Data on clinical response to treatment at week 24 (ACR 20, ACR 50 and ACR 70) were extracted from the two matching-adjusted indirect comparison studies of secukinumab and adalimumab11,12 (Table 1). Although both publications compare the same treatments, different methodologies were used and the data used to determine effectiveness were from different clinical trials, so a priori, discordant results are to be expected. While Nash P. et al.11 found that response rates were numerically and statistically higher for secukinumab compared to adalimumab, Strand V. et al.12 found that, although response rates were numerically higher for adalimumab compared to secukinumab, these differences were not statistically significant. Given the discrepancies between both sources with respect to their methodologies and, consequently, their results, the data from the two available articles was analyzed separately. This way, it was possible to assess and compare the results from both perspectives and there was no loss of information that could be useful for decision-making, since these are the only comparative studies between both treatments for PsA.

The main difference in methodology between the two articles is centred on the clinical trials selected for the comparisons. Whereas Nash P. et al.11 looked at the pivotal FUTURE 2 (secukinumab 150mg versus placebo) and ADEPT (adalimumab 40mg versus placebo) trials, Strand V. et al.12 also included the pivotal FUTURE 1 trial (secukinumab 150mg versus placebo). The reason Nash P. et al.11 gave for excluding the FUTURE 1 study was the fact that the dose of secukinumab that was administered was not the one approved on the summary of product characteristics (SmPC)13 and that the induction phase consisted of a 10mg/kg intravenous dose at weeks 0, 2 and 4. Strand V. et al.12 were aware of this limitation, so they performed a sensitivity analysis that did not include the FUTURE 1 study. Although they indicate that the efficacy of ACR 20 and ACR 50 responses of adalimumab compared to secukinumab were 6.4% lower and 5.9% lower, respectively, while the ACR 70 response was 0.6% higher (no statistically significant differences) authors did not provide detailed results thus these data has not been included in our analysis.

This data was used to determine the number of patients in each cohort with a clinical response (ACR 20/50/70) at 24 weeks. For example (Fig. 2), using the ACR 20 results reported in the Nash P. et al.11 analysis, we can see how 10 patients in cohort A start out by receiving treatment with secukinumab at a dose of 150mg and that at 24 weeks, 8 (81.0%)11 continue receiving the same treatment until the end of the time horizon while the dose administered to the other 2 (19%) would be increased (secukinumab 300mg). With respect to cohort B, of the initial 10 patients, 6 would continue to receive adalimumab 40mg until the end of the time horizon while the other 4 would switch to secukinumab 300mg. We proceeded in the same way with regard to the study conducted by Strand V. et al.12 (Fig. 2).

Fig. 2.

Basis for estimating the number of patients in each cohort who responded to treatment at 24 weeks.

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Only the notified ex-factory price14 has been taken into account, after the 7.5% discount was applied as per the deductions under Royal Decree-Law 8/201015 (Table 2). In the case of adalimumab, the biosimilar drug with the lowest price has been considered.

We calculated the cost of treatment by multiplying the notified ex-factory price per dose of each presentation by the number of doses required over the time horizon analyzed (Table 3). For secukinumab, we took into account the induction and maintenance phases as recommended in the SmPC,12 applicable to secukinumab 150mg for TNFi-naive patients and to secukinumab 300mg for inadequate responders to TNFi, along with the option of increasing the dose from 150mg to 300mg according to clinical response.12 Hence, when calculating the cost of the treatment for the cohort of patients who receive adalimumab 40mg and who switch to secukinumab 300mg after 24 weeks, the induction and maintenance phases are imputed for secukinumab. This is not the case for patients who start treatment with secukinumab 150mg and whose dose is increased to secukinumab 300mg after 24 weeks, since only the dose is increased (Table 3).

We used the data on efficacy and cost of treatment to calculate the costs for cohort A and cohort B and the difference between the two. The results are shown for the first year, the second year and in total, as well as for each of the clinical response criteria (ACR 20, 50 and 70). Given that there are discrepancies in the results of the two articles that have been published so far on the clinical efficacy of secukinumab versus adalimumab11,12 as assessed by matching-adjusted indirect comparison, the results are shown separately for each.

We also performed a sensitivity analysis to assess the impact on the results of a modification in the notified ex-factory price of adalimumab, while maintaining the cost of secukinumab unchanged, as we considered a probable scenario in which the available evidence points to lower efficacy of adalimumab versus secukinumab. For this, results were calculated using discount rates ranging between 0 and 100% (in increments of 5%) on the notified ex-factory price for adalimumab. The results of the sensitivity analysis are shown for the total costs (first and second years) and for each of the clinical response.

The results obtained show greater efficiency when secukinumab 150mg is used as the first biologic treatment for patients with PsA and the dose is subsequently increased in cases where clinical response is not achieved, compared to first biologic treatment with adalimumab 40mg and, in the event of inadequate response, switching to secukinumab 300mg. These results were consistent across the different periods analyzed, i.e., during the first and second years (and in total), at all levels of clinical response (ACR 20, 50 and 70) and using the efficacy data from the reports published by Nash P. et al.10 and Strand V. et al.11 (Table 4 and Table 5, respectively).