Inclusion Criteria:

• Participants must have completed their current respective Pulmonary Arterial Hypertension (PAH) sotatercept clinical study and its requirements, and must not have discontinued early.
• Participants must be willing to adhere to the study visit schedule and understand and comply with all protocol requirements.
• Participants must have the ability to understand and provide written informed consent.
• Females of childbearing potential must:
  • Have a negative pregnancy test as verified by the investigator prior to starting study drug administration; she must agree to ongoing pregnancy testing during the course of the study and until 8 weeks after the last dose of the study drug;
  • If sexually active, have used, and agree to continue to use highly effective contraception without interruption, for at least 28 days prior to starting the investigational product, during the study (including dose interruptions), and for 16 weeks (112 days) after discontinuation of study drug;
  • Refrain from breastfeeding a child or donating blood, eggs, or ovum for the duration of the study and for at least 16 weeks (112 days) after the last dose of study drug. 
• Male participants must:
  • Agree to use a condom, defined as a male latex condom or non latex condom NOT made out of natural (animal) membrane (e.g., polyurethane), during sexual contact with a pregnant female or a female of childbearing potential while participating in the study, during dose interruptions, and for at least 16 weeks (112 days) following investigational product discontinuation, even if he has undergone a successful vasectomy;
  • Refrain from donating blood or sperm for the duration of the study and for 16 weeks (112 days) after the last dose of study drug.
• Participants must agree not to participate in any other trials of investigational drugs/devices while they are enrolled in the A011-12 study.

Exclusion Criteria:

• Not enrolled in a PAH parent study at the time of enrollment.
• Missed more than the equivalent of 4 consecutive doses between the end of parent study and the start of this study.
• Presence of an ongoing serious adverse event that occurred during a PAH sotatercept clinical study that is assessed to be possibly or probably related to sotatercept.
• Pregnant or breastfeeding females.

Eligibility last updated 11/11/21. Questions regarding updates should be directed to the study team contact.