A recent trial for people who had failed both infliximab and humira, showed good results with simponi ( anti tnf mechanism is different). They can increase the usual dosing if needed.
The sub cutaneous route is less effective as you say, but the drug still enters the blood stream.
In my case, although I responded well to both humira, and then infliximab, neither was able to limit ongoing damage. I'm in a small minority of stubborn cases. Not many people fail every drug option.
The last option for treatment in those cases may be a stem cell transplant, though data is scarce. (In UC those cases get colectomies.)