Looking at PTCT royalty agreement with Royalty Pharma. Doing some rough estimates it looks like to me it is designed to give Royalty Pharma it's 43% on the first 20b in sales of the PTCT drug. At that point the royalty agreement tops out and royalties revert back to PTCT.
Royalty Pharma has been very good at these agreements. I believe they are being conservative in their own estimates of the potential sales of the PTCT drug and how soon those sales would reach 20b. The sooner they do so the quicker Royalty P gets there money and the better the return on investment for them.
Looking at this agreement I'm left with the feeling that for Royalty Pharma to be anywhere near right in their analysis, before paying 650m for these rights, the PTCT drug has to be HUGELY successful. So much so that I don't see how it doesn't cut into spinraza sales by a large amount. It will be interesting to see how this plays out.