Biosimilar adalimumab is making its way to patients, some of whom have expressed concerns about the presence of citrate in some of the available biosimilars.
Biosimilar adalimumab recently entered the European marketplace, and swift adoption by health systems eager to benefit from cost savings means that biosimilar versions are making their way to patients, some of whom have expressed concerns about the presence of citrate in some of the available biosimilars. In the United Kingdom, the National Health Service (NHS) Specialist Pharmacy Service has issued an update on biosimilar adalimumab with a focus on injection site reactions (ISRs) that may be related to the citrate buffer used in some formulations of adalimumab.
The early formulation of the reference adalimumab, Humira, used a citrate buffer to maintain the product within a predefined pH range. Similar systems are also used in products like etanercept and dulaglutide. In pivotal trials, this formulation of the reference Humira was linked with ISRs in 12.9% of patients.
Later, AbbVie, maker of the reference drug, reformulated its product to remove the citrate buffer in an effort to reduce both the product’s injection volume and the incidence of ISRs.
According to the NHS report, there is some weak evidence, derived from 2 small phase 2 studies, to support claims that citrate-free adalimumab, delivered via a 29-gauge needle, may provide some advantage over the original formulation, delivered by 27-gauge needle, in terms of reduced post-injection pain. However, the report’s authors point out, there is no consistent evidence that shows that the difference in discomfort between the 2 options persists longer than 15 minutes.
The report also details the excipients used in the biosimilar adalimumab products available in the NHS system, as well as data on ISRs:
Notably, among the adalimumab products available in syringe presentations, neither the reference nor any of the biosimilars’ devices contain latex. However, among adalimumab products available as prefilled pens, both Amgevita and Hyrimoz have needle covers that contain a derivative of latex, which could make them unsuitable for patients with latex allergies.