FDA Approves Pfizer’s TUKYSA Regimen for First-Line Maintenance in HER2+ Metastatic Breast Cancer
Pfizer Inc. announced that the U.S. Food and Drug Administration (FDA) has approved TUKYSA® (tucatinib) in combination with trastuzumab and pertuzumab for the maintenance treatment of adults with unresectable, locally advanced or metastatic human epidermal growth factor receptor 2-positive (HER2+) breast cancer following induction treatment.
The FDA decision expands the use of TUKYSA into an earlier stage of metastatic HER2-positive breast cancer and introduces a chemotherapy-free maintenance treatment option for patients who have completed initial induction therapy. The approval is based on results from the Phase 3 HER2CLIMB-05 trial, which demonstrated that the TUKYSA-based regimen significantly prolonged progression-free survival (PFS) compared with placebo plus trastuzumab and pertuzumab.
The regulatory decision represents an important expansion of the role of tucatinib in HER2-positive metastatic breast cancer. TUKYSA was initially approved in 2020 in combination with trastuzumab and capecitabine for adults with advanced unresectable or metastatic HER2-positive breast cancer after at least one prior anti-HER2-based regimen in the metastatic setting. The new approval moves the therapy into the frontline maintenance setting and provides another approach for maintaining disease control after induction treatment.
The new indication is particularly significant because the approved regimen does not include chemotherapy during the maintenance phase. Patients receiving the combination of TUKYSA, trastuzumab and pertuzumab can therefore continue HER2-directed treatment without capecitabine as part of the maintenance regimen.
“Since its first approval in 2020, TUKYSA has become an important treatment for patients with second-line HER2+ metastatic breast cancer. Today’s FDA approval marks the next chapter for TUKYSA, bringing it into the front-line maintenance setting and offering patients a chemotherapy-free option that can help delay disease progression after initial treatment,” said Aamir Malik, Executive Vice President and Chief U.S. Commercial Officer at Pfizer.
“This approval reflects Pfizer’s commitment to advancing therapies across the breast cancer treatment journey and delivering meaningful new options for people living with metastatic breast cancer,” Malik added.
HER2CLIMB-05 Demonstrated Longer Progression-Free Survival
The FDA approval is supported by data from the randomized Phase 3 HER2CLIMB-05 clinical trial. The study evaluated whether adding tucatinib to trastuzumab and pertuzumab could extend disease control when used as maintenance therapy following induction treatment in patients with HER2-positive unresectable locally advanced or metastatic breast cancer.
The trial met its primary endpoint, demonstrating a statistically significant improvement in progression-free survival for patients who received the TUKYSA-based regimen.
The primary endpoint analysis showed a 35.9% reduction in the risk of disease progression or death for patients treated with TUKYSA, trastuzumab and pertuzumab compared with patients receiving placebo, trastuzumab and pertuzumab.
The investigator-assessed hazard ratio for progression or death was 0.64, with a 95% confidence interval of 0.51 to 0.80 and a two-sided p-value of less than 0.0001.
Median investigator-assessed PFS was 24.9 months in the TUKYSA arm, compared with 16.3 months in the placebo arm. This represented an 8.6-month difference in the median amount of time patients lived without their cancer progressing.
The findings indicate that continued HER2-directed treatment incorporating tucatinib can provide a meaningful extension of disease control following initial induction therapy.
The HER2CLIMB-05 findings are particularly relevant because metastatic breast cancer remains a chronic and potentially life-threatening disease in which treatment objectives often include delaying progression while maintaining quality of life and managing treatment-related toxicities.
“The treatment landscape for HER2+ metastatic breast cancer has evolved dramatically over the past decade, but many patients still experience disease progression despite initial benefit from therapy,” said Erika Hamilton, M.D., principal investigator of HER2CLIMB-05 and Chief Development Officer, Late Phase and Director of Breast Cancer Research for Sarah Cannon Research Institute.
“The HER2CLIMB-05 findings support TUKYSA plus trastuzumab and pertuzumab as a chemotherapy-free maintenance strategy that allows us to target HER2-positive tumors from multiple angles and can help prolong disease control,” Hamilton said.
Expanding HER2-Directed Treatment Options
HER2 is a protein that can promote the growth and survival of cancer cells. In HER2-positive breast cancer, tumor cells have higher-than-normal levels of the HER2 protein, making HER2 an important therapeutic target.
Over the past several decades, advances in HER2-targeted therapies have substantially changed the treatment landscape for patients with HER2-positive breast cancer. Trastuzumab and pertuzumab are established HER2-directed antibodies, while tucatinib is a small-molecule tyrosine kinase inhibitor designed to selectively inhibit HER2 signaling.
The combination of these therapies provides multiple mechanisms for targeting HER2-positive tumors.
The new FDA approval extends this strategy into the maintenance phase after induction treatment. Instead of continuing an induction regimen indefinitely, eligible patients can transition to a chemotherapy-free maintenance approach consisting of tucatinib, trastuzumab and pertuzumab.
This treatment strategy could be particularly relevant as physicians seek to balance sustained tumor control with treatment tolerability over the long-term management of metastatic disease.
The availability of a chemotherapy-free maintenance regimen may also provide physicians with greater flexibility in designing treatment plans based on individual patient circumstances, prior response, tolerability and ongoing disease control.
Safety Findings From HER2CLIMB-05
The safety profile observed in HER2CLIMB-05 was generally consistent with the established safety profile of TUKYSA, although the trial identified an increased severity of hepatotoxicity.
Most hepatotoxicity events were generally asymptomatic and reversible following dose modification and/or discontinuation. However, liver-related adverse events remain an important consideration when using the regimen and require appropriate monitoring during treatment.
The most commonly reported adverse events occurring in at least 20% of patients included diarrhea, musculoskeletal pain, hepatotoxicity, nausea, fatigue, rash and vomiting.
Serious adverse reactions occurring in at least 1% of patients included hepatotoxicity, which was reported in 3.9% of patients.
The trial also reported one patient who experienced a fatal adverse reaction associated with drug-induced liver injury.
These findings underscore the importance of monitoring liver function and managing treatment-related adverse events when administering tucatinib in combination with trastuzumab and pertuzumab. Dose modifications or treatment discontinuation may be required for certain patients depending on the severity of adverse events.
While the safety profile was broadly consistent with the known characteristics of TUKYSA, the increased severity of hepatotoxicity observed in the combination underscores the need for clinicians to remain attentive to liver-related toxicities throughout treatment.
A New Maintenance Approach Without Chemotherapy
One of the most important aspects of the FDA decision is the chemotherapy-free nature of the approved maintenance regimen.
Patients with metastatic HER2-positive breast cancer may receive systemic therapy over extended periods because treatment is generally intended to control rather than permanently eliminate metastatic disease. As a result, treatment tolerability becomes increasingly important as patients remain on therapy.
The ability to maintain HER2-directed treatment while removing chemotherapy from the maintenance phase could offer a different balance between efficacy and treatment burden.
In HER2CLIMB-05, the addition of tucatinib to trastuzumab and pertuzumab produced a median PFS of nearly 25 months, compared with just over 16 months for the placebo-based combination.
The 8.6-month improvement in median PFS provides a measurable indication of the additional disease control achieved with tucatinib.
The regimen also builds on an established therapeutic backbone. Trastuzumab and pertuzumab have long played important roles in HER2-positive breast cancer, while tucatinib brings targeted inhibition of HER2 signaling into the maintenance setting.
Building on TUKYSA’s Established Role
TUKYSA first received FDA approval in 2020, establishing tucatinib as an important targeted treatment option for HER2-positive metastatic breast cancer.
The therapy’s earlier indication was focused on patients with unresectable or metastatic HER2-positive breast cancer after at least one prior anti-HER2-based regimen in the metastatic setting. Its use in combination with trastuzumab and capecitabine provided patients with an option in later-line treatment.
The latest approval substantially broadens the potential use of the therapy by introducing tucatinib earlier in the metastatic treatment journey.
For Pfizer, the expansion also demonstrates the company’s strategy of investigating additional clinical settings for established medicines. Instead of limiting TUKYSA to later-line treatment, the company has generated evidence supporting its use as part of a maintenance strategy following induction.
The approach reflects the continuing evolution of HER2-positive breast cancer treatment, where multiple targeted therapies are being evaluated across different stages and lines of treatment.
Clinical Evidence Published and Presented
Results from HER2CLIMB-05 were previously published in the Journal of Clinical Oncology and presented at the 2025 San Antonio Breast Cancer Symposium (SABCS).
Publication of the data provides the broader oncology community with access to the detailed clinical findings underlying the FDA decision, while presentation at a major breast cancer meeting has helped place the results within the context of ongoing developments in HER2-positive disease.
The data from the study support the use of TUKYSA in combination with trastuzumab and pertuzumab as a maintenance strategy following induction treatment in appropriate patients.
The publication and regulatory approval together add to the clinical evidence supporting tucatinib as part of the evolving treatment landscape for HER2-positive metastatic breast cancer.
Implications for Patients With Metastatic HER2-Positive Breast Cancer
The FDA approval provides oncologists with an additional treatment option for adults with unresectable locally advanced or metastatic HER2-positive breast cancer who have completed induction treatment.
By allowing patients to continue HER2-directed therapy without chemotherapy during maintenance, the regimen may help physicians manage the long-term nature of metastatic disease while continuing to pursue meaningful disease control.
The improvement in median PFS observed in HER2CLIMB-05 suggests that adding tucatinib to trastuzumab and pertuzumab can delay progression compared with trastuzumab and pertuzumab alone.
For patients and clinicians, the decision to use the regimen will depend on individual clinical factors, treatment history, response to induction therapy and the potential risks associated with adverse events, including hepatotoxicity.
Overall, Pfizer’s latest FDA approval expands the clinical role of TUKYSA from a later-line treatment into the frontline maintenance setting. Supported by the HER2CLIMB-05 Phase 3 results, the decision introduces a chemotherapy-free maintenance strategy that delivered a statistically significant and clinically meaningful improvement in progression-free survival.
As treatment for HER2-positive metastatic breast cancer continues to evolve, the new indication adds another targeted option to the treatment sequence and reinforces the importance of sustained HER2 inhibition in efforts to prolong disease control.
About the Phase 3 HER2CLIMB-05 Trial
- The HER2CLIMB-05 trial is a randomized, double blind, placebo-controlled, pivotal Phase 3 study evaluating the efficacy and safety of TUKYSA compared to placebo, both in combination with trastuzumab and pertuzumab, as maintenance therapy for patients with HER2+ metastatic breast cancer (MBC) following induction therapy in the front-line setting.
- HER2 is overexpressed in up to 15-20% of breast cancers and is associated with poor prognosis, with an estimated five-year survival rate of 41% to 47%, depending on hormone receptor status.1-3
- Trial participants who completed induction therapy of trastuzumab, pertuzumab, and a taxane, with no evidence of progression, were randomized to receive TUKYSA in combination with trastuzumab plus pertuzumab (n=326) or placebo in combination with trastuzumab plus pertuzumab (n=328).
- The primary endpoint is PFS as assessed by the investigator. Overall survival is a key secondary endpoint.
Continuing Pfizer’s Legacy of Leadership in Breast Cancer
Pfizer has been a leader in breast cancer for over 25 years, and today we have five medicines and one biosimilar approved to treat different subtypes of the disease, reaching over 4.9 million patients worldwide.
In the U.S., TUKYSA is already a National Comprehensive Cancer Network® (NCCN®) Category 1 second-line plus treatment for HER2+ MBC patients. This approval extends the reach of TUKYSA as part of a front-line maintenance regimen, bringing patients a new option to delay disease progression without the need for continued chemotherapy and helping physicians further individualize treatment plans to best meet the needs of each unique patient.
About TUKYSA® (tucatinib)
TUKYSA (tucatinib) is an orally administered tyrosine kinase inhibitor of HER2. TUKYSA is approved in combination with trastuzumab and pertuzumab for the maintenance treatment of adult patients with unresectable locally advanced or metastatic HER2-positive breast cancer following induction treatment. TUKYSA has also been approved in combination with trastuzumab and capecitabine to treat adults with HER2-positive advanced unresectable or MBC, including patients with brain metastases who have received one or more prior anti-HER2 breast cancer treatments in the metastatic setting.
The full U.S. Prescribing Information for TUKYSA can be found here. There may be a delay as the document is updated with the latest information. It will be available as soon as possible. Please check back for the updated full information shortly.