Industry perspective on a holistic container closure integrity approach to parenteral combination products.

Biologics are being developed more and more as parenteral combination products with drug delivery devices. The maintenance of sterility is imperative for such medical devices throughout their life cycle. Therefore, the container closure integrity (CCI) should, preferably, be built into the overall process, and not just demonstrated during the final testing of the combination product. The integrity is an important Critical Quality Attribute (CQA) and in the scope of specific considerations and studies during the combination product life cycle i.e., design robustness, assembly processes, storage (to end of shelf life), and shipping prior to patient use. The goal of this paper is to summarize an industry holistic approach to ensure CCI, for a combination product, and to build a scientifically based justification that Quality (in terms of CCI) is built into the overall process. Current analytical approaches used for characterization or Good Manufacturing Practice (GMP) CCI testing during combination product development will be described. However, the use of quality by design (QbD) during product development can reduce or eliminate routine batch level or stability testing of the combination product.

Biosynthesis of a fluorescent protein with extreme pseudo-Stokes shift by introducing a genetically encoded non-natural amino acid outside the fluorophore.

A novel kind of fluorescent protein relying on the intramolecular interplay between two different fluorophores, one of chemical origin and one of biological origin, was developed. The fluorescent non-natural amino acid l-(7-hydroxycoumarin-4-yl)ethylglycine was site-specifically incorporated into the recombinant enhanced cyan fluorescent protein (eCFP) at a permissible surface position ∼20 Å away from the protein fluorophore using amber suppression in Escherichia coli with an engineered cognate Methanococcus jannaschii tRNA synthetase. The resulting eCFP(Cou) exhibited almost quantitative intramolecular Förster resonance energy transfer (FRET) between its two fluorophores, showing brilliant cyan emission at 476 nm upon excitation in the near-UV at 365 nm (a wavelength easily accessible via conventional laboratory UV sources), in contrast to its natural counterpart. Thus, this fluorescent protein with unprecedented spectroscopic properties reveals an extreme apparent Stokes shift of ∼110 nm between the absorption wavelength of the coumaryl group and the emission wavelength of eCFP.

Engineering of an orthogonal aminoacyl-tRNA synthetase for efficient incorporation of the non-natural amino acid O-methyl-L-tyrosine using fluorescence-based bacterial cell sorting.

We describe a strategy for the rapid selection of mutant aminoacyl-tRNA synthetases (aaRS) with specificity for a novel amino acid based on fluorescence-activated cell sorting of transformed Escherichia coli using as reporter the enhanced green fluorescent protein (eGFP) whose gene carries an amber stop codon (TAG) at a permissive site upstream of the fluorophore. To this end, a one-plasmid expression system was developed encoding an inducible modified Methanocaldococcus jannaschii (Mj) tyrosyl-tRNA synthetase, the orthogonal cognate suppressor tRNA, and eGFP(UAG) in an individually regulatable fashion. Using this system a previously described aaRS with specificity for O-methyl-L-tyrosine (MeTyr) was engineered for 10-fold improved incorporation of the foreign amino acid by selection from a mutant library, prepared by error-prone as well as focused random mutagenesis, for MeTyr-dependent eGFP fluorescence. Applying alternating cycles of positive and negative fluorescence-activated bacterial cell sorting in the presence or in the absence, respectively, of the foreign amino acid was crucial to select for high specificity of MeTyr incorporation. The optimized synthetase was used for the preparative expression of a modified uvGFP carrying MeTyr at position 66 as part of its fluorophore. This biosynthetic protein showed quantitative incorporation of the non-natural amino acid, as determined by mass spectrometry, and it revealed a unique emission spectrum due to the altered chemical structure of its fluorophore. Our combined genetic/selection system offers advantages over earlier approaches that relied wholly or in part on antibiotic selection schemes, and it should be generally useful for the engineering and optimization of orthogonal aaRS/tRNA pairs to incorporate non-natural amino acids into recombinant proteins.