TRANSLATIONAL SCIENCE
TRANSLATIONAL SCIENCE strain, which expresses fully human antibodies and is unable to produce mouse antibodies. Step 5: Fully human mabs are then produced using hybridomas. Antibody-producing B cells isolated from the XenoMouse® are used to produce a hybri doma. Hybridoma cells are created by a fusion of B cells with an immortal cell line, which then produce large quantities of identical, cloned antibodies [5]. BiTE® technology In many therapeutic situations it is essential to bring the treating antibody close to the target. This is especially the case in oncology, when antibodies are used to tackle disseminated malignant cells. One strategy aimed at harnessing the cytotoxic activity of T cells to target cancer cells is the use of bi-specific T cell engager (BiTE®) antibody constructs. Dr. Uwe Fraass ufraass@amgen.com BiTE® constructs are recombinant constructs that are designed to utilize the binding properties of the variable domains of two monoclonal antibodies. One of the two domains is specifically designed to target Tumor cell-specific BiTE® antibody Single-chain antibody 1 T cell-specific antibody V H V H V L V L Single-chain antibody 2 Linker EDUCATION V H , variable heavy chain; V L , variable light chain Figure 3: Engineering a BiTE® antibody construct from two monoclonal antibodies. 44
TRANSLATIONAL SCIENCE AMG 145 Evolocumab binds the PCSK9 catalytic domain – prevents simultaneous binding to LDL-R AMG 145 = Evolocumab • More LDL-R • Lower plasma LDL-C was shown to reduce the risk of MACE (major adverse cardiac events) [10]. Figure 4: Evolocumab is a fully human monoclonal antibody directed against PCSK9 (modified according to [8]). an antigen on the surface of a tumor cell and the other engages exclusively with a T cell specific antibody such as CD3 on the surface of the T cell (Figure 3). When the BiTE® antibody construct forms a bridge between the T cell and tumor cell, a reversible interaction between the cell types is formed, activating the T cell to promote target cell lysis. Perforin and granzymes are highly toxic molecules that are stored within the T cell. Upon T cell activation, these are released into the ‘cytolytic synapse’ and promote necrosis and apoptosis of the target cell. A single BiTE®-activated cytotoxic T cell can engage target antigen-binding regions of multiple cancer cells and initiate lysis. An advancement is under investigation to prolong the half-life of these molecular constructs. In 2016 the BiTE scFc-format developed at Amgen Research Munich was selected as AMGEN’s scaffold for all half-life extended BiTE programs to target a variety of disseminated cancers [6, 7]. Fully human IgG2 mab evolocumab Common for many indications of mabs and peptid-based treatments is the challenge of the protein amount production (scale-up) and the need to assure satisfactorily high protein plasma levels to neutralize the target in longevity. Such is notable along the suppression of the soluble PCSK9i protein (Figure 4). Only once the PCSK9i serum level is held below a required low threshold can the LDL-C receptor escape its PCSK9-mediated lysosomal degradation to bind more LDL-C. As a result, a rather high protein amount has to be incorporated in an s.c. injection volume which may pose challenges in terms of managing formulation and viscosity of the final product. This was successfully established with the fully human IgG2 mab evolocumab (Repatha®) which has been approved for the treatment of hypercholesterolemia and mixed dyslipidemia since 2015 [8, 9]. Mit freundlicher Unterstützung der Amgen GmbH References: 1. Evaluate Pharma; Citeline’s Pharma projects Pipeline Service, Jan 2015; vfa bio; Company information; BCG analysis; Medical Biotechnology in Germany 2015, BCG/vfa bio. 2. Available from https://www.amgenscience.com/immuno-oncology-research [Last accessed February 25, 2018]. 3. Macdougall I. Semin Nephrol 2000; 20: 375–81. 4. Ridker P et al. N Engl J Med 2017; 376 (16): 1527–39. 5. Jakobovits A et al. Nat Biotechnol 2007; 25: 1134–43. 6. Baeuerle PA et al. Curr Opin Mol Ther 2009; 11: 22–30. 7. Nagorsen D, Baeuerle PA. Exp Cell Res 2011; 317: 1255–60. 8. Chan JC et al. PNAS 2009; 106 (24): 9820–5. 9. Evolocumab package insert, 2017. 10. Sabatine MS et al. N Engl J Med 2017; 376: 1713–22. EDUCATION 45
