The Multibillion-Dollar Molecule: How Zumilokibart’s Phase 2 Success Sparked AbbVie’s Acquisition

Over the past year, zumilokibart (APG777), Apogee Therapeutics' investigational anti–IL-13 monoclonal antibody, has moved from a promising phase 2 candidate to one of the most closely watched assets in atopic dermatitis (AD), culminating in AbbVie’s recent agreement to acquire Apogee for approximately $10.9 billion. Taken together, the data package built across the phase 2 APEX trial suggests a drug that could change how dermatologists think about biologic dosing in moderate to severe AD.

Zumilokibart is a subcutaneous, half-life-extended monoclonal antibody that selectively targets interleukin-13 (IL-13), a cytokine central to the type 2 inflammation that drives AD. It joins an existing class of approved IL-13–targeted therapies, tralokinumab (Adbry; LEO Pharma) and lebrikizumab (Ebglyss; Eli Lilly and Company), as well as dupilumab (Dupixent; Sanofi and Regeneron), which works upstream by blocking the IL-4 receptor alpha subunit shared by IL-4 and IL-13 signaling. What distinguishes zumilokibart within this landscape is its extended half-life, which is designed to sustain cytokine suppression with less frequent dosing than currently approved options.

APEX Part A: Maintenance Through 52 Weeks

Part A of the APEX study (NCT06395948) tested whether responses could be sustained with dramatically less frequent maintenance dosing—every 3 months or every 6 months—following induction, at a 360-mg dose.¹ Among patients who had responded by week 16, 75% on 3-month dosing and 85% on 6-month dosing maintained an Eczema Area and Severity Index (EASI) score of 75 at week 52; validated investigator’s global assessment (vIGA) scores of 0 or 1 were maintained by 86% and 78% of patients, respectively.

The more unexpected finding involved the full-treated population, including patients who had not yet met response thresholds at week 16. Rather than plateauing, this group continued to show deepening improvement across lesional and itch measures through 52 weeks—a pattern investigators described as distinct from what is typically seen with existing therapies. The safety profile through 52 weeks was consistent with other IL-13–targeted agents, with noninfective conjunctivitis, upper respiratory tract infection, and nasopharyngitis as the most common treatment-emergent events.

Emma Guttman-Yassky, MD, PhD, chair of dermatology at the Icahn School of Medicine at Mount Sinai, presented the late-breaking 52-week data at the American Academy of Dermatology 2026 meeting and highlighted the significance of continued deepening responses beyond week 16, noting that this is particularly encouraging for patients who had not fully responded during the first 16 weeks of treatment. In a follow-up interview with Dermatology Times, Guttman-Yassky said patients consistently ask for less frequent injections, and that zumilokibart‘s maintenance schedule of roughly 2 to 4 doses per year represents “the dream” many patients have been requesting. She also pointed to the trial’s EASI-100 findings, comparable to a Psoriasis Area and Severity Index score of 100 in psoriasis, as unusual for a biologic in AD.

"This can definitely be a first-line treatment. I always do shared decision-making with the patients, but anyone with moderate to severe disease who is seeking fast action and doesn't want injections all the time...this definitely will be a very good drug for them. It ticks many boxes,” Guttman-Yassky said.

APEX Part B: Building the Case With Induction Data

APEX Part B, a placebo-controlled dose-ranging study, randomly assigned patients to high-, mid-, or low-dose zumilokibart or placebo.² The trial met its primary end point, with 65.9% of mid-dose patients achieving EASI-75 at week 16 vs 23.4% on placebo. All key secondary end points were also met, including vIGA 0/1 (46.0% vs 10.9%), EASI-90 (47.4% vs 9.3%), and a clinically meaningful reduction of an itch numerical rating score (I-NRS) of 4 or higher (50.5% vs 13.9%). Complete skin clearance, EASI-100, was reached by 16.5% of mid-dose patients compared with 3.4% on placebo. 

Notably, 20.6% of mid-dose patients achieved a composite of very low disease activity (EASI-90 plus I-NRS 0/1). The mid dose was selected for phase 3 based on efficacy comparable to the high dose but a lower rate of noninfective conjunctivitis (10.6% vs 20.7%). Additionally, induction required only 4 injection days, compared with 9 for the current standard of care.

Christopher Bunick, MD, PhD, associate professor of dermatology at Yale School of Medicine and editor in chief of Dermatology Times, called the results potentially “best-in-AD among biologics and on par numerically with [Janus kinase] inhibitor responses,” noting that the part B findings at week 16 were highly consistent with earlier part A data. Ruth Ann Vleugels, MD, MPH, MBA, director of the AD program at Mass General Brigham and professor of dermatology at Harvard Medical School, agreed, emphasizing the significance of the robust induction efficacy along with the previous data.

"Together with part A data demonstrating that zumilokibart can be dosed every 3 to 6 months in maintenance with continuous and even enhanced efficacy, we are seeing a strong clinical profile that offers what dermatologists are looking for in clinical practice,” Vleugels said in a news release.² 

AbbVie’s $10.9 Billion Bet on the Future of AD Biologics

That data package helped set the stage for AbbVie's announced acquisition of Apogee, under which AbbVie will acquire all outstanding shares for $135.11 per share in cash, a deal expected to close in the third quarter of 2026 pending regulatory and shareholder approvals.³ The acquisition brings zumilokibart, along with Apogee's broader pipeline—including APG273, a combination IL-13/TSLP antibody in development for asthma—into AbbVie's immunology portfolio.

“The purchase of Apogee by AbbVie is going to send shockwaves through the AD community,” Bunick told Dermatology Times at the 2026 Revolutionizing Atopic Dermatitis Conference in Nashville, Tennessee. “A company that has experience bringing molecules to market with extended half-life is now going to be in charge of piloting zumilokibart through phase 3 studies.”

The Road Ahead: Phase 3 and Beyond

Phase 3 trials (ADventure 1, ADventure 2, and ADventure TCS) are planned to begin in the second half of 2026, evaluating zumilokibart as monotherapy and in combination with topical corticosteroids. Apogee is also planning phase 2 studies in eosinophilic esophagitis and asthma. A regulatory submission could target a 2029 commercial launch, pending clinical and regulatory outcomes. Overall, the phase 2 findings represent an exciting display of innovation in AD therapy, but definitive conclusions about zumilokibart's place in practice await confirmation from the ongoing phase 3 program.

References

1. Apogee Therapeutics announces positive phase 2 part A 52-week data of zumilokibart (APG777), demonstrating maintenance and deepening of responses with every 3- and 6-month dosing in moderate-to-severe atopic dermatitis. News release. Apogee Therapeutics. March 23, 2026. Accessed July 14, 2026. https://investors.apogeetherapeutics.com/news-releases/news-release-details/apogee-therapeutics-announces-positive-phase-2-part-52-week-data

2. Apogee Therapeutics announces positive 16-week part B induction dose optimization results from phase 2 APEX trial of zumilokibart in moderate-to-severe atopic dermatitis. News release. Apogee Therapeutics. May 27, 2026. Accessed July 14, 2026. https://investors.apogeetherapeutics.com/news-releases/news-release-details/apogee-therapeutics-announces-positive-16-week-part-b-induction

3. AbbVie to Acquire Apogee Therapeutics, Deepening Immunology Portfolio. News release. AbbVie. June 22, 2026. Accessed July 14, 2026. https://news.abbvie.com/2026-06-22-AbbVie-to-Acquire-Apogee-Therapeutics,-Deepening-Immunology-Portfolio