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May 15, 2009 (Vol. 29, No. 10)

Strategies for Removing Viruses from Cell Lines

Firms Pursue New and More Effective Methods in Their Efforts to Reduce Risk

  • Generic Data Use

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    Viresolve membrane is available in Micro, Modus, and Magnus formats, which are designed to fit in all processes and enable productivity gains in all production scales, according to Millipore.

    In February, the EMEA issued a final guideline governing the use of generic data in viral reduction. “The guidance can drive up the cost of studies,” because of the seemingly contradictory aspects contained within it, noted James Berrie, Ph.D., senior group leader, purification development, Lonza Biologics. Dr. Berrie will discuss the use of generic data in more detail at the upcoming “Viral Safety for Biologica” meeting.

    For example, he explained, the guidance allows the use of generic viral reduction data along with two spiking studies that show reduction. Reducing the scope of the study in this way reduces the cost by targeting process steps, “yet two studies don’t prove the mathematical principle.” Therefore, he said, “the scope of the study should be taken into account in the context of this new regulatory guideline, even though some aspects can appear contradictory.”

    Generic data has been used successfully as part of the license application by companies that have a downstream process that doesn’t vary, and also antibodies of the same type, Dr. Berrie elaborated. For contract manufacturers like Lonza, however, the challenges are different because, “we don’t have our own products and so don’t own the data.”

    Consequently, generic virus reduction data can be used by CMOs with repeat customers who have a manufacturing pipeline for a particular product. “That’s good for customers with a pipeline, but be very careful about variability in the process,” Dr. Berrie cautioned.

    He advised  performing a gap analysis focused on the process parameters to identify any variables that could affect virus reduction. That includes the downstream process variables as well as any fluctuations in the compound ingredients themselves.

    With customer approval, CMOs could, in theory, pool data to derive generic virus- reduction data that could then be used to benefit members of that pool, Dr. Berrie speculated. “Customers who hadn’t contributed to that pool would still have to perform wet studies. Having said that, Lonza has a downstream process for mAbs, so we know what reduction factors you could expect to see.”

    Such information, he explained, may be used as a starting point from which to base decisions to evaluate particular steps. The goal, Dr. Berrie explained, is to use generic virus-reduction data to allow researchers to focus their efforts on steps that have the greatest potential for virus reduction, effectively ignoring steps with reductions of one log or less.

    Lonza has found that the capacity for virus-reduction changes, even across such robust steps as a low pH hold and virus-reduction filtration. “In some process steps we see a reduction of virus removal with more dilution, making it less good.”

    The “Viral Safety for Biologica” conference will also include an update on cold ethanol fractionation from Herbert Dichtelmüller, Ph.D., director of virus validation of Biotest.

    Cold fractionation is an important purification method for organizations involved with the blood supply. “However, the European guidelines leave some space for interpretation, and some, not all, regulators in Europe believe that the steps of fractionation are not reliable enough,” Dr. Dichtelmüller explained.

    “Cold ethanol fractionation does not inactivate viruses, but partitions viruses into the precipitate together with the waste protein. Viruses can be recovered from the precipitate almost without loss,” Dr. Dichtelmüller said. Partitioning, however, is not equally effective for all viruses, and varies with the step and the virus.  “Therefore, validation is essential and robustness is required.”

    Although the details of his latest research are, as yet, not public, Dr. Dichtelmüller showed that cold ethanol fractionation is a relevant virus-removal procedure. His lab has performed and evaluated 280 studies on cold ethanol fractionation to determine its effectiveness. That method “is working reliably for the precipitation of fraction III or I/III for immunoglobulins, and for precipitation and removal of fraction II/III or I/II/III, and precipitation and removal of fraction IV/IV (both steps of the albumin fractionation process),” he says.

    While cold ethanol fractionation contributes to viral safety of immunoglobulins and albumin, it can never be the only measure to remove viruses from the products. Further inactivation steps are essential.

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