Because research on real humans and real diseases is exceptionally difficult. Clinical research is notoriously expensive, results are likely to differ from non-human (preclinical) models, and trials take forever to get started, gather enough data, and get a drug actually reviewed and approved. So even when everyone is excited by the preclinical data, there are so many barriers (both scientific and non-scientific) that getting to an approved drug is pretty unlikely.
This sounds ethically questionable to me. I wouldn't rule it out entirely, but I'd want to see a well-reasoned argument, both technical and moral, that it was likely to lead to greatly reduced suffering for patients. Even then.... growing a body without a brain likely would not produce a model organism with predictive ability for human diseases.
I believe it could for a large number of tests. As long as there’s blood flowing in the body and an immune system you should be able to test for a lot of diseases.
As someone whose mother died to pancan, I could really care less on any of the brainwashed old farts in their churches or parliaments.
None of that matters to me or the people suffering from cancers, it’s al Knut a selfish obstruction attaching religion to the research material
A more practical option is using brain-dead humans for medical testing. This was discussed recently in the journal Science, using the term "physiologically maintained deceased". As they say, this "traverses complex ethical and moral terrain". (I've seen enough zombie movies to know how this ends up :-)
There are multiple examples in the literature of people leading perfectly ordinary lives whilst unknowingly having no more than 5% of the typical amount of brain matter (typically because of hydrocephalus). For example, https://www.science.org/doi/10.1126/science.7434023 from 1980.
The brain is indeed incredibly resilient - some kids with serious epilepsy get an entire hemisphere taken out - but which 5% you're left with matters enormously.
