How to estimate the minimum number of subjects that should be enrolled for phase 1 of a clinical trial?
The objective of phase 1 is to test for the safety, side effects, dose etc. I know we usually use less subjects compare to phases II and III. But what is the appropriate minimum number of subjects for phase 1? How to estimate this number?
Hi,
The topic was discussed in another thread:
https://www.researchgate.net/post/How_to_calculate_sample_size_of_phase_1trial
Best regards
Tomasz
Thank you Tomasz Grabowski . I had already seen this topic, but I am confused with the resources provided because they are not specifically designed for phase 1 of clinical trials (I know how to estimate sample size related to power of statistical tests for example but this is usually appropriate for phases II-III). I read many times that the number of subjects for phase 1 is smaller than for phases II-III, but I fail to find proper explanations on how to estimate the right number.
Hi,
To be honest, in the case of the pharmaceutical industry work practice is that it depends on many different topics:
- study specificity (biosimilar; NCE etc.)
- subject (healthy, patients)
- drug specificity
- indication (rare disease)
- variability of the objectives of the study
This is why regulators state that in phase one 12-80 subjects could be involved but its range is optimized within the interaction with Health Authorities (FDA, EMA, national authorities) within scientific advice meetings for example after the presentation of specific documentation like Briefing Books. This kind of approach makes possible case-by-case analysis and precise justification of the range of the study and sample size optimization. Of course, it's an industrial perspective and common practice. So in practice, there is no simple answer but rather some kind of approach with stepwise justification. The reference below could be more helpful,
Ref.
https://www.ema.europa.eu/en/documents/scientific-guideline/ich-e-8-general-considerations-clinical-trials-step-5_en.pdf
Tomasz
You can use the STATA or Epi Info softwares for the estimation of sample size.
There is no fixed number of subjects that should be enrolled in phase 1 of a clinical trial. The number of subjects required depends on the specific objectives of the trial, the population being studied, the type of intervention being tested, the dose and administration schedule, and the number of groups being studied.
There are different methods for estimating sample size for phase 1 of a clinical trial, but the most commonly used methods are:
Regardless of the method used, it is important to consider the ethical and practical implications of enrolling a large or small number of subjects in phase 1 trials. The safety of the subjects should always be the primary concern, and the sample size should be sufficient to detect meaningful differences in the outcomes of interest.
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