I never did like the expression: “killing two birds with one stone.” Why would anyone want to kill a bird, let alone two!? I do like the idea of achieving two purposes with a single action, though, especially if that means helping fight illness and disease. One instance where this is being realised is in the development of advanced biologics, such as bispecific monoclonal antibodies. These molecules combine the specificity of two antibodies and simultaneously address different antigens or epitopes.
Blinatumomab was the first bispecific antibody to be granted US FDA approval back in 2014 for the treatment of acute lymphoblastic leukemia, with more than 40% of patients achieving complete remission. Since then we have seen numerous bispecific antibodies enter and progress through clinical trials. In the future we look set to benefit hugely from these ingenious molecules, in particular for the treatment of cancer and autoimmune diseases.
However, the production of bispecifics is challenging, especially within a single host cell where promiscuous pairing of the component can occur. A range of strategies to overcome the challenges of bispecific production are currently being explored within the field.
Following production, the engineering success of bispecific antibody molecules must be evaluated. Typically, the bispecific IgG component of the IgG mixture is quantified by Liquid Chromatography (LC) in conjunction with Mass Spectrometry (MS).
A study using native mass analysis of complex mixtures of antibodies demonstrated that the peak width of a single antibody charge state was narrower for an Orbitrap instrument compared to a Q-TOF instrument; this was shown to improve the quantification accuracy. What’s more, for the Orbitrap, the centroid of the peak was shifted to slightly lower and closer to the expected mass, due to more efficient desolvation and reduced adduct formation under native conditions.
More recently a robust high-throughput method for quantitative analysis of bispecific IgG preparations using novel online liquid chromatography, in conjunction with an extended mass range Orbitrap-based high resolution mass spectrometer, was developed. The method demonstrates exquisite sensitivity and has essential utility in evaluating bispecific antibody designs for the development of this important class of therapeutics.