Primrose Bio presents this scientific poster at PEGS Europe 2026. Authors Jeff Allen, Nathaniel Howitz, Elizabeth Orchard, Michael Bacica, Mathew Samano, Russell Coleman and Diane Retallack describe how the Pfenex Expression Technology® platform supports preclinical VHH-ADC development through site-specific non-canonical amino acid incorporation in Pseudomonas fluorescens, with production titers of about 15 g/L at 2 L fermentation scale.
ABSTRACT:
Amber suppression technology has matured over the past 25 years, enabling incorporation of non-canonical amino acids (ncAAs) for site-specific conjugation and expanded therapeutic functionality. However, implementation has been limited by toxicity from off -target ncAA incorporation and substantially reduced protein yields at fermentation scale. We adapted an orthogonal aminoacyl-tRNA synthetase/tRNA pair for Pseudomonas fluorescens, the basis of the Pfenex Expression Technology® platform, to overcome these limitations. The system successfully incorporated para-azidophenylalanine (pAzF) into a novel anti-GPCR VHH candidate while maintaining production titers of approximately 15 g/L at 2 L high-cell-density fermentation scale, comparable to its canonical counterpart. This approach preserves production economics while improving conjugation specificity and expanding protein functionality. We describe the identification of suitable conjugation sites, host-strain engineering, and scale-up to support preclinical in vivo evaluation.
