I'm having trouble making sense of this. Pancreatic cancer that has escaped first-line treatment is, unfortunately, not rare. FDA has been very permissive about letting small distinctions break orphan drug exclusivity. And anyway, an extra few years of exclusivity for a single indication is unlikely to extend the protection for Jakafi.
Frankly, with the fine tuning of JAK selectivities that we're seeing, Ruxolitinib is unlikely to be a long-term survivor anyway. Its affinity for the marrow compartment, needed to fight MF, is going to be a disadvantage in most other indications. The noise we're hearing from R&D suggests that maybe twice as much selectivity for JAK 1 over 2 might make a better agent vs MF. It may be the penicillin K of the JAK modifiers (first really good drug in class, enormously valuable, but quickly superseded)
So I don't see why this designation was sought, why it was granted, or what good it does now that it has been granted.