Biotech Values

[mcbio]

To me the ETa Affinity between sitaxsentan and RE-021 are both extremely low (and ambrisentan isn't too out of the ball park either). So it seems Martin is playing with degrees in selling RE-021 as the *only*.

Per that slide 15, the affinity to ET-A for RE-021 is much greater than that of sitaxsentan and ambrisentan (9.3nM vs. .430nM and 1nM, respectively). RE-021 is one of the more potent in that whole slide in terms of affinity to ET-A, only behind zibotentan (21nM), clazosentan (9.5nM), and tezosentan (18nM). However, unlike those three, RE-021 has much, much less affinity towards ET-B (particularly with respect to clazosentan and tezosentan). So it does seem that RE-021 could be striking that right balance between affinity towards ET-A (efficacy) and lack of affinity towards ET-B (safety). Obviously, this all still remains to be seen in the clinic.

All told, given the ~$60M market cap, I'm thinking about a position here. I particularly like the fact that Martin mentioned at Roth that the second drug for PKAN, RE-024, will enter the clinic later this year. RTRX will most likely need to dilute later this year but I like the fact that Martin has a big stake and the last offering was fairly small.

Do you know what type of reduction in Proteinuria Retrophin think will be clinically meaningful?

I don't know the answer here.