xB3 is a peptide that binds to the LRP1 receptor. The LRP1 receptor is highly/densely expressed at the BBB. Other technologies, such as those that target the transferrin receptor (TfR), are at a disadvantage because the transferrin receptor is not as highly/densely expressed at the BBB. More LRP1 at the BBB equals more doors. Less TfR at the BBB equals less doors. This is an oversimplification of the process, but I am trying to explain the analogy to you. The number of doors (receptors at the BBB) is limiting for crossing the BBB. So the more doors available, the more cargo that can cross. There are also some nice videos on the BiOasis web page that you might want to check out if this concept is hard for you to grasp.

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