PFE: JAK1/JAK3/TYK2 (with some impact on JAK2) INCY: JAK1/JAK2 VRTX: JAK3
JAK3 is expressed only in immune cells.
Peter, RIGL is also set to go into the clinic with a JAK3 inhibitor with the key focus being for transplant rejection. They too cite the fact that JAK3 is "critical to immune system activation and is an attractive target because its expression is limited to key cells in the immune system." See: http://www.rigel.com/rigel/JAK3 .
Any comments on the use of a JAK3 inhibitor in a transplant rejection setting? I believe that's a very large market opportunity for RIGL.