Improved secretion of recombinant human IL-25 in HEK293 cells using a signal peptide-pro-peptide domain derived from Trypsin-1.

OBJECTIVE: To compare the effects of human Trypsin-1 signal peptide and pro-peptide on the expression and secretion efficiency of human Interleukin-25 from mammalian cells. RESULTS: The signal peptide and combined signal peptide-pro-peptide sequence of human Trypsin-1 improved the secretion of human IL-25 from 1.7 to 3.2 µg/ml and 1.7 to 8.2 µg/ml, respectively. Deletion analysis identified the minimal Trypsin-1 derived secretion domain that maintains improved human Interleukin-25 production and secretion. The presence of Trypsin-1 pro-peptide sequence does not affect the function of secreted human Interleukin-25. CONCLUSION: The Trypsin-1 signal peptide-pro-peptide sequence increased human IL-25 expression and secretion in mammalian cells by fivefold.

'In-Format' screening of a novel bispecific antibody format reveals significant potency improvements relative to unformatted molecules.

Bispecific antibodies (BsAbs) are emerging as an important class of biopharmaceutical. The majority of BsAbs are created from conventional antibodies or fragments engineered into more complex configurations. A recurring challenge in their development, however, is the identification of components that are optimised for inclusion in the final format in order to deliver both efficacy and robust biophysical properties. Using a modular BsAb format, the mAb-dAb, we assessed whether an 'in-format' screening approach, designed to select format-compatible domain antibodies, could expedite lead discovery. Human nerve growth factor (NGF) was selected as an antigen to validate the approach; domain antibody (dAb) libraries were screened, panels of binders identified, and binding affinities and potencies compared for selected dAbs and corresponding mAb-dAbs. A number of dAbs that exhibited high potency (IC50) when assessed in-format were identified. In contrast, the corresponding dAb monomers had ∼1000-fold lower potency than the formatted dAbs; such dAb monomers would therefore have been omitted from further characterization. Subsequent stoichiometric analyses of mAb-dAbs bound to NGF, or an additional target antigen (vascular endothelial growth factor), suggested different target binding modes; this indicates that the observed potency improvements cannot be attributed simply to an avidity effect offered by the mAb-dAb format. We conclude that, for certain antigens, screening naïve selection outputs directly in-format enables the identification of a subset of format-compatible dAbs, and that this offers substantial benefits in terms of molecular properties and development time.