Pay tends to be below industry average.
No clear path to promotions or even interest from managers for promoting from within (many external hires for roles I was more that qualified for)
Internal jobs you apply for (I applied for roughly 20) will just ghost you. I got no replies from every job except for one. I interviewed for 1 job out of the 20 or so I applied to and guess what, after the interviews, ghosted. I spend over a month trying to get a response from someone on whether or not I got that job.
Honestly Amgen can be a great stop and is a respected company, but unless you are willing to wait 10 years to move up, better to just do 2-3 years then move on to another company.