Structure Elucidation and Biological Activity of the Oversulfated Chondroitin Sulfate Contaminant in Baxter Heparin

Abstract

From late December 2007 to February 2008, the number of adverse responses to heparin infusions rose noticeably above baseline levels in North America, ultimately resulting in a widespread recall of all heparin vial products made by Baxter Healthcare. Using various analytical techniques and the de novo synthesis of a fully sulfated chondroitin sulfate (FSCS) derivative, the authors have confirmed the identity of the contaminant as an oversulfated chondroitin sulfate (OSCS) and have also defined the heterogeneity and concentration of this contaminant in various lots of heparin. Using both contaminated heparin products and the synthetically produced derivative, the authors have shown that the OSCS produces a dose-dependent hypotension in both pigs and rats and that the response in rats can be abrogated with bradyzide, a rodent-selective B(2) bradykinin receptor antagonist. The no observed effect level (NOEL) for this contaminant appears to be approximately 1 mg/kg, corresponding to a contamination level in finished lots of heparin of approximately 3%. Using human plasma, the OSCS derivative was shown to activate kallikrein. These data provide insight into the etiology of the adverse events, particularly refractory hypotension, observed in patients who were exposed to heparin contaminated with OSCS.

Chemically Oversulfated Glycosaminoglycans Are Potent Modulators of Contact System Activation and Different Cell Signaling Pathways

“…S2B). Consistent with our published observations that the heparins are not contaminated with OSCS alone (7,8); the published CE data (6,34) also showed that an OSHS co-migrated with heparin (see Ref. 6, supplemental Fig.…”

“…S9, last panel), and there are two heparin contaminant peaks that migrated before heparin in contaminated heparin by employing a high resolution CE method (see Ref. 34, Fig. 2).…”

“…One peak was named fully sulfated CS and the other was named partially sulfated OSCS in the published report (34). In addition, we found that less sulfated DS and HS (OSDS-M, OSDS-L and OSHS-M, OSHS-L) had several proton signal peaks such as 2.04, 2.07, 2.10, and 2.12 ppm for OSHS-M and OSHS-L and/or OSDS-M and OSDS-L, which made the 2.07 Ϯ 0.02 and 2.12 Ϯ 0.02 ppm proton chemical shifts not specific for DS and OSDS, respectively, in contrast to the published reports (6,34). Because the heparin contaminant that migrated before heparin, based on CE analysis, was defined as OSCS or heparin contaminant during the past 2 years, we decided to choose all the OSGAGs that migrated like OSCS (Fig.…”

Characterization of currently marketed heparin products: Adverse event relevant bioassays

“…Because of the symptoms and the known ability of dextran sulfate to activate the contact system [3], research quickly focused on OSCS mediated activation of the contact system as a prime biochemical mechanism to link contaminated heparin with the adverse events. In subsequent research, OSCS was found to activate the kallikrein-kinin (KK) pathway in human plasma and this pathway was proposed to cause the production of vasoactive mediators such as bradykinin (BK) and the anaphylatoxins C3a and C5a in a factor XIIa (FXIIa) dependent manner [4][5][6][7][8]. Consistent with this hypothesis, OSCS alone and OSCS contaminated heparin induced hypotension in swine or rat blood pressure models [4,5,7].…”

“…In subsequent research, OSCS was found to activate the kallikrein-kinin (KK) pathway in human plasma and this pathway was proposed to cause the production of vasoactive mediators such as bradykinin (BK) and the anaphylatoxins C3a and C5a in a factor XIIa (FXIIa) dependent manner [4][5][6][7][8]. Consistent with this hypothesis, OSCS alone and OSCS contaminated heparin induced hypotension in swine or rat blood pressure models [4,5,7]. Thus a model was proposed where OSCS facilitates the autocatalytic activation of FXII to FXIIa which in turn activates the conversion of plasma pre-KK to KK [9].…”