One-sided significance threshold of less than 0.1 in Phase 2 clinical trial

agree with simon I would like to add that in an indication with severe mortality like AML the cost of a Type II Error is huge. the worst-case scenario isn’t advancing a mediocre drug to Phase 3 (the Phase 3 trial will eventually catch that). The worst-case scenario is a Type II error (false negative)—abandoning a potentially life-saving drug because our statistical hurdles were too strict for a small sample size. If we demand a strict alpha = 0.025 (one-sided) in a Phase 2 trial, we either:

• Tank our statistical power, making it very likely that we miss active drugs.
• Inflate our sample size so much that the Phase 2 trial costs as much and takes as long as a Phase 3 trial.

Relaxing the threshold to 10% can be looked as an intentional trade-off. the sponsors are usually happy to accept a 1 in 10 chance of a false positive (in phase 2) to ensure we maintain 80-90% power to detect a true signal.