Phage display is a technique that can be used to screen for antibodies (or their fragments) that bind to a specific target antigen. DNA sequences encoding the antibody fragments are inserted into bacteriophages, which then display (that is, express) the antibody fragments on their surface. When the resulting phage library is exposed to the immobilized target antigen, phages that express antigen-specific antibody fragments are retained. MedImmune sued Novartis, alleging that the methods used to produce ranibizumab, an antibody fragment that targets vascular endothelial growth factor (VEGF), infringed on MedImmune's phage display patents.
Specifically, MedImmune alleged that the process by which ranibizumab was produced infringed the patent claim that described the production of phages that express binding molecules, which have “a range of binding specificities” to different antigens on their surface. But the Court agreed with Novartis, holding that because the production of ranibizumab started with an antibody that was specific to the target antigen of interest (that is, VEGF), which was followed by subsequent steps — that involved phage display — to identify antibody fragments with improved affinity, the manufacture did not involve the production of phages that had a range of binding specificities. So ranibizumab did not infringe on the patents.
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