Abstract PS9-59: Pooled efficacy analysis from two phase 3 studies in patients receiving eflapegrastim, a novel, long-acting granulocyte-colony stimulating factor, following TC for early-stage breast cancer

Background: Eflapegrastim (Rolontis®, Efla) represents the first novel, long-acting granulocyte-colony stimulating factor (G-CSF) to be introduced in more than 15 years. Efla consists of a recombinant human G-CSF analog conjugated to a human IgG4 Fc fragment via a polyethylene glycol linker. Preclinical, clinical, and pharmacodynamic/pharmacokinetic data have shown increased potency for Efla versus pegfilgrastim (Peg). Both independent, randomized Phase 3 studies comparing Efla and Peg for prophylaxis of chemotherapy-induced neutropenia in patients with early-stage breast cancer (ESBC) met the primary endpoint of non-inferiority in duration of severe neutropenia (SN; ANC 75kg. The safety profiles, including AEs and discontinuations, for Efla and Peg were comparable, and >99% of all patients received full dose of TC on schedule. The majority (67%) of patients with SN experienced a 1 day duration, occurring between Days 7 and 8 after TC. Mean duration of SN for Efla was statistically lower than for Peg (0.24 vs. 0.36 days; p=0.029). The above statistical significance was maintained for Efla after adjusting for demographic and baseline characteristics, namely age, weight, enrolling geographical region, and treatment setting in a multivariate model. Similarly, the incidence of SN for Efla was statistically lower than Peg in Cycle 1 (17.5% vs 24%; relative risk reduction [RRR]=27%; p=0.043). Univariate analysis of the incidence of SN showed a significant risk reduction in favor of Efla (8.6% vs 14.1%; p=0.034) for patients weighing >75kg (p=0.034). Multivariate analysis of SN showed significant odds ratio of SN for age ≥65 years and baseline ANC >6 × 109/L in favor of Efla (OR=0.42 and 0.39, respectively). The incidence of SN in Cycles 2-4 was comparable between treatment groups. Also, the incidence of febrile neutropenia and neutropenic complications was similar with 75kg. Eflapegrastim is a novel, long-acting and potent recombinant human G-CSF which may provide an attractive option in supporting patients at risk for SN-related complications. Citation Format: Lee S Schwartzberg, Gajanan Bhat, Alvaro Restrepo, Osama Hlalah, Inderjit Mehmi, Yong Wha Moon, Seungjae Baek, Shanta Chawla, Francois Lebel, Patrick Wayne Cobb. Pooled efficacy analysis from two phase 3 studies in patients receiving eflapegrastim, a novel, long-acting granulocyte-colony stimulating factor, following TC for early-stage 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 PS9-59.