration, unless associated with an ongoing AE and discussed with the Sponsor's medical monitor (MM) (or designee).
2. Have any other condition or reason that, in the opinion of the Investigator or in the opinion of the Sponsor's MM (or designee) in consultation with the Investigator, would prohibit the subject from participating in the study.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 5/21/2024. Questions regarding updates should be directed to the study team contact.