I have no expertise from which to guess the likelihood of...

I have no expertise from which to guess the likelihood of success, but I do have a little understanding of statistics. From several reviews I've read the Ph 2 to Ph 3 success rate (ie Ph 2 considered successful enough to move to Ph 3) is about 30% for normal drugs, but 44% to 50% for orphan drugs.

If they each trial is complete independent, then taking a midpoint of 47% average success the chance all 4 are successful would be 5%. The chance that at least 1 is successful is 92%, the chance none are successful is 8%

However, they are not independent, as it's the same drug being used across all 4 trials on diseases with similar mechanisms. This means the likelihood they are all successful or all not successful is higher.

Its hard to say how much by though.

The quoted success rates are across all orphan drugs which would include completely new drugs.

NNZ-2591 is arguably not completely new, but is related to NNZ-2566, with a similar mechanism of action. Daybue has succeeded, so theoretically this increases the likelihood of success for NNZ-2591.

I don't know how much this increases the likelihood of success, but you'd think it would be a reasonable amount.

It's not possible to calc the %, but you'd have to think it's more likely than not each trial will be successful. Maybe 70% at a stab?

And if one is successful it's also likely most or all will be successful.

Note the average ph3 to approval for orphan drugs is about 65% from what I've read.

Although there is risk, you'd have to think it's certainly better odds than the roulette table.

The likelihood none of the trials is successful is statistically small, ie it's pretty unlikely.