I remember the interview in TLSR, that's what got me looking into the PRV program. I think RVX thought they could wiggle into a paediatric rare disease designation and then apply for a PRV via PNH. That was in 2015. Last year when I asked the company as to how that was going they said they had come up against some unexpected "challenges". If you are interested in the facts around PRV and orphan designation the FDA site and raps.org are good places to start.