“Since a trial halt at 75% would need p=.005 or possibly p=.001 that 42 days means that with the few extra patients at 42 days the DSMC thought that was a good possibility.“

This is a misrepresentation of the DSMC’s request, or mostly just an opinion on the 42 day request. There’s no indication the DSMC desired to see 42 day data in order to halt the trial for efficacy because “there’s a few extra patient’s data” at 42 days. If the 28 mortality endpoint was tending towards stat sig at 50%, the DSMC would’ve simply requested a 75% interim analysis and not specified to also see 42 day data. More likely is that the DSMC notes that either a primary or secondary endpoint COULD be better at 42 days than 28 days. This doesn’t mean the trial won’t be successful at 28 days, but that 42 days could also lead to approval.