Pfizer’s IBRANCE Wins FDA Approval in HR+/HER2+ Metastatic Breast Cancer, Expanding CDK4/6 Use Into New Maintenance Setting
Pfizer has secured a significant new U.S. regulatory milestone for IBRANCE (palbociclib), with the U.S. Food and Drug Administration approving the CDK4/6 inhibitor in combination with trastuzumab, with or without pertuzumab, and endocrine therapy for the maintenance treatment of adults with hormone receptor-positive (HR+), HER2-positive locally advanced or metastatic breast cancer following induction therapy. The approval extends the reach of one of the most established medicines in metastatic breast cancer and gives clinicians a new option for a patient population that has historically had limited data to guide long-term maintenance treatment decisions. (U.S. Food and Drug Administration)
The decision is based on results from the Phase 3 PATINA trial, a registrational study sponsored by Alliance Foundation Trials, LLC (AFT) that evaluated whether adding IBRANCE to anti-HER2 therapy and endocrine therapy could improve outcomes in patients with HR+/HER2+ metastatic breast cancer after they had completed induction treatment. According to the FDA and Pfizer, the study showed that the addition of palbociclib reduced the risk of disease progression or death by 24% compared with anti-HER2 therapy and endocrine therapy alone, supporting the drug’s move into this maintenance setting. (U.S. Food and Drug Administration)
The approval is notable because it expands IBRANCE beyond the HR+/HER2-negative metastatic breast cancer population in which it first established itself as a standard-of-care therapy. With this new indication, Pfizer says IBRANCE becomes the first and only CDK4/6 inhibitor approved for patients with HR+ metastatic breast cancer regardless of HER2 status, positioning the drug as a broader backbone therapy across multiple combination regimens in metastatic disease. (U.S. Food and Drug Administration)
New Option for a Distinct Breast Cancer Subtype
The newly approved indication targets a relatively small but clinically important subset of metastatic breast cancer. Roughly 10% of all breast cancers are classified as HR-positive and HER2-positive, a subtype sometimes described as “double-positive” or “triple-positive” disease because tumors may express estrogen and/or progesterone receptors alongside HER2 overexpression. While therapies targeting HER2 have transformed outcomes for many of these patients, long-term disease control remains challenging because resistance to treatment frequently emerges over time. (Pfizer)
Historically, this subgroup has occupied a somewhat complex space in breast cancer treatment. Patients with HR+/HER2+ disease often receive HER2-targeted therapy, such as trastuzumab and pertuzumab, alongside chemotherapy during the initial phase of metastatic treatment. Once that induction phase is completed and the disease is controlled, clinicians must decide how best to maintain that response and delay progression for as long as possible. Endocrine therapy and anti-HER2 therapy have formed the backbone of maintenance treatment, but the role of CDK4/6 inhibition in this subtype had remained largely unproven until the PATINA data emerged. (U.S. Food and Drug Administration)
That is why the FDA decision carries weight beyond the label expansion itself. It effectively validates the concept that CDK4/6 inhibition—already well established in HR+/HER2-negative disease—can also provide benefit in a HER2-positive, hormone receptor-positive metastatic setting when layered onto standard anti-HER2 and endocrine treatment.
PATINA Trial Established the Clinical Basis for Approval
The approval was supported by the PATINA study (NCT02947685), a randomized, open-label Phase 3 trial that enrolled 518 patients with HR-positive, HER2-positive locally advanced or metastatic breast cancer who had no evidence of disease progression after induction treatment with a taxane and trastuzumab, with or without pertuzumab, for advanced disease. Patients were randomized to receive either palbociclib in combination with trastuzumab, with or without pertuzumab, and endocrine therapy, or anti-HER2 therapy plus endocrine therapy alone. Treatment continued until disease progression or unacceptable toxicity. (U.S. Food and Drug Administration)
The study’s primary efficacy endpoint was investigator-assessed progression-free survival (PFS) using RECIST criteria. According to the FDA’s review, the palbociclib-containing regimen achieved a hazard ratio of 0.76 compared with the control arm, corresponding to a 24% reduction in the risk of progression or death. The one-sided p-value was 0.0134, meeting the threshold for statistical significance. At the time of the analysis, overall survival data were not yet mature. (U.S. Food and Drug Administration)
Pfizer has emphasized that the PATINA results offer an important answer to a long-standing clinical challenge in this disease subtype: how to keep metastatic HR+/HER2+ breast cancer under control after a good initial response to induction therapy. By extending the time patients remain free from disease progression, the company and trial investigators argue that IBRANCE can strengthen the maintenance treatment strategy for this population.
Trial Results Build on Growing Interest in CDK4/6 Use Beyond HER2-Negative Disease
The PATINA findings have already attracted considerable attention in oncology circles. Results from the trial were previously published in The New England Journal of Medicine and presented at the 2024 San Antonio Breast Cancer Symposium, giving the data a high-profile scientific platform well before the formal FDA decision. (Pfizer)
For years, CDK4/6 inhibitors such as palbociclib have played a major role in HR+/HER2-negative metastatic breast cancer, where they have reshaped first-line treatment and become a foundational component of endocrine-based therapy. But whether the same strategy could work in HER2-positive disease was an open question, partly because HER2-targeted therapy already plays such a dominant role in that setting and partly because HR+/HER2+ metastatic breast cancer has historically been underrepresented in dedicated registrational studies.
PATINA was designed to address that gap directly. It is the first registrational trial to explore the use of CDK4/6 inhibition in the HR+/HER2+ metastatic breast cancer subtype, making the FDA approval a milestone not only for Pfizer but also for the broader treatment landscape in this disease category. (Pfizer)
Safety Profile Consistent With Known IBRANCE Experience
From a safety perspective, the FDA said the tolerability profile of IBRANCE in PATINA was consistent with what has already been observed in prior studies and clinical use of the drug. The prescribing information continues to include warnings and precautions for neutropenia, interstitial lung disease/pneumonitis, and embryo-fetal toxicity. In the PATINA study, the most commonly reported adverse events were hematologic toxicities, including decreased white blood cell count and reduced neutrophil counts. Non-hematologic side effects included diarrhea, infections, stomatitis, and fatigue, and were generally described as mild to moderate in severity. (U.S. Food and Drug Administration)
The FDA-approved dosing regimen for the new indication mirrors the established oral schedule used for IBRANCE in other settings: 125 mg once daily for 21 consecutive days followed by seven days off treatment, completing a 28-day cycle. Dosing for trastuzumab, pertuzumab, and endocrine therapy follows the respective product labeling. (U.S. Food and Drug Administration)
The fact that no unexpected new safety signals emerged in the trial is important for clinicians considering whether to add another active therapy into the maintenance phase of treatment. In metastatic breast cancer, maintaining quality of life and balancing efficacy with long-term tolerability are essential considerations, especially in patients who may remain on therapy for extended periods.
Pfizer Frames Approval as a New Chapter for IBRANCE
Pfizer has positioned the approval as another important chapter in the long commercial and clinical history of IBRANCE. Since its original FDA approval in 2015, the drug has become one of the most recognizable names in HR+ metastatic breast cancer treatment. The company says IBRANCE has been prescribed to more than 900,000 patients worldwide and is approved in more than 100 countries, underscoring its status as one of the foundational medicines in the CDK4/6 inhibitor class. (MarketScreener)
Aamir Malik, Pfizer’s Chief U.S. Commercial Officer and Executive Vice President, said the approval broadens the impact of IBRANCE by extending CDK4/6 inhibition to patients with HR+ metastatic breast cancer regardless of HER2 status. He described the decision as further evidence that IBRANCE can serve as a CDK4/6 inhibitor backbone across multiple treatment combinations, particularly for patients who continue to face challenges related to resistance. While clearly commercial in tone, the message reflects Pfizer’s strategy of reinforcing IBRANCE’s role not just as an early leader in CDK4/6 therapy, but as a durable brand with continued relevance in an evolving metastatic breast cancer market. (MarketScreener)
Investigators Say Approval Addresses an Ongoing Maintenance Challenge
Clinical investigators involved with the trial have also emphasized the practical relevance of the approval. Otto Metzger, M.D., principal investigator of the PATINA study for Alliance Foundation Trials and a medical oncologist at Dana-Farber Cancer Institute, said resistance to dual anti-HER2 and endocrine therapy remains a major challenge for patients with HR+/HER2+ metastatic breast cancer, even when they initially respond well to treatment. Based on the PATINA findings, he said the addition of IBRANCE during maintenance can meaningfully extend the time patients go without disease progression and gives oncologists a new evidence-based strategy for optimizing maintenance therapy in this setting. (MarketScreener)
That perspective is important because the maintenance phase of metastatic treatment is often where oncologists try to maximize durability of benefit while minimizing unnecessary toxicity. The availability of a new FDA-approved regimen in this context gives physicians another validated option for trying to keep disease under control for longer.
Broader Implications for the Metastatic Breast Cancer Landscape
The new indication arrives at a time when the metastatic breast cancer treatment landscape is becoming increasingly segmented by biomarker status, prior treatment history, and resistance mechanisms. HER2-positive disease alone now includes multiple lines of targeted therapy options, from trastuzumab-based regimens to antibody-drug conjugates and tyrosine kinase inhibitors. At the same time, hormone receptor-positive disease continues to evolve with CDK4/6 inhibitors, oral SERDs, protein degraders, and other endocrine-based strategies.
Within that increasingly complex environment, the approval of IBRANCE for HR+/HER2+ maintenance therapy fills an important niche. It gives clinicians a way to bring CDK4/6 inhibition into a subtype that had not previously had an FDA-approved therapy in this class, and it does so in a maintenance setting where delaying progression can meaningfully affect both patient experience and treatment sequencing.
For Pfizer, the approval reinforces the staying power of IBRANCE more than a decade after its original launch. For oncologists, it adds a new evidence-backed maintenance option for a difficult-to-manage breast cancer subtype. And for patients with HR+/HER2+ metastatic disease, it may offer a longer period of disease control after initial therapy—an outcome that remains one of the central goals of metastatic breast cancer care.
About the PATINA Trial
PATINA (AFT-38) was a randomized, open-label global Phase 3 study to evaluate the efficacy and safety of IBRANCE® (palbociclib) in combination with anti-HER2 therapy (trastuzumab or trastuzumab plus pertuzumab) and endocrine therapy compared to anti-HER2 therapy and endocrine therapy alone as a first-line maintenance therapy (following induction treatment) for patients with HR+, HER2+ MBC.
While Pfizer provided funding support for the trial, PATINA was also supported by an academic collaboration led by Alliance Foundation Trials, LLC (AFT) as the global sponsor in partnership with six international cancer research groups in the U.S.(PrECOG), France (French Breast Cancer Intergroup Unicancer), Germany (GBG), Italy (Fondazione Michelangelo), Portugal and Spain (SOLTI), and Australia and New Zealand (Breast Cancer Trials).
Study participants who received a median of 6 cycles of induction treatment were randomized to receive IBRANCE, in addition to anti-HER2 therapy and endocrine therapy (n=261), or anti-HER2 therapy and endocrine therapy alone (n=257). The primary endpoint was progression-free survival (PFS) as assessed by the investigator. Overall survival is a secondary endpoint and is not yet mature.
About IBRANCE® (palbociclib)
IBRANCE is an oral inhibitor of CDKs 4 and 6,ii which are key regulators of the cell cycle that trigger cellular progression.iii,iv In the U.S., IBRANCE is indicated for the treatment of adult patients with HR+, HER2- advanced or metastatic breast cancer in combination with an aromatase inhibitor as initial endocrine-based therapy; or with fulvestrant in patients with disease progression following endocrine therapy.
IBRANCE is indicated in combination with inavolisib and fulvestrant for the treatment of adult patients with endocrine-resistant, PIK3CA-mutated, HR-positive, HER2-negative, locally advanced or metastatic breast cancer, as detected by an FDA-approved test, following recurrence on or after completing adjuvant endocrine therapy.
IBRANCE is also indicated in combination with trastuzumab, with or without pertuzumab, and endocrine therapy for the maintenance treatment of adult patients with HR-positive, HER2-positive locally advanced or metastatic breast cancer following induction treatment.
