One of the issues could be that you cant know without studies that it wont harm you as the disease progresses past a certain point
I think this is why you cant get the antibody infusion past a certain point. There is some evidence it could harm you.
If I am hospitalized with a vent shoved down my throat, I'll take that chance. I'd try anything under the Compassionate Use provisions. But it would take an agreeable family member to make things happen depending on how far along you might be. Sounds like an Advanced Directive to one's Health Care Surrogate might be in order. Get the ducks aligned before the need. Time to update some paperwork.
Kind of ironic in our litigious world that “it might harm you and you will live” is worse than letting someone die without trying.