Scientists at ImClone Systems, a wholly owned subsidiary of Eli Lilly & Co., are using Sartorius Stedim Biotech’s antibody polishing platform, Sartobind Salt Tolerant Interaction Chromatography (STIC) to improve the platform process, according to Kenneth Kang, Ph.D., a senior scientist and the head of the purification team in the bioprocess sciences department.
In order to process higher titer cell culture and meet higher production requirements, Dr. Kang and his team evaluated higher capacity protein A resin as well as alternatives. They also worked to integrate a higher capacity AEX polishing step while incorporating single-use devices, reducing the process steps and developing a buffer that was both “process- and product-friendly.”
Sartobind STIC is based on the use of a polyallylamine ligand covalently coupled to a double-porous membrane. This feature allows a higher flow rate and a shorter processing time, speeding the purification process and possibly reducing costs. In order to achieve the optimum conditions, Dr. Kang and his team set up a Sartobind 96-well plate configuration with a vacuum manifold. They tested four different human antibodies under a wide range of pH and ionic strength conditions in order to arrive at the most effective purification configuration.
The beauty of 96-well plates is that each well constitutes a micro-experiment, allowing a multidimensional plot to be assembled resulting in a fine-tuning of conditions that would not be possible through conventional macroscale evaluation. Considering each mAb has a unique physical-chemical profile, the approach followed by ImClone scientists facilitates the development of optimal purification conditions for each individual antibody.
The results of these screening and optimization protocols allowed Dr. Kang and his co-workers to design an alternative mAb polishing step, while reaching an acceptable process performance. A critical modification of the process was the elimination of the post protein A tangential flow filtration step.
“These newly improved modifications, including the developed polishing step, can be easily integrated into current mAb purification platforms if needed, especially for problematic candidates that do not behave well in the current production process,” Dr. Kang added.
John Milne, Ph.D., technical manager at Biouetikon, discussed his company's experiences with single-use technologies in the contract manufacturing of biologics. “In principle we would anticipate lower initial capital expenditures, shorter facility development time, lower validation costs and expenditure of time resources, and fewer constraints on the existing facilities layout,” Dr. Milne indicated.
Every step in downstream processing has separate challenges for single-use technologies. For buffer preparation, magnetically coupled stirrers allow the system to remain closed and sterile. Single-use bioreactors are now available in sizes up to 2,000 L. These are highly complex systems, as many parameters must be monitored in the course of a run.
“Many case studies have now shown that single-use stirred tank bioreactors can mimic reusable bioreactors in geometry, design, cell growth, viability, and specific product expression. The technology has advanced to the point that a completely disposable process manufacturing train is now possible.”
In membrane chromatography, single-use technologies can offer some dramatic advantages, such as 95% less buffer consumption, simple setup protocols, and higher throughput for trace impurity removal than traditional packed columns. There is no packing, no regeneration, and no re-use validation required.
However, concerns have been voiced regarding a number of aspects of disposable implementation, such as high cost and a lack of continued innovation within the industry.
There is also the issue of extractables and leachables, compounds that could migrate from the disposable unit into the biologic material being processed. A thorough evaluation of all the materials that the product comes in contact with is difficult in earlystage development, given time requirements and the rapid turnover of different artificial materials. It is an ongoing issue that will require analytical expertise and the use of a stringent risk-assessment framework.