Apitegromab Clinical Naked monospecific

Dagbay et al. Structural basis of specific inhibition of extracellular activation of pro- or latent myostatin by the monoclonal antibody SRK-015. (https://www.jbc.org/content/295/16/5404.short). Full-length human and murine Myostatin and GDF11 proteins were stably integrated into FLP-INTM T-REXTM 293 cells (Life Technologies, Carlsbad, CA) and expressed according to manufacturer’s instructions (Uniprot reference numbers: O14793, O08689, O95390, Q9Z1W4). Fully human anti-myostatin and anti-GDF11 antibodies were identified using a phage library displaying scFvs (single chain variable fragments)64. Separate antibody discovery campaigns were run using recombinant human proMyostatin, latent Myostatin, and proGDF11 for both positive and negative selection as appropriate to obtain antibodies with the desired binding profile. Antibodies were cloned and expressed using standard techniques, and binding profiles assessed on a FortéBio Octet QKe in various formats according to manufacturers directions (Supplementary methods). To potentially reduce immunogenicity, SRK-015 was generated from its parental version, SRK-015P, by introduction of five mutations in the variable domain. These antibodies are identical in the complementarity determining regions (CDRs) and have similar affinities and functional activity both in vitro and in vivo. muSRK-015P is identical to SRK-015P but contains a murine IgG1 constant region instead of a human IgG4 constant region. SRK-015, an optimized version of the best myostatin selective antibody identified in our screen (SRK-015P, P stands for “parental”). SRK-015 was engineered by replacing five resides in the variable domain of SRK-015P outside of the complementarity-determining region (the residues which contact the myostatin precursors). SRK-015 showed a slight increase in affinity for myostatin precursors.