Novel Subcutaneous, At-Home Breast Cancer Treatment Approved

Phesgo (pertuzumab/trastuzumab/hyaluronidase-zzxf; Genentech) has been approved by the FDA as a subcutaneous (SC) treatment for adult patients with metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer or early-stage HER-2 positive disease.

The treatment works by disrupting cancer cell growth through pertuzumab and trastuzumab binding to HER2. This approval comes on the heels of Phesgo’s efficacy and safety results from 500 patients enrolled in the FeDeriCa open label, multicenter, randomized trial that compared treatment with it with IV pertuzumab and IV trastuzumab.

In a statement, Genentech said it is the first time the company has combined 2 monoclonal antibodies in a single SC injection.

There are 2 phases of dosing. Phesgo’s initial dose contains pertuzumab 1200 mg, trastuzumab 600 mg, and hyaluronidase 30,000 units over 8 minutes. A second dose contains pertuzumab 600 mg, trastuzumab 600 mg, and hyaluronidase 20,000 units and is given every 3 weeks for 5 minutes.

There is a warning attached for women who are pregnant, as the treatment can harm the fetus or a newborn child. It addition, women who are thinking of becoming pregnant are advised that taking the combination treatment within 7 months of becoming pregnant is another risk factor for fetal harm.

Other warnings include those for heart failure and lung toxicity, both of which health care professionals (HCPs) and patients should be informed. In return, HCPs need to monitor using parameters similar to “those used with [intravenous (IV)] pertuzumab and IV trastuzumab,” noted the FDA’s press release touting Phesgo’s approval.

“Currently, most patients with HER2-positive breast cancer receive trastuzumab and pertuzumab at infusion centers. With a new administration route, Phesgo offers an out-patient option for patients to receive trastuzumab and pertuzumab,” said 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.

Pazdur, a 2019 Giants of Cancer Care® recipient for his community outreach, highlighted how continuing to account for the increased vulnerability of patients with cancer during the coronavirus disease 2019 (COVID-19) pandemic necessitated the sped-up approval process. Phesgo’s application for FDA approval came in 4 months ahead of schedule.

Initial administration of Phesgo’s fixed-dose combination of pertuzumab and trastuzumab—the therapeutic ingredients which are identical to IV pertuzumab and IV trastuzumab—with hyaluronidase takes place in combination with chemotherapy:

• As neoadjuvant treatment for HER2-positive, locally advanced, inflammatory, or early-stage disease
• As adjuvant treatment for HER2-positive early-stage disease with a high recurrence risk
• With docetaxel for HER2-positive metastatic disease in the absence of prior anti-HER2 treatment or chemotherapy

A qualified HCP is allowed to continue the treatment in the home setting following completion of chemotherapy.

This latest approval for HER2-positive disease follows approvals of tucatinib (Tuksya, Seattle Genetics) in April and neratinib (Nerlynx, Puma Biotechnology) in February, both in the advanced or metastatic setting.

Adverse effects for Phesgo are alopecia, nausea, diarrhea, anemia, asthenia, worsening of chemotherapy-induced neutropenia, and anaphylaxis or hypersensitivity. These last 2 AEs call of discontinuation of Phesgo. Injection-site reactions are also possible due to it being an SC drug.