Evaluating use of disease-modifying therapies for multiple sclerosis using claims data.

Objective: The aim of this work is to evaluate trends in the utilisation, cost, and switching patterns of disease-modifying treatments (DMTs) for relapsing-remitting multiple sclerosis (RRMS) under the pharmaceutical benefits scheme (PBS) in Australia from 2010 to 2021. Methods: A retrospective analysis was conducted using PBS claims data for 14 listed DMTs. Key outcomes included treatment uptake, switching behaviour, patient persistence, per-patient dosage, and direct drug costs. Results: The cohort comprised 2,315 RRMS patients initiating DMTs between 2010 and 2021 (73% women; mean age 41.9 years). Over the study period, the number of patients receiving DMTs increased 5-fold, while total PBS expenditure on DMTs rose 4.5-fold (from AUD 109.4M to AUD 492.9M), representing a compound annual growth rate of 13.6%-significantly outpacing overall PBS expenditure growth. High-efficacy (HE) DMTs progressively replaced low-efficacy (LE) therapies for both treatment initiation and switching. Median treatment persistence was higher for HE DMTs (25.5 months) compared to LE DMTs (20.8 months). HE DMTs generally incurred higher per-patient costs; however, elevated annual dosages of the LE drug interferon Beta-1a resulted in higher costs than some HE therapies. Conclusion: Rising PBS expenditure on DMTs was primarily driven by increasing patient numbers, shifts from low- to high-efficacy therapies, and longer treatment persistence. Analysis of individual DMT utilisation identified higher-than-expected use of interferon beta-1a relative to defined daily doses benchmarks, contributing to increased treatment costs. Overall, the findings demonstrate the value of claims data for postmarket monitoring of medicine utilisation and expenditure, and for informing policy review aimed at sustainable resource allocation.