Here is the design of a clinical trial:

Official Title: Autologous Stem Cells in Achilles Tendinopathy

Included conditions:
- Achilles Tendinitis, Right Leg
- Achilles Tendinitis
- Achilles Degeneration
- Achilles Tendon Thickening
- Tendinopathy
- Achilles Tendinitis, Left Leg

Study Armgroups:
- {'label': 'Autologous Mesenchymal Stem Cells', 'type': 'EXPERIMENTAL', 'interventionNames': ['Biological: Autologous Mesenchymal Stem Cells']}

Interventions:
- {'type': 'BIOLOGICAL', 'name': 'Autologous Mesenchymal Stem Cells', 'armGroupLabels': ['Autologous Mesenchymal Stem Cells'], 'otherNames': ['Mesenchymal Stem Cells', 'Stromal Cells', 'Stem Cells', 'Cell Therapy']}

Primary Outcomes:
- {'measure': 'The primary safety outcome will be the incidence rate of Serious Adverse Reaction (SAR).', 'description': 'The primary safety outcome is the incidence rate of SARs. This will be expressed as the proportion of participants experiencing a SAR at any time over the 24 week follow-up period. Primary outcomes will be assessed by adverse events reporting, clinical assessment and ultrasound.', 'timeFrame': '6 months'}

Please estimate the sample size based on the assumption: 
95%, 80%, and 50% confidence levels were used to rule out true SAR rates. No formal power calculation was performed as this is a proof-of-concept pilot study.
Power and sample size
        Sample size was determined to ensure a predetermined level of accuracy for the incidence of SARÂ using an exact binomial CI. With 10 participants, if no SAR is observed we can rule out a true SAR rate of 31% or greater with 95% confidence, or a true SAR rate of 21% or greater with 80% confidence, or a true SAR rate of 13% or greater with 50% confidence. With six participants for the interim analysis, if no SAR is observed we can rule out a true SAR rate of 46% or greater with 95% confidence, or a true SAR rate of 32% or greater with 80% confidence, or a true SAR rate of 21% or greater with 50% confidence. Since the study is a proof-of-concept pilot study, no formal power calculation was performed.