Blame the FDA and... realize biology is a fucking mess. Specially with novel therapeutic vectors. We've rushed before in clinical trials that have maimed and killed humans.

I remember one of those, guess what happened? The field was frozen for almost 10 years. Nobody wanted to put money or political face on and have the same thing happen again.

So it takes years and years of mountains of paperwork and money and tests and more paperwork to prove safety first and then efficacy. I'd rather do most of these by compassionate use, but... I'm not in charge.