Dato-DXd for Breast Cancer: Uses, Efficacy, and Side Effects

Datopotamab deruxtecan, sold under the brand name Datroway and commonly abbreviated Dato-DXd, is an antibody-drug conjugate approved to treat certain forms of advanced breast cancer. The U.S. Food and Drug Administration granted approval in January 2025 for adults with hormone receptor-positive, HER2-negative metastatic breast cancer who have already been treated with endocrine therapy and chemotherapy. But the drug’s story extends well beyond that single approval, with recent trial results in triple-negative breast cancer and early-stage disease suggesting it could reshape treatment across multiple breast cancer subtypes.

What Dato-DXd Is and How It Works

Dato-DXd belongs to a class of cancer drugs called antibody-drug conjugates, or ADCs. The concept is sometimes described as a guided missile: a lab-made antibody locks onto a specific protein on the surface of cancer cells, gets pulled inside the cell, and then releases a toxic payload that kills the cell from within. In Dato-DXd’s case, the antibody targets a protein called TROP2, and the payload is a potent topoisomerase I inhibitor called DXd, which damages the cell’s DNA and triggers cell death.

TROP2 is found on the surface of many solid tumors, but it is especially common in breast cancer. Research shows that TROP2 is expressed across all breast cancer subtypes, with particularly high levels in triple-negative breast cancer and hormone receptor-positive disease, and somewhat lower levels in HER2-positive tumors.¹² That broad expression is what makes TROP2 an attractive drug target: it gives the antibody something to grab onto in a wide range of breast cancers.

Preclinical work showed that once Dato-DXd binds to TROP2, it gets internalized into the cancer cell, travels to compartments called lysosomes, and releases DXd, which damages DNA and triggers the cell to self-destruct.³ More recent laboratory research has also found that Dato-DXd can trigger what scientists call immunogenic cell death, a form of cell death that alerts the immune system to the presence of cancer. The drug also has a “bystander effect,” meaning that when it kills TROP2-expressing cancer cells, the released payload can diffuse to and kill neighboring cancer cells that may not express TROP2 themselves.⁴ That bystander activity matters because tumors are often a patchwork of cells with varying levels of TROP2.

Approval in HR-Positive, HER2-Negative Breast Cancer

The approval that put Dato-DXd on the map came from the phase III TROPION-Breast01 trial, which enrolled patients with hormone receptor-positive, HER2-negative metastatic breast cancer who had already received at least one round of chemotherapy for advanced disease. This is the most common subtype of breast cancer, and once endocrine therapy and initial chemotherapy stop working, options become limited and less effective.

TROPION-Breast01 compared Dato-DXd to the investigator’s choice of standard chemotherapy. The results showed that Dato-DXd cut the risk of disease progression or death by about 37% compared to chemotherapy, and this benefit held up across patient subgroups.⁵ Beyond tumor shrinkage, patients on Dato-DXd also reported better quality of life, with delays in the worsening of overall health status, pain, and physical functioning compared to those on standard chemotherapy.⁶

Based on these results, Dato-DXd was approved in Japan in December 2024, in the United States in January 2025, and subsequently in the European Union. Regulatory review is underway in Canada and China.⁷ The approved dose is 6 mg per kilogram of body weight given intravenously every three weeks, a regimen that modeling studies determined provides the best balance of tumor control and tolerability.⁸

Results in Triple-Negative Breast Cancer

Triple-negative breast cancer, which lacks hormone receptors and HER2, is generally harder to treat and has fewer targeted therapy options. The TROPION-Breast02 trial tested Dato-DXd against standard chemotherapy as a first-line treatment in patients with advanced or metastatic triple-negative disease. The results were striking: median progression-free survival was roughly 11 months with Dato-DXd compared to about 6 months with chemotherapy, nearly doubling the time before the disease worsened. Overall survival also improved, with a median of about 24 months on Dato-DXd versus roughly 19 months on chemotherapy.⁹

These numbers are meaningful because triple-negative breast cancer has historically had the bleakest prognosis among breast cancer subtypes once it becomes metastatic. While Dato-DXd is not yet approved specifically for triple-negative disease, the TROPION-Breast02 data will likely form the basis for a regulatory submission in that setting.

Side Effects and How They Differ From Standard Chemotherapy

Dato-DXd’s side-effect profile is different from conventional chemotherapy, and understanding those differences matters for anyone considering or starting the drug. The most common side effects include mouth sores (stomatitis), nausea, hair thinning or loss, and eye-related issues. Among these, the one that gets the most clinical attention is interstitial lung disease, or ILD, a type of inflammation in the lungs that can range from mild to life-threatening.¹⁰

To put the lung risk in context, it helps to look at a closely related drug, trastuzumab deruxtecan (T-DXd), which uses the same DXd payload but targets HER2 instead of TROP2. Across multiple large breast cancer trials, T-DXd-related ILD occurred in roughly 10 to 17% of patients, with most cases being low grade but a small percentage resulting in death.¹¹ The ILD rates with Dato-DXd in the TROPION-Breast01 trial were reported to be lower than those seen with T-DXd, though the concern remains serious enough that monitoring protocols are standard for all patients receiving the drug.

Stomatitis Management

Mouth sores deserve special mention because they are the most frequent side effect of Dato-DXd and the one that most directly affects daily life. Expert consensus panels have developed specific prevention and management guidelines. The core recommendation is to start a preventive oral care routine on day one of treatment, before any mouth sores appear. This includes gentle brushing with a soft toothbrush after meals, daily flossing (unless it causes pain), and using a steroid-containing mouthwash, preferably one with dexamethasone.¹²¹³

Experts also recommend oral cryotherapy as a preventive strategy and emphasize that early detection through self-checks and regular follow-up calls with the care team can catch mouth sores before they become severe. For more serious cases, dose adjustments or temporary pauses in treatment may be needed.¹⁴ The fact that multiple independent expert panels have published guidance on this issue underscores how seriously clinicians take it and how proactive management can make a meaningful difference in tolerability.

Combination With Immunotherapy

Some of the most exciting data for Dato-DXd come not from using it alone, but from pairing it with the immunotherapy drug durvalumab. The BEGONIA trial tested this combination as a first-line treatment for patients with advanced triple-negative breast cancer, and the response rates were remarkable: roughly 79 to 82% of patients saw their tumors shrink significantly. Median progression-free survival in one arm of the trial reached 14 months, and median overall survival had not yet been reached at the time of reporting, meaning most patients were still alive.¹⁵ The safety profile of the combination was manageable, with no new safety signals beyond what had already been seen with each drug individually.

The scientific rationale for combining an ADC with immunotherapy traces back to the immunogenic cell death mechanism described earlier. When Dato-DXd kills cancer cells in a way that alerts the immune system, adding an immune checkpoint inhibitor like durvalumab could amplify that immune response, essentially turning the tumor into its own vaccine while simultaneously removing the brakes on immune cells. Whether this combination will ultimately prove better than Dato-DXd alone in a head-to-head trial is still being studied, but the early signal is strong enough that multiple large trials are exploring it.

Moving Into Earlier-Stage Disease

All of the approvals so far have been for advanced or metastatic breast cancer, meaning cancer that has spread or cannot be removed surgically. But there is growing interest in using Dato-DXd earlier in the course of disease, before surgery, where the goal is to shrink the tumor and potentially eliminate it entirely.

The I-SPY2.2 trial, a phase 2 platform trial that tests multiple experimental combinations for high-risk early-stage breast cancer, tested Dato-DXd plus durvalumab as the first block of neoadjuvant therapy (given before surgery). In patients with immune-positive tumors, the combination met the prespecified threshold for success. Across all treatment blocks, pathologic complete response rates matched what would be expected with standard care, but over half of patients achieved that result after the Dato-DXd/durvalumab combination alone, and 92% reached it without needing the traditionally harsh doxorubicin-cyclophosphamide chemotherapy regimen.¹⁶ The most common side effect was stomatitis, and no patients receiving the Dato-DXd block alone developed adrenal insufficiency, a concern sometimes seen with immunotherapy combinations.

A larger phase III trial called TROPION-Breast04 is now underway to formally test whether Dato-DXd plus durvalumab can replace or reduce the need for traditional chemotherapy in early-stage triple-negative and hormone receptor-low, HER2-negative breast cancer.¹⁷ If this trial succeeds, it could represent a fundamental shift in how early breast cancer is treated, potentially sparing many patients from some of the most debilitating aspects of conventional chemotherapy while achieving equivalent or better outcomes.

How Dato-DXd Compares to Sacituzumab Govitecan

Dato-DXd is not the only TROP2-targeting ADC. Sacituzumab govitecan (sold as Trodelvy) was approved earlier and has become a standard treatment for metastatic triple-negative breast cancer after prior therapy. Both drugs bind to the same target, but they are not interchangeable. They differ in their antibody components, the chemistry that links the antibody to the payload, and the specific payload molecule, all of which influence how each drug behaves in the body, its potency, and its side-effect profile.¹⁸

In practice, sacituzumab govitecan tends to cause more gastrointestinal side effects like diarrhea and significant drops in white blood cell counts (neutropenia), while Dato-DXd is more associated with stomatitis and eye-related issues. Because the drugs have different toxicity profiles and somewhat different mechanisms, there is interest in understanding whether patients who progress on one might still benefit from the other. No large trial has directly compared the two head-to-head or formally tested sequential use, but the fact that they affect the body differently offers some theoretical hope for sequencing strategies.

Drug Resistance and What Limits Effectiveness

Like all cancer drugs, Dato-DXd eventually stops working in most patients as tumors develop resistance. Researchers are beginning to understand why. Preclinical studies using cancer cell lines engineered to resist Dato-DXd found that the resistance did not appear to come from any single dramatic change. There were minor reductions in TROP2 levels and small changes in drug efflux pumps (the molecular pumps cancer cells use to flush out toxic drugs), but none of these alone was enough to explain the resistance.¹⁹

Instead, a deeper molecular analysis revealed that resistant cells had lost a protein called SLFN11, which is involved in DNA damage response. Loss of SLFN11 has been linked to resistance to other DNA-damaging drugs as well, so this finding fits a broader pattern. Resistant cells also showed reduced activity in their internalization machinery (the system that pulls the drug inside the cell) and dampened interferon response genes, which are part of the immune signaling network. These findings are early-stage, but they point toward potential strategies to overcome resistance, such as combining Dato-DXd with drugs that restore SLFN11 function or that boost the interferon pathway.

Cost and Access Considerations

ADCs are among the most expensive drugs in oncology, and Dato-DXd is no exception. While published cost-effectiveness analyses have focused primarily on trastuzumab deruxtecan (the HER2-targeting ADC that shares the same payload), those studies highlight just how high the financial bar is for this drug class. One analysis of HER2-low metastatic breast cancer found that using T-DXd followed by chemotherapy cost roughly $282,000 per patient, compared to about $176,000 for chemotherapy alone, and that a 41% price reduction would be needed for T-DXd to meet standard cost-effectiveness thresholds in the U.S.²⁰ Given that Dato-DXd is in the same drug class and manufactured by the same company, the financial dynamics are likely similar.

Access varies substantially by country and insurance coverage. In the United States, most patients access Dato-DXd through commercial insurance or Medicare, often with manufacturer-sponsored copay assistance programs. In countries with public health systems, reimbursement decisions depend on the results of formal health technology assessments, which weigh clinical benefit against cost. The EU approval and ongoing regulatory reviews in Canada and China will gradually expand global access, but for many patients worldwide, the price of ADCs remains a significant barrier. This economic reality adds urgency to the early-stage trials, where a positive result could mean giving the drug to a much larger population of patients with curable disease, fundamentally changing the value proposition.

Ocular Side Effects

One side effect that gets less attention in headlines but genuinely affects patients is eye-related toxicity. Ocular events, including dry eyes, blurred vision, and in some cases more significant corneal changes, have been reported in clinical trials of Dato-DXd. The mechanism is not entirely clear, but TROP2 is expressed in certain eye tissues, which may explain why a drug designed to home in on that protein could affect the eyes as an off-target consequence. Patients starting Dato-DXd are generally advised to have a baseline eye exam and to report any visual changes promptly. In most cases, these side effects are manageable and reversible, but they can be alarming if you are not expecting them. Awareness matters because early intervention, including lubricating eye drops or dose adjustments, can prevent progression to more serious problems.