18 October 2025 marked the presentation of the highly anticipated OptiTROP-Breast02 trial at the 2025 European Society for Medical Oncology (ESMO) Congress, taking place in Berlin, Germany from 17 to 21 October. Sichuan Kelun-Biotech presented findings from their Phase III trial which compared sacituzumab tirumotecan (sac-TMT), a trophoblast cell surface antigen 2 (TROP2)-directed antibody-drug conjugate, with a TOPO2 targeting payload, against physician’s choice of chemotherapy in metastatic hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2) breast cancer (BC) patients.
Eligible patients had received between one and four previous lines of chemotherapy including at least one taxane and a CDK4/6 inhibitor in any setting. This multicentre, randomised trial was conducted exclusively in China, but Sichuan-Kelun has now partnered with Merck & Co to commercialise sac-TMT in markets outside the country. Sac-TMT will compete with two other TROP-2 targeted ADCs already approved in this space: Gilead’s Trodelvy (sacituzumab govitecan) and AstraZeneca and Daiichi Sankyo’s Datroway (datapotamab dereuxtecan). There is also indirect competition from AstraZeneca and Daiichi Sankyo’s Enhertu (trastuzumab deruxtecan) which continues to expand use in HER2-low BC, shrinking the potential patient population eligible for TROP2-targeted ADCs.
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The OptiTROP-Breast02 trial randomised patients 1:1 to receive either sac-TMT or physician’s choice chemotherapy arms. Sac-TMT significantly improved median progression-free survival (PFS) from 4.1 months in the control arm to 8.3 months in the experimental arm (hazard ratio [HR] 0.35, 95% confidence interval: 0.26, 0.48). Median overall survival (OS) was not yet reached at this prespecified interim analysis though a favourable trend was observed with 7.5% of patients experiencing OS events in the experimental arm compared to 18.6% of patients in the control arm (HR, 0.33, 95% CI: 0.18, 0.61). Safety signals were comparable, but significant, in both arms with 62.0% of patients in the experimental arm experiencing grade ≥3 treatment related adverse (TRAEs) events compared to 64.8% in the control arm. While the incidence of grade ≥3 TRAEs was high, none of the patients on the experimental arm discontinued the treatment due to them.
While the trial results were positive, questions remain regarding the clinical positioning of Sac-TMT in the HR+/HER2 negative BC landscape. OptiTROP-Breast02 reported more favourable HRs for PFS and OS than those seen in Datroway’s Tropion-Breast 01 or Trodelvy’s TROPiCS-02; however both comparator studies were conducted globally, and the difference may be an artefact of patient composition.
To gain US Food and Drug Administration or European Medicines Agency approval, Kelun in collaboration with Merck & Co will likely need to conduct a global confirmatory Phase III trial to validate the findings. GlobalData’s analyst consensus forecast for Sac-TMT reaches $3.7 billion in 2031, while Datroway and Trodelvy gain $3.1 billion and $2.3 billion respectively in the same year. Despite Datroway and Trodelvy’s head start in western markets, Sac-TMT could overtake them in sales.
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