Humira patent expires in about 3 years and all revenue/income from this drug vanishes soon. ABT is smart to deal with this worry now and meanwhile unloads its debt by separating ABBV. Humira probably could not make as much as unloaded ABT debt. This is like selling Humira now for a very good primum. On the other hand, ABT will put time and money on other part of its business that is much more stable and has long term income.
"all revenue/income from this drug vanishes soon" There have been many analyses of this situation, and you apparently haven't read any of them. The sudden cessation of revenue following patent expiry that you describe is what happens with small molecule pharmaceuticals that are easily synthesized and easily developed as generics. With a biological such as Humira, the path to approval of a generic is much more complex. There will inevitably be erosion of revenue from Humira - competitors are on and coming to the market - but that's a different scenario - and it will also serve to discourage development of generics for Humera. The longterm success of ABBV depends on its pipeline, which at the moment is undefined.
When SLXP main drug went generic, it became a penny stock. However, its good management rebuilt the company in pat few years.
Unfortunately, the whole ABBV pipeline cannot compensate the loss of Humira revenue even you assume 100% success of the pipeline.
ABT probably calculated the future revenue and income and got scared from Humira future.
You have no idea what your talking about....Humira has legs way past the expiration of 3 years. Do the research. Biosimiliars are probably not even coiming to the US anytime soon plus ABBV has one of the best pipelines in the Pharma industry. Great long term investment!!