On April 17, 2020, as part of Project Orbis, the U.S. Food and Drug Administration (FDA) approved tucatinib (Tukysa™) in combination with chemotherapy (trastuzumab and capecitabine) for the treatment of adult patients with advanced forms of HER2-positive breast cancer that can’t be removed with surgery or have spread to other parts of the body, including the brain, and who have received one or more prior treatments. 

FDA Approves First New Drug Under International Collaboration, a Treatment Option for Patients With HER2-Positive Metastatic Breast Cancer 

FDA collaborated with the Australian Therapeutic Goods Administration (TGA), Health Canada, Singapore’s Health Sciences Authority (HSA), and Swissmedic (SMC) on the review. This is the first Project Orbis partnership between FDA, HSA and SMC. Although FDA approved tucatinib on April 17, the application is still under review at the other agencies.  

Collaboration among international regulators may allow patients with cancer to receive earlier access to products in other countries that may have significant delays in regulatory submissions, regardless of whether the product has received FDA approval.  

Early availability of new therapies and adoption as standard of care around the world may help increase the international conduct of cancer clinical trials, potentially accelerating the development of anticancer products. With a framework for concurrent submission and review of oncology drugs, Project Orbis facilitates collaboration to identify any regulatory divergence across review teams. 

“FDA’s Project Orbis provides a framework for concurrent submission and review of oncology drug applications among FDA’s international collaborators. We are pleased to work with our Singapore and Switzerland colleagues for the first time and to continue working alongside our Australian and Canadian colleagues as we facilitate new treatment options for patients—like today’s first new molecular entity under Project Orbis,” Richard Pazdur, MD, director of the FDA’s Oncology Center of Excellence and acting director of the Office of Oncologic Diseases in the FDA’s Center for Drug Evaluation and Research, said. “This approval represents an additional targeted treatment option for patients with HER2-positive breast cancer. The clinical trial supporting this approval enrolled and specifically studied patients with active brain metastases in addition to the overall population enrolled, which also demonstrated benefit in this subgroup.” 

HER2-positive breast cancer, which makes up approximately one-fifth of breast cancers, can develop when the body has too much HER2 protein, which promotes the growth of cancer cells. More than 25% of women with metastatic HER2-positive breast cancer will develop brain metastases. 

“We recognize that patients with cancer constitute a vulnerable population at risk of contracting the coronavirus disease,” Pazdur said. “In this critical time, we remain steadfast in our commitment to patients with cancer and doing everything we can to expedite oncology product development. Tucatinib was approved four months prior to the FDA goal date, providing an example of this commitment and showing how our regular work in reviewing treatments for patients with cancer is moving forward without delay.” 

Tucatinib is a kinase inhibitor, meaning it blocks a type of enzyme (kinase) and helps prevent cancer cells from growing. Tucatinib is approved for treatment after patients have taken one or more anti-HER2–based regimens in the metastatic setting. FDA approved tucatinib based on the results of a clinical trial enrolling 612 patients who had HER2-positive advanced unresectable or metastatic breast cancer and had prior treatment with trastuzumab, pertuzumab, and ado-trastuzumab emtansine (T-DM1). Patients with previously treated and stable brain metastases, as well as those with previously treated and growing or untreated brain metastases, were eligible for the clinical trial, and 48% of enrolled patients had brain metastases at the start of the trial. 

The primary endpoint was progression-free survival (PFS), or the amount of time the tumor did not grow. The median PFS in patients who received tucatinib, trastuzumab, and capecitabine was 7.8 months compared to 5.6 months in those patients who received placebo, trastuzumab, and capecitabine. Overall survival and PFS in patients with brain metastases at baseline were key secondary endpoints. The median overall survival in patients who received tucatinib, trastuzumab, and capecitabine was 21.9 months compared to 17.4 months in patients who received placebo, trastuzumab, and capecitabine. The median PFS in patients with brain metastases at baseline who received tucatinib, trastuzumab, and capecitabine was 7.6 months compared to 5.4 months in patients who received placebo, trastuzumab, and capecitabine. 

Common side effects for patients taking tucatinib were diarrhea, palmar-plantar erythrodysesthesia, nausea, fatigue, hepatotoxicity, vomiting, stomatitis, decreased appetite, abdominal pain, headache, anemia, and rash. 

Tucatinib can cause serious side effects, including severe diarrhea associated with dehydration, acute kidney injury, and death. Healthcare professionals should advise patients to notify their healthcare provider and start antidiarrheals as clinically indicated if diarrhea occurs. If patients are experiencing severe diarrhea, tucatinib should be interrupted or the dosage reduced. Tucatinib can also cause severe hepatotoxicity. Healthcare professionals should monitor liver tests in patients taking tucatinib every three weeks or as clinically indicated. 

Women who are pregnant or breastfeeding should not take tucatinib because it may cause harm to a developing fetus or newborn baby. Females of reproductive potential and males with female partners of reproductive potential should use effective contraception during treatment with tucatinib and for at least one week after the last dose. Refer to the Full Prescribing Information of trastuzumab and capecitabine for pregnancy and contraception information. 

In addition to the international collaboration with TGA, Health Canada, HSA, and SMC, the review used the Real-Time Oncology Review (RTOR) pilot program, which can streamline the submission of data prior to the completion and submission of the entire clinical application. RTOR, as well as assessment aid, facilitated discussions among the regulatory agencies and regulatory review. 

FDA granted the application priority review and breakthrough therapy designation, which expedites the development and review of drugs that are intended to treat a serious condition, when preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over available therapies. Tucatinib was also granted fast-track designation, which expedites the review of drugs to treat serious conditions and fill an unmet medical need. Tucatinib received orphan drug designation, which provides incentives to assist and encourage the development of drugs for rare diseases.  

Healthcare professionals should report all serious adverse events suspected to be associated with the use of any medicine and device to FDA’s MedWatch Reporting System or by calling 800-FDA-1088.