Baricitinib Demonstrates Superior Efficacy Over Azathioprine in Adults with Moderate-to-Severe Atopic Dermatitis: Results from a Randomized Head-to-Head Trial

Highlights

• Baricitinib (4 mg daily) combined with topical corticosteroids (TCS) achieved a significantly higher EASI 75 response rate (65%) compared to azathioprine plus TCS (15%) at week 12.
• The mean baseline-adjusted post-treatment EASI scores were 5.60 for baricitinib versus 12.61 for azathioprine, representing a large effect size (Cohen’s d = -0.93).
• A 75% reduction in SCORing Atopic Dermatitis (SCORAD 75) was achieved by 55% of the baricitinib group compared to only 15% in the azathioprine group.
• Both systemic treatments were well-tolerated throughout the 12-week study period, with no serious adverse events or treatment discontinuations reported.

The Evolving Landscape of Atopic Dermatitis Management

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease characterized by intense pruritus, xerosis, and eczematous lesions. For many adults, the condition progresses to a moderate-to-severe state that significantly impairs quality of life, sleep, and mental health. While topical therapies remain the cornerstone of treatment for mild disease, patients with moderate-to-severe AD frequently require systemic intervention to achieve adequate control.

Historically, traditional immunosuppressants like azathioprine, cyclosporine, and methotrexate have been used off-label to manage refractory AD. However, these agents often come with concerns regarding slow onset of action and potential long-term toxicities. The emergence of targeted therapies, particularly Janus kinase (JAK) inhibitors, has revolutionized the therapeutic approach. Baricitinib, a selective JAK1/2 inhibitor, has shown promise in clinical trials by rapidly modulating the signaling pathways of key cytokines involved in AD pathogenesis, such as IL-4, IL-5, IL-13, and IL-31. Despite the proliferation of new therapies, head-to-head clinical trials comparing these novel agents against traditional systemic treatments are essential for optimizing clinical decision-making and healthcare resource allocation.

Study Design and Methodology

In a single-centre, open-label randomized head-to-head trial (NCT05969730), researchers compared the efficacy and safety of baricitinib versus azathioprine. The study enrolled 40 adults diagnosed with moderate-to-severe atopic dermatitis who were candidates for systemic therapy. Participants were randomly assigned in a 1:1 ratio to one of two groups:

• Group 1: Baricitinib 4 mg daily combined with topical corticosteroids (TCS) and 10% urea cream.
• Group 2: Azathioprine (1.5–2.5 mg/kg daily) combined with TCS and 10% urea cream.

The primary endpoint of the study was the proportion of patients achieving at least a 75% reduction in the Eczema Area and Severity Index (EASI 75) from baseline at week 12. Secondary endpoints included changes in SCORing Atopic Dermatitis (SCORAD), the Investigator’s Global Assessment (vIGA-AD), the Itch Numeric Rating Scale (NRS), Skin Pain NRS, and patient-reported outcomes such as the Patient-Oriented Eczema Measure (POEM), Dermatology Life Quality Index (DLQI), and the Hospital Anxiety and Depression Scale (HADS).

Key Findings: Superiority of JAK Inhibition

Efficacy Measures

At the conclusion of the 12-week treatment period, baricitinib demonstrated a clear and statistically significant advantage over azathioprine. In the baricitinib group, 65% (n = 13/20) of patients achieved the primary endpoint of EASI 75, compared to only 15% (n = 3/20) in the azathioprine group. This 50% difference (95% CI 23.9–76.1; P = 0.002) highlights the rapid and robust clinical response associated with JAK inhibition.

The mean EASI scores further underscored this disparity. After adjusting for baseline values, the post-treatment mean EASI score for the baricitinib group was 5.60, whereas the azathioprine group remained significantly higher at 12.61. The resulting difference of -7.01 (95% CI -11.86 to -2.17; P = 0.006) corresponds to a large effect size (Cohen’s d = -0.93), indicating a substantial clinical benefit for those on baricitinib.

Similar trends were observed in the SCORAD 75 achievement rates. Over half (55%) of the patients in the baricitinib group reached this threshold, compared to 15% in the azathioprine group (difference 40%, 95% CI 13.2–66.8; P = 0.01).

Patient-Reported Outcomes and Quality of Life

While the primary clinical markers showed significant differences, both groups experienced improvements in validated measures of disease burden. Improvements were noted in the vIGA-AD, Itch NRS, and Skin Pain NRS scores. Additionally, both groups saw reductions in POEM, DLQI, and HADS scores, reflecting a general improvement in the psychological and functional impact of the disease. While there was a trend favoring baricitinib across these secondary patient-reported outcomes, the differences between the two groups did not reach statistical significance in this specific cohort, likely due to the trial’s sample size.

Safety and Tolerability

Safety is a paramount concern when selecting systemic therapies for AD. In this trial, both baricitinib and azathioprine were remarkably well-tolerated. No serious adverse events (SAEs) were recorded in either group. Furthermore, there were no treatment discontinuations due to adverse effects, suggesting that at the dosages provided, both drugs have a manageable safety profile over a 12-week horizon. It is important to note, however, that the study’s duration (12 weeks) and small sample size may not capture rare or long-term safety signals associated with these medications.

Clinical Implications and Expert Commentary

The results of this trial provide high-quality evidence that baricitinib, when combined with TCS, offers a superior alternative to azathioprine for the management of moderate-to-severe AD. The rapid onset of action and the high rate of EASI 75 achievement make baricitinib a compelling choice for clinicians looking to stabilize patients with high disease activity.

From a mechanistic perspective, the success of baricitinib over azathioprine is biologically plausible. Azathioprine is a prodrug that interferes with purine metabolism, thereby inhibiting the proliferation of T and B lymphocytes. While effective, this process is relatively slow and non-specific. In contrast, baricitinib directly targets the intracellular signaling of multiple pro-inflammatory cytokines that drive the ‘atopic itch-scratch cycle’ and skin barrier dysfunction. This targeted approach likely explains the more profound reduction in EASI and SCORAD scores observed in the study.

However, clinicians should interpret these results within the context of the study’s limitations. As a single-centre, open-label trial with 40 participants, the findings may not be fully generalizable to all ethnic populations or those with significant comorbidities. Furthermore, the 12-week duration provides a snapshot of short-term efficacy but does not address the comparative long-term maintenance of remission or the longitudinal safety of JAK inhibitors versus traditional immunosuppressants.

Conclusion

The head-to-head comparison of baricitinib and azathioprine reveals that baricitinib + TCS is significantly more effective in reducing disease severity in adults with moderate-to-severe atopic dermatitis. With a 65% EASI 75 response rate and a large effect size relative to azathioprine, baricitinib represents a powerful tool in the dermatological armamentarium. While both treatments demonstrated excellent safety over 12 weeks, the superior clinical efficacy of baricitinib suggests it should be prioritized for patients requiring rapid and substantial improvement in their skin condition and quality of life.

Funding and Trial Registration

This study was registered at ClinicalTrials.gov under the identifier NCT05969730. Funding details and specific institutional support are documented within the original publication in the British Journal of Dermatology.

References

1. Malekan M, Rahmatpour Rokni G, Gholizadeh N, et al. Efficacy and safety of baricitinib versus azathioprine, both combined with topical corticosteroids, in patients with moderate-to-severe atopic dermatitis: a single-centre randomized open-label trial. Br J Dermatol. 2026;194(3):461-469. doi:10.1093/bjd/ljaf456.
2. Simpson EL, Lacour JP, Spelman L, et al. Baricitinib in patients with moderate-to-severe atopic dermatitis and inadequate response to topical corticosteroids: results from two randomized monotherapy phase III trials. Br J Dermatol. 2020;183(2):242-255.
3. Menges D, Aschwanden MS, Enzmann FB, et al. Systematic review and network meta-analysis of systemic treatments for moderate-to-severe atopic dermatitis. J Allergy Clin Immunol. 2021;148(4):1017-1028.