Just for completeness here is a snapshot of the Royalty rate on Promcata (and some of their other drugs too) from Ligand's 10-K. They do one of the best jobs that I have seen of disclosing royalties!
Totally agree with you on LGND's royalty disclosures. Aside from watching Promacta and seeing if the drug ever gets a material ramp-up in revenues, LGD-4665 looks like one of the pipeline drugs to keep a close eye on given the high royalty rate potentially due LGND (14.5% of sales).