Biotech Values

[drbio45]

Details of the comparison between ambrisentan and sitaxsentan (thelin) that I wonder about but never hear discussed:

1. sitaxsentan trials enrolled patients with connective tissue disease which is a more severe form of PAH; how did that affect trial outcome, especially with regards to liver failure rates? My understanding is that the liver dysfunction is partially related to the disease which is why you see liver enzyme increases in the placebo group.

2. the original concept behind ERAs was to counterbalance the high endothelin levels seen in PAH patients and heart failure patients which is thought to cause constriction by binding to the Endothelin A receptor. Thein has a greater specificity for the A receptor than the B receptor and is the only ERA shown in the clinic to reduce endothelin levels. Does this cause the drug to be more effective with long term dosing?

3. Recent cc with Encysive, company stated that 40% of tracleer patients stop the drug due to no efficacy -- is this because of point 2?

I agree that at this point, the street sees ambrisentan as the better drug....I suspect that many docs who treat PAH have the same idea. What I wonder is if that is a valid assumption.

it appears that Myogen learned a lot about the data from the way Encysive ran their trials. they kept out patients that wouldn't would show the best drug effect. they also changed the definition of liver elevations which seemed to fool analysts.

the thing that has bothered me is that the FDA has held up encysives drug for over a year so there could be data about the safety of the drug that we are unaware of.

Thelin also didn't get priority review and ambrisentan did. that has weighed in my mind.

As investors we do not get all the data that the fda does