01/03/2025
On January 17, 2025, the FDA approved Datopotamab deruxtecan-dlnk, Dato-DXd, (Datroway) for hormone receptor positive (HR+), HER2-negative metastatic breast cancer (MBC) following endocrine-based therapy and 1-2 prior lines of chemotherapy based on results from the TROPION-Breast01 Ph3 study. Then on January 27, it was announced that Trastuzumab-deruxtecan, T-DXd (Enhertu) was approved in the 1st line setting after progression on endocrine-based therapy in HER2-low and ultralow HR+ MBC based on results from the DESTINY-Breast06 Ph3 study. This builds on Enhertu’s prior approval as 2L chemotherapy based on efficacy data from DESTINY-Breast04.
With now 3 ADCs approved (Enhertu, Datroway and Trodelvy), where does the newcomer fit in the treatment paradigm of HR+/HER2- MBC?
To answer this question, it’s important to analyze TROPION-Breast01data in light of the efficacy and safety data as well as mechanisms of action and resistance of its 2 other competitors
Key points from these data:
- In the trials leading to their approval, Enhertu, Trodelvy and Datroway were compared to physician’s choice of chemotherapy and not head-to-head
- The 3 ADCs share a similar mechanism of action. DXd, the payload of Datroway and Enhertu and SN38, the payload of Trodelvy inhibit topoisomerase activity) and/or target (Datroway and Trodelvy target TROP2 receptor on BC cells). Because of this, cross-resistance occurs. Several retrospective studies have shown that trodelvy’s activity is modest at best in HR+/HER2-low MBC patients who already received and progressed on Enhertu. We don’t have data reporting on the activity of Datroway following Enhertu, but it’s likely that similar cross-resistance mechanisms exist limiting Datroway’s efficacy post-Enhertu.
- The pivotal ADC trials were conducted in different patient populations, DESTINY-Breast04 and TROPION-Breast01 included somewhat of a similar HR+ patient population (In both trials, 60% of patients had only 1 prior line of chemotherapy in the metastatic setting) and with the limitations of cross-trial comparison, PFS benefit with Enhertu appears to be far superior to that of Datroway. Even if the OS data end up being positive for Datroway, Enhertu’s approval in the 1st line chemo setting in HER2-low and ultralow breast cancer has made it an unchallenged contender and Datroway may find its small niche in the 2nd line setting in the small proportion of patients who are not HER2-low or ultralow
- Datroway’s finds its real competition in the later-line setting (3L+) with Trodelvy. With a more appealing toxicity profile (particularly BM suppression and neutropenia) and low rates of drug-related pneumonitis, Datroway will likely dominate the market share for 3L+ in HR+ MBC if the eagerly awaited, TropionBreast01 OS data are positive
My two cents:
- Enhertu’s has become the de facto 1-2 chemo choice in HR+/HER-low and ultralow MBC, and differentiating HER2 0 vs HER2 ultralow has become of bane of our pathologists’ existence
- Datroway currently finds its market share in 2L setting in the small proportion of HR+MBC patients who are truly and consistently HER2 0 and may outperform trodelvy’s current market share in the 3L+ setting if TropionBreast01 OS data are positive. However, questions on the actual efficacy of either drug post-Enhertu and how to recognize patients who are likely to experience significant PFS benefit from either drug post-Enhertu remain unanswered.
On January 17, 2025, the Food and Drug Administration approved datopotamab deruxtecan-dlnk (Datroway, Daiichi Sankyo, Inc.), a Trop-2-directed antibody and topoisomerase inhibitor conjugate, for adult patients with unresectable or metastatic, hormone receptor (HR)-positive, human epidermal growth fa