HS235 for PAH in Adults: Adding an Activin Inhibitor to Background Therapy

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This is a Phase 1b/2 multicenter, randomized, double‑blind, placebo‑controlled trial evaluating the safety, pharmacokinetics, pharmacodynamics, and efficacy of HS235 plus background PAH therapy in adults with WHO Group 1 PAH. Participants receive HS235 or placebo across multiple doses while continuing their usual PAH medications and diuretics. Key eligibility includes adults 18+ with PAH, functional class II–IV, and specific hemodynamic criteria, as well as adequate 6-minute walk distance. The study aims to determine whether HS235 provides added benefit beyond standard care and to characterize its safety and PK/PD profile.

Why it matters

Who can join: the full rules

Inclusion Criteria:

Participants are eligible to be included in the study only if they meet all of the following criteria:

1. Male and female participants, 18 years of age and older.
2. Body Mass Index (BMI) 18.5 and 40 kg/m2 and body weight at or below 120 kg.
3. Baseline RHC performed during the Screening Period documenting:

   1. A minimum PVR of ≥ 5 Wood units (WU) or ≥ 400 dyn·sec·cm-5 and,
   2. A pulmonary artery wedge pressure (PAWP) of ≤ 15 mm Hg.
4. Diagnosis of WHO pulmonary arterial hypertension (PAH) Group 1.
5. Symptomatic PAH classified as WHO Functional class II to IV.
6. On stable doses of at least 2 approved background PAH therapies and diuretics.
7. 6-Minute Walk Distance (6MWD) ≥ 150 m and ≤ 500 m repeated twice during screening.
8. Ability to adhere to study visit schedule and understand and comply with all protocol requirements.

Exclusion Criteria:

1. PH WHO Groups 2, 3, 4 or 5.
2. Hospitalization for any worsening medical condition or major surgery within 4 weeks prior to screening.
3. Any symptomatic coronary disease events.
4. History of heart transplant or on heart transplant list.
5. Uncontrolled systemic hypertension.
6. History of restrictive, constrictive or congestive cardiomyopathy.
7. History of significant mitral regurgitation or aortic regurgitation valvular disease.
8. Untreated or poorly controlled moderate or severe obstructive sleep apnea.
9. A diagnosis of worse than moderate COPD or worse than mild ILD.
10. Cerebrovascular event within 90 days prior to screening
11. A pneumonectomy or lobectomy
12. Having received an activin signaling inhibitor such as sotatercept at any time prior to screening
13. A Hgb \> sex-specific ULN
14. Platelets count \< 100,000/mm3
15. Severe (stage ≥4) renal failure with eGFR \< 30 mL/min/m2
16. Abnormally elevated liver function enzymes (ALT or AST \> 3X ULN, or total bilirubin \> 1.5X ULN).

Where it's running

• Investigational Site-102
  Tampa, Florida, United States Recruiting
• Investigational Site-101
  Boston, Massachusetts, United States Recruiting
• Investigational Site-104
  Providence, Rhode Island, United States Recruiting
• Investigational Site-305
  Barcelona, Spain Recruiting
• Investigational Site- 301
  Barcelona, Spain Recruiting
• Investigational Site-308
  Madrid, Spain Recruiting

Study contacts

• Study coordinator: US GSK Clinical Trials Call Center
• Email: GSKClinicalSupportHD@gsk.com
• Phone: 877-379-3718

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Other studies for the same condition or treatment. Recruiting studies are listed first.

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.