Lessons learned from the contamination of heparin

Abstract

Heparin is unique as one of the oldest drugs currently still in widespread clinical use as an anticoagulant, a natural product, one of the first biopolymeric drugs, and one of the few carbohydrate drugs. Recently, certain batches of heparin have been associated with anaphylactoid-type reactions, some leading to hypotension and death. These reactions were traced to contamination with a semi-synthetic oversulfated chondroitin sulfate (OSCS). This Highlight reviews the heparin contamination crisis, its resolution, and the lessons learned. Pharmaceutical scientists now must consider dozens of natural and synthetic heparinoids as potential heparin contaminants. Effective assays, which can detect both known and unknown contaminants, are required to monitor the quality of heparin. Safer and better-regulated processes are needed for heparin production.

Fig. 1

The structures of the major (A) and minor (B) repeating disaccharides comprising heparin where X =SO₃⁻ or H, and Y =SO₃⁻ or COCH₃.

Fig. 2

Heparin’s antithrombin III binding site and its structural variants.

Fig. 3

Flow chart of the preparation of heparin from animal tissues. Chart A is performed under little or no regulatory control in rural communities while chart B is performed under cGMP in FDA-inspected facilities.

Fig. 4

Timeline of the heparin crisis.

Fig. 5

¹H-NMR spectra acquired at 800 MHz and assignment of heparin, contaminated heparin and OSCS contaminant. A. ¹H-NMR spectrum of heparin. a, H1 GlcNS, GlcNS6S; b, H1 IdoA2S; c, H1 IdoA; d, H5 IdoA2S; e, H1 GlcA; f, H6 GlcNS6S; g, H2 IdoA2S; h, H6⁰ GlcNS6S; i, H3 IdoA2S; j, H4 IdoA2S; k, H5 GlcNS5S; l, H6 GlcNS; m, H4 GlcNS6S; n, H3 GlcNS, GlcNS6S; o, H2 GlcA; p, H2 GlcNS6S; q, acetyl CH₃. B. ¹H-NMR spectrum of contaminated heparin; peaks with red arrows show peaks not observed in heparin. C. ¹H-NMR spectrum of OSCS contaminant. r, H4 GalNAc2S4S6S; s, H3 GlcA2S3S; t, H1 GlcA2S3S; u, H1 GalNAc2S4S6S; v, H2 and 4 of GlcA2S3S; w, H6 GalNAc2S4S6S; x, H5 GlcA2S3S; y, H2,3 and 5 GalNAc2S4S6S; and z, acetyl CH₃ of GalNAc2S4S6S.

Fig. 6

Contaminant stability in processes used in preparing LMWHs.

Fig. 7

Current understanding of the biological activities associated with OSCS acute toxicity.

Fig. 8

Structure of Arixtra^®

Fig. 9

Heparin and heparan sulfate biosynthesis.

Fig. 10

The stepwise chemoenzymatic synthesis of an anticoagulant heparin.