1.1. Study Question

A cost-utility analysis (CUA) was conducted to compare the use of aripiprazole to the use of quetiapine in the adjunctive treatment of major depressive disorder (MDD) in adult patients who had an inadequate response to prior antidepressant therapy (ADT) during the current episode. A secondary analysis was conducted comparing adjunctive treatment with aripiprazole to adjunctive treatment with quetiapine, olanzapine, or risperidone.

1.2. Treatment

Aripiprazole (Abilify), as an adjunct to ADT.

1.3. Comparators

The primary comparator for the economic evaluation was quetiapine extended release (Seroquel XR), as this is the only atypical antipsychotic (AAP) approved by Health Canada for specific use in MDD, alone or as an adjunct to ADT. Quetiapine is currently funded as a general benefit across all provinces in Canada.

The approved dose for quetiapine ranges from 50 mg per day up to 300 mg per day, while the submitted model assumed that quetiapine would always be used at its highest approved dose (300 mg per day).⁶ The manufacturer justified the use of the highest dose by arguing that the efficacy profile of aripiprazole was more aligned with quetiapine 300 mg per day; however, this was based on an indirect treatment comparison (ITC) submitted by the manufacturer, in which the results of quetiapine 150 mg per day and 300 mg per day were pooled as one intervention. Therefore, assuming that all patients would be treated with quetiapine 300 mg per day would create a bias against quetiapine due to the higher price of quetiapine 300 mg per day and its lower efficacy. Furthermore, the model assumed that quetiapine would always be used as an adjunct to ADT; however, some patients could benefit from quetiapine when used as monotherapy.⁷

Several other AAPs (asenapine, clozapine, lurasidone, olanzapine, paliperidone, and risperidone) are also available in Canada for the treatment of mental health disorders. According to the manufacturer’s report, IMS Brogan data indicates that olanzapine and risperidone, in particular, are often used off-label in the adjunctive treatment of non-responsive MDD; olanzapine has approximately 14% of the market share in Ontario for the treatment of MDD, while risperidone has approximately 13% of the market share in Ontario.⁴ Olanzapine and risperidone, along with quetiapine, were included in a scenario analysis against aripiprazole.

1.4. Type of Economic Evaluation

The manufacturer undertook a CUA. This is appropriate given the potential impact this disorder may have on quality of life, according to Canadian Agency for Drugs and Technologies in Health (CADTH) Guidelines for the Economic Evaluation of Health Technologies.⁸

The analysis takes a public payer perspective. This is appropriate according to CADTH guidelines.⁸ A scenario analysis was conducted from the societal perspective.

1.5. Population

The Health Canada indication for aripiprazole is as an adjunct to antidepressants for the treatment of MDD in adult patients who had an inadequate response to prior antidepressant treatments during the current episode. The manufacturer requested reimbursement for the Health Canada indication.