Real-World Evidence in Psoriatic Arthritis: PRO-SPIRIT Study

She begins by referring to earlier head-to-head trials: the SPIRIT H2H study (2019) used a combined ACR50 and PASI 100 endpoint and showed superiority over adalimumab.¹ The EXCEED trial (2020) did not demonstrate superiority on the ACR20 endpoint,² and the SELECT-PsA study (2021) also showed non-superiority when upadacitinib was compared with adalimumab at the 15 mg licensed dose.³

The SPIRIT H2H week-24 DAPSA remission and MDA results again showed ixekizumab’s superiority over adalimumab¹, but randomized controlled trial populations often differ from the patients seen in routine practice, creating a gap between trial outcomes and real-world experience.

PRO-SPIRIT was designed to address this gap. The study enrolled 1,200 patients with psoriatic arthritis and, unusually for an industry-led project, assessed not only ixekizumab but also other IL-17A inhibitors, TNF-alpha inhibitors, and additional modes of action. Its key evaluations included joint and skin effectiveness at week 12 and a broad range of patient-reported outcomes.⁴

PRO-SPIRIT is a 24-month, prospective, real-world multicenter study. Eligible participants were 18–80 years old, had a confirmed psoriatic arthritis diagnosis for at least six months before baseline, and were initiating or switching to a new biologic or targeted synthetic DMARD based on country-specific indications.⁵

The primary objective is to describe 24-month treatment persistence, effectiveness, and healthcare resource use in patients newly starting therapy. Secondary objectives assess these outcomes by drug class and for ixekizumab specifically at 3, 6, 12, 18, and 24 months.The results discussed are from the on-label population, beginning with baseline demographics and clinical characteristics. ^4,6

Baseline data showed that treatment groups were not evenly distributed. Most patients initiated a TNF inhibitor, followed by ixekizumab, with a fair number starting JAK inhibitors and smaller numbers starting other drugs. Patients in the ixekizumab group typically had a longer disease duration and were more likely to have received a prior biologic or targeted synthetic DMARD.^4,6

Swollen and tender joint counts were similar across groups. The key differences were in skin severity, patients with more extensive psoriasis were more often started on therapies expected to offer greater skin efficacy.^7,8

At week 12, cDAPSA remission/LDA rates were similar between the TNF inhibitor group and secukinumab 150 mg, which is expected given its use in TNF-naïve patients or those with milder skin disease. In both groups, about half were on a conventional DMARD and about half had prior targeted therapy exposure.^4,6

For other modes of action, including ixekizumab, 44% of patients achieved remission or LDA at week 12. These groups had biological targeted DMARD exposure, up to 81% in the secukinumab 300 mg cohort and around 40% were also on additional DMARDs. Smaller numbers in the ustekinumab and IL-23 groups make those results harder to interpret. ^4,6

In the JAK inhibitor group, most patients had previously received a biological targeted systemic DMARD, and nearly half were also on a conventional DMARD. At week 12, 45% achieved DAPSA remission or LDA.⁹

Looking at cDAPSA outcomes at month three, fewer patients remained in high disease activity with TNF inhibitors, IL-17 inhibitors, and JAK inhibitors. Lower LDA or remission rates were seen with ustekinumab, and joint responses were generally similar across groups, except with ustekinumab and IL-23 inhibitors, which often take longer to respond.⁹

The PRO-SPIRIT data also show meaningful improvements in joint swelling and tenderness. Instead of using a composite cDAPSA score, the analysis looked at absolute change from baseline. By week 12, ixekizumab achieved a −2.7 reduction in swollen joint count—almost identical to the TNF inhibitor group. Considering that many ixekizumab patients had previously failed a TNF inhibitor, these results are encouraging. Similar reductions were seen with JAK inhibitors. For tender joint counts, responses were broadly comparable across modes of action, except for ustekinumab, which showed only a moderate reduction.^4,6,9

Differences between modes of action become clearer when looking at skin outcomes. As expected, TNF inhibitors showed lower skin responses, while IL-17 inhibitors and anti-IL-23 agents demonstrated stronger effects. In patients with moderate-to-severe psoriasis at baseline (body surface area >3%), the proportion achieving <3% BSA by week 12 reflected these patterns, with ixekizumab showing the greatest improvement from baseline.^4,6

Moving beyond the PRO-SPIRIT data, clinical trials in psoriatic arthritis and psoriasis show that ixekizumab has been used in thousands of patients with a consistent long-term safety profile. Injection-site reactions were the main signal in earlier trials using the original formulation. A small signal for Candida infections has also been observed.¹⁰

Key takeaways from PRO-SPIRIT show that ixekizumab delivers an early response by three months across both joint and skin domains, with good effectiveness even in biologic-experienced patients. It also had the highest three-month skin response among the groups.^4,6

Ixekizumab’s long-term safety is well established, with up to five years of data and no new safety signals across 24 clinical trials.^10,11,12

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