A humanized transferrin receptor 1-transferrin model supports functional iron homeostasis and therapeutic delivery across the blood-brain barrier.

The transferrin receptor 1 (TfR1)-transferrin (TF) axis is central to iron homeostasis and represents a validated route for delivering biologics across the blood-brain barrier (BBB). We developed human-specific anti-TfR1 nanobodies (NewroBus) that exploit this pathway, but their lack of cross-reactivity with rodent TfR1 limits conventional preclinical testing. To overcome this, we generated knock-in rats in which the coding sequences of the endogenous Tfrc and Tf genes were replaced with their h...