The challenges of measuring the safety and efficacy of investigational drugs that target chronic, difficult-to-treat or rare diseases in more narrowly defined patient subpopulations have increased the scope of clinical trials and the burden to execute them in the past 15 years. Other factors affecting

中文翻译：

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试验观察：临床试验设计复杂性的趋势

在过去的15年中，针对以更狭窄定义的患者亚群为对象的，针对慢性，难治性疾病或罕见疾病的研究药物的安全性和有效性进行测量的挑战增加了临床试验的范围和执行这些试验的负担。其他影响因素