Also of interest that none of the buyers were their corporate partners
There are two reasons for this:
1. Japanese pharmas didn't have many partnership in oncology with US companies before. So, they didn't have the chance to buy their partners from the past. They have a few partnership now.
2. There are very few high quality non-partnered oncology drugs out there. Japanese pharmas paid premium prices for these buyout, so the quality they chose were quite high.