By Jay Grisolano, PhD and Stephanie Ritz, PhD
Approximately a quarter of breast cancer patients are classified as HER2-positive, according to Kantar Health’s 2016 Treatment Architecture data. 1 Effective targeted agents for the HER2 receptor, such as Herceptin (trastuzumab; Roche) and Perjeta (pertuzumab; Roche), have been developed for this particular patient segment and have greatly improved clinical outcomes for these patients. Despite these major advances, the need for improved early stage treatments still exists to keep disease from reaching an incurable stage. Currently, up to one in three early stage HER2+ patients treated with Herceptin in combination with chemotherapy eventually recur.2 In an effort to address this unmet need, Roche is conducting the Phase 3 APHINITY trial (NCT01358877) evaluating the combination of Herceptin, Perjeta, and chemotherapy in the adjuvant setting, hoping to improve upon these outcomes.
The triplet combination of Herceptin, Perjeta, and chemotherapy was initially approved in the HER2+ metastatic setting for first-line patients based on data from the Phase III CLEOPATRA trial, showing addition of Herceptin and Perjeta to chemotherapy improved median progression-free survival (PFS) and median overall survival (OS).3 In addition, the triplet has already demonstrated efficacy in early stage disease. The Phase II NEOSPHERE study (NCT00545688) compared Herceptin plus docetaxel with or without Perjeta in the neoadjuvant setting. Results reported at ASCO 2015 and published in Lancet Oncology showed a significantly improved complete response without an increase in cardiotoxicity (Herceptin / docetaxel: pCR 21.5%; Herceptin / docetaxel / Perjeta: pCR 39.3%, p=0.0063). Additionally, the risk of disease progression or recurrence was reduced by 31% and 40%.4 Based on these data, the triplet neoadjuvant regimen was granted approval in September 2013.
Now Roche is pushing to move their triplet combination into the adjuvant setting with APHINITY, results of which were presented today at the 2017 Annual Meeting of the American Society of Clinical Oncology (ASCO).5 APHINITY is an international, double-blind, placebo-controlled Phase III trial evaluating the efficacy of Herceptin plus chemotherapy with or without Perjeta in the adjuvant setting. The study enrolled 4,805 patients of lymph-node-positive and -negative status with confirmed HER2 positivity, as defined by IHC3+ or FISH-/CISH-positive. Patients received 6 to 8 cycles of chemotherapy with Herceptin (8mg/kg) and Perjeta (840 mg)/placebo, followed by Herceptin (6 mg/kg) and Perjeta (420 mg)/placebo alone every 3 weeks for one year (52 weeks) of treatment. At the time of presentation, the primary endpoint of invasive disease-free survival (IDFS) in the overall population was 92.3% in the triplet arm versus 90.6% seen in the control arm (p=0.045) at four years; however, subgroup analysis suggested that clinical benefit for IDFS appeared to be limited to node-positive and hormone receptor-negative cohorts. The disease-free interval and recurrence-free interval was modestly improved (DFI: 93.4% v. 92.3%, p=0.033; RFI: 95.2% vs. 94.3%, p=0.043); however, the addition of Perjeta did not improve the distant recurrence-free interval. No difference was noted in median overall survival at first interim analysis (97.7% v. 97.7%, p=0.467), but only one-quarter of data points needed for final analysis had been collected.
The most common Grade 3/4 adverse events associated with the triplet arm included neutropenia in 16.3% of patients (versus 15.7% in the control arm), febrile neutropenia in 12.1% of patients (versus 11.1% in the control arm, anemia in 6.9% of patients (versus 4.7% in the control arm), and diarrhea in 9.8% of patients (versus 3.7% in the control arm), which was predominately observed during the administration of chemotherapy. Cardiac toxicity was low and similar between the two arms.
Based on these data, it will be interesting to see how physicians adopt the triplet regimen in the adjuvant setting if it gains accelerated approval. Physician attendees vocalized great concerns during today’s session regarding the financial burden of adding Perjeta for a modest 1.7% IDFS benefit, despite its favorable tolerability profile. It may be essential for Roche to find specific subsets of patients who benefit most from the triplet in order for physicians to seriously consider integrating the addition of Pejeta into their practice. Another concern is whether Perjeta retreatment of a patient who recurs with metastatic disease will still be effective. It was mentioned that trials are being initiated to evaluate retreatment with Perjeta. Given the modest efficacy of APHINITY and the current absence of data supporting retreatment with the triplet beyond progression, physicians may to choose to save Perjeta until the metastatic setting. These issues may make it difficult to compete with Puma’s HER2 tyrosine kinase inhibitor, neratinib, which already has a PDUFA date set for July. Data supporting Puma’s application for approval is based on the Phase III ExteNET (NCT02400476) study, which showed a 2% benefit in 2-year DFS (2-year rate: 93.9% vs. 91.6%, p=0.0009) with a relatively well-tolerated toxicity profile.6 Subgroup analysis showed that neratinib may be more effective in ER-positive patients, which could help Puma find its niche in this space should neratinib receive approval.
Nevertheless, APHINITY did meet its primary endpoint showing that addition of Perjeta to Herceptin and chemotherapy as adjuvant treatment achieved a statistically significant improvement in IDFS. These data suggest that the triplet may become an option for adjuvant treatment of HER2+ early breast cancer.