A biopharma company looking to expand its production capabilities needed a way to improve its quality while increasing its throughput. Previously, production batches were processed within cleanrooms which would then be decontaminated between each batch. It was found that a move from cleanrooms to processing isolators could offer the increase in production the company was looking for as long as the sterilization cycle time could be kept short enough. In this case, the company wanted a cycle time of less than two hours. Chlorine dioxide gas was explored to see if either could fulfill their requirements of achieving a 6-log sporicidal kill in less than two hours. Due to the nature of the product, this had to be accomplished in the presence of a potentially heavy biological load. Testing found chlorine dioxide gas able to meet the requirements, and the company switched to processing batches within isolators. The next step was validating the chlorine dioxide decontamination process.
Cycle development and validation
Cycle development for the chlorine dioxide gas decontamination cycles was performed by placing biological indicators (BIs) throughout the isolator. Biological indicators consisting of over one million geobacillus stearothermophilus spores impregnated on paper and wrapped in Tyvek were used. Cycle development started with the suggested cycle of 65% relative humidity, held for 30 minutes of condition time, followed by a chlorine dioxide gas concentration of 5 mg/L held for 30 minutes. Gas concentration is accurately monitored and precisely controlled utilizing an integrated UV-VIS spectrophotometer. This ensures that each cycle is repeatable by completing a cycle only when all process parameters are met. Some of the processing isolators had different configurations and layouts, but the suggested cycle was used for all isolators at the onset of cycle development. Both the processing isolator and the packaging isolator have two glove ports and are approximately 100 cubic feet in volume.
The initial cycle proved to be effective; however, multiple cycles were tested and the final cycle chosen to be written into their procedure was 65% relative humidity, held for 10 minutes of condition time, followed by a chlorine dioxide gas concentration of 5 mg/L held for 50 minutes. It was decided to shift some cycle time from the condition step over to the exposure step as a conservative measure to increase the contact time of the gas. This chosen cycle provided an 85 minute overall cycle time, inclusive of aeration where the gas is removed from the isolator. The same cycle was used in all of their isolators, as the configuration did not affect the efficacy of the decontamination cycle.
Validation of the decontamination cycle then took place by verifying efficacy of three consecutive cycles in each isolator. The isolators consisted of a main chamber, an airlock, and a fill location. Approximately 40 biological indicators were placed in the production isolator. For the packaging isolator, 25 BIs were placed in the packaging main chamber, 13 in the airlock, and 21 in the mix/fill section in order to test the efficacy of the cycle throughout the isolator. They were placed in various horizontal and vertical planes as well as in the hard to reach sections of the manufacturing tools that are located inside the isolator.
As part of the PQ, three decontamination cycles were performed in the over the course of one day. Once the cycles were complete, the biological indicators were dropped into growth media under aseptic conditions and incubated for seven days. BI controls were used as well, with non-exposed biological indicators being dropped into growth media as a means of ensuring that the biological indicators were viable. This was then duplicated until three validation cycles had been performed in each isolator. Upon completion of the incubation period, all BIs exposed to chlorine dioxide gas during the validation cycles were found to exhibit no growth within the media, providing validation of the chosen decontamination cycle. Control indicators were found to exhibit biological growth within the media after a period of 24 hours.
The biopharma company has been producing product and sterilizing the isolators for over one year. Both the switching of the production process to isolators as well as the actual sterilization of the isolators has been successful. Sterilization times are what they were planned. The process was so successful that additional isolators are in the works.
Kevin Lorcheim received his B.S. in Mechanical Engineering from Rutgers University. He has been with ClorDiSys Solutions Inc. of Lebanon, N.J. since 2006 as an engineer, helping to design and launch new products and solutions for contamination control. www.clordisys.com
This article appeared in the July/August 2014 issue of Controlled Environments.