A TROP2 antibody-drug conjugate beat chemotherapy in treated EGFR lung cancer

For lung cancers driven by an EGFR mutation, a targeted tablet such as osimertinib is usually the first treatment, and it works well — until, eventually, the cancer finds a way around it. What to do next has long meant falling back on chemotherapy. A phase 3 trial published in The Lancet on 26 October tested a newer option in that gap [s1].

What the drug is

Ruzaltatug rezetecan is an antibody-drug conjugate aimed at TROP2, a protein found on the surface of many non-small-cell lung cancers. The antibody recognises TROP2 and carries a chemotherapy payload to the cells that display it, the aim being to deliver the toxic effect to the tumour rather than throughout the body [s1]. It is a different strategy from the EGFR-targeted tablets that come before it and from the conventional chemotherapy it was tested against.

The sequence matters here. For most patients, the EGFR tablet is the opening move and does the heavy lifting for a year or more; the hard problem is what comes after it stops working. Chemotherapy has filled that slot by default rather than by strong evidence that it is the best available option, which is what makes a head-to-head test against a newer drug worth running.

HERON-Lung01 asked a specific question: once an EGFR-mutated lung cancer has progressed despite a targeted tyrosine kinase inhibitor, does this TROP2-directed drug delay progression longer than the standard chemotherapy that would otherwise be used?

How the trial was built

HERON-Lung01 was a randomised, open-label, phase 3 trial conducted in China, registered as NCT06671379; the Lancet report is an interim analysis [s1][s2]. It enrolled 498 people with EGFR-mutated advanced NSCLC whose disease had progressed after treatment with an EGFR tyrosine kinase inhibitor, and randomly assigned 250 to ruzaltatug rezetecan and 248 to chemotherapy [s1].

The drug was given at 8.0 mg/kg [s1]. The control arm received a standard regimen: pemetrexed at 500 mg/m² plus either carboplatin (AUC 5) or cisplatin at 75 mg/m² for four cycles, followed by maintenance pemetrexed [s1]. The primary endpoint was progression-free survival, read by a blinded independent central review panel that did not know which treatment each patient was receiving [s1].

What it found

The primary endpoint favoured the antibody-drug conjugate. Median progression-free survival was 8.3 months with ruzaltatug rezetecan against 5.4 months with chemotherapy, a hazard ratio for progression or death of 0.47 (95% CI 0.36–0.60; one-sided p<0.0001) [s1]. Follow-up was still short at this interim look, with a median of 7.7 months (95% CI 7.1–8.3) [s1].

On safety, the two arms were closer than the efficacy gap might suggest. Grade 3 or higher treatment-related adverse events occurred in 41% of the ruzaltatug rezetecan group (101 of 248 treated) versus 39% of the chemotherapy group (93 of 239) [s1]. The pattern of severe effects differed: a lowered neutrophil count was more common with ruzaltatug rezetecan (26% versus 19%), while severe anaemia was more common with chemotherapy (6% versus 11%) [s1]. A lowered white-cell count overall was equally common in the two arms, at 12% each [s1]. Treatment was discontinued because of related side effects in 1% of each arm — three patients on each side — which suggests that, for most people, the newer drug was no harder to stay on than chemotherapy despite its longer hold on the disease [s1].

What is, and is not, established

What HERON-Lung01 supports is that, in EGFR-mutated NSCLC that has progressed after a targeted tyrosine kinase inhibitor, ruzaltatug rezetecan delayed progression longer than standard pemetrexed-platinum chemotherapy, with a similar overall rate of severe treatment-related side effects [s1]. For a setting where chemotherapy has been the default, that is a meaningful alternative.

The qualifications matter. This is an interim analysis with short follow-up, and overall survival — whether people lived longer — was not yet available, so the most important question remains open [s1]. The trial was open-label, which is why the blinded central review of scans is the safeguard against bias in reading progression [s1]. It was conducted entirely in China, so generalisability to other populations is not established [s1]. And ruzaltatug rezetecan is investigational; these results describe a trial, not an approved treatment [s1].

Red flags: anyone on an antibody-drug conjugate or chemotherapy who develops a fever, severe fatigue, breathlessness, or signs of infection should contact their oncology team, as these can signal low blood counts. This article describes research and is not medical advice. Treatment choices after targeted therapy fails are for patients and their treating oncologists.