Here is the design of a clinical trial:

Official Title: Biologic Abatement and Capturing Kids' Outcomes and Flare Frequency in Juvenile Spondyloarthritis (BACK-OFF JSpA)

Included conditions:
- Juvenile Spondyloarthritis

Study Armgroups:
- {'label': 'TNFi Standard Therapy', 'type': 'ACTIVE_COMPARATOR', 'description': 'Continue fixed standard treatment (i.e., no change from current therapy)', 'interventionNames': ['Other: Standard TNFi Therapy']}
- {'label': 'TNFi fixed longer dosing intervals', 'type': 'EXPERIMENTAL', 'description': 'Fixed longer dosing intervals of TNFi (i.e., increased time between doses)', 'interventionNames': ['Other: TNFi fixed longer dosing intervals']}
- {'label': 'TNFi Therapy Withdrawal', 'type': 'EXPERIMENTAL', 'description': 'Stop TNFi treatment', 'interventionNames': ['Other: Stop TNFi treatment']}

Interventions:
- {'type': 'OTHER', 'name': 'Standard TNFi Therapy', 'description': 'Participants randomly assigned to this arm will continue taking their TNFi medication as currently prescribed.', 'armGroupLabels': ['TNFi Standard Therapy']}
- {'type': 'OTHER', 'name': 'TNFi fixed longer dosing intervals', 'description': 'Participants randomly assigned to this arm will increase the time between TNFi medication doses.\n\n* Adalimumab- from every 2 to 3 weeks\n* Certolizumab- from every 2 to 4 weeks\n* Etanercept- from every 1 to 2 weeks\n* Golimumab- from every 4 to 6 weeks\n* Infliximab- from baseline to baseline + 2 weeks', 'armGroupLabels': ['TNFi fixed longer dosing intervals']}
- {'type': 'OTHER', 'name': 'Stop TNFi treatment', 'description': 'Participants randomly assigned to this arm will stop TNFi medication.', 'armGroupLabels': ['TNFi Therapy Withdrawal']}

Primary Outcomes:
- {'measure': 'Juvenile Spondyloarthritis (JSpA) flare', 'description': "JSpA flare is defined as clinically meaningful worsening in ≥3 of the following: caregiver/patient assessment of well-being, physician assessment of disease activity, caregiver/patient assessment of pain, physical function, and active joint count. Meaningful change for well-being, disease activity, and pain are an increase of ≥2 on visual analogue scale (range 0-10 with higher scores indicating poorer well-being, higher disease activity, and higher magnitude of pain). Meaningful change in function is defined as ≥3 unit change in the PROMIS mobility or upper extremity T-scores. The Patient-Reported Outcomes Measurement Information System (PROMIS) short forms include 8 questions and a T-score of '50' represents the healthy population mean score with standard deviation of 10. Active joint count is defined as the number of joints with swelling or, in the absence of swelling, limitation of motion accompanied by pain or warmth as per the physician examination.", 'timeFrame': '12 months'}

Please estimate the sample size based on the assumption: 
The study aims for 80% power at a 0.05 significance level for the primary hypothesis and 80% power at a 0.025 significance level for the secondary hypothesis. For Objective 2, 92% power at a significance level of 0.02 is assumed, with a within-subject correlation of 0.3 and a clinically meaningful change of 0.5 standard deviation (SD) units.
Sample size {14}
        We aim to recruit 198 subjects in total with 66 randomized to each arm, with an anticipated 10% loss to follow-up. Based on the data in the C-OPTIMISE trial [26], we anticipate the cumulative flare rate in the BACK-OFF JSpA standard dosing group by month 12 (end of the active study) will be approximately 16%. With 60 patients in standard treatment group and 60 in fixed longer dosing group, and a 16% cumulative flare rate in the standard dosing group, a non-inferiority comparison using the logrank test achieves 80% power at a 0.05 significance level when the non-inferiority bound is 2.5 and the hazard ratio (HR) is 1. Stated simply, if the cumulative rate of flare in the standard TNFi dose group is 16%,
        we can declare noninferiority if the HR non-inferiority bound is â¤2.5 and the cumulative flare rate in the fixed longer dosing arm is no more than 31%. This meets the acceptable noninferiority margin of an absolute difference of 15% in the cumulative flare rate that was determined by consensus of BACK-OFF JSpA site PIs. This non-inferiority margin is also in accordance with other recent published TNFi dose reduction trials [27â30]. To test our secondary hypothesis, which is that the TNFi stop arm is inferior to each of other two arms (standard TNFi dose and fixed longer TNFi dosing), the logrank test achieves 80% power at a 0.025 significance level (to adjust for multiple comparisons of the secondary hypotheses) to detect a difference of 3.2 in the hazard ratio.
        For Objective 2, with an evaluable N=60 in each arm we will have 92% power at a significance level of 0.02 to detect a time-average difference of 0.5ÃSD between any two arms in pain interference if we account for repeated measures (3 times on average, ranging from 2 to 4) by assuming a within-subject correlation of 0.3. FDA guidance suggests that 0.5 standard deviation (SD) units is the level of group-level change in PROs that is clinically meaningful, which we will be powered to detect [31].