Low molecular weight heparin biosimilars: how much similarity for how much clinical benefit?

The development of biosimilar versions of low molecular weight heparins (LMWHs) raises real medical concerns. To illustrate this, we have chosen as an example the specific clinical setting of antithrombotic management of acute coronary syndromes (ACS). In this indication, the LMWH enoxaparin has consistently shown its superiority in terms of efficacy when compared to unfractionated heparin (UFH) and in a number of direct or indirect comparisons to other LMWHs. For this reason, enoxaparin has become the gold standard for anticoagulation in cardiology, recommended by practice guidelines and extensively used in everyday practice. We are concerned by the fact that some patients might be treated with a biosimilar copy of enoxaparin, on the basis of simplified criteria that are not specific enough to differentiate between different available LMWHs and are thus unable to differentiate between enoxaparin and a biosimilar. In the absence of evidence from clinical trials, especially in ACS, we believe that it is difficult to ensure that the benefit/risk ratio of enoxaparin and its copy are equivalent. In addition to efficacy, safety issues also have to be taken into consideration, since biosimilars consist of glycan chain mixtures that exhibit specific immunoallergic features. Contamination of raw material with other glycans or xenobiotic material during extraction and fractionation may trigger potentially harmful immune reactions.