Safety and immunologic consequences of IL-17A antagonism (infections, hypersensitivity)

IL-17A antagonists demonstrate a favorable safety profile with the primary immunologic consequence being an increased risk of mild-to-moderate mucocutaneous Candida infections, while serious infections, opportunistic infections, and hypersensitivity reactions remain uncommon and other safety outcomes stable over long-term follow-up.

Abstract

IL-17A antagonists demonstrate a favorable safety profile across psoriasis, psoriatic arthritis, and ankylosing spondylitis, with the most consistent safety signal being an increased risk of Candida infections. Candida infection rates varied by indication (2.2-2.9 per 100 patient-years in psoriasis, 1.5 in psoriatic arthritis, 0.7 in ankylosing spondylitis), were predominantly mild-to-moderate and mucocutaneous, and showed a dose-response relationship with secukinumab (3.55 per 100 subject-years at 300 mg versus 1.85 at 150 mg). In contrast, serious infection rates remained low (1.2-1.9 per 100 patient-years) with no significant increase compared to placebo, opportunistic infections were rare (<0.2 per 100 patient-years), and no tuberculosis reactivation cases occurred in pooled clinical trials. Hypersensitivity reactions were uncommon, with injection site reactions occurring at low rates (0.6-1.6 per 100 patient-years with secukinumab), though rates varied substantially between different IL-17A antagonists. Anti-drug antibody development occurred in less than 1% of patients without clinical consequences.

Other safety outcomes remained low and stable in long-term follow-up. Major adverse cardiovascular events occurred at rates below 0.7 per 100 patient-years without temporal increase, malignancy incidence remained at or below 1 per 100 patient-years, inflammatory bowel disease was uncommon (0.01-0.4 per 100 patient-years), and neutropenia was generally mild and transient. Comprehensive pooled analyses including over 12,000 patients with up to 5 years of exposure and post-marketing surveillance data exceeding 96,000 patient-years demonstrated no increase in serious adverse events, infections, or other safety outcomes over time, supporting the long-term safety of IL-17A antagonism across inflammatory conditions.

Results

Characteristics of Included Studies

This review included 10 sources comprising primary randomized controlled trials, systematic reviews and meta-analyses, and pooled analyses with post-marketing surveillance data examining IL-17A antagonists across multiple indications.

Infection Outcomes

Overall Infection Rates

Infection rates varied across studies and indications, with most reporting exposure-adjusted incidence rates per 100 patient-years.

Hypersensitivity and Immunogenicity Outcomes

Injection Site Reactions

Hypersensitivity reactions were uncommon with IL-17A antagonists. The reporting rate for hypersensitivity was 2.4 per 100 patient-years in the pooled analysis by Deodhar et al.. Development of treatment-emergent anti-drug antibodies (ADAs) occurred in less than 1% of patients, with no discernible impact on efficacy or pharmacokinetics.

Other Safety Outcomes

Major adverse cardiovascular events (MACE) remained low across all indications and studies, with rates below 0.7 per 100 patient-years. In the psoriatic arthritis trial by Mease et al., four patients receiving secukinumab experienced stroke (0.6 per 100 patient-years) and two had myocardial infarction (0.3 per 100 patient-years), compared to zero events in the placebo group. Additionally, malignancy incidence remained low and stable across indications.

Synthesis

Safety outcomes with IL-17A antagonists showed clear patterns that varied by indication and patient population. Candida infection rates were highest in psoriasis patients (2.2-2.9 per 100 patient-years), intermediate in psoriatic arthritis (1.5 per 100 patient-years), and lowest in ankylosing spondylitis (0.7 per 100 patient-years). Furthermore, serious infection rates showed the inverse pattern, being highest in psoriatic arthritis patients (1.8-1.9 per 100 patient-years) and lowest in ankylosing spondylitis (1.2 per 100 patient-years). These patterns reflect differences in baseline mucocutaneous immune function and the extent of IL-17-dependent defense mechanisms at different anatomic sites.

The strongest evidence for IL-17A antagonist safety comes from large pooled analyses with post-marketing surveillance, showing no increase in serious infections, inflammatory bowel disease, malignancy, or MACE over time, providing reassurance about long-term safety.