Mandatory nonmedical switching from originator to biosimilar infliximab in patients with inflammatory arthritis and psoriasis in British Columbia: a cohort study.

BACKGROUND

In 2019, British Columbia's public drug plan, PharmaCare, was the first in Canada to implement a nonmedical switching policy from originator infliximab to its biosimilar, for patients with inflammatory arthritis or psoriasis. We aimed to detect signals of impact on health services utilization during the first year of policy implementation and to provide early data to policy-makers.

METHODS

We constructed cohorts of users of originator infliximab: 3 historical cohorts (2016-2018) and 1 policy cohort (2019). We extracted data from BC Ministry of Health databases from 2015 to 2020, as we followed each cohort for 365 days from May 27 of each cohort's respective year. We excluded patients with gastrointestinal conditions and those not covered by PharmaCare. We examined the cumulative incidence of infliximab prescription refills, switching to other biologic drugs and use of additional health services. A log-likelihood ratio of 1.96 compared with the null hypothesis was used as the threshold for differences between the policy cohort and the historical cohorts.

RESULTS

The study included a total of 572 unique patients: 520 in the 2016 historical cohort, 461 in the 2017 historical cohort, 423 in the 2018 historical cohort and 377 in the policy cohort (with some patients included in multiple cohorts; 335 [58.6%] were included in all 4 cohorts). During months 8 and 9 of follow-up, a transient signal was observed in infliximab refills (7.2% decrease in refilling infliximab for the fourth time for the policy cohort, log-likelihood ratio > 1.96). An anticipated increase in visits to specialists was observed from month 4 forward (15.0%, log-likelihood ratio > 1.96). No signal was observed for increased use of other health services (log-likelihood ratio < 1.96).

INTERPRETATION: Early monitoring did not detect signals of negative impacts on health services use during the first year of the policy. Detailed, longer-term cohort studies and hypothesis-testing methods could provide additional assurance about the safety of the policy.