Antibody-drug conjugates are moving from late-line rescue therapy to first-line anchors in breast cancer. Enhertu plus pertuzumab is now approved first line in HER2-positive disease, and Datroway is approved first line in metastatic triple-negative disease. The competitive question has shifted from whether an ADC works to where it belongs in the treatment sequence.
Why is the next ADC competition about sequencing, not approval?
Antibody-drug conjugates, or ADCs, have moved from being promising late-line medicines to becoming central to the future of breast cancer treatment[1]. The next question is no longer whether ADCs work. It is more consequential: which ADC will be used first, in which patient, and what treatment options will it preserve or displace after progression?
That question is beginning to reshape breast cancer strategy for AstraZeneca and Daiichi Sankyo, Gilead, Roche/Genentech, Pfizer and a growing group of ADC-focused biotech companies. For companies developing new ADCs, the commercial and clinical prize is not simply another positive response-rate study. It is earning a defensible place in the treatment sequence.
Breast cancer has never been one treatment market. Treatment decisions are already shaped by tumour subtype, biomarker status, disease setting, previous therapy and patient-specific considerations[2]. ADCs add another layer of complexity, because an ADC that moves into an earlier line does more than expand its eligible population. It can redefine what follows.
How is the breast cancer ADC treatment pathway decided?
The strategic pathway is increasingly a five-step decision sequence. Each step carries its own question in the ADC era. Select a step to see what is at stake.
01 Subtype / biomarker
HER2-positive, HER2-low, HR-positive/HER2-negative and triple-negative breast cancer now have different ADC opportunities and constraints. Broader HER2 categories and TROP2 targeting are expanding the potential addressable population[3].
02 Line of therapy
Earlier use may create more value, but can also change what remains viable after progression. Moving into an earlier line is not only a bigger eligible population; it rewrites the post-progression conversation for every patient who would have received the ADC later.
03 ADC choice
Enhertu is now a first-line anchor in HER2-positive disease[5]. Datroway is the first TROP2-directed ADC approved for first-line metastatic triple-negative disease[10], where Gilead's Trodelvy holds an established position. In practice the choice is also shaped by safety: interstitial lung disease, neutropenia, ocular toxicity and other adverse-event profiles can shape sequencing[4].
04 Combination strategy
The ability to combine with HER2-targeted agents, endocrine therapy or immunotherapy may determine movement into earlier settings. Enhertu's first-line HER2-positive approval is a combination approval, with pertuzumab[5].
05 Next treatment
A product's role may depend on whether clinicians believe another ADC can be used afterward. Evidence on what should follow trastuzumab deruxtecan remains limited, and a multicentre study is examining Enhertu and Datroway sequencing in both directions[11].
The result is a treatment landscape where individual assets may no longer be evaluated in isolation. Their value increasingly depends on where they fit in a pathway that is still being written.
Which ADC is approved first-line for HER2-positive breast cancer?
Enhertu. In December 2025 the US FDA approved Enhertu plus pertuzumab for first-line treatment of unresectable or metastatic HER2-positive breast cancer[5]. AstraZeneca and Daiichi Sankyo reported that the combination reduced the risk of disease progression or death by 44% versus the previous standard THP regimen in the pivotal study[6].
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March 2026: US Priority Review, early breast cancer
Priority Review granted for Enhertu in the post-neoadjuvant setting for patients with residual invasive disease, based on data showing a 53% reduction in the risk of invasive disease recurrence or death versus T-DM1.[7]
With this approval, we are bringing Enhertu to the earliest setting for HER2-positive metastatic breast cancer, where optimizing efficacy has an important impact on longterm outcomes. The treatment approach with Enhertu plus pertuzumab in DESTINY-Breast09 sets a new benchmark of more than three years without disease progression or death for patients in this setting.
AstraZeneca, December 2025 [6]
The importance of this shift goes beyond one label expansion. Moving Enhertu into first line changes the post-progression conversation for patients who previously would have received the ADC later. AstraZeneca and Daiichi Sankyo are also seeking to move Enhertu earlier in HER2-positive early breast cancer through the post-neoadjuvant filing[7].
The message is clear: the value of an ADC is increasingly linked to whether it can become a treatment anchor rather than a treatment after progression.
Trodelvy or Datroway: which TROP2 ADC comes first in TNBC?
Both now hold approvals in triple-negative breast cancer, in different positions. Gilead's Trodelvy established an important position in metastatic TNBC. In May 2026 the FDA approved Datroway, developed by AstraZeneca and Daiichi Sankyo, for adults with unresectable or metastatic TNBC who are not candidates for PD-1/PD-L1 inhibitor therapy[8], and in June 2026 the EMA's CHMP issued a positive opinion for the same first-line metastatic setting[9].
Datroway is the first TROP2-directed antibody drug conjugate approved for the 1st-line treatment of metastatic triple-negative breast cancer.
| Trodelvy (Gilead) | Datroway (AstraZeneca / Daiichi Sankyo) | |
|---|---|---|
| Setting | Established position in metastatic triple-negative breast cancer | First-line unresectable or metastatic TNBC, patients not candidates for PD-1/PD-L1 inhibitor therapy [8] |
| Approval status | Approved, established in metastatic TNBC | FDA approved May 2026 [8]; CHMP positive opinion June 2026 for the same first-line setting [9][12] |
| Strategic position | Defending and extending its role as TROP2 competition moves into earlier settings | First TROP2-directed ADC approved for first-line metastatic TNBC [10] |
| Open question | Whether clinicians will reach for it after another TROP2 ADC has been used | Whether TROP2 choice will be decided by disease setting, prior therapy, toxicity profile and what can follow |
The open sequencing question is whether clinicians will increasingly decide between ADCs based on disease setting, prior therapy, toxicity profile and the ability to use another ADC later.
That is especially important because evidence on what should follow trastuzumab deruxtecan remains limited. A multicentre study is examining sequencing of Enhertu and Datroway in both directions, underscoring that the most important clinical question may now be the order of treatment rather than the isolated performance of either drug[11].
What will decide ADC sequencing besides efficacy?
ADCs are often discussed through headline efficacy results. Those results matter, but they are unlikely to be the only determinant of sequencing. Seven factors will shape where an ADC lands in the treatment pathway.
| Differentiation factor | What companies need to demonstrate |
|---|---|
| Depth and durability of benefit | A clinically meaningful advantage in the intended patient population |
| Biomarker strategy | A clear and practical way to identify the patients most likely to benefit |
| Safety profile | Manageable toxicity that allows treatment in the intended line and combination |
| Treatment burden | Administration, monitoring and supportive-care requirements that fit real-world practice |
| Combination rationale | Compatibility with HER2-targeted therapy, endocrine therapy, immunotherapy or other agents |
| Sequencing logic | A credible answer to what should precede and follow the ADC |
| Resistance strategy | Evidence that the product can retain relevance after prior ADC exposure |
This creates a more demanding development environment for emerging ADC companies. A novel target or payload may not be enough if the asset does not answer a practical sequencing question.
How does ADC pathway adoption differ between the US and EU?
The US and EU will draw on much of the same clinical evidence, but the path from data to routine treatment may not be identical. In the US, FDA approvals and guideline updates can quickly alter the clinical conversation. In the EU, the regulatory pathway is followed by country-level decisions around adoption, clinical practice and implementation[12].
Enhertu's first-line HER2-positive approval and Datroway's first-line TNBC approval both demonstrate how a new indication can change the treatment map rapidly in the US. Datroway's positive CHMP opinion in June 2026 is an important regulatory step, but each country's clinical pathway and treatment practice will influence how quickly it becomes established[12].
| United States | European Union | |
|---|---|---|
| Primary change mechanism | FDA approval and guideline evolution | European regulatory action followed by country-level practice and implementation |
| Key clinical question | Which new label changes the standard of care first? | How will new evidence be incorporated across different national pathways? |
| Major sequencing driver | Trial readouts, label expansion and US expert practice | Shared trial evidence, European approvals and country-specific treatment norms |
| Implication for companies | Rapid medical education around new treatment order | Country-sensitive evidence communication and pathway understanding |
The science may be global. The sequence is often local.
What are the leading ADC companies signaling?
The current ADC landscape points to several strategic moves. The important shift is that companies are not simply competing to launch another ADC. They are competing to shape the treatment logic around the ADC.
| Company | What it is signaling |
|---|---|
| AstraZeneca / Daiichi Sankyo | Building a broad breast cancer ADC franchise across HER2-positive, HER2-low, HR+/HER2-negative and TROP2-defined populations [13] |
| Gilead | Defending and extending Trodelvy's role as TROP2 competition moves into earlier settings |
| Roche / Genentech | Evolving a HER2 franchise as Enhertu moves earlier and changes the role of established HER2 therapies |
| Pfizer | Evaluating how to build a differentiated oncology position as ADC competition becomes more intense |
| Emerging ADC biotech companies | Pursuing novel targets, payloads, dual-payload designs and safety improvements that may create a distinct sequencing role |
For AstraZeneca and Daiichi Sankyo, the ambition appears to be a connected franchise across several breast cancer populations. For Gilead, the priority is likely to be protecting Trodelvy's relevance as the TROP2 category evolves. For Roche, the challenge is to preserve and adapt HER2 treatment strategy as an ADC moves from a later-line option to a first-line anchor.
Where can an emerging ADC company still win?
For smaller ADC companies, breast cancer is both an opportunity and a warning. The market is large, scientifically active and receptive to new mechanisms, but established companies are moving assets into earlier settings and setting expectations around efficacy, safety and sequencing. A promising ADC now needs to answer a more specific question: what point in the breast cancer treatment pathway can this product own?
Seven questions every emerging ADC strategy should answer from the outset
- 01Select a patient population that is not merely large, but strategically defensible.
- 02Build a biomarker plan that fits clinical decision-making.
- 03Design trials that clarify the intended line of therapy.
- 04Demonstrate a safety and administration profile that supports use in that setting.
- 05Develop evidence on how the product performs before or after established ADCs.
- 06Identify combinations that move the asset into a more valuable treatment position.
- 07Avoid relying on a single response-rate signal when the market is increasingly focused on durability and sequence.
For emerging companies, the strongest opportunity may not be to displace Enhertu, Datroway or Trodelvy directly. It may be to solve the unanswered question those medicines leave behind: what should come next?
What is still unresolved in the ADC sequencing race?
Public trial data and regulatory actions reveal an industry moving ADCs earlier in breast cancer. They do not yet settle the questions that will decide long-term treatment use. Five remain open.
- Sequencing
- How willing will oncologists be to sequence one ADC after another? Evidence after trastuzumab deruxtecan remains limited, and bidirectional Enhertu and Datroway sequencing is only now being studied in a multicentre trial [11].
- Safety trade-offs
- Which safety trade-offs will be acceptable in first-line or early-stage settings, where patients previously received established regimens with well-understood profiles [4]?
- Biomarkers
- Will broader biomarker definitions, including wider HER2 categories and TROP2 targeting, make treatment pathways clearer or more complex [3]?
- Combinations
- Which combinations will prove durable enough to displace established regimens, the way Enhertu plus pertuzumab displaced THP in first-line HER2-positive disease [5][6]?
- Next generation
- Which next-generation ADCs will offer a genuine improvement rather than another option in an already crowded class?
These questions sit with the people shaping breast cancer care: oncologists, breast cancer KOLs, clinical investigators, oncology pharmacists, pathology and diagnostics leaders, competitor and former-industry executives, and care-delivery stakeholders.
The next breast cancer ADC winner may not be the company with the most impressive standalone dataset. It may be the company that gives clinicians the clearest answer to a more practical question: where does this treatment belong, and what should come after it?
Frequently asked questions about ADC sequencing in breast cancer
Sources: the 13 verified links behind this whitepaper
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OncLive: Introduction and evolution of antibody-drug conjugates in breast cancer
https://www.onclive.com/view/introduction-and-evolution-of-antibody-drug-conjugates-in-breast-cancer - 02
Frontiers in Cell and Developmental Biology (2025), article 1669592
https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2025.1669592/full - 03
PubMed Central, PMC9509625
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9509625/ - 04
ScienceDirect, article S1040842824000179
https://www.sciencedirect.com/science/article/abs/pii/S1040842824000179 - 05
FDA: approval of fam-trastuzumab deruxtecan-nxki with pertuzumab for unresectable or metastatic HER2-positive breast cancer
https://www.fda.gov/drugs/drug-approvals-and-databases/fda-approves-fam-trastuzumab-deruxtecan-nxki-pertuzumab-unresectable-or-metastatic-her2-positive - 06
AstraZeneca press release, December 2025: Enhertu approved in the US for first-line HER2-positive metastatic breast cancer
https://www.astrazeneca.com/media-center/press-releases/2025/enhertu-approved-in-us-for-1l-her2-metastatic-bc.html - 07
AstraZeneca press release, March 2026: Enhertu granted Priority Review in the US as post-neoadjuvant treatment for HER2-positive early breast cancer
https://www.astrazeneca.com/media-center/press-releases/2026/enhertu-granted-priority-review-in-the-us-as-post-neoadjuvant-treatment-for-patients-with-her2-positive-early-breast-cancer.html - 08
FDA: approval of datopotamab deruxtecan-dlnk for unresectable or metastatic triple-negative breast cancer
https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-datopotamab-deruxtecan-dlnk-unresectable-or-metastatic-triple-negative-breast-cancer - 09
European Medicines Agency: Datroway variation record
https://www.ema.europa.eu/en/medicines/human/variation/datroway - 10
AstraZeneca press release, May 2026: Datroway approved in the US for first-line triple-negative breast cancer
https://www.astrazeneca.com/media-center/press-releases/2026/datroway-approved-in-us-for-1l-triple-negative-bc.html - 11
Dana-Farber Cancer Institute, clinical trial 24-251
https://www.dana-farber.org/clinical-trials/24-251 - 12
AstraZeneca press release, June 2026: Datroway recommended for approval in the EU for TNBC
https://www.astrazeneca.com/media-center/press-releases/2026/datroway-recommended-for-approval-in-eu-for-tnbc.html - 13
Business Wire, December 2025: Daiichi Sankyo breast cancer ADC portfolio updates from five trials at SABCS
https://www.businesswire.com/news/home/20251208780034/en/Daiichi-Sankyo-Showcases-Strength-of-Industry-Leading-ADC-Portfolio-with-Latest-Research-Updates-from-Five-Landmark-Breast-Cancer-Trials-at-SABCS
This whitepaper is an analysis of public regulatory actions, company statements and published literature. It is not medical advice, not a treatment recommendation, and not investment advice. Regulatory status and clinical evidence change; consult the linked primary sources and qualified professionals.
Hero photograph: Edward Jenner / Pexels.