This month, I will address some biotech applications that are PAT-friendly and will save loads of lab and sampling time. A number of years ago (~1988), I suggested that inserting a Near Infrared (NIR) probe into a fermentation vat would give some great information about the reaction’s progress. I was informed (by a biochemist) that the reactions were both in water and far too complex for NIRS. I pointed out that, for a simple fermentation, you needn’t know all the chemicals in “the pot,” but merely needed to monitor the spectrum. When it stopped changing, the reaction had stopped and was either complete or needed feedstock added. Sounded too simple, I guess. Plus, unlike mid-range Infrared (IR), NIR is merely annoyed by water, not completely absorbed by it.

One early example of a “simple reaction,” the fermentation of E. coli (Escherichia coli) was published1 in 1996. It shows the validation of a NIRS method, wherein a simple probe was installed in a fermentation tank. The data were gathered and equations generated for the measurement of acetate, ammonium, biomass and glycerol, simultaneously, in real-time. A second article in 20002 is a good review of the state of the art at that time.

A later study, performed by some applications chemists at NIRSystems (now Metrohm) on CHO (Chinese Hamster Ovaries) cell cultures developed an equation for the real-time testing of glucose, ammonia, titer, methionine, lactate, glutamate and glutamine with a single spectrum.

Should a company not wish to change to a RTR (real-time-release) paradigm or are constrained by the product owner (“client” to contract manufacturers) to current analytical techniques, at a minimum, using NIR or Raman would indicate times to withdraw samples for lab testing. Why is that important? Simply put, biological reactions are not all the same.

Depending upon the vessel, temperature control, initiator stock, feeding rates and such, the reaction could take +/- 100% of the time indicated on the manufacturing instructions. Taking unneeded samples places a burden on the lab, costs money (reagents, etc.), and is one more chance for the process to be contaminated and/or an operator being exposed to live bacteria. At a minimum, use process analytical technology (PAT) techniques to augment current practices.

A PAT vs. GMP reality check

This lesson applies to solid dosage forms as well and biologicals. Several years ago, while I was consulting at a medium-sized pharma company, I had the occasion to chat with a member of the consulting group that was performing an audit (at the company’s behest). Over coffee, we traded “war stories” of some of the strange things we saw over the years. His example was, to say the least, eye opening.

They had audited a company to see if the sources of OOS (out of specification) batches could be determined. They did a survey of failing versus passing lots and who was the operator for each. A cursory correlation of the data showed that, in almost every case where a lot failed, a new/junior operator was doing the work. Before simply declaring that the company needed more or longer training periods, they held one-on-one meetings with all the operators. What they found was pretty telling.

It seems that there were “flaws” in the master manufacturing formula (MMF) that the older, more experienced operators knew and “sort of” fixed, on the fly. Tweaking the process is, of course, verboten under cGMP regulations, so they never wrote down the changes nor did they notify management of the problem. They assumed that, since it was an older product, the management would be fain to open a can of worms with an ANDA. The failures? That was the “newbies” being good soldiers and strictly following the MMF, errors and all, leading to numerous failures.

Need I say the what the older/experienced people were doing was precisely what we call PAT! PAT, in its simplest form is monitoring and modifying each step to generate a product with approved physical and chemical properties, based on what was determined to be “a quality product.” 
 
References

1.  NIR Spectroscopic Determination of Acetate, Ammonium, Biomass, and Glycerol in an Industrial Escherichia coli Fermentation” J.W. Hall et al., Applied Spectroscopy, 50 (1), 102 (1996)
2. “Near-Infrared Spectroscopy – Key to Improved Biopharmaceutical Manufacturing from Animal Care Culture?” J. Crowley et al., European Pharmaceutical Review, 5 (3), (2000).

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Emil W. Ciurczak
DoraMaxx Consulting

Emil W. Ciurczak has worked in the pharmaceutical industry since 1970 for companies that include Ciba-Geigy, Sandoz, Berlex, Merck, and Purdue Pharma, where he specialized in performing method development on most types of analytical equipment. In 1983, he introduced NIR spectroscopy to pharmaceutical applications, and is generally credited as one of the first to use process analytical technologies (PAT) in drug manufacturing and development.