Abstract PS10-24: Infusion related reactions in the phase 3 SOPHIA trial of margetuximab + chemotherapy vs trastuzumab + chemotherapy in patients with pretreated HER2+ metastatic breast cancer

Abstract

Abstract Background: Margetuximab (M) is an investigational Fc-engineered, anti-HER2 monoclonal antibody with the same epitope specificity as trastuzumab (T). Relative to T, Fc engineering of M increases binding affinity for the activating Fc receptor (FcR) CD16A and decreases affinity for the inhibitory FcR CD32B. The SOPHIA trial (NCT02492711) randomized pretreated HER2+ MBC patients to either M or T, each with chemotherapy (C). M+C improved progression-free survival (PFS) benefit over T+C. Infusion related reactions (IRR) have been observed after infusion of therapeutic proteins, typically during the first infusion, with a first-dose incidence of up to 40% for T (Herceptin Prescribing Information®). A retrospective analysis of 197 patients showed 16% IRRs on T, mostly after the first infusion; this rate was lower with (10%) compared to without (19%) premedication (Thompson, 2014). Here, we report IRR safety and tolerability data in the SOPHIA trial patients following HER2-targeted antibody therapy. Methods: The open-label Phase 3 SOPHIA trial enrolled patients with HER2+ MBC after at least 2 prior anti-HER2 therapies, including pertuzumab; 91% in both groups also received ado-trastuzumab emtansine. Randomization of 536 patients was 1:1 to M (15 mg/kg IV q3w) or T (6 [8 loading dose] mg/kg IV q3w), each with Investigator selected C (standard dose capecitabine, eribulin, gemcitabine, or vinorelbine). M was given as 120-minute infusions. T was given as a 90-minute infusion in Cycle 1, then a 30-minute infusion from Cycle 2 onward. Recommended elective premedication included acetaminophen, ibuprofen, diphenhydramine, ranitidine, dexamethasone, or equivalents. IRR safety analyses were conducted on 530 patients (264 M+C and 266 T+C) that received any study therapy. Results: A higher proportion of patients experienced IRRs on the M arm (35 [13.3%]) than on the T arm (9 [3.4%]). Most IRRs in both groups were severity Grade 1 or 2, occurred on Cycle 1 Day 1, and resolved within 24 hours. In patients receiving M, Grade 3 IRR occurred in 4 patients (1.5%), including 3 after vinorelbine and 1 after eribulin. Adverse events associated with Grade 3 IRRs included chills, fever, nausea, diarrhea, dyspnea, and/or hypertension. Two patients receiving M (0.8%) discontinued due to IRR, versus none on T. Of patients with IRRs, the most common symptoms in both treatment groups were chills (M: 17 [48.6%]; T: 5 [55.6%]) and fever (M: 13 [37.1%]; T: 2 [22.2%]). There was no observed hypotension in either group. In both groups, more than half of IRR events were addressed by dose interruption only. All IRRs all were medically manageable. IRR rates were higher in patients without premedication for both groups. Of 264 subjects receiving M, 218 (82.6%) received premedication and 46 (17.4%) did not; IRRs were observed in 28 (12.8%) of those receiving premedication and 7 (15.2%) of those not premedicated. All 4 patients on M with Grade 3 IRRs received premedication, 3 with steroids. Of 266 subjects receiving T, 173 (65%) received premedication and 93 (35%) did not; IRRs were observed in 5 (2.9%) of those receiving premedication and 4 (4.3%) of those not premedicated. IRR risk was unaffected by chemotherapy subgroup or CD16A genotype. Conclusions: In the SOPHIA trial, IRR events occurred in a greater proportion of patients on M than on T. Most were mild to moderate in severity, limited to Cycle 1, and resolved on the same day. Symptom patterns were similar between groups, and premedication did not eliminate the hazard of IRRs in either group. Severe IRRs and discontinuations due to IRRs were rare. IRRs on first infusion of M appear to resemble those observed following first infusion of T. Citation Format: Javier Cortes, Fatima Cardoso, Giuseppe Curigliano, William J Gradishar, Seock-Ah Im, Hope S Rugo, Shakeela W Bahadur, Alfredo Falcone, Serafin Morales Murillo, David A Riseberg, Antonino Musolino, Trevor M Feinstein, Miguel H Abreu, Young-Hyuck Im, Yelena Novik, Timothy Pluard, Lupe G Salazar, Rossana Berardi, Viorela Pop, Shengyan Hong, Kenneth Jacobs, Edwin Rock, Mark D Pegram. Infusion related reactions in the phase 3 SOPHIA trial of margetuximab + chemotherapy vs trastuzumab + chemotherapy in patients with pretreated HER2+ metastatic breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS10-24.