New developments in quantitative polymerase chain reaction applied to control the quality of heparins

Heparin is a widely used intravenous anticoagulant comprised of a very complex mixture of glucosaminoglycan chains, mainly derived from porcine intestinal mucosa. Recent contamination of heparin with oversulfated (OS) chondroitin sulfate resulted in a significant number of deaths, triggering a rapid revision of product monographs and the introduction of new analytical methods to limit as far as possible the chances of another occurrence of such a phenomenon. The distribution of heparin-processing units across the globe prevents their complete fool-proof auditing. Therefore, the implementation of additional orthogonal analytical techniques for quality control (QC) of heparin batches is highly important. We perform routine quantitative polymerase chain reaction (Q-PCR) release tests to confirm the quality of all crude heparin batches received by sanofi-aventis. The routine test used provides information on the animal species of origin as requested by the US Pharmacopoeia (USP) and European Pharmacopoiea monographs. Here, we demonstrate that the Q-PCR test is inhibited by OS glycosaminoglycans at concentrations as low as 0.5% (w/w versus heparin) and can be used as an additional safeguard to monitor levels of potentially harmful contaminants without any increased workload. In response to a request from the USP, we also describe the development of a Q-PCR method for monitoring nucleotidic impurities in pure heparin, which is able to detect amplifiable DNA at concentrations lower than 0.1 ng DNA per milligram of heparin. This increased sensitivity makes this modified Q-PCR method a potential candidate for inclusion as a QC requirement in future monographs.