If by chance Enbrel patent do not hold. They would rather get rid of the INBU than have Otezla. AZ means that they gain access to MedImmune assets and Roxa from Fibrogen/AZ would be added to Neph business. Neph isn't sexy but not many companies are in it and Amgen holds a strong position.
The winner here in this merger for Amgen is gaining TSLP and bolstering oncology with BTK which fits into hem/onc business that Amgen was hoping to be a leader in. CTGF antibody adds to onc and respiratory if Amgen is able to acquire TSLP full rights with a merger with AZ.