> But there are areas where there is no reasonable way to replace animal testing. Two specific examples for which animal testing seems essential: 1. Predictio

> But there are areas where there is no reasonable way to replace animal testing. Two specific examples for which animal testing seems essential: 1. Prediction of nanoparticle clearance from in vitro studies does not correlate with clearance in vivo. If you want to know where the particles go (do they hit the target organ/tumor at all? do they ever leave the body?) you need to do in vivo testing. 2. Adolescent idiopathic adolescent scoliosis can now be treated by vertebral tethering and growth modulation, not just bracing or fusion. Zimmer Biomet Spine recently had a device approved to deliver this treatment [0]. Exploratory research to establish cause-effect relationships between tethering and growth modulation depended on large animal models. It's not good to accidentally make a patient's spine worse because you don't understand what's going on. [0] https://www.fda.gov/medical-devices/recently-approved-devices/tethertm-vertebral-body-tethering-system-h190005 https://www.fda.gov/medical-devices/recently-approved-device...