If I had to guess, I'd say very low single-digit royalties. PCOP royalties always ran low - typically 5% or so, and given this one wasn't even their compound the royalties would likely be even lower. I'd bet on closer to 3% than to 6%.
I think it's probably safe to say that ASTX will be potentially due double-digit royalties from AZN on their partnered BACE inhibitor given that, per the terms of their 2003 agreement (http://www.globenewswire.com/newsroom/news.html?d=37305 ), ASTX was to provide the initial series of small molecule inhibitors and apply their own high throughput X-ray crystallography and other tech to aid in the development of BACE inhibitors that AZN would fund.