"Could this lead to approval of B in Europe where one of the stated paths to approval was demonstration of efficacy/safety by a 2nd drug class member? (If I'm remembering this correctly.)"
That was one of the considerations, but from the EU perspective, the biggest flaw in the B filing was a failed primary endpoint in the pivotal trial. Prior to unblinding, FDA had communicated to PTLA that they planned on using a slightly different population for calculating the primary endpoint than that specified in the protocol and by chance, it was this modified population that gave the final analysis a statsig result.
Besides, what good is an EU approval if the drug is not commercially viable?
For now, PTLA share appreciation is dependent on increasing revenue, potential A label expansion, advancing the C program and potential partnering, all IMO in that order of importance. I'm reasonably optimistic that the things keep improving from here. Garland was smart to air out all the dirty laundry early on and focus on the areas ripe for improvement.