I get that it is unlikely to work and even if it did, the damage is likely irreversible but at least then the parents could have some closure. There must be a reason this isn't an option?? Other than needing emergency FDA approval.
Well I don't know! I'm not a doctor, I havent seen his case notes in person, but here's a vague guess, if you'll let me have a stab at it?
The medication can only be given to him while he's alive
To keep him alive they need to keep ventilating and supporting whatever other organs they are artificially supporting
They would have to continue doing this for the duration of the treatment
It is taking invasive painful (usually) equipment to keep his organs supported for all this time.
The longer he is on a breathing tube the more likely he is to develop a chest infection and dye painfully whilst on life support, as opposed to having the machines taken out and dying peacefully
Just because the meds go in his feed tube, do not mean they're harmless, the other interventions which they are using now to keep him alive do a lot of harm, carry a lot of risk.
The treatment might have side effects. Just because it's not delivered via a hurty needle doesn't mean it won't cause internal pain