AstraZeneca Just Broke the IL-33 Curse in COPD

The IL-33 graveyard is where AstraZeneca makes its money

For years, the scientific consensus on interleukin-33 (IL-33) as a target in chronic obstructive pulmonary disease was blunt: it would not work. Multiple companies pursued antibodies against the protein and collectively watched them fail. Investors priced AstraZeneca’s own tozorakimab near zero. CEO Pascal Soriot admitted as much on the company’s second-quarter earnings call, saying, “Tozorakimab is a product nobody thought would work. We ourselves had a very low probability of success.”

Tuesday’s full data from two Phase 3 trials did not just vindicate that bet. They upended the architecture of COPD treatment itself.

The drug reduced moderate and severe flare-ups by 29 to 34 percent across broad patient groups — former smokers, current smokers, and every category of blood eosinophil count. It worked in people whose eosinophils sit below 150 cells per microliter, a population currently written off by every approved biologic and often dismissed by clinical guidelines as unlikely to respond to inhaled therapies. In the lowest-eosinophil subgroup, flare-ups still fell by 23 percent. In the highest subgroup, at or above 300, the reduction hit 43 percent.

That range is unprecedented for a COPD biologic. It means tozorakimab does not require a biomarker gatekeeper before it enters a patient’s regimen. If the FDA grants approval in the first quarter of 2027 — as currently expected under priority review — prescribers will not need to run an eosinophil test to decide whether to offer it. That changes everything about how the drug will be adopted.

Who wins when the biomarker requirement disappears

Regeneron and Sanofi already run the COPD biologic market through Dupixent, and GSK holds the smaller Nucala franchise. Both drugs work primarily in patients with elevated eosinophils. As Soriot noted, roughly only 10 percent of COPD patients currently receive any biologic at all, compared with 30 to 40 percent of asthmatics. The ceiling on those products was always set by that lab value, not by the size of the disease.

Tozorakimab removes that ceiling.

AstraZeneca raised its peak annual sales forecast to more than $5 billion on the back of the data. The company’s overall revenue target by 2030 is $80 billion. Even a fraction of that $5 billion peak would meaningfully widen the gap. The unmet need is vast: an estimated 16 million to 26 million Americans live with COPD, diagnosed or not, and it remains the fifth-leading cause of death in the country.

Dupixent and Nucala do not disappear. Patients and doctors who already respond to them will likely stay on their current therapy. But tozorakimab opens an entirely new cohort — the majority of COPD patients who were previously excluded from the biologic conversation. That is not incremental growth. That is a new market layer.

How AstraZeneca outmaneuvered its own skeptics

The scientific reason for tozorakimab’s success may be as important as the commercial one. Earlier IL-33 programs largely focused on blocking a single inflammatory pathway. AstraZeneca designed tozorakimab to inhibit two distinct IL-33 pathways simultaneously, targeting not only inflammation but also mucus production and airway remodeling — two other core drivers of COPD progression.

That dual-pathway approach may sound like a marginal mechanistic detail. In practice, it is the difference between a drug that works in one narrow inflammatory subtype and one that works across the clinical spectrum. COPD is not a single disease. It is a cluster of overlapping pathophysiologies, and a single-pathway inhibitor tends to capture only one of them. By hitting two pathways, tozorakimab hits more of the disease. The data support that reading: the benefit scales with eosinophil count but never drops to zero.

It also explains why other IL-33 programs faltered. They targeted the right protein through the wrong lens. AstraZeneca’s bet was that the biology demanded a broader intervention than the field was willing to build.

Who loses and what gets contested

GSK and the Regeneron-Sanofi alliance own the current COPD biologic space. Their advantage was the biomarker moat — eosinophil testing created a natural filter that limited tozorakimab’s addressable population if it had performed like earlier candidates. With tozorakimab showing activity across all eosinophil bands, that moat evaporates.

Competitors will respond. Expect Regeneron and Sanofi to push Dupixent harder into COPD’s existing indications and to explore combination strategies with inhaled therapies. GSK will lean on Nucala’s first-mover status and its simpler dosing schedule. But AstraZeneca now controls the narrative around who qualifies for biologic treatment in the first place, and that is a structural advantage.

Prescribers face their own unsettlement. Dr. Meilan Han of University of Michigan Health, who investigated the trials, said she will likely start patients with low eosinophil counts on tozorakimab. But she also flagged a genuine ambiguity: no head-to-head trials compare the new drug against Dupixent or Nucala in high-eosinophil patients. That means clinicians will not know whether to position tozorakimab before, after, or alongside existing biologics until real-world evidence accumulates. Han called for additional subgroup analyses before she feels comfortable making treatment-algorithm decisions. The Global Initiative for Chronic Obstructive Lung Disease (GOLD) committee, which writes the international treatment guidelines, will face intense pressure to incorporate the new data — another open question with commercial consequences.

The environmental tailwind nobody is pricing in

There is a second headwind behind this drug that the market may undervalue. COPD incidence is not shrinking. Air pollution and wildfire smoke continue to expand, and both damage lung tissue and trigger exacerbations. AstraZeneca’s Ruud Dobber pointed out that not everyone with COPD has a smoking history — many patients develop the disease from environmental exposures alone. These patients tend to fall into the low-eosinophil bucket, the very group that previously had no biologic option.

If smoking rates continue to decline while environmental exposure rises, the demographic most likely to benefit from tozorakimab grows rather than shrinks. That makes the $5 billion+ peak forecast potentially conservative rather than optimistic.

What happens next

The FDA decision timeline is the first concrete event. Priority review means a target date around early 2027. European and Chinese regulatory submissions are already underway. AstraZeneca is simultaneously running a Phase 2 trial in severe asthma and a Phase 3 study in severe viral lower respiratory tract disease, both using the same IL-33 platform. If either program shows signal, the commercial upside multiplies beyond COPD.

The bigger story, though, is structural. For two decades, COPD treatment relied on inhaled bronchodilators and steroids — symptomatic relief, not disease-modifying therapy. Biologics changed that for a subset of patients with high eosinophils. Tozorakimab extends that shift to the broader population. Whether it becomes the cornerstone of COPD biologic therapy or one option among several will depend on pricing, guideline placement, and real-world prescribing patterns. But the era of biologics being reserved for a narrow inflammatory subtype is over.

AstraZeneca bet against its own consensus and won. The question now is whether the rest of the industry can catch up to the logic of what just worked.