Combinatorial screening of proteins
The advancements in genomic research and increased numbers of sequenced genomes require expression systems that allow fast
production of the proteins under investigation. Cell-free expression systems can provide a useful tool for rapid screening
and analysis of protein function, which is important for protein-drug discovery and development. DNA molecules can be amplified,
transcribed, and translated in microplate wells and the expressed protein can be assayed immediately (15). Recently, HTS in
a cell-free wheat germ system led to the discovery of a novel malaria vaccine candidate (16). Finally, the linear scalability
allows proteins identified in display-based selections and HTS to be immediately scaled for production of multiple gram quantities,
thus avoiding the delays and challenges of conventional mammalian cell line development.
Currently, cell-based expression technologies exhibit several limitations with respect to protein production at all phases
of the drug discovery and development pipeline. Rapid production of proteins with novel chemical modifications, such as ADCs,
are particularly challenging. E. coli-based cell-free protein synthesis systems, however, provide robust, rapid,and scalable protein production. The E. coli-based OCFS system, in particular, allows rapid and multiplexed production of various difficult to express proteins and opens
the unprecedented ability to explore therapeutics beyond the 20 amino acids that define today's proteins (17). The OCFS, combined
with rational protein design and the focused use of libraries of nnAAs, allows for rapid exploration and identification of
protein therapeutics, moving from the exploratory stage to clinical scale-up on an unprecedented, rapid timescale.
Conclusion
Growing demand for new and better biopharmaceuticals has led to sophisticated advances in protein synthesis that now allow
for:
- Rapid production of target proteins, including those that are difficult to express in cell-based expression systems
- Straightforward scalability of protein expression from HTS to commercial levels
- Combinatorial screening of many proteins to identify and optimize drug candidates
- Introduction of site-specific chemical modifications, including nnAAs into proteins to improve pharmacological properties
These new approaches to protein expression will revolutionize the development of biopharmaceuticals, and open up the possibility
to create drugs that were previously inaccessible, and even unimaginable until now.
Trevor Hallam* is chief scientific officer and Christopher Murray is vice-president of research, both at Sutro Biopharma, 310 Utah Ave, Suite 150, South San Francisco, CA 94080, thallam@sutrobio.com
.
* To whom all correspondence should be addressed
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