Thanks for pointing out the presentation. I took a look at it. FYI Thelin is Sitaxentan. I looked up why it was removed it was because of liver tox (I believe Tracleer has a black box warning about raising liver enzymes). I'm not sure about liver side effects with Letairis (I think its safer). Tracleer's patent life runs out in 2015 (EDIT I thought it was sooner but looked it up and saw 2015). I believe Letairis is around that as well.
Did the presentation cause you to increase your odds of success for RE-021 or are you still pretty skeptical? If I ever do take a position, it would only be a relatively small one. There are certainly plenty of risks here.