Cost optimizing tocilizumab therapy in stable rheumatoid arthritis: a dose de-escalation nomogram to prevent overuse and unnecessary costs.

BACKGROUND

The conventional 8 mg/kg tocilizumab (TCZ) dose regimen for rheumatoid arthritis (RA) yields higher serum trough concentrations (TCZtrough) than needed (> 1 mg/L) for C-reactive protein normalization and disease control. We evaluated the registered dosing approach by TCZtrough assessment using pharmacokinetic (PK) modelling and introduced a practical TCZtrough-guided dose reduction nomogram.

METHODS

This prospective cohort study examined RA patients with stable disease activity undergoing intravenous TCZ treatment. A population PK model was constructed utilizing literature PK-data, TCZtrough, and dosing information. The derived model enabled prediction of TCZtrough guided dose de-escalation constructed in a nomogram. Dose reduction was implemented in a study subgroup, involving a reassessment of TCZtrough and maintenance of disease activity control.

RESULTS

In 39 patients treated according to the registered dose-scheme, the baseline mean TCZtrough was 27.6 mg/L (SD 12.6). Simulations using the constructed PK-model demonstrated that a 0.4-4.6 mg/kg dose reduction was feasible in 36 patients (92%). The simulated reduction corresponds with an annual cost-reduction of approximately 25% per patient. Twelve consecutive patients were selected for the prospective validation of a model-based dose reduction nomogram. In all patients TCZtrough remained above 1 mg/L upon reduction, while the median TCZtrough decreased by 25 mg/L. After 18 months, 75% (n = 9) of these patients continued to receive reduced TCZ dosages, while maintaining stable disease.

CONCLUSIONS

TCZtrough guided dose de-escalation based on a proposed nomogram results in considerable cost reductions, while efficacy is maintained in most patients. Through routine monitoring of TCZtrough in stable RA patients, dose reduction can be implemented, potentially leading to optimization of cost-effective TCZ therapy. Key Points • Tocilizumab (TCZ) levels at a registered dosage (8 mg/kg) substantially exceed the minimally required concentration for disease control. • Although the pharmacokinetics of TCZ are well established, TCZ trough levels (TCZtrough) are rarely used to guide individualized dose reduction strategies in routine RA practice. • When reducing TCZ use, dose reduction is preferred above extending the dose interval for achieving sufficient TCZtrough. • Dose de-escalation based on TCZtrough measurement and a nomogram leads to a substantial dose reduction while maintaining efficacy, potentially reducing TCZ costs by 25%.