An Ugly Reality, Failed Batches

Have you ever wondered how your batch success, or failure rate compares to others in the industry?

Sooner or later everyone involved in bioprocessing faces the ugly reality of a failed batch. Whether its a small bench scale bioreactor batch testing a new process parameter, a pilot scale bioreactor being used to generate product for early downstream testing and analytical development or a manufacturing scale bioreactor being used to produce product for use in an important clinical trial, a failed batch can really ruin your day.

The 5th Annual Report and Survey of Biopharmaceutical Manufacturing Capacity and Production was published earlier this year and some of the findings are summarized in a recent article in Genetic Engineering News. Its a short article that is worth reading to gain some overall perspective on industry trends but I thought I would highlight a couple of main points here.

The results of the survey indicate that the overall total batch failure rate among 434 biopharmaceutical developers was 7% and that the difference in failure rate was fairly similar between small and large scale facilities. For facilities operating at scales of less than 1,000L the failure rate was 6.6% while for those operating at scales larger than 1,000L the rate was 7.6%.

The article in GEN also listed the top four causes of batch failures for both large and small-scale facilities.

Large-Scale (1,000L or greater)

1. Contamination
2. Operator Error
3. Equipment Failure
4. Failure to meet specification

Small-Scale (less than 1,000L)

1. Material Failure
2. Equipment Failure
3. Product Cross-contamination
4. Contamination

I would imagine that with the adoption of disposable systems for both upstream and downstream applications the incidence of product cross-contamination should start to decline.

The fact the operator error was the second leading cause of batch failures in larger scale facilities indicates the importance that proper employee training can have on overall success rates.

Update: See the September 2008 issue of BioProcess International for another article summarizing the findings from the survey mentioned in the above post... slightly more detail is provided in this article.

On-Line Cell Counting

Yesterday I wrote about automated cell counters for off-line determination of cell density and viability in bioreactor cultures and today I thought I would briefly expand on the topic by discussing instruments for on-line biomass determination.

Without an on-line biomass probe one would typically sample a bioreactor once or twice a day, which during a two week culture would mean having anywhere from 14 to 28 data points for cell density and viability. While this has been sufficient to allow for the development of numerous successful processes, having a continuous stream of cell density data from an on-line probe could provide a greater level of insight into how a process is running without having to remove a large number of samples from the reactor and thereby increasing the risk of contamination.

In a process development setting, an on-line probe could provide real-time data about how a given process change impacts cell density and viability. It could be feasible to incorporate the data into a feedback control loop that could make process changes (e.g. feed rate, pH setpoint, temperature, etc.) based on changes in cell density or viability.

In a manufacturing setting, having a on-line cell density probe could help mitigate contamination risk by reducing excess sampling for cell density counts. Additionally on-line biomass probes could help a biotech company in their efforts to implement their process analytical technology (PAT) initiatives.

There are two main classes of instruments that can be used for on-line biomass determination: capacitance-based probes and optical-based probes. Aber Instruments and Fogale Biotech both manufacture capacitance-based biomass probes and Optek manufactures an optical-based probe. (There may be other manufacturers of these types of instruments but these are the first ones that come to mind.) The primary difference between the two classes of probes is that the capacitance probes measure only the number of viable cells in a culture while the optical probes measure the total cell density.

When culture viability is close to 100% both of these classes of probes should be suitable for biomass determination but when the culture viability begins to decline, a capacitance probe should be better able to detect the decrease in viable cells than an optical probe.

Are We Missing Something?

Long ago when I first started working with mammalian cell cultures performing cell counts of bioreactor samples was a bit of a tedious process. You had to stain the sample with Trypan blue, load the hemacytometer slide and place it under the microscope and then proceed to tally the number of live and dead cells contained within a certain number of squares on a grid pattern that was etched onto the slide. One important element of this procedure was to make sure and choose the correct dilution factor for the sample so that you wouldn't load a sample on the slide that had so many cells that it was unreasonable to count. Hopefully, if your cell culture process is doing well, the number of cells in the bioreactor are increasing each day and you would therefore need to increase the dilution factor of your sample to account for this. (Typically the cell density in the reactor plateaus at a point in the culture and further increases in dilution factor become unnecessary.) In our group, we would typically perform two cell counts for each bioreactor sample and average the results to obtain the total and viable cell density for the culture. This process wasn't so bad when we had only a few bioreactors in the lab but over time more reactors were added and the burden of counting cells increased. At its most challenging, it could take a person between 1-2 hours to count samples from 8 bench scale bioreactors. It could be painful!

Back in 1999, Innovatis, a German company, developed an automated cell counting instrument known as Cedex that is based on the same trypan blue dye exclusion method that is traditionally used to count mammalian cells. When I first saw the Cedex in mid-2000 I was a bit skeptical that it could really do a good job counting cells but after working with the instrument for a bit and after conducting a head-to-head comparison between it and a hemacytometer, it became clear that this was a new, more efficient way, of counting cells. Because it was an automated instrument this meant that all cell counts would be handled in exactly the same manner; no more concerns about dilution errors during sample preparation; no more concerns that an operator becomes less efficient on their 15th cell count compared to their first cell count. Additionally the instrument was capable of counting a greater number of cells per sample and could could also provide information on cell size distribution. With the Cedex a cell count took only about 2-3 minutes per sample including cleaning. This meant we would count samples from 8 bioreactors in about 30 minutes!

There are now additional automated cell counters available. Beckman Coulter has developed the Vi-Cell series of counters and Nova Biomedical has their BioProfile Flex which is an automated modular analyzer for cell culture analysis that has a cell density / cell viability module.

Having these automated methods of cell counting has certainly helped streamline the process of monitoring cell cultures and improved the ability of scientists and engineers to develop improved processes. The only minor downside to the advent of these remarkable instruments is that people who are new to the bioprocess industry may never have to learn how to perform cell counts by hand.

When using a microscope and a hemacytometer to count cells we would also have the opportunity to look at the condition of the cells over the duration of a culture and observe changes in cell morphology. These observations, along with the cell count data, would provide overall "picture" of how the cells in a culture are doing. Although I would not give up the benefits that automated cell counters have added to bioprocess development, are we going to forget to look at the cells under a microscope anymore?

cGMP for Phase 1 Investigational Drugs

Back in July of this year the FDA issued a new direct final rule and associated guidance document that exempts most Phase 1 investigational drugs from complying with cGMP's. It is worth reviewing these documents to gain insight into the guidance that a company is not necessarily required to comply with all sections of 21 CFR parts 210 and 211 for products manufactured for a Phase 1 clinical trial. 

The FDA still retains oversight of all drugs used in Phase 1 trials and will continue to review the CMC section of each IND application to ensure that product safety and quality requirements are met.

This new rule will not likely change how large drug manufacturers approach how they produce products for Phase 1 trials since they likely already have the facilities and quality procedures in place for full GMP compliance. For small start-up organizations this new change may help streamline the drug development process.

For more on this topic see this piece written by Laura Bush the editor of BioPharm International magazine.

BioProcess Conferences

Two bioprocess related conferences worth bringing to your attention -- the American Chemical Society's 236th National Meeting in Philadelphia which just ended on August 21st, and the upcoming BioProcess International Conference & Exhibition which is being held from September 23-26th in Anaheim, CA.

Even though the ACS meeting is over, you can still check out the technical program for the Division of Biochemical Technology (and for all participating divisions for that matter) and review the presentation abstracts. Sometimes when attending conferences its tough to attend all of the presentations or view all of the posters that interest you. Its helpful to be able to look at the program, find the appropriate contact information and then email the presenters / authors and ask for a copy of their presentation. Even if you couldn't attend the conference in person, being able to contact the presenters and inquire about their work is a great way to stay current with the latest happenings in industry and academia.

The BioProcess International Conference has four tracks:

• Production & Economics
• Scaling Up from Bench Through Commercialization
• Cell Culture & Upstream Processing
• Recovery & Purification

After briefly reviewing the conference agenda, it looks like it has something interesting to offer just about anyone who works in the bioprocessing field.

Inaugural Post

Welcome to Bioprocess Buzz! This will be a blog where I will share various information that I find that relates to bioprocessing in the biotechnology and pharmaceutical industries.

A little about my professional background: I have worked in the biotech industry for over 16 years, the entire time in the bioprocess discipline. In my most recent position I worked for 13 years performing cell culture development work, including process optimization, technology transfer and project management.