# IL-17A Blockade in Psoriatic Arthritis and Axial Spondyloarthritis ## Clinical evidence for IL-17A blockade in psoriatic arthritis and axial spondyloarthritis IL-17A blockade with ixekizumab or secukinumab demonstrates robust and sustained efficacy for both psoriatic arthritis and axial spondyloarthritis, with clinically meaningful improvements in joint symptoms, axial manifestations, and skin disease, accompanied by an acceptable safety profile characterized primarily by increased mucocutaneous candida infections. ## Abstract IL-17A blockade demonstrates consistent efficacy across the spectrum of psoriatic arthritis and axial spondyloarthritis in multiple randomized controlled trials. In radiographic axial spondyloarthritis, ixekizumab achieved ASAS40 response rates of 48-52% at week 16 versus 18% with placebo, while secukinumab showed approximately 60% ASAS20 responses across trials. In non-radiographic axial spondyloarthritis, ixekizumab demonstrated ASAS40 rates of 30-40% versus 13-19% with placebo at weeks 16 and 52. For psoriatic arthritis, meta-analytic evidence shows pooled ACR20 response relative risks of 2.04 (95% CI: 1.79-2.33), with individual trials reporting ACR20 rates of 50-62% versus 17-30% with placebo at week 24. Skin manifestations improved substantially, with PASI 75 response rates of 69-75% versus 7.5% placebo at week 12. TNF-naive patients showed greater absolute benefits than TNF-experienced populations, though both groups demonstrated significant improvements. The safety profile was generally favorable, with treatment-emergent adverse event rates of 57-77% and low serious adverse event rates (6% or less). Candida infections occurred more frequently with IL-17A inhibition (4.7% with secukinumab 300 mg), though most were mild to moderate. Discontinuation rates due to adverse events were low (2.4%), and treatment discontinuation rates were actually lower in IL-17A inhibitor groups versus placebo (RR 0.54). These data establish IL-17A blockade as an effective therapeutic option for both psoriatic arthritis and axial spondyloarthritis with an acceptable benefit-risk profile. ## Methods We analyzed 10 sources from an initial pool of 200, using 7 screening criteria. Each paper was reviewed for 8 key aspects that mattered most to the research question. **Records from Elicit search** n = 200 Papers screened using: Population, Intervention, Study Design, Clinical Outcomes, Age Group, Sample Size, Publication Type n = 200 Papers screened out n = 190 Papers included for extraction n = 10 ## Paper search We performed a semantic search across over 138 million academic papers from the Elicit search engine, which includes all of [Semantic Scholar](https://www.semanticscholar.org/) and [OpenAlex](https://openalex.org/). We ran this query: “Clinical evidence for IL-17A blockade in psoriatic arthritis and axial spondyloarthritis” The search returned 200 total results from Elicit. We retrieved 200 papers most relevant to the query for screening. ## Screening We screened in sources based on their abstracts that met these criteria: - **Population**: Does the study include patients diagnosed with psoriatic arthritis and/or axial spondyloarthritis (including ankylosing spondylitis and non-radiographic axial spondyloarthritis)? - **Intervention**: Does the study involve IL-17A blockade therapy (secukinumab, ixekizumab, or other IL-17A inhibitors)? - **Study Design**: Is the study design a randomized controlled trial, controlled clinical trial, systematic review, or meta-analysis? - **Clinical Outcomes**: Does the study report clinical outcomes such as disease activity measures, functional assessments, quality of life, radiographic progression, or safety outcomes? - **Age Group**: Does the study include adult patients (≥18 years)? - **Sample Size**: Does the study have an adequate sample size (≥10 participants) and is it NOT a case report or case series? - **Publication Type**: Is this a full-text publication (not just a conference abstract)? We considered all screening questions together and made a holistic judgement about whether to screen in each paper. ## Data extraction We asked a large language model to extract each data column below from each paper. - **Study Design**: Extract study design details including: - Type of study (phase II/III RCT, open-label extension, observational, etc.) - Duration of follow-up - Sample size (total randomized and completed) - Number of study sites and geographic locations - Funding source - **IL-17A Agent**: Extract details about the IL-17A blocking therapy including: - Specific agent name (secukinumab, ixekizumab, brodalumab, etc.) - Dosage and dosing regimen - Route of administration - Loading dose details if applicable - Duration of treatment period - **Patient Population**: Extract patient characteristics relevant to psoriatic arthritis and axial spondyloarthritis including: - Specific diagnosis (PsA, axial SpA, ankylosing spondylitis, or mixed) - Disease duration - Prior biologic exposure (naive vs. experienced, specific prior agents) - Baseline disease activity scores (ACR criteria, ASAS criteria, BASDAI, etc.) - Key inclusion/exclusion criteria - Demographics (age, gender, HLA-B27 status if reported) - **Comparator Groups**: Extract details about control/comparator groups including: - Placebo control details - Active comparator agents (adalimumab, other TNF inhibitors, etc.) with dosing - Randomization ratio - Crossover or rescue therapy provisions - Concomitant medications allowed (NSAIDs, conventional DMARDs, etc.) - **Joint Efficacy Outcomes**: Extract all efficacy outcomes related to joint/musculoskeletal manifestations including: - ACR20/50/70 response rates with timepoints - ASAS20/40 response rates with timepoints - Disease Activity Score (DAS28, ASDAS, etc.) changes - Physical function measures (HAQ-DI, BASFI, etc.) - Radiographic progression/structural damage measures - Time to response and sustained response data - Primary endpoint achievement and statistical significance - **Skin Efficacy Outcomes**: Extract efficacy outcomes specifically related to psoriatic skin manifestations including: - PASI response rates (PASI 75/90/100) with timepoints - Physician Global Assessment (PGA) scores - Body Surface Area (BSA) involvement changes - Nail psoriasis improvements if assessed - Time to skin clearance - **Safety Profile**: Extract comprehensive safety data for IL-17A blockade including: - Overall adverse event rates - Serious adverse events with specific details - Infections (overall rates, serious infections, opportunistic infections, candida infections) - Cardiovascular events (MI, stroke, heart failure) - Malignancies - Laboratory abnormalities - Discontinuation rates due to adverse events - Deaths and causes - Immunogenicity/anti-drug antibodies if assessed - **Risk of Bias**: Assess and extract study quality indicators including: - Randomization method and adequacy - Allocation concealment - Blinding of participants, investigators, and outcome assessors - Completeness of follow-up and handling of missing data - Selective outcome reporting concerns - Industry sponsorship and author conflicts of interest - Use of intention-to-treat vs. per-protocol analysis ## Results ### Characteristics of Included Studies The review included 10 sources comprising 7 primary randomized controlled trials (RCTs), 2 systematic reviews/meta-analyses, and 1 narrative review. Four studies evaluated ixekizumab, five evaluated secukinumab, and two meta-analyses evaluated multiple IL-17 inhibitors. | Study | Full text retrieved? | Study design | Duration | Sample size | Funding | Geographic scope | |----------------------------------------|----------------------|-----------------------------------|--------------------------|-------------------------------|-----------------------|-------------------------------------------------------------------| | van der Heijde et al., 2018 | Yes | Phase III RCT | 52 weeks with optional 2-year extension | 341 randomized | Eli Lilly and Company | 84 sites in 12 countries across Europe, Asia, North America | | Deodhar et al., 2019 | No | Phase III RCT | 52 weeks | 303 randomized (105 placebo, 96 ixekizumab Q4W, 102 ixekizumab Q2W) | Eli Lilly and Company | 107 sites in 15 countries | | Baeten et al., 2013 | No | Phase II proof-of-concept RCT | Week 6 efficacy, week 28 safety | 30 randomized (24 secukinumab, 6 placebo), 29 completed | Novartis | 8 sites in Europe (4 Germany, 2 Netherlands, 2 UK) | | Baraliakos et al., 2020 | Yes | Phase 3b RCT | 52 weeks | 498 randomized, 425 completed (85%) | Novartis | 97 centers in Europe, Russia, Israel | | Naik et al., 2017 | Yes | Systematic review and meta-analysis | 12-24 weeks | 1,718 in treatment arm, 840 in placebo arm | Industry-sponsored | Not reported | | Mease et al., 2015 | No | Phase III RCT | 52 weeks | 606 randomized | Novartis Pharma | Not reported | | Mease & McInnes, 2016 | Yes | Narrative review of phase III trials| At least 52 weeks | Not reported | Novartis Pharma | Not reported | | González Alonso et al., 2022 | Yes | Systematic review and meta-analysis | Week 12 primary timepoint | 23 studies included | AbbVie | Not reported | | Aparicio et al., 2021 | Yes | Narrative review of phase III trials and real-world studies | Up to 5 years | Not reported | Novartis | Not reported | | Mease et al., 2016 | Yes | Phase III RCT (SPIRIT-P1) | 24 weeks double-blind, 3 years total | 417 randomized, 382 completed 24 weeks | Eli Lilly and Company | Not reported | The primary studies enrolled biologic-naive or biologic-experienced patients with active disease. Van der Heijde et al. included only biologic-naive patients with radiographic axial spondyloarthritis, while Deodhar et al. enrolled patients with non-radiographic axial spondyloarthritis. The PsA trials (Baraliakos, Mease 2015, Mease 2016) included patients meeting CASPAR criteria. Baseline disease activity was substantial across studies, with BASDAI scores ≥4 in axial SpA trials and active joint counts in PsA trials. ## Joint and Axial Efficacy Outcomes ### Axial Spondyloarthritis Studies The ixekizumab COAST-V trial in radiographic axial SpA demonstrated superior efficacy over placebo at week 16, with ASAS40 response rates of 52% (ixekizumab Q2W), 48% (ixekizumab Q4W), 36% (adalimumab), and 18% (placebo). Both ixekizumab dosing regimens achieved statistical significance versus placebo (p<0.0001). In non-radiographic axial SpA (COAST-X), ixekizumab showed sustained efficacy with ASAS40 responses at week 16 of 40% (Q2W) and 35% (Q4W) versus 19% placebo, and at week 52 of 31% (Q2W) and 30% (Q4W) versus 13% placebo. Both primary endpoints were statistically significant (p≤0.0037). The early proof-of-concept secukinumab trial in ankylosing spondylitis achieved ASAS20 response rates of 59% versus 24% placebo at week 6, with 99.8% probability of superiority. The MAXIMISE trial in PsA with axial manifestations reported ASAS20 responses at week 12 of 63% (secukinumab 300 mg), 66% (150 mg), and 31% (placebo), with ASAS40 responses of 44% (300 mg), 40% (150 mg), and 12% (placebo). Responses were sustained through week 52, with ASAS20 rates of 80-81% across secukinumab groups. The comprehensive review by Aparicio et al. synthesized data from multiple MEASURE trials, reporting ASAS20 response rates of approximately 60% across MEASURE 1, 2, and 3, and 58.4% in MEASURE 5. The PREVENT study in TNF-naive patients showed ASAS40 rates of 41.4% and 42.2%. Long-term data demonstrated sustained improvements over 2-3 years, with mean radiographic progression (mSASSS) of only 0.3 and 95.3% of patients without baseline syndesmophytes remaining free of new syndesmophytes at week 104. ### Psoriatic Arthritis Studies The ACR response rates demonstrated consistent efficacy of IL-17A inhibition in PsA. In the Mease et al. 2015 trial, secukinumab achieved ACR20 response rates at week 24 of 50.0% (150 mg) and 50.5% (75 mg) versus 17.3% placebo (p<0.001), with ACR50 responses significantly better than placebo and sustained improvements through 52 weeks. The SPIRIT-P1 trial of ixekizumab showed ACR20 responses at week 24 of 62.1% (Q2W) and 57.9% (Q4W) versus 30.2% placebo (p≤0.001), with ACR50 and ACR70 improvements evident as early as weeks 4 and 8. Disease activity measured by DAS28-CRP decreased by -2.04 (Q2W) and -1.96 (Q4W) versus baseline, and physical function improved with HAQ-DI changes of -0.50 (Q2W) and -0.44 (Q4W). Radiographic progression measured by mTSS was minimal: 0.08 (Q2W) and 0.17 (Q4W) compared to placebo. Meta-analytic evidence from Naik et al. demonstrated pooled relative risks for achieving ACR20 of 2.04 (95% CI: 1.79-2.33; p<0.001) at week 12 and 2.01 (95% CI: 1.72-2.34; p<0.001) at week 24. ACR50 responses showed relative risks of 3.94 (95% CI: 2.83-5.49) at week 12 and 3.37 (95% CI: 2.83-4.32) at week 24. ACR70 responses demonstrated relative risks of 6.03 (95% CI: 2.12-17.18) at week 12 and 5.65 (95% CI: 3.57-8.95) at week 24. The González Alonso et al. meta-analysis confirmed these findings with odds ratios at week 12 of 3.60 (95% CI: 2.85-4.55) for ACR20, 10.85 (95% CI: 6.20-18.94) for ACR50, and 7.94 (95% CI: 4.23-14.91) for ACR70. ## Skin Efficacy Outcomes Skin outcomes were primarily reported in PsA trials. The SPIRIT-P1 trial showed robust PASI 75 response rates at week 12 of 75.3% (ixekizumab Q4W) and 69.5% (Q2W) versus 7.5% placebo, with responses observed as early as week 4. Nearly half of patients with ≥3% affected body surface area achieved complete psoriasis clearance. Nail psoriasis improved substantially with ixekizumab, with mean NAPSI score changes at week 24 of -14.0 (Q4W) and -15.5 (Q2W) versus -2.4 placebo. Complete nail psoriasis resolution occurred in 36.5% of ixekizumab Q2W patients. The González Alonso meta-analysis reported a pooled odds ratio for PASI75 at week 12 of 21.26 (95% CI: 13.72-32.95), demonstrating substantial skin efficacy across IL-17 inhibitor trials in PsA. ## Safety Profile ### Overall Adverse Events and Infections Treatment-emergent adverse event rates varied across studies. In COAST-X, overall adverse events occurred in 57% (placebo), 66% (ixekizumab Q4W), and 77% (ixekizumab Q2W). The MAXIMISE trial reported non-serious adverse events in 47% (placebo) versus 36-39% in secukinumab groups. The SPIRIT-P1 trial showed adverse event rates of 47.2% (placebo), 64.4% (adalimumab), and 65.7-66.4% (ixekizumab). The most common adverse events across trials were nasopharyngitis, upper respiratory tract infections, and injection site reactions. Infections showed similar frequencies across treatment groups in most studies, though the Naik meta-analysis found no significant increase in infection risk (RR: 1.06, 95% CI: 0.91-1.23). Serious infections occurred at low rates. COAST-V reported one serious infection each in the ixekizumab Q2W (1%), Q4W (1%), and adalimumab (1%) groups, with none in placebo. COAST-X documented one serious infection in the ixekizumab Q4W group. The MAXIMISE trial reported 7 serious infections across treatment groups. Aparicio et al.’s review noted low exposure-adjusted incidence rates for serious infections, with no active tuberculosis reactivation cases and rare new latent TB infection (EAIR 0.08 per 100 patient-years). ### Candida and Opportunistic Infections Candida infections emerged as a recognized adverse event with IL-17A blockade. COAST-V reported one Candida infection (1%) in the adalimumab group. The MAXIMISE trial documented 8 non-serious Candida infections. Mild-to-moderate candidiasis occurred in 4.7% of patients receiving secukinumab 300 mg in the studies reviewed by Mease & McInnes. The Naik meta-analysis found Candida infections trended higher but not statistically significant (RR: 3.35, 95% CI: 0.75-14.95). No treatment-emergent opportunistic infections were reported in COAST-V, and the Naik meta-analysis found no tuberculosis cases. ### Serious Adverse Events and Cardiovascular Events Serious adverse event rates were generally low. The MAXIMISE trial reported serious adverse events in 6% of secukinumab-treated patients, with no single event occurring more than once. The Naik meta-analysis found no significant difference in serious adverse events between IL-17 inhibitors and placebo (RR: 0.82, 95% CI: 0.42-1.59). Cardiovascular events were rare but notable. The MAXIMISE trial documented ischaemic cardiomyopathy, cardiogenic shock, myocardial infarction, and ischaemic stroke, with one fatal event from ischaemic cardiomyopathy not considered study drug-related. The Mease et al. 2015 study reported 4 strokes (0.6 per 100 patient-years) and 2 myocardial infarctions (0.3 per 100 patient-years) in secukinumab groups versus none in placebo, though the study was not large or long enough to definitively evaluate these uncommon events. SPIRIT-P1 reported no major cerebrocardiovascular events. ### Malignancies, Laboratory Abnormalities, and Other Safety Outcomes Malignancy rates were low. COAST-V reported no malignancies, while COAST-X found none through 52 weeks. The MAXIMISE trial documented 3 malignancies: small cell lung cancer, metastases to the spine, and an adrenal neoplasm. Aparicio et al. reported a malignancy EAIR of 0.85 per 100 patient-years. SPIRIT-P1 found no malignancies during the study period. Laboratory abnormalities were infrequent. COAST-V showed no increased risk of Grade 3 or 4 neutropenia. SPIRIT-P1 reported Grade 1 and 2 neutropenia but no Grade 3 or higher. Treatment discontinuation rates due to adverse events were low, ranging from 2.4% in SPIRIT-P1 to rates consistent with previous IL-17A inhibitor data in MAXIMISE. The Naik meta-analysis found lower discontinuation rates in treated versus placebo groups (RR: 0.54, 95% CI: 0.31-0.93), suggesting better tolerability. No deaths occurred in COAST-V, COAST-X, or SPIRIT-P1. The MAXIMISE trial reported one death from ischaemic cardiomyopathy not considered related to study drug. Immunogenicity was low. COAST-V found low frequencies of anti-drug antibodies with no association with immune reactions or reduced efficacy. SPIRIT-P1 reported 11 patients developing anti-ixekizumab antibodies, with none having detectable neutralizing antibodies. Aparicio et al. noted anti-drug antibodies in only 0.68% of AS patients and 0.35% of PsA patients. ## Synthesis The evidence demonstrates consistent efficacy of IL-17A blockade across the spectrum of psoriatic arthritis and axial spondyloarthritis, with some important distinctions based on disease phenotype and prior treatment exposure. ### Efficacy Across Disease Subtypes In radiographic axial spondyloarthritis, ixekizumab achieved ASAS40 responses of 48-52% at week 16, while secukinumab showed approximately 60% ASAS20 response rates across multiple MEASURE trials. In non-radiographic axial SpA, ixekizumab demonstrated lower but still significant ASAS40 rates of 30-40% at weeks 16 and 52. This pattern suggests greater absolute response rates in patients with established structural disease, which may reflect differences in disease duration (16 years mean symptom duration in COAST-V versus active disease without definite radiographic changes in COAST-X) or underlying disease biology. However, both phenotypes showed statistically significant improvements over placebo, establishing efficacy across the axial SpA spectrum. For PsA with predominantly peripheral arthritis, ACR20 response rates ranged from 50-62%, comparable to radiographic axial SpA responses. In PsA with axial manifestations specifically (MAXIMISE trial), ASAS20 responses of 63-66% at week 12 exceeded those in pure axial SpA trials, potentially reflecting the selected population with both peripheral and axial disease or the higher baseline inflammatory burden. ### Context-Dependent Efficacy: TNF-Naive Versus TNF-Experienced Populations The Aparicio review noted greater benefits in TNF inhibitor-naive patients compared to those with prior TNF exposure. In the PREVENT study of non-radiographic axial SpA, TNF-naive patients achieved ASAS40 rates of 41-42%, while the broader population including TNF-experienced patients showed 30-40% ASAS40 responses in COAST-X. This finding aligns with the general principle that biologic-naive populations respond more robustly to targeted therapies, whether reflecting less refractory disease biology or the absence of treatment-induced immunological changes. Both populations benefit from IL-17A blockade, but effect sizes are larger in biologic-naive cohorts. ### Dose-Response Relationships Ixekizumab dosing at 80 mg every 2 weeks versus every 4 weeks showed minimal differences in efficacy across studies. In COAST-V, ASAS40 rates were 52% (Q2W) versus 48% (Q4W); in COAST-X, 40% (Q2W) versus 35% (Q4W) at week 16; and in SPIRIT-P1, ACR20 rates were 62.1% (Q2W) versus 57.9% (Q4W). These modest differences suggest both regimens operate near the plateau of the dose-response curve, with Q4W providing substantial efficacy at lower cumulative drug exposure. For secukinumab, the MAXIMISE trial directly compared 300 mg versus 150 mg dosing and found nearly identical ASAS20 responses (63% versus 66%) at week 12 and sustained responses at week 52 (81% versus 80%). This equivalence contrasts with psoriasis dosing where 300 mg showed superiority, suggesting disease-specific dose requirements or ceiling effects in joint outcomes. ### Safety Signal Interpretation While overall infection rates were not significantly increased (RR 1.06), the pattern of Candida infections emerged consistently across studies. The non-significant pooled RR of 3.35 (95% CI: 0.75-14.95) reflects low absolute event rates but consistent directional effects, with 8 non-serious cases in MAXIMISE and 4.7% incidence at the 300 mg secukinumab dose. This mechanistic expectation based on IL-17’s role in mucocutaneous immunity appears clinically manageable, with most infections being mild to moderate. The cardiovascular events reported in the Mease et al. 2015 study (4 strokes, 2 MIs in secukinumab groups versus none in placebo) must be interpreted cautiously given the study’s acknowledgment that it was insufficiently powered for rare events. The MAXIMISE trial’s cardiovascular events occurred in a population with baseline metabolic risk factors common in PsA. Without consistent signals across all trials and with no events in SPIRIT-P1, these findings may reflect background cardiovascular disease in inflammatory arthritis populations rather than drug-specific effects, though continued surveillance remains warranted. The finding of lower discontinuation rates in treated versus placebo groups (RR 0.54) supports overall tolerability, with most discontinuations driven by insufficient efficacy rather than adverse events. ## References - [P. Mease, I. McInnes, B. Kirkham, A. Kavanaugh, P. 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