Abstract PD3-10: Safety results from a randomized, double-blind, phase 3 study of ABP 980 compared with trastuzumab in patients with breast cancer
Authors: Kolberg H-C , Demetriou GS , Zhang N , Tomasevic Z , Hanes V 
Published: February 2018

Background: Analytical, functional, and pharmacokinetic similarity between the proposed biosimilar ABP 980 and trastuzumab (TRAS) has been shown. Similar efficacy and safety have also been demonstrated in the neoadjuvant phase of the phase 3 comparative clinical study. Here we focus on the safety and immunogenicity results from the adjuvant phase of this study.

Methods: The objective of this study was to compare ABP 980 with TRAS in women with HER2 positive early breast cancer. After run-in anthracycline-based chemotherapy, patients were randomized 1:1 to intravenous ABP 980 or TRAS plus paclitaxel Q3W for 4 cycles. Surgery was completed 3-7 weeks after the last dose of neoadjuvant study drug. After surgery, patients who initially received TRAS were allocated to either continue TRAS (TRAS/TRAS arm) or undergo a single switch to receive ABP 980 (TRAS/980 arm) and patient who initially received ABP 980 continued to receive ABP 980 (980/980 arm) Q3W for up to 1 year. This report is based on safety data collected at the time of primary analysis, when all patients had completed the first post-surgery clinical visit or had withdrawn. The majority of patients had completed the study at the time of this analysis.

Results: 725 patients were randomized; 364 and 361 patients were randomized to ABP 980 and TRAS, respectively, in the neoadjuvant phase. Following surgery, 349 patients in the 980/980 arm, 171 patients in the TRAS/TRAS arm, and 171 patients in the TRAS/980 arm entered the adjuvant phase. Adverse events (AEs) during the adjuvant phase are shown in Table 1; data from the neoadjuvant safety phase have been previously reported.

Table 1 980/980 (N = 349)TRAS/TRAS (N = 171)TRAS/980 (N = 171)AE category, n (%)   Any AE201 (57.6)89 (52.0)98 (57.3)Any grade ≥3 AE27 (7.7)10 (5.8)10 (5.8)Any fatal AE001 (0.6)Any serious AE14 (4.0)4 (2.3)4 (2.3)AEs of Interest, n (%)   Infections and infestations46 (13.2)14 (8.2)21 (12.3)Neutropenia37 (10.6)16 (9.4)13 (7.6)Infusion reactions27 (7.7)10 (5.8)15 (8.8)Hypersensitivity11 (3.2)3 (1.8)7 (4.1)Pulmonary toxicity3 (0.9)2 (1.2)1 (0.6)Cardiac failure01 (0.6)1 (0.6)LVEF decline by ≥10% and to below 50%, n/N* (%)9/313 (2.9)3/154 (1.9)3/153 (2.0)LVEF = left ventricular ejection fraction; N* = Number of patients with data available

One patient in the TRAS/980 arm developed binding antibodies during the adjuvant phase; this patient tested negative for neutralizing antibodies. In the neoadjuvant phase, 2 patients in the ABP 980 arm and 2 in the TRAS arm developed binding antibodies but tested negative for neutralizing antibodies. The percent of patients with disease progression or recurrence or death was 5.2% in the 980/980 arm, 5.3% in the TRAS/TRAS arm, and 2.9% in the TRAS/980 arm. The estimated hazard ratio from a stratified Cox proportional hazards regression model for 980/980 versus TRAS/TRAS was 1.01 (90% CI: [0.530, 1.930]) and for TRAS/980 versus TRAS/TRAS was 0.48 (90% CI: [0.181, 1.292]).

Conclusions: Safety of ABP 980 is similar to TRAS in patients with HER2+ early breast cancer in both the neoadjuvant and adjuvant phases and consistent with the historical safety profile of TRAS. The immunogenicity profile of ABP 980 is low and consistent with TRAS.

Citation Format: Kolberg H-C, Demetriou GS, Zhang N, Tomasevic Z, Hanes V. Safety results from a randomized, double-blind, phase 3 study of ABP 980 compared with trastuzumab in patients with breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD3-10.