Palmoplantar pustulosis represents a chronic, debilitating dermatosis characterized by sterile, neutrophil-rich intraepidermal pustules on the palms and soles. Clinicians frequently encounter immense therapeutic frustration because conventional therapies yield unpredictable outcomes. However, recent scientific advances have turned clinical attention toward intracellular signalling pathways. In particular, the emerging role of upadacitinib in palmoplantar pustulosis has ignited substantial clinical excitement. By targeting Janus kinase 1, targeted therapy interrupts downstream cytokine cascades that sustain neutrophilic infiltration and persistent cutaneous inflammation. Consequently, novel clinical data now offer much-needed optimism for dermatologists managing recalcitrant disease presentations.

The Mechanism and Rationale for Upadacitinib in Palmoplantar Pustulosis

Palmoplantar pustulosis creates persistent physical distress, marked by recurring crops of painful, sterile pustules on thick acral skin. Historically, clinicians have categorized the condition under the psoriasis spectrum, but therapeutic responses to classical antipsoriatic biologics often disappoint. In fact, antagonists targeting interleukin-17 or interleukin-23 fail to deliver consistent clearance in this distinct pustular phenotype. Researchers now recognize that the disease biology relies heavily on intricate cytokine signalling networks involving interleukin-6, interleukin-22, and interferons. Consequently, intracellular blockade provides a compelling therapeutic strategy.

Janus kinase inhibitors disrupt these inflammatory cascades by blocking the signal transducer and activator of transcription pathway. Upadacitinib functions as an oral, highly selective inhibitor of Janus kinase 1, offering enhanced selectivity over other kinase family members. By specifically preventing cytokine-receptor signalling, upadacitinib downregulates the chemoattractants that orchestrate neutrophilic recruitment into intraepidermal pustules. Furthermore, this targeted mechanism dampens keratinocyte hyperproliferation and mitigates epidermal barrier dysfunction. Because patients with pustular disease frequently present with debilitating fissures that impair daily manual tasks and mobility, achieving rapid enzymatic suppression represents a critical clinical goal. Therefore, evaluating upadacitinib in palmoplantar pustulosis addresses an urgent therapeutic void in modern medical dermatology.

Design and Methodology of the JAKPPPOT Trial

Conducting clinical trials in palmoplantar pustulosis remains notoriously complex due to low disease prevalence and unique patient demographics. For instance, high rates of tobacco smoking and systemic cardiovascular comorbidities often deter trial participation or increase participant attrition. To determine whether a definitive randomised controlled trial is truly viable, investigators initiated the JAKPPPOT study at a national specialist dermatology centre in the United Kingdom. This open-label, assessor-blinded feasibility trial evaluated adult patients suffering from moderate-to-severe disease.

Eligible participants received oral upadacitinib once daily for a treatment duration of eight weeks. However, while clinicians administered standard 30 mg doses, they thoughtfully applied a reduced 15 mg regimen for individuals classified as higher cardiovascular or thromboembolic risk. In addition, the study protocol incorporated pre-established primary feasibility endpoints centered on three domains: recruitment consent rates, patient adherence, and overall treatment acceptability. Crucially, researchers harmonized study procedures and outcome measures with a previous clinical trial in pustular psoriasis, known as the APRICOT study. Consequently, this deliberate alignment permitted direct comparison with historic placebo control data. Finally, through linear mixed-effects modelling, investigators adjusted for baseline disease characteristics to derive an unbiased, exploratory estimate of true therapeutic efficacy.

Feasibility Metrics, High Adherence, and Patient Acceptability

The trial demonstrated remarkable success across all prespecified feasibility benchmarks, proving that clinical trial protocols for this challenging condition can succeed. Specifically, investigators contacted 67 potentially eligible candidates, and 28 individuals provided formal consent, reflecting a consent rate of 41.8%. Ultimately, 20 participants commenced active therapy, comprising a predominantly female cohort of 85% with a mean age of 46.0 years. These demographic characteristics accurately mirror the real-world population presenting to hospital clinics.

Adherence outcomes proved particularly encouraging for long-term clinical implementation. Exactly 19 of the 20 enrolled participants achieved adherence levels of 80% or greater throughout the eight-week treatment timeline. Overall, the mean proportion of covered treatment days reached an impressive 95.7%, demonstrating excellent patient compliance with daily oral dosing. Furthermore, 18 out of 19 completing participants rated the therapeutic intervention as acceptable or completely acceptable on a post-treatment Likert scale. In addition, these findings indicate that patients find daily oral small molecules far more convenient and tolerable than cumbersome topical ointments or frequent systemic injections. Consequently, the study team confirmed that participants readily embrace this treatment protocol, establishing solid justification for transitioning to a larger multi-centre trial.

Exploratory Efficacy Signals and Historic Comparator Data

Beyond operational feasibility, the JAKPPPOT trial revealed dramatic improvements in objective cutaneous disease activity. Investigators utilized the Palmoplantar Pustulosis Psoriasis Area and Severity Index to evaluate clinical responses systematically. At baseline, participants exhibited substantial cutaneous involvement, with a mean severity score of 20.3. However, following eight weeks of upadacitinib therapy, this score plummeted to an average of 4.6. In stark contrast, individuals receiving historic placebo showed minimal change, shifting from 18.0 at baseline to 15.4 at week eight.

When researchers applied Gaussian mixed-effects models to adjust for baseline variables, the relative treatment difference reached -12.3 in favor of upadacitinib. Therefore, this significant separation underscores a profound therapeutic effect. Moreover, responder analyses corroborated this striking divergence. An astounding 100% of patients treated with upadacitinib attained a 50% improvement in disease severity, compared to merely 16.1% in the historic placebo arm. Similarly, 65.0% achieved a 75% improvement with upadacitinib, whereas only 3.2% of placebo recipients met this benchmark. Because pustular flares severely compromise quality of life, such high response rates within eight weeks emphasize the exceptional potency of targeted kinase inhibition.

Safety Observations and Practical Clinical Considerations

Evaluating safety remains paramount whenever physicians initiate Janus kinase inhibitors, particularly among populations with frequent cardiovascular risk factors. In the JAKPPPOT trial, investigators noted that the adverse event profile remained consistent with known drug characteristics. Specifically, the most frequently observed adverse events included mild headaches, acneiform eruptions, and transient upper respiratory tract infections. Importantly, no new safety signals or unexpected serious adverse events emerged during the eight-week intervention window.

Nevertheless, practicing dermatologists must exercise meticulous clinical caution when applying these findings in day-to-day healthcare environments. Because patients with palmoplantar pustulosis frequently report smoking histories, clinicians should perform thorough cardiovascular and thromboembolic assessments before starting treatment. Furthermore, dose stratification, such as selecting 15 mg instead of 30 mg for higher-risk individuals, represents a prudent strategy to safeguard patient health while retaining therapeutic efficacy. Additionally, physicians must screen for latent infections, notably tuberculosis and viral hepatitis, which remain highly prevalent across endemic healthcare settings. In conclusion, the JAKPPPOT trial provides compelling justification for definitive, multi-centre active-comparator trials, paving the way for transformational advances in managing this intractable pustular disorder.

Frequently Asked Questions

How does upadacitinib improve symptoms in palmoplantar pustulosis?

Upadacitinib acts as a selective oral Janus kinase 1 inhibitor that directly interrupts intracellular inflammatory signalling cascades. By blocking downstream pathways triggered by interleukin-22, interferon-gamma, and other pro-inflammatory mediators, the drug prevents the ongoing recruitment and activation of neutrophils in epidermal sweat duct ridges. Consequently, patients experience a rapid cessation of sterile pustule eruption, marked diminution of erythema, and noticeable healing of painful palmoplantar fissures, ultimately improving physical function.

Why did the JAKPPPOT study use a historic control cohort?

Investigators utilized historic placebo data from the harmonized APRICOT trial because palmoplantar pustulosis is an uncommon condition with substantial recruitment hurdles. High smoking prevalence and medical comorbidities among affected individuals often make recruiting large placebo cohorts challenging. Therefore, comparing feasibility cohort outcomes against standardized historic control datasets allowed researchers to generate robust, baseline-adjusted effect size estimates without unnecessarily withholding active therapy from patients suffering from severe and painful refractory cutaneous lesions.

What safety monitoring is required when prescribing upadacitinib for pustular skin disease?

Clinicians must evaluate baseline cardiovascular risks, thromboembolic history, latent tuberculosis, and viral hepatitis before initiating upadacitinib therapy. Additionally, routine laboratory monitoring should track complete blood counts, hepatic transaminases, serum creatinine, and lipid profiles at regular intervals during treatment. Because Janus kinase inhibitors slightly increase the risk of herpes zoster and respiratory infections, physicians must maintain vigilance, encourage appropriate adult vaccinations, and adjust dosages when treating elderly or high-risk patients.

Disclaimer: This content is for informational and educational purposes only. It is not intended to provide medical advice or to be a substitute for professional medical advice, diagnosis, or treatment. Patients should always consult their physician or other qualified health care provider for specific medical guidance. Refer to the latest local and national guidelines for clinical practice.

References

1. Gleeson D et al. Upadacitinib for Palmoplantar Pustulosis: An Open-label, Assessor-blinded Feasibility Study Using Historic Control Data (JAKPPPOT). Br J Dermatol. 2026 Sep 26. doi: undefined. PMID: 42791196.
2. Zheng Y, Zhang X, Wang H, Yang R, Luo S. Clinical efficacy and safety of upadacitinib in the treatment of palmoplantar pustulosis: A single-center retrospective study. Indian J Dermatol Venereol Leprol. 2025;91:540-3.
3. Du N, Yang J, Zhang Y, Lv X, Cao L, Min W. Successful treatment of refractory palmoplantar pustulosis by upadacitinib: report of 28 patients. Front Med (Lausanne). 2024;11:1472391.