What is the 'billion dollar barrier' in delivering gene therapies?

Question

Accepted Answer

_Getting genetic cargo to a tumor, and not to the liver, has blocked the field for 15 years._

> Somehow you have to get this DNA to the tumor, and that's where lipid nanoparticles come in. You've probably already had them in a COVID vaccine. The problem is that within 10 minutes they're in your liver and out of your body, because the liver flushes out everything that doesn't belong. So to treat any cancer other than liver cancer you need a completely different lipid nanoparticle. For 15 years that has been called the billion dollar barrier.

Source: [Tomorrow's Medicine, with Cyriac Roeding (eCornell Keynote)](https://ecornell.cornell.edu/keynotes/view/K052126/)

Q&A, lipid nanoparticles

What is the 'billion dollar barrier' in delivering gene therapies?