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Mar 15, 2010 (Vol. 30, No. 6)

Oligo Therapeutics Enriching Pipelines

As Development Escalates, Delivery Strategies, Chemistries, and Modifications Also Improve

  • Sourcing Raw Materials

    Agilent is continuing to develop Process Analytical Technology for monitoring process steps in real-time, as well as LC/MS and MS-MS technology to enhance the analysis of amidite purity.

    “Identification of degradation products and process-related impurities that couple during oligo synthesis is key to setting meaningful raw material specifications,” says Metz. As more products move into later stage development, “there could be pressure on the amidite supply by 2013, and security of supply will be an important commercialization factor to consider.”

    “While there are currently stable Western sources, multisourcing options from Asia are also being developed. Agilent has built analytical centers of excellence in both India and China and plans to use these resources to work with new amidite supplies to “help them better understand their starting raw materials and processes and to control amidite impurities.”

    Agilent’s goal is to ensure a more efficient and reliable supply chain by creating “supplier partnerships” that will allow for in-process testing and prerelease of amidites to Agilent in-country. After processing, the amidites would be analyzed for purity and impurity levels before they are sent on to Agilent’s manufacturing facility in Boulder, where they would then undergo regular GMP testing prior to use in production.

    Agilent has completed proof-of-concept for its thin-film evaporation and spray-drying technologies, and these are now available as processing options in early-stage development for products expected to require large-scale manufacturing as they progress toward commercialization.

    The company is building a commercial-scale thin film evaporator to support one of its late-stage programs. Both the thin-film evaporation and the spray-drying technologies reduce “product time-at-temperature,” which translates to less chance for thermal degradation, explains Metz. They also provide for higher-throughput compared to current rotary evaporation and lyophilization technologies.

  • Quantifying Oligos in Clinical Samples

    Hybridization assays for quantifying oligo drug levels in biological samples have advantages over conventional chromatographic techniques such as capillary gel electrophoresis or HPLC. The main advantage is the high sensitivity of ELISA assays, the small sample volumes required, and the ease of use, with little or no sample clean-up required prior to assay processing.

    In fact, “oligo levels can be measured in homogenized tissue samples without any prior extraction,” says Helen Legakis, research scientist in immunochemistry laboratory services at Charles River Laboratories. In contrast, tissue samples are subjected to sonication and enzyme digestion to break down the tissue membranes.

    As oligo-based therapeutics are mainly administered parenterally, a high assay sensitivity is essential to characterize their pharmacokinetic and toxicokinetic properties following systemic administration. This is particularly important at “the terminal elimination phase, characterized after near-complete distribution of the drug has occurred,” notes Legakis.

    To achieve optimal sensitivity, Charles River designs its probes to include Locked Nucleic Acid inserts, which contain a rigid bicyclic structure in the ribofuranose ring. This reduces the background noise of the assay and increases the thermal melting temperature of the oligo analyte and the complementary probe. The increased binding affinity to the probe prevents competitive re-annealing of double-stranded analytes to their complementary strand, Legakis explains.

    Looking to the future, Legakis sees a growing demand for multiplexing technologies coupled to an ELISA-based assay format. With the emergence of multiple therapeutic targets, these methods will be able to measure more than one analyte in a multianalyte drug cocktail in a single well.

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