At the American Society of Clinical Oncology (ASCO) Annual Meeting, held 30 May-3 June 2025, primary results were presented from the ASCENT-04/KEYNOTE-D19 study investigating Gilead’s Trodelvy, a trophoblast cell surface antigen 2 (TROP 2)-directed antibody-drug conjugate (ADC), in combination with Keytruda (pembrolizumab), versus standard-of-care (SOC) chemotherapy plus pembrolizumab in patients with PD-L1-positive (CPS ≥10) metastatic triple-negative breast cancer (TNBC). The study aimed to determine whether the addition of Trodelvy, currently approved in the third-line setting for TNBC, could enhance the efficacy of Keytruda in the first-line treatment of this aggressive breast cancer subtype.
The data demonstrated an improvement in median progression-free survival (PFS), with 11.2 months observed in the ADC-immunotherapy combination arm compared to 7.8 months in the SOC arm, at a median follow-up of 14 months. Notably, patients receiving Trodelvy and Keytruda experienced a 35% reduction in the risk of disease progression (hazard ratio [HR], 0.64). The combination also achieved a higher overall response rate (60% versus 53%) and a longer duration of response (16.5 months versus 9.2 months) compared to SOC. The frequency of treatment-related adverse events (AEs) was comparable between arms; however, only 12% of patients discontinued treatment due to AEs in the Trodelvy-Keytruda arm versus 31% in the SOC arm.
These findings support the expectation that Trodelvy combined with Keytruda will become the new SOC in PD-L1-positive TNBC, shifting the frontline treatment paradigm from chemoimmunotherapy to ADC-based immunotherapy - a growing trend across tumour types in the metastatic setting. Gilead is positioning itself as a key player in human epidermal growth factor receptor 2-negative metastatic breast cancer, currently sponsoring several Phase III trials evaluating Trodelvy: as monotherapy for frontline metastatic TNBC patients ineligible for PD-L1-based therapy (ASCENT-03); in combination with Keytruda in early-stage TNBC (ASCENT-05); and in HR-positive patients previously treated with endocrine therapy (ASCENT-07). GlobalData’s analyst consensus forecast projects Trodelvy sales to reach $2.2bn by 2030.
Gilead will face competition in the frontline PD-L1-ineligible TNBC setting from Daiichi Sankyo’s TROP-2-directed ADC, Datroway, currently in Phase III (TROPION-BREAST02), and Bristol Myers Squibb’s izalontamab brengitecan, a bispecific EGFRxHER3 ADC entering Phase III in July. Nevertheless, following the positive ASCENT-04 results, Gilead is expected to secure US Food and Drug Administration approval and capture a significant share of the frontline PD-L1-positive TNBC market.
