The dual IL-17A and IL-17F-inhibiting nanobody sonelokimab demonstrated robust efficacy in treating psoriatic arthritis (PsA) in the phase 2 ARGO trial, with response rates continuing to improve through 24 weeks of treatment. The randomized, double-blind, placebo-controlled study enrolled 207 patients across multiple treatment arms and met its primary endpoint with statistically significant improvements in joint and skin outcomes.
Primary Efficacy Results
The ARGO trial successfully met its primary endpoint, with significantly greater proportions of patients treated with sonelokimab achieving ACR50 response compared to placebo at week 12. Patients receiving sonelokimab 120 mg with induction dosing achieved a 46.5% ACR50 response rate (odds ratio = 4.0, 95% CI = 1.4-11.3, P < 0.01), while those on 60 mg with induction achieved 46.3% (odds ratio = 3.6, 95% CI = 1.3-9.9, P < 0.05), compared to 20.0% with placebo.
Response rates continued to improve through week 24, with 58.1-61.0% of patients randomized to sonelokimab achieving ACR50 response. Notably, patients who switched from placebo to sonelokimab 120 mg at week 12 showed substantial improvement, with 54.1% achieving ACR50 response at week 24, representing a 34.1% increase from week 12 to week 24.
Skin Clearance and Composite Outcomes
Sonelokimab demonstrated exceptional efficacy in skin clearance, with the key secondary endpoint of PASI 90 response at week 12 being met. Patients treated with sonelokimab 60 mg with induction achieved 76.9% PASI 90 response (odds ratio = 25.8, 95% CI = 5.4-122.8, P < 0.001), while those on 120 mg with induction achieved 59.3% (odds ratio = 8.3, 95% CI = 2.1-33.3, P < 0.01), compared to 15.4% with placebo.
Complete skin clearance (PASI 100) was achieved by 37.5-57.7% of patients treated with sonelokimab at week 12, improving to 59.4-63.0% by week 24. The composite endpoint of ACR50 + PASI 100 was achieved by up to 51.9% of patients treated with sonelokimab at week 24, while up to 48.1% achieved the higher threshold composite of ACR70 + PASI 100.
Multidomain Disease Activity
Minimal disease activity (MDA), a comprehensive measure encompassing multiple disease domains, was achieved by 43.9% of patients treated with sonelokimab 60 mg with induction versus 20.0% with placebo at week 12 (nominal P = 0.022). The proportion of patients achieving MDA continued to increase to week 24, reaching 61.0% and 51.2% in the sonelokimab 60 mg and 120 mg with induction arms, respectively.
Sonelokimab demonstrated benefits in patient-reported outcomes, with improvements in PsAID-12 scores versus placebo at week 12 (nominal P < 0.01 for all doses versus placebo). Improvements were sustained across multiple PsAID domains, including activities, anxiety, coping, depression, discomfort, fatigue, functional capacity, pain, shame, skin problems, sleep disturbance and social participation through week 24.
Safety Profile
Sonelokimab was well-tolerated with a safety profile consistent with IL-17 family cytokine inhibition. Any-grade treatment-emergent adverse events occurred in 29.3-39.5% of patients across sonelokimab arms during the 12-week placebo-controlled period, compared to 38.5% with placebo. Through the full 24-week study period, 45.1% and 58.8% of patients experienced treatment-emergent adverse events in the 60 mg and 120 mg dose groups, respectively.
The most frequently occurring adverse events in sonelokimab-treated patients were nasopharyngitis (5.2-6.1%), upper respiratory tract infection (4.1-6.1%), injection-site erythema (3.1-3.7%) and headache (2.4-4.1%). Importantly, there were no cases of inflammatory bowel disease, depression, suicidal ideation and behavior, or adverse events of elevated liver enzymes above three times the upper limit of normal in patients treated with sonelokimab.
Four cases of mild or moderate oral candidiasis were reported (2.1-2.4% across dose groups), with no cases of recurrent candidiasis or esophageal candidiasis observed. Serious treatment-emergent adverse events and those leading to treatment discontinuation were infrequent, with no serious adverse events in either sonelokimab dose group deemed treatment-related.
Subgroup Analyses and Clinical Implications
The ARGO trial was notable as the first PsA study to stratify patients by sex, addressing an increasingly recognized factor affecting treatment response. The efficacy of sonelokimab was largely comparable across key subgroups, with female patients achieving key clinical outcomes at similar or numerically higher rates than male patients. Clinical benefit appeared maintained regardless of sex, weight, concomitant methotrexate treatment, or disease severity at baseline.
According to Philip J. Mease, director of rheumatology research at Providence Swedish Medical Center in Seattle, sonelokimab "is a promising product that is now in the midst of phase 3 trials." The study results support the theoretical advantage of dual IL-17A and IL-17F inhibition, as preferential elevation of IL-17F compared with IL-17A has been described in psoriatic tissue, and existing evidence suggests that IL-17A neutralization alone may not be sufficient for full disease control in PsA.
Study Design and Patient Population
The ARGO trial enrolled patients 18 years of age or older with confirmed PsA diagnosis, active disease defined by tender joint count ≥3 and swollen joint count ≥3, and either currently active psoriasis or dermatologist-confirmed history of psoriasis. Key exclusion criteria included prior exposure to more than two biologics and previous failure of IL-17 or TNF inhibitors.
Baseline characteristics were similar across treatment arms, with 49.3% of patients being female and 17.4% having previously received at least one biologic DMARD. Overall, 71.0% of patients were receiving concomitant methotrexate at baseline. The study demonstrated low discontinuation rates, with fewer than 3% of patients discontinuing treatment in the first 12 weeks and 4.8% discontinuing through 24 weeks.
The encouraging results from this phase 2 study have led to the initiation of two ongoing phase 3 trials: IZAR-1 (NCT06641076) in biologic-naive PsA patients and IZAR-2 (NCT06641089) in patients with prior inadequate response or intolerance to biologic TNF inhibitors, which will further establish sonelokimab's potential as a future treatment for psoriatic arthritis.
