[palmer]

...and it kills or cripples the other 5%???

That's all they test for in phase 1. Not efficacy, just safety. If it killed or crippled anyone they would not have proceeded to phase 2.

[dhs12345]

And if it failed, do you think that we’d know it?

[corkoman]

...and it kills or cripples the other 5%??? That's all they test for in phase 1. Not efficacy, just safety. If it killed or crippled anyone they would not have proceeded to phase 2.

Other way around - Phase 1 is efficacy. If it doesn't work it doesn't go to Phase 2. Phase 2 is to assess best dose / dose frequency. Phase 3 is safety and efficacy.

There is Phase 4 post-marketing for more safety and efficacy data.