Despite being the least abundant immunoglobulin G in human plasma, IgG4 are used therapeutically when weak effector functions are needed. The increase in engineered IgG4-based antibodies on the market led us to study the patent landscape of IgG4 Fc engineering, i.e., patents claiming modifications in the heavy chain. Thirty-seven relevant patent families were identified, comprising hundreds of IgG4 Fc variants focusing on removal of residual effector functions (since IgG4s bind to FcγRI and weakly to other FcγRs), half-life enhancement and IgG4 stability. Given the number of expired or soon to expire major patents in those 3 areas, companies developing blocking antibodies now have, or will in the near future, access to free tools to design silenced, half-life extended and stable IgG4 antibodies.

尽管是人血浆中免疫球蛋白G含量最低的一种，但当需要弱效应子功能时，IgG4仍可用于治疗。市场上基于工程IgG4的抗体的增加促使我们研究了IgG4 Fc工程的专利态势，即要求对重链进行修饰的专利。确定了37个相关的专利家族，包括数百个IgG4 Fc变异体，这些变异体专注于去除残留的效应子功能（因为IgG4s与FcγRI结合且弱于其他FcγRs），半衰期增强和IgG4稳定性。考虑到这三个领域已到期或即将到期的主要专利数量，开发封闭抗体的公司现在已经或将在不久的将来使用免费工具来设计沉默，半衰期延长且稳定的IgG4抗体。