Why Did GSK Pay $1.9B for Momelotinib, an Oral Ph. III Myelofibrosis Candidate?

Momelotinib, an oral JAK1/2 inhibitor for myelofibrosis, is going to GSK as part of a $1.9 billion acquisition of Sierra Oncology. Anyone that’s ever worked on a kinase program probably looked at this structure and raised their eyebrows. $1.9 billion for another JAK2 inhibitor? It’s probably not super selective either, you might think… and you’d be right. But details here are actually pretty interesting.