While they present a cost-saving opportunity, safety data on biosimilars is still limited, warns IBD specialist

There is an absence of data on adverse reactions or potential development of anti-drug antibodies caused by the use of biosimilars, warns Dr Greg Moore, Head of IBD at Monash Medical Centre in Melbourne and a Senior Lecturer in the Department of Medicine, Monash University.

In a piece for the Medical Journal of AustraliaDr Moore argues that biosimilars are concerning for prescribers because the absence of safety data does not imply safety.

Brands that can be substituted by the pharmacist when dispensed are indicated in the PBS by an ‘a-flag’, and these currently include infliximab and basaglar. Under Australian legislation, the only way a prescriber can ensure a patient is continued on the initially prescribed biologic agent as opposed to an ‘a-flagged’ biosimilar is to tick “brand substitution not permitted”.

“These drugs are not considered to be identical or to have demonstrated bioequivalence with the originator biological medicine,” argues Dr Moore.

While cost savings accompany the listing of biosimilars on the PBS, Dr Moore warns that biologics are immunogenic and can result in antibody formation, reactions, and loss of efficacy with time.

“Given that biosimilar drugs are not identical, there is a theoretical risk that switching between agents may result in the development of neutralising anti-drug antibodies (ADAs) and subsequent loss of response,” he says.

Dr Moore joins other people and organisations who have expressed concern about safety risks associated with biosimilars, including the Australian Rheumatology Association and Medicines Australia.

“The arrival of biosimilars is welcomed by clinicians for the cost savings they bring to our health system, but ongoing studies and pharmacovigilance are required in a framework that captures clinical response data,” he says.

“[But] the minimisation of unnecessary switches until more safety data are available is recommended.”

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