SUMMARY: The FDA on September 30, 2013 granted accelerated approval to PERJETA® (Pertuzumab) for use in combination with HERCEPTIN® (Trastuzumab) and other chemotherapy for the neoadjuvant (preoperative) treatment of patients with HER2-positive, locally advanced, inflammatory, or early stage breast cancer (either greater than 2 cm in diameter or with positive lymph nodes), as part of a complete treatment regimen for early breast cancer. Following surgery, patients should continue to receive HERCEPTIN® to complete one year of treatment. The HER family of receptors consist of HER1, HER2, HER3 and HER4. 
These proteins are transmembrane tyrosine kinases and are involved in normal cell growth and differentiation. HER1 is also known as Epidermal Growth Factor Receptor or EGFR. These receptors are activated following ligand binding, receptor pairing or dimerization and phosphorylation. This dimerization (receptor pairing) occurs often within the HER family of receptors. This has been no ligand identified for HER2 receptor, although it is able to form homo and heterodimers with other members of the HER family readily. Dimerization of HER2 and HER3 is believed to produce the strongest mitogenic signaling and activates two important pathways that regulate cell survival and growth – Mitogen Activated Protein Kinase (MAPK) pathway and PhosphoInositide 3-Kinase (PI3K) pathway. For this reason inhibiting HER2 dimerization appears to be an important step in the treatment of cancer. Overexpression of HER2 in breast cancer has been associated with higher risk for relapse as well as overall survival. Approximately 20 percent of breast cancers are HER2-positive. HERCEPTIN® is a humanized monoclonal antibody targeting HER2. It binds to the extracellular subdomain IV of the receptor and disrupts ligand independent HER2 downstream cell signaling pathways. PERJETA® is a recombinant, humanized, monoclonal antibody that binds to the HER2 subdomain II and blocks ligand dependent HER2 heterodimerization with other HER receptors, ie. HER3, HER1 and HER4. Thus HERCEPTIN® along with PERJETA® provide a more comprehensive blockade of HER2 driven signaling pathways. The accelerated approval of PERJETA® for the neoadjuvant treatment of breast cancer was based on a randomized, multicenter, open-label, phase II trial, in which 417 patients with HER2-positive, operable, locally advanced or inflammatory breast cancer (T2-4d), were randomly assigned to receive preoperative therapy with either HERCEPTIN® plus TAXOTERE® (Docetaxel), PERJETA® plus HERCEPTIN® and TAXOTERE®, PERJETA® plus HERCEPTIN® or PERJETA® plus TAXOTERE®. Patients in the three drug group received preoperative therapy with PERJETA®, HERCEPTIN® and TAXOTERE® every 3 weeks for a total of 4 cycles and following surgery, all patients received 3 cycles of Fluorouracil, ELLENCE® (Epirubicin), and CYTOXAN® (Cyclophosphamide) – (FEC) IV every 3 weeks and HERCEPTIN® was continued every 3 weeks for a total of one year of therapy. The primary endpoint was pathological Complete Response (pCR) rate defined as the absence of invasive cancer in the breast. The FDA definition of pCR is the absence of invasive cancer in the breast and lymph nodes. All treatment groups were well balanced. Seven percent of patients had inflammatory breast cancer, 32% had locally advanced cancer and 70% had clinically node-positive breast cancer. Forty-seven percent of the patients had hormone receptor-positive disease. The FDA defined pCR rates were 39.3% in the PERJETA® plus HERCEPTIN® and TAXOTERE® group and 21.5% in the HERCEPTIN® plus TAXOTERE® group (P=0.0063). Of Interest, the pCR rates in the three drug group were lower in patients with hormone receptor positive tumors compared to patients with hormone receptor negative tumors. The most common adverse events in the three drug group were alopecia, diarrhea, nausea and neutropenia. Other significant side effects included decreased cardiac function, infusion-related reactions, hypersensitivity reactions and anaphylaxis. Based on clinical studies, for the neoadjuvant treatment of breast cancer, PERJETA® should be administered every 3 weeks for 3 to 6 cycles as part of one of the following treatment regimens for early breast cancer. • Four preoperative cycles of PERJETA® in combination with HERCEPTIN® and TAXOTERE® followed by 3 postoperative cycles of Fluorouracil, ELLENCE® and CYTOXAN® (FEC). • Three preoperative cycles of FEC alone followed by 3 preoperative cycles of PERJETA® in combination with TAXOTERE® and HERCEPTIN®. • Six preoperative cycles of PERJETA® in combination with TAXOTERE®, Carboplatin, and HERCEPTIN® (TCH). Following surgery, patients should continue to receive HERCEPTIN® to complete 1 year of treatment. The accelerated approval by the FDA was based solely on the improved pCR rate with the three drug combination with no demonstrable improvement in event-free survival or overall survival. A confirmatory phase III trial is underway, with results expected in 2016. Gianni L, Pienkowski T, Im YH, et al. Lancet Oncol. 2012;13:25-32
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