During the manufacture of biopharmaceuticals, including monoclonal antibodies, therapeutic proteins, and vaccines, among others, which are produced in cells, residual host cell DNA contamination must be controlled to acceptable levels to avoid potential safety risks such as immunogenicity and oncogenicity. Demonstration of host cell DNA reduction or removal from the cell substrate by accurate and sensitive tests to quantify such impurities is required during in-process testing or at release of a drug substance.

USP General Chapter <509> Residual DNA Testing contains validated measurement methods of residual host cell DNA in recombinant therapeutic products produced in either Escherichia coli (E. coli) or Chinese hamster ovary (CHO) cell lines.

USP Reference Standards for E. coli and CHO genomic DNA (gDNA) have been developed and validated to determine the residual amount of genomic DNA content in a sample and to demonstrate system suitability for these analytical procedures. This effort is a step forward towards USPs commitment to help ensure quality and safety of medicines globally.

Genomic DNA Reference Standards Characterization Methods

Each gDNA has been highly characterized with respect to:

• DNA Concentration value 
  • Concentration of DNA (ng/µL) was determined as per Chapter <509> Residual DNA Testing, qPCR Analysis
    • Multiple USP laboratories and collaborator laboratories each performed two assays with three qPCR preparations per assay
  • Verification of DNA concentration by low volume DNA quantification method (A260) 
  • Appearance by visual evaluation
  • Identification by qPCR as per method Chapter <509> Residual DNA Testing, qPCR Analysis
    • The primers and probe used in the qPCR analysis for CHO or E. coli gDNA are specific to CHO or E. coli gDNA, and only amplify CHO or E. coli gDNA, respectively.
  • Standard Curve Run by qPCR
    • Multiple USP laboratories and collaborator laboratories generated the standard curve with the respective USP gDNA Reference Standard and the results passed the system suitability requirements in Chapter <509> Residual DNA Testing, qPCR Analysis, which demonstrates the respective USP gDNA Reference Standard is suitable for its compendial use.