Fig. 3

Schedule of events. Study assessments will be performed over 45 days for each cohort. The schedule lists all the interventions, tests, and pre- and post-test assessments that will be performed at screening (days − 28 to − 3), cardiopulmonary exercise testing (CPET) at baseline (day 1), treatment (days 8 and 15), and safety follow-up (day 45) visits. Adverse event assessments and interval history reviews will be conducted at each visit. 6MWT 6-minute walking test, 6MWD 6-minute walking distance, BP blood pressure, DASI Duke Activity Status Index, ECG electrocardiogram, HR heart rate, HRR heart rate recovery, NYHA New York Heart Association, O₂ oxygen, PAH pulmonary arterial hypertension, PFT pulmonary function testing, PGI-S Patient Global Impression of Severity, PK pharmacokinetic, RPE rating of perceived exertion, SPO₂ peripheral oxygen saturation, WHO World Health Organization. *Potential patients will be screened approximately 3 days (≤ 28 days) before baseline CPET visit 2. ^†Patients will be scheduled for treatment CPET visit 3, approximately 7 days after the baseline CPET visit 2. ^‡If a patient prematurely discontinues the study any time before dosing or treatment CPET visit 3 because of an adverse event or patient safety concern, the patient should return to the clinic as soon as possible for an early termination study visit. ^§Medical history will include a detailed PAH disease-specific medical history. ^IIClinical laboratory tests may be repeated at the baseline CPET visit 2 if screening laboratory results are deemed clinically significant and warrant repeat testing. Clinical laboratory includes hematology, chemistry, and urinalysis. Prothrombin time international normalized ratio will also be tested in patients taking oral vitamin K antagonists. ^¶Urine or serum pregnancy test at screening visit 1 required and a urine or serum pregnancy test at visit 3 and visit 4. **Either a single 0.5-mg dose (cohort 1) or a single 1.0-mg dose (cohort 2) of RT234 will be administered 30 minutes before CPET at visit 3 and 30 minutes before the 6MWT at visit 4. ^††Interval history will include any signs, symptoms, or events experienced by the patient since the previous study visit. ^‡‡Physical examinations at screening will be complete; all other physical examinations will be symptom directed. ^§§Height will be obtained only at screening visit 1. ^{II II}Resting vital signs (BP, HR, respiration rate, body temperature, and pulse oximetry [SPO₂]) after resting for 5 minutes (sitting). Vital signs should be taken before any blood draw. BP, HR, and SPO₂ will also be measured during CPET and into recovery (HR via continuous ECG monitoring during CPET and for 6 minutes post CPET, BP assessment every 2 minutes during CPET and for 6 minutes post CPET, and SPO₂ assessment every minute during CPET and for 6 minutes post CPET) and at treatment 6MWT visit 4 (before RT234 dosing; 5 and 15 minutes post dose before 6MWT at 30 minutes post dose; and at 60 and 120 minutes post dose). ^¶¶Continuous ECG monitoring will be collected during CPET and for 6 minutes post CPET. ***PFT may be completed at screening and/or baseline to confirm eligibility if historical PFT results within 6 months before screening are not available. ^†††During the screening period, two 6MWTs will be performed at least 2 days apart, and the mean of the distance walked will be used for eligibility. If tolerable for the patient, the two 6MWTs at screening can be performed on the same day after a minimum of 2 hours between each test. The two screening 6MWDs must have a relative difference (i.e., [absolute difference between the two 6MWDs] / [mean of the two 6MWDs]) of ≤ 15%. If the difference is > 15%, a third 6MWT will be done during screening. If after the third 6MWT the relative distance is still > 15%, the Sponsor Medical Monitor will be contacted. The two longest 6MWDs will be averaged to determine the baseline 6MWD. ^‡‡‡ The CPET assessments conducted at Visits 2 (pre dose) and 3 (post dose) will be conducted at approximately the same time of day (within 2 hours). ^§§§PGI-S before CPET and at 2 minutes cool down off treadmill but still wearing the mask, then at 5-minute intervals: 7, 12, and 17 minutes with the mask off. For the 6MWT, PGI-S will be taken before and at 2 minutes after completion of the test. ^{II II II}Modified Borg Dyspnea Scale assessment every minute during CPET and for 6 minutes post CPET. ^¶¶¶Borg RPE Scale assessment every 2 minutes during CPET and for 6 minutes post CPET. ****Angina Scale assessment every 2 minutes during CPET and for either 6 minutes post CPET or, if indicated, until symptom recovery. ^††††DASI assessment 10 minutes post CPET. ^‡‡‡‡PK samples will be collected at visits 3 and 4 before RT234 dosing; at 3, 15, and 30 minutes post dose; immediately at the end of the exercise period; and at 45, 75, 120, 180, and 240 minutes post dose