On February 28, 2019, the FDA approved a combination of the HER2/neu receptor agonist trastuzumab plus the endoglycosidase hyaluronidase-oysk (Herceptin Hylecta; Genentech) subcutaneous (SC) injection for adults with HER2-overexpressing breast cancer in the adjuvant setting, as part of a regimen with chemotherapy or as monotherapy after multimodality anthracycline-based therapy; and as first-line treatment for metastatic disease, in combination with paclitaxel, or as monotherapy after ≥1 chemotherapies in the metastatic setting. This SC injection is a new formulation of intravenous (IV) trastuzumab.
The FDA approval of this new formulation was based on results of 3 clinical trials of patients with HER2-positive breast cancer. In the HannaH trial, patients were randomized to chemotherapy plus the SC combination or to IV trastuzumab, followed by surgery and additional cycles of their assigned trastuzumab-based therapy. In total, 45.5% of patients in the SC arm and 40.7% in the IV arm had a pathologic complete response. In the SafeHER trial, the safety and tolerability profile of the SC combination plus chemotherapy was consistent with that of IV trastuzumab plus chemotherapy. In the PrefHER trial, a patient preference study of the SC versus IV formulations, 86% of patients preferred the SC formulation.
The most common (≥10%) adverse effects in patients with early breast cancer who received trastuzumab plus hyaluronidase-oysk SC injection included fatigue, joint pain, diarrhea, injection-site reaction, upper respiratory tract infection, rash, muscle pain, nausea, headache, swelling, flushing, fever, cough, and pain in extremity.
