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Discounting phase 2 results when planning phase 3 clinical trials.

S Kirby1, J Burke, C Chuang-Stein

  • 1Pfizer Limited, Ramsgate Road, Sandwich, UK, CT13 9NJ. simon.kirby@pfizer.com

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Improving phase 3 trial sample size planning involves adjusting phase 2 data to mitigate bias. This research uses assurance and bias-adjusted estimates for more reliable clinical trial design.

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Area of Science:

  • Clinical Trial Design
  • Biostatistics
  • Pharmaceutical Development

Background:

  • Sample size planning is critical for phase 3 clinical trials.
  • Phase 2 trial data is often used for phase 3 sample size planning.
  • Bias can arise from selecting favorable phase 2 results and population heterogeneity.

Purpose of the Study:

  • To enhance phase 3 trial sample size planning using phase 2 data.
  • To investigate bias adjustment methods for phase 2 treatment effect estimates.
  • To evaluate 'launch criteria' for progressing development to phase 3.

Main Methods:

  • Utilized an approach based on the concept of assurance.
  • Adjusted (discounted) phase 2 treatment effect estimates using multiplicative and additive methods.
  • Conducted simulations to investigate launch criteria with and without bias adjustment.
  • Supplemented simulation results with empirical evidence.

Main Results:

  • Bias adjustment of phase 2 estimates is necessary when planning phase 3 sample sizes.
  • Simulations demonstrated the impact of bias adjustment on sample size calculations.
  • Empirical evidence supports the need to discount phase 2 results for phase 3 planning.

Conclusions:

  • Discounting phase 2 results is recommended for robust phase 3 sample size planning.
  • The proposed bias adjustment methods improve the reliability of clinical trial design.
  • Recommendations are provided based on simulation and empirical investigations.