Development of methods for data quantitation of spiked salmon host cell DNA in protamine sulfate by qPCR

Protamine sulfate (PS) is an approximately 4 kDa cationic polypeptide derived from chum salmon used to reverse heparin-induced anticoagulation in patients. Because the presence of residual host cell salmon DNA (resDNA) in PS drug product can pose safety concerns, processing steps during PS manufacturing are designed to target the reduction of these impurities. However, given protamine׳s positively charged structure, isolating and measuring negatively charged residual DNA is challenging. Suitable resDNA methods for PS require the generation of host DNA reference materials, efficient DNA extraction procedures and assay sensitivity and accuracy as high as possible. Here, optimization data are shown for the extraction of DNA present in PS drug products and for the generation of reference standard from protease-digested research grade chum salmon DNA. The lower limit of quantitation (LLOQ) for the reference standard determined from protease-digested DNA (0.0025-156.25 pg/μL) was 0.0025 pg/μL. The extraction procedure LLOQ, determined from DNA (0.01-1.25 pg/μL) spiked into PS samples, was 5 pg DNA per mg PS. The data supporting the LLOQs were evaluated using acceptance criteria of 70-130% recovery with % correlation coefficient (CV) ≤ 25% for DNA concentrations and curve metrics (slopes, R ² and y-intercepts) within 2SD of the mean. The data presented here complement a broader study (Sommers et al., 2018) [1] and are particularly useful for the development of resDNA methods for challenging drug products.