Biological medicines (biologics) are agents derived from a biological source. As a consequence, they are complex and there is a high degree of variability between molecules of the same active substance. Biosimilars are medicines that are closely related, pharmaceutically and therapeutically, to their reference biologic. However, biosimilars are not identical to, and cannot be characterised as bioequivalent to, the reference biologic in the way that generic small molecules drugs are bioequivalent to the innovator drug. Regulatory approval of a biosimilar involves comparability, but not bioequivalence or necessarily substitutability, with the reference product.
In Australia, like most other jurisdictions, following registration of a biosimilar on the Australian Register of Therapeutic Goods (ARTG) it is necessary to overcome an additional regulatory hurdle in order for a biosimilar to be substituted for the reference product by a pharmacist. However, the regulatory drive in Australia towards substitution of biosimilars at pharmacy level is unique.
See our article here for more in relation to these issues: Biosimilars: balancing access to affordable medicines with safety