Here is the design of a clinical trial:

Official Title: An Investigator-initiated, Multicenter, Phase 3, Randomized, Single-blind, Double-dummy, Parallel-group Study of Evaluate the Efficacy and Safety of Edoxaban Versus Warfarin (Vitamin K Antagonist) in Subjects With Chronic Thromboembolic Pulmonary Hypertension Taking Warfarin (Vitamin K Antagonist) at Baseline: KABUKI

Included conditions:
- CTEPH

Study Armgroups:
- {'label': 'Edoxaban group', 'type': 'ACTIVE_COMPARATOR', 'interventionNames': ['Drug: Edoxaban', 'Drug: Warfarin Potassium placebo']}
- {'label': 'Warfarin group', 'type': 'ACTIVE_COMPARATOR', 'interventionNames': ['Drug: Warfarin Potassium', 'Drug: Edoxaban placebo']}

Interventions:
- {'type': 'DRUG', 'name': 'Edoxaban', 'description': '- Edoxaban 30 mg/60 mg tablet according to body weight. 60 kg or less: 30 mg once daily, over 60 kg: 60 mg once daily, reduced to 30 mg once daily depending on renal function and concomitant medications', 'armGroupLabels': ['Edoxaban group']}
- {'type': 'DRUG', 'name': 'Warfarin Potassium', 'description': '- Warfarin K 1 mg tablets once daily (Dose adjusted with target PT-INR of 1.5-2.5)', 'armGroupLabels': ['Warfarin group']}
- {'type': 'DRUG', 'name': 'Warfarin Potassium placebo', 'description': '- Warfarin K 1 mg placebo tablets once daily', 'armGroupLabels': ['Edoxaban group']}
- {'type': 'DRUG', 'name': 'Edoxaban placebo', 'description': '- Edoxaban 30 mg/60 mg placebo tablet according to body weight. 60 kg or less: 30 mg once daily, over 60 kg: 60 mg once daily, reduced to 30 mg once daily depending on renal function and concomitant medications', 'armGroupLabels': ['Warfarin group']}

Primary Outcomes:
- {'measure': 'Ratio of 1-year resting PVR to baseline resting PVR', 'timeFrame': 'Week 48 of treatment'}

Please estimate the sample size based on the assumption: 
A non-inferiority test with a one-tailed significance level α=0.025 and statistical power β=0.9. A 20% dropout rate is also considered.
Sample size
          Non-inferiority margin and sample size are determined according to the FDA Non-Inferiority Clinical Trials to Establish Effectiveness Guidance for Industry. The 1âyear/baseline PVR ratio for a hypothetical placebo group (ie, CTEPH subjects without anticoagulation) is estimated to be 1.54 based on exhaustive literature review and expert opinions. The PVR ratio in the warfarin group is 1.09 (SD 1.22) based on our clinical database.27 Although the experience and available haemodynamic data for patients with CTEPH taking edoxaban are limited, data for all DOACs including edoxaban in our database shows that the change in PVR is comparable to that of warfarin. Hence, in this sample size calculation, the point estimate and SD of the PVR ratio for the edoxaban group was assumed to be same as that of warfarin.27The ratio of placebo PVR ratio/warfarin PVR ratio (M1) is 1.41. The non-inferiority margin (M2), which is 50% of M1, is calculated to be 1.19. A 20% increase in the PVR ratio is acceptable as a margin of measurement error. For a non-inferiority test with one-tailed significance level Î±=0.025, the sample size required to ensure adequate statistical power Î²=0.9 would be 30âcases per group (60âcases in two groups). Taking into account a 20% dropout rate, the sample size for this study is set at 74âpatients (37 in the edoxaban group and 37 in the warfarin group).