Trastuzumab rezetecan, a HER2-directed antibody-drug conjugate, in patients with advanced HER2-mutant non-small-cell lung cancer (HORIZON-Lung): phase 2 results from a multicentre, single-arm study.

Background: Trastuzumab rezetecan (also known as SHR-A1811) is a novel antibody-drug conjugate consisting of a humanised HER2-directed monoclonal antibody, cleavable tetrapeptide-based linker, and DNA topoisomerase I inhibitor. In the phase 1 portion of this phase 1/2 study, trastuzumab rezetecan showed preliminary anti-tumour activity and a favourable safety profile in patients with HER2-mutant non-small-cell lung cancer (NSCLC). We present phase 2 results from the study, which aimed to further evaluate the activity and safety of trastuzumab rezetecan at the recommended dose.

Methods: In this multicentre, single-arm, phase 2 trial, conducted in 35 hospitals in China, we recruited patients aged 18-75 years, with locally advanced or metastatic NSCLC with an activating HER2 mutation and an Eastern Cooperative Oncology Group performance status score of 0-1, who had disease progression after or were intolerant to platinum-based chemotherapy and anti-PD-1 treatment or anti-PD-L1 treatment. Trastuzumab rezetecan was administered at 4·8 mg/kg intravenously once every 3 weeks. The primary endpoint was objective response rate assessed by an independent review committee in patients who received at least one cycle of study treatment. All patients who received at least one cycle of study treatment were included in safety analyses. This study is registered with ClinicalTrials.gov, NCT04818333, and is ongoing but not recruiting.

Findings: Between April 14, 2023, and Dec 14, 2023, 94 patients were enrolled and treated. 42 (45%) patients were male, 52 (55%) female, 92 (98%) were Han Chinese, and two (2%) were other ethnicity Chinese. At data cutoff (June 14, 2024), the median duration of follow-up was 8·7 months (IQR 7·0-10·4). 69 (73%; 95% CI 63·3-82·0) of 94 patients had a confirmed objective response, as assessed by independent review committee. The most common grade 3-4 treatment-related adverse events were decreased neutrophil count (38 [40%] patients), decreased white blood cell count (25 [27%]), anaemia (22 [23%]), decreased platelet count (10 [11%]), and decreased lymphocyte count (seven [7%]). Treatment-related serious adverse events occurred in 22 (23%) patients, which were decreased platelet count (six [6%]), decreased neutrophil count (six [6%]), interstitial lung disease (five [5%]), decreased white blood cell count (four [4%]), anaemia (four [4%]), vomiting (three [3%]), pneumonia (three [3%]), hyponatraemia (two [2%]), and pyrexia (one [1%]), small intestinal obstruction (one [1%]), nausea (one [1%]), and chronic obstructive pulmonary disease (one [1%]). There were no treatment-related deaths.

Interpretation: Trastuzumab rezetecan showed clinically meaningful activity and manageable safety in patients with previously treated HER2-mutant NSCLC. Further trials are justified.

Funding: Jiangsu Hengrui Pharmaceuticals, National Multi-disciplinary Treatment Project for Major Diseases, Collaborative Innovation Center for Clinical and Translational Science by the Ministry of Education & Shanghai.

Translation: For the Chinese translation of the abstract see Supplementary Materials section.