PLX/KMDA—…how similar the competing enzymes have to be before they are judged to be "the same chemical entity" and thus disallowed under orphan exclusivity.
The criteria may vary to some degree according to jurisdiction. EU orphan exclusivity runs for 10 years, while FDA orphan exclusivity runs for 7 years; on this basis alone, one would expect some differences in how the regs are applied.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”