Page:Amgen Inc. v. Sanofi.pdf/7

Rh atoms of the amino acids interact with each other, they create folds that result in complex three-dimensional shapes. Ibid. Scientists refer to an antibody’s intricate topography as its “tertiary structure.” Id., at 10.

An antibody’s structure does much to dictate its function—its ability to bind to an antigen and, in some instances, to block other molecules in the body from doing the same. “For an antibody to bind to an antigen, the two surfaces have to fit together and contact each other at multiple points.” Id., at 11. But just because an antibody can bind to an antigen does not mean that it can also block. To bind and block, the antibody must establish a sufficiently broad, strong, and stable bond to the antigen. See ibid. Different antibodies have different binding and blocking capacities based on the amino acids that compose them and their three-dimensional shapes. See id., at 11–12.

Despite recent advances, aspects of antibody science remain unpredictable. For example, scientists understand that changing even one amino acid in the sequence can alter an antibody’s structure and function. See id., at 14. But scientists cannot always accurately predict exactly how trading one amino acid for another will affect an antibody’s structure and function. Ibid. As Amgen’s expert testified at trial: “ ‘[T]he way in which you get from sequence to that three-dimensional structure isn’t fully understood today. It’s going to get a Nobel Prize for somebody at some point, but translating that sequence into a known three-dimensional structure is still not possible.’ ” Id., at 14–15.

While the immune system naturally produces an army of antibodies to protect us from various harms, scientists are now able to engineer antibodies to assist in treating diseases. Some of these lab-made antibodies target not foreign agents but the body’s own proteins, receptors, and ligands. “While naturally occurring in our bodies, these [proteins,