The Medicine King’s house was robbed.

The legend of Dupixent (dupilumab, hereafter Dupi) continues, with projected sales of approximately $18.291 billion in 2025, a 25.2% increase year-over-year.

Unbeknownst to many, behind Dupi’s rapid growth, an unexpected rival has “stolen the market.”

On March 5th, Gilead Sciences released its 2025 financial report, highlighting the commercial success of IL-31 monoclonal antibody Nemolizumab (hereafter Nemo), which has attracted market attention. It was approved by the FDA for adult nodular prurigo in August 2024 and by the EU for moderate-to-severe atopic dermatitis (AD) and adult prurigo nodularis (PN) in February 2025. In its first full year of commercialization, Nemo achieved $452 million in sales. With this strong momentum, Gilead has raised Nemo’s global peak sales guidance from over $2 billion to over $4 billion.

Initially, Nemo was not favored by the market, due to the limited ceiling of the nodular prurigo market and its moderate efficacy in AD (skin lesion improvement), which ranked below many competitors.

Now, Nemo’s unexpectedly strong performance has shown that beyond absolute skin lesion improvement, there remains a huge unmet market for treating atopic dermatitis and nodular prurigo, capable of spawning new blockbuster drugs.

01

The most unlikely rival “stealing the market”

The core pathogenic pathway in AD is the Th2-driven immune inflammatory response. Compared to upstream targets like IL-4/IL-31 and OX40, Nemo targets IL-31, a downstream mediator of Th2-driven pruritus, not a broader inflammatory regulator. Naturally, it does not have an advantage in skin lesion efficacy indicators such as EASI-75 and IGA 0/1.

Comparing the 16-week phase 3 clinical data of approved AD biologics, Nemo’s EASI-75 and IGA 0/1 rates are 12%-15% and 11%-12%, respectively, far below IL-4/IL-13 antibodies, which reach over 30% and 17%-28%.

Losing to the current strongest autoimmune drug king is not shameful (after all, the molecules that lose can queue up at the door). The key is that Nemo targets Dupi’s weaknesses and creates differentiation.

Pruritus is the most core and painful symptom for AD patients. Modern treatment concepts regard “rapid and strong itch relief” as equally or even more important than skin lesion clearance. In fact, Dupi’s onset of action is not fast enough.

Clinical trials and real-world studies show that patients using Dupi experience a reduction in pruritus scores (WI-NRS) starting from week 2, with significant relief typically occurring between weeks 2 and 4.

In contrast, Nemo’s rapid itch relief is unmatched among biologics, surpassing Dupi. Gilead’s previous AD clinical data show that within 2 days, 10.7% of patients achieved PP-NRS improvement ≥4 points, compared to only 2.9% with placebo.

Additionally, in a study on refractory chronic pruritus (CPUO) involving 12 patients with an average baseline PP-NRS of 9, after 4 weeks of Nemo treatment, the average PP-NRS dropped to 0.9, with 10 of the 12 patients experiencing significant itch relief within 24 to 72 hours.

In contrast, a retrospective trial of Dupi in 15 CPUO patients achieved pruritus relief, with the NRS pruritus score decreasing by an average of 7 points, but the median time to reach this endpoint was 19 months.

According to Goldman Sachs data, real-world studies of Dupi show incomplete itch relief (about 50% of patients do not reach PP-NRS 4), leaving a gap for fast-acting, deep-acting drugs like Nemo to “steal the market.”

02

Dupi’s initial loss of PN market share, with room for AD

The nodular prurigo (PN) field is currently a “dual dragon contest.” Dupi was approved first in 2022 and has dominated most of the market in recent years. However, since Nemo’s launch in 2024, this situation is changing.

IQVIA data shows that by the end of 2024, about 50% of Dupi prescriptions in the US came from AD, and about 4% from PN. Although PN accounts for a smaller share within Dupi’s indications, the market landscape is worth noting.

While both AD and PN are skin diseases characterized by intense pruritus, and uncontrolled AD patients often develop PN, AD is a primary, inflammation-driven skin disease, whereas PN is secondary, caused by the pruritus-scratch cycle. Multiple overseas analysts estimate the global PN market to be around $2 billion to $4 billion.

In the PN field, Nemo’s commercialization momentum is very strong. Several overseas KOLs indicate that PN patients are more inclined to use Nemo.

Survey data from 32 dermatologists abroad show that, aside from safety data, most consider pruritus control as the most important parameter, with over 60% believing Nemo is superior to Dupi in itch control; regarding safety, most see them as comparable.

Currently, prescription data shows Nemo’s market share in PN is gradually increasing, with potential to surpass Dupi in the future.

A Bank of America survey at the end of 2024 indicates that, four months after launch, Nemo captured 19% of the market share, demonstrating its popularity in PN treatment.

Similarly, nearly 60% of current Nemo users switched from Dupi, and this trend is expected to continue into 2025. Some overseas dermatology KOLs predict that 44% of PN patients will use Nemo, with forecasts suggesting Nemo could eventually dominate over 50% of the treatment market. The increase in Nemo’s market share is driven by two factors: upgrading to first-line therapy and plans to convert about one-third of current Dupi-treated PN patients to Nemo.

PN is just a niche segment; capturing the AD market and expanding volume is only a matter of time.

The AD market shows high enthusiasm for treatments beyond Dupi. For example, Eli Lilly’s Ebglyss (IL-13 antibody) quickly gained market share within two months of launch.

Although Nemo does not currently have an advantage in initial prescriptions for AD patients, it targets the market of Dupi’s poor responders, including those with low response rates, tolerance issues over time, or intolerance. Data suggest these groups account for approximately 25%-28% of AD patients.

Based on ultimate sales projections, a peak of over $40 billion for Gilead’s Nemo seems unlikely. We estimate peak prescriptions for PN and AD might be around a 3:7 or 1:1 ratio.

03

There are still many opportunities in AD waiting to be explored

Nemo has almost set a benchmark for all AD pipeline drugs. With its “excellent itch relief, rapid onset, and safety comparable to Dupi,” it has captured between $2 billion and $4 billion in market share, proving that there is still much room for growth in the AD market—if you can meet patients’ clinical needs.

A series of biotech startups worldwide are also creating market volatility with different clinical advantages, making the market more dynamic.

From the perspective of long-term skin lesion clearance, Nektar’s Rezpeg, in a 2b trial for moderate-to-severe AD, showed that 71% of patients in the high-dose group (24 μg/kg) achieved EASI-75 after 12 weeks, and 80% maintained this effect 36 weeks after stopping treatment. The stock surged over 150% on the day of data release.

From the perspective of oral molecule compliance and efficacy, Corvus’s SQL achieved an impressive 75% EASI-75 at week 8 in a 1b AD trial, with subsequent EASI-75 values only second to Upadacitinib (which has a black box warning and potentially better early safety). The stock rose over 165% after the data was announced.

From the current safety standpoint, Kymera’s KT-621 in a 1b trial showed no serious adverse events (SAEs) or treatment-related adverse events, representing excellent early safety data (Dupi’s 12-week trial reported some SAEs and conjunctivitis risks). The stock increased over 45% after the data release.

Conclusion: The core patent of Dupi expires in 2028. As the patent cliff approaches, more “differentiated” drugs are expected to chip away at the hundreds of billions of dollars market behind Dupi. Nemo’s “market stealing” phenomenon and early clinical differentiation data from multiple biotech firms are becoming increasingly common.