CANCER HIGHLIGHT | Potency Assay for Bispecific Antibody Constructs

Blog Highlights:

• What is a bispecific antibody?
• How is a potency assay for a bispecific antibody for cancer immunotherapy performed?
• How can MarinBio help you with cell-based assays?

Bispecific antibodies typically link killer T cells to a tumor target resulting in killing of the target.  A common form of a bispecific is the Fab₂ binding site for the CD3-antigen binding site on killer T cells, and a Fab2 binding site for a tumor antigen. Fab2 is the portion of an antibody, comprised of part of the light chain and part of the heavy chain held together by a disuflfide bond that imparts the specificity of the binding.

We develop potency assays for bispecifics with extreme precision and accuracy in EC50 values.  The killer cell is a cytotoxic T cell line, avoiding variation with different donor blood T cells. The target cell is typically a cancer cell prelabeled with a fluorescent dye. Killing is measured by release of the dye into the supernatant.  The assay uses about 3 killer T cells to 1 target cell and the reaction is complete in 2-3hr.

Example, T cell killing of CD33 bearing myeloid leukemia with a bispecific antibody, two Fab2 regions linked together.

The time course of the killing is shown below with ten concentrations of bispecific construct, all conditions in triplicates, in a 96 well plate. There was almost complete killing at 120 minutes of coincubation with the top concentration of the bispecific construct.

Accuracy of the method is shown below.  Ten concentrations of fresh Reference Standard and one and two times free/thaw material were tested, all conditions in triplicate, in a 96 well plate.  The graph shows that the material is stable to two freeze / thaws and that the method is highly precise and accurate.

Marin Biologic Laboratories provides solutions in protein/gene analytical and biological assays and other services for our many clients, with or without GLP/GMP conditions. Marin Biologic develops, validates, and performs a variety of assays for

• GMP potency assay for lot release, GLP assays
• ELISA, PK and PD studies, immunogenicity (Anti-Drug Antibodies), neutralizing antibodies
• Humoral and cellular immunity assays. 
• Cell-based assays, proliferation and toxicity assays
• Molecular, Biochemical and Biology services, protein production, purification, enzyme assays, cloning, transfections
• Radioactivity procedures and analysis. 

Marin Biologic Laboratories is a contract laboratory for pharmaceutical and biotech industries. We have been operating for over 25 years and we take pride in our science as well as the quality of our communication. We specialize in development and validationof cell based assays and immunoassays as well as enzyme assays, protein and RNA expression, transfections, protein purification, and radioactivity methods.  We are FDA inspected.  We would like to help meet your requirements in a timely and cost effective way.

We have developed and performed a variety of human and murine cellular immunology assays ex vivo, macrophage/monocyte activation, lymphocyte proliferation and cytokine production and cell surface markers (FACS analysis), NK, ADCC, cytotoxic T lymphocyte (CTL), complement killing, etc.  Our niche is to take projects encompassing several fields such as biochemistry, molecular and cell biology and bring them to a rapid and successful conclusion.  Companies with seemingly intractable problems of imprecision in bioassays, detecting low levels of protein analytes, or interference by blood and other biological matrices have turned to us for solutions.

Our staff has developed and validated ELISA and bioassays for numerous Ab projects including Fab, Fab2, bispecifics, PEG conjugates, and Antibody-Drug Conjugates (ADC). ).  This includes potency assays for drug at IND, clinical phase 1, 2 and 3, registration and marketing stages and ELISA for PK/TK in animals and humans at these stages.  We also validate host antibody to drug and neutralizing antibody assays.