Prevention of disulfide bond reduction during recombinant production of polypeptides

What is this patent about?

’869 is related to the field of recombinant protein production, specifically addressing the technical challenges associated with maintaining the structural integrity of disulfide-containing polypeptides. During the harvesting and purification of proteins like antibodies from host cell cultures, such as CHO cells, the mechanical stress of cell lysis often releases intracellular components into the media. This environment can trigger unwanted chemical reactions that compromise the protein's tertiary structure, leading to a loss of biological activity and therapeutic efficacy.

The underlying idea behind ’869 is that the unintended reduction of disulfide bonds during harvest is driven by an active thioredoxin enzyme system fueled by metabolic cofactors released from lysed cells. The inventors realized that the thioredoxin system, which requires NADPH generated through the pentose phosphate pathway and glycolysis, acts as a potent reducing agent in the harvested cell culture fluid. By targeting the availability of these reducing equivalents or inhibiting the enzymes themselves, the invention effectively halts the biochemical cascade that breaks the critical inter-chain and intra-chain bonds of the antibody.

The claims of ’869 focus on a method for preventing this disulfide bond reduction by air sparging the culture fluid following the fermentation stage. The independent claim specifically requires introducing air into either the pre-harvest or harvested culture fluid to maintain a dissolved oxygen (dO2) level of at least 10%. This physical intervention serves as a non-directed inhibitory measure that shifts the redox potential of the fluid, ensuring that the environment remains sufficiently oxidizing to counteract the enzymatic reduction process.

In practice, the invention works by continuously replenishing oxygen levels in the harvest tanks to deplete the supply of NADPH and G6P, which are essential for thioredoxin activity. While the patent describes various chemical inhibitors—such as gold complexes, metal ions like copper sulfate, and EDTA—the claimed implementation utilizes air flow to maintain an oxidizing state. This approach is particularly effective in large-scale manufacturing environments where mechanical lysis is high, as it provides a scalable way to protect the antibody without necessarily adding complex chemical reagents to the mixture.

This method differs from prior approaches by identifying the specific enzymatic root cause of bond instability in the harvest fluid rather than just treating it as a general degradation issue. By maintaining a specific oxygen saturation threshold, the process prevents the conversion of NADP+ to its reduced form, thereby starving the thioredoxin system of the energy it needs to attack the antibody's disulfide bridges. This ensures that the resulting harvested cell culture fluid contains intact, properly folded antibodies suitable for subsequent high-purity therapeutic applications.