Korean patients with atopic dermatitis (AD) -- the most common form of eczema -- aren’t short on complaints, but for many, it starts on the face. Lesions across the forehead or neck can upend social lives and sleep schedules.

So when LEO Pharma’s Adtralza (tralokinumfab) showed fewer eye-related side effects and stronger control in those hard-to-treat areas, dermatologists began paying closer attention.

The drug, a selective interleukin-13 (IL-13) inhibitor, targeting a key cytokine that drives type 2 inflammation, isn’t just aiming for better skin. It’s gunning for Dupixent (dupilumab)’s grip on Korea’s moderate-to-severe AD market with a cheaper price tag and the option to reduce injection frequency to once every four weeks.

But it’s running into a familiar wall: a payer system that still bars patients from switching between biologics -- even when the current drug stops working.

Adtralza takes aim at Dupixent in visible lesions and eye safety

“In head and neck dermatitis, the lesions tend to cluster in smaller areas, so it’s hard to reach the EASI-23 reimbursement threshold,” said Professor Lee Ji-hyun of Seoul St. Mary’s Hospital, referring to the severity score used to qualify for biologics. “And yet these patients suffer most, because those are the areas everyone can see.”

Lee’s remarks came during a press conference last week marking one year since Adtralza’s reimbursement approval in Korea, where it’s indicated for adults and adolescents with chronic severe AD. LEO still trails Dupixent in market share, but it’s aiming where the incumbent stumbles: the face.

“We’ve seen consistent reductions in EASI scores across all body regions in four-year tralokinumab data,” Lee added. “And fewer than 1 percent of patients reported paradoxical erythema or eye-related events. That matters, because head and neck dermatitis is one of the most burdensome phenotypes we see in practice.”

A Korean study spanning 52 weeks found that nearly 1 in 5 Dupixent patients developed facial erythema -- persistent redness often tied to inflammation -- while 17.2 percent experienced conjunctivitis, an eye irritation that can lead to discomfort, tearing or blurred vision. 

Sanofi Korea didn’t dispute the figures but emphasized that most cases are “rare and manageable” without discontinuation. “These reactions aren’t unique to Dupixent,” the company said, adding they may reflect “underlying disease mechanisms more than any one therapy.”

Still, the visual burden of AD remains a key factor for patients and a critical consideration for dermatologists aiming to reduce psychological distress.

Adtralza’s main differentiator is its flexibility. After 16 weeks, patients who reach near-clear skin can stretch out injections to every four weeks. According to LEO, more than 90 percent of patients who switch from biweekly to monthly Adtralza dosing after 16 weeks maintain EASI-75 response rates, a standard measure indicating a 75 percent improvement in eczema severity. Dupixent, by contrast, sticks to a biweekly schedule, which Sanofi Korea defends as “the most evidence-backed and durable regimen to date.”

Policy gridlock limits switching as both sides stake out long-term value

But durability only matters if patients stay on the drug. In a real-world Dutch study, Dupixent showed a treatment continuation rate of 70 percent at 18 months -- nearly double that of tralokinumab (39.4 percent), abrocitinib (51.5 percent), or baricitinib (20.4 percent). “This reflects superior long-term safety and efficacy compared to other available treatments,” Sanofi Korea said.

It’s also worth noting that Dupixent was the first and only advanced treatment for eczema available for several years. According to the study, almost 27 percent of patients eventually switched to a second therapy, underscoring the growing need for personalized strategies, particularly in cases involving sensitive or highly visible areas such as the face and hands.

Beyond patient retention, Sanofi Korea is leaning on biology to make its case. Dupixent blocks both IL-4 and IL-13 by targeting a shared receptor, IL-4Rα, which the company says allows for "broader control of type 2 inflammation over the long-term." 

Sanofi says this dual blockade not only reduces allergic flare-ups but also helps repair the skin’s protective barrier and improves symptoms throughout the body in ways IL-13-only therapies can’t fully replicate. 

LEO sees it differently. In nearly five years of follow-up in the ECZTEND trial, patients on tralokinumab showed reduced levels of inflammatory markers like TARC and periostin, with skin gene expression shifting toward a non-lesional profile. By week 248, 92.9 percent had reached EASI-75, while 66.7 percent achieved clear or almost-clear skin on the IGA scale. Dermatology Life Quality Index scores remained below 5, indicating minimal impact on daily living.

“Patients stayed clear, slept better, and reported less itching, without new safety signals emerging,” Lee said. That kind of consistency, she added, is what makes Adtralza a compelling alternative for patients with persistent facial symptoms or intolerance to eye side effects.

Sanofi Korea countered that adverse events like conjunctivitis are far less common in Dupixent’s other approved indications, suggesting the root cause may lie in the disease itself rather than the drug.

And while LEO points to fewer eye events in its own long-term trials, Sanofi says the jury is still out. “Facial reactions have also been seen with IL-13 inhibitors,” the company said.

There’s also a theory gaining traction among Korean dermatologists that Dupixent’s IL-4Rα inhibition could indirectly activate TH17 pathways, which plays a role in inflammation. This shift, they say, could encourage the growth of Malassezia, a yeast commonly found on the face and neck, and potentially worsen symptoms in those areas. “We need more research to confirm that,” said Lee. “But it might explain the head-and-neck outcomes we’re seeing.”

Reimbursement restrictions remain a flashpoint. To qualify, Korean patients must exceed a 23-point EASI score -- a threshold Lee said many with facial or hand lesions fail to meet despite severe distress.

“In head and neck AD, lesions are concentrated in small areas, so the overall body surface area affected is small and it’s hard to exceed the 23-point EASI threshold,” she explained. “We need evaluation metrics that weigh factors like itch intensity and psychological impact, not just visible surface area.”

Hand eczema is another focus. “Even when it doesn’t take up much body surface area, it affects everything the patient does,” said Professor Lee Dong-hun of Seoul National University Hospital (SNUH) during last week's conference. “I’ve seen strong responses to Adtralza, and clinical trials are underway to validate that.”

LEO said it is wrapping up a global phase 3 study in moderate-to-severe atopic hand eczema, with results expected by the end of the year. The trial, which includes Korean sites, could help expand the drug’s reach in new patient groups, the company added.

Meanwhile, regulatory reform is moving slowly. Korea’s March policy shift allowed cross-switching between Janus kinase (JAK) inhibitors and biologics, but not between biologics themselves. That means a patient on Dupixent who experiences side effects can’t be moved to Adtralza unless they first cycle through a different drug class.

Sanofi Korea, for its part, said it supports more flexible sequencing -- as long as it’s evidence-based, but confirmed no head-to-head trial is planned.

For now, clinicians are left weighing dose schedules, cost, and side effect profiles against rigid policy. “We’re at the point where we can start tailoring therapy based on body-region response, comorbidities, and patient preferences,” said Lee of SNUH. “And in older patients or those with chronic conditions, JAK inhibitors aren’t always viable.”