Phase 1b Asthma Data Highlight Durable IL-13 Suppression with Zumilokibart

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease driven largely by type 2 (T2) immune dysregulation, with interleukin-13 (IL-13) now recognized as a central pathogenic cytokine. IL-13 contributes to epidermal barrier dysfunction, pruritus, and chronic inflammation through direct effects on keratinocytes, sensory neurons, and immune cells. As a result, IL-13 has emerged as a validated therapeutic target in dermatology, with multiple biologics demonstrating clinical benefit.¹ Despite these advances, unmet needs remain, particularly regarding durability of response, dosing frequency, and long-term disease control.

Apogee Therapeutics recently reported positive interim results from a phase 1b trial of zumilokibart (APG777), a novel half-life-extended monoclonal antibody targeting IL-13, in patients with mild to moderate asthma enriched for type 2 inflammation.² Although conducted in a respiratory population, these findings are relevant to dermatology clinicians given the shared immunopathology between asthma and AD and Apogee’s parallel late-stage clinical development of zumilokibart in atopic dermatitis.

MORE: APG777 May Ease Burden on Patients With AD, Guttman-Yassky Discusses APG777 as a Potential Breakthrough in AD, APG777 Trial Demonstrates Efficacy, Safety in AD

Mechanistic Relevance to AD

IL-13 is a key driver of AD, contributing to skin barrier disruption, epidermal thickening, and ongoing type 2 inflammation. Several measurable indicators of IL-13 activity are known to track with disease severity and response to treatment.³ One such indicator is fractional exhaled nitric oxide (FeNO), which, although measured in asthma, reflects IL-13–driven inflammation and has been widely used as a marker of type 2 immune activity.⁴

As a result, findings from the phase 1b asthma study provide useful indirect evidence about how strongly and how long zumilokibart can block IL-13 activity—features that are particularly important for chronic skin diseases like AD, where sustained control over time is essential.

Overview of Phase 1b Asthma Study

The randomized, double-blind, placebo-controlled phase 1b study enrolled 19 adults with mild to moderate asthma and baseline FeNO ≥25 ppb, selecting for a type 2–high population analogous to patients with moderate to severe AD. Participants received a single 720 mg dose of zumilokibart or placebo and were followed for up to 32 weeks.

Primary objectives focused on safety and tolerability, while secondary and exploratory endpoints included FeNO suppression and lung function measures.

Safety Profile and Dermatologic Relevance

Zumilokibart was reported to be well tolerated, with no Grade 3 or higher treatment-emergent adverse events and no serious adverse events. The only adverse event observed in more than 1 patient was gastroesophageal reflux disease (2 patients). Importantly for dermatologists, no conjunctivitis, injection-site reactions, or anti-drug antibodies were observed.

Conjunctivitis has emerged as a clinically relevant adverse event with some IL-13–targeting therapies in AD. While conclusions cannot be drawn from a small, single-dose asthma study, the absence of ocular or cutaneous safety signals in this dataset is notable and will be closely scrutinized in ongoing and future AD trials.

Pharmacodynamic Findings and Implications for AD Treatment

The most clinically informative outcome was the magnitude and durability of FeNO suppression following a single dose. Zumilokibart achieved a mean maximum FeNO reduction of 45 ppb, representing approximately a 60% decrease from baseline. Suppression was maintained through 16 weeks in all treated patients and extended to 32 weeks in those with longer follow-up.

For the field of dermatology, these findings suggest sustained IL-13 pathway inhibition consistent with extended dosing intervals. In AD, where chronic disease management often necessitates years of therapy, reduced dosing frequency may improve adherence, patient satisfaction, and long-term disease control.

Integration with Atopic Dermatitis Clinical Program

Apogee is concurrently advancing zumilokibart in AD through the phase 2 APEX program, with induction and maintenance data expected in 2026 and plans to initiate phase 3 trials in the second half of the year. The asthma phase 1b results complement earlier dermatology data by reinforcing the biologic’s durability, systemic IL-13 suppression, and favorable tolerability profile.

Additionally, improvements in asthma and sinusitis symptoms observed in AD patients with comorbid type 2 diseases in earlier trials further support the concept of zumilokibart as a “pipeline-in-a-product” targeting shared inflammatory pathways across organ systems.

Conclusion

While derived from a small asthma study, the phase 1b interim data for zumilokibart provide mechanistic and translational insights relevant to dermatologists managing AD. The demonstrated durability of IL-13 inhibition after a single dose, coupled with a favorable early safety profile, aligns with key therapeutic goals in AD. Ongoing phase 2 and planned phase 3 AD trials will be critical in determining whether these pharmacodynamic advantages translate into sustained clinical benefit and differentiation within an increasingly competitive AD treatment landscape.

References

1. Napolitano M, di Vico F, Ruggiero A, Fabbrocini G, Patruno C. The hidden sentinel of the skin: An overview on the role of interleukin-13 in atopic dermatitis. Front Med (Lausanne). 2023 Apr 18;10:1165098. doi: 10.3389/fmed.2023.1165098.
2. Apogee Therapeutics announces positive interim results from phase 1b trial of zumilokibart (APG777), its potentially best-in-class anti-IL-13 antibody, in patients with mild-to-moderate asthma and highlights 2026 anticipated milestones and outlook. News release. Apogee Therapeutics. Published January 6, 2026. Accessed January 7, 2026. https://investors.apogeetherapeutics.com/news-releases/news-release-details/apogee-therapeutics-announces-positive-interim-results-phase-0
3. Sander N, Stölzl D, Fonfara M, et al. Blockade of interleukin-13 signalling improves skin barrier function and biology in patients with moderate-to-severe atopic dermatitis. Br J Dermatol. 2024;191(3):344-350. doi:10.1093/bjd/ljae138
4. Maniscalco M, Fuschillo S, Mormile I, Detoraki A, Sarnelli G, Paulis A, Spadaro G, Cantone E; PATH-2 TASK FORCE. Exhaled nitric oxide as biomarker of type 2 diseases. Cells. 2023 Oct 25;12(21):2518. doi: 10.3390/cells12212518.