Background: Infliximab is a chimeric monoclonal antibody directed against TNF-α, with proven efficacy in IBD. Reported loss of response is 15–40% per year. There is evidence to suggest that the development of anti-infliximab antibodies plays a major part in this. Antibodies may develop and not be associated with failure, however in this setting it is thought that infliximab does not have ongoing efficacy for maintaining remission. Whilst therapeutic drug level monitoring could optimise anti-TNF use, it could also be associated with cost savings, but the long-term cost savings are unknown. Not only this, it is likely that it will optimise the use of anti-TNF therapy and guide on future therapies improving long-term patient outcomes.
Our aim is to show that the use of therapeutic drug level and antibody monitoring is associated with cost savings by stopping unnecessary anti-TNF, or dose de-escalation of therapy.
Methods: By interrogating our local IBD database and searching patient records we identified all patients receiving anti-TNF therapy, the indication for performing therapeutic drug and antibody levels.
We identified patients in which results of the drug levels and antibody status alone influenced the future treatment strategy, then calculated the costs and cost savings made when treatment was altered.
Maintenance therapy with biosimilar Remsima costs £3510 per year, calculations were based on the assumption that all patients were receiving Remsima.
Results: 104 patients receiving infliximab between 2013 and 2016 had infliximab levels checked at a total cost of £7280.
26 (25%) patients were identified as having their treatment changed as a direct result of the drug levels and antibody status.
18 (69%) patients in remission with positive antibodies and undetectable trough levels had infliximab withdrawn with an annual cost saving of £63,180.
6 patients in remission had the Remsima dosing interval lengthened to 12 weeks due to high trough levels of infliximab with a cost saving of £7020 per annum.
2 patients had the Remsima interval reduced to 6 weeks based on low drug trough level at an increased cost of £3510 per annum.
No patient had a change in biologic drug based on drug levels alone.
The total annual cost saving from the introduction of therapeutic drug level and antibody monitoring was £59,410 based on using Remsima. This cost saving would be increased to £140,920 if originator infliximab had been used.
Conclusions: The use of therapeutic drug monitoring at a district general hospital leads to significant cost savings in the use of infliximab therapy.