A comparison of eflapegrastim to pegfilgrastim in the management of chemotherapy‐induced neutropenia in patients with early‐stage breast cancer undergoing cytotoxic chemotherapy (RECOVER): A Phase 3 study

) is a novel, long-acting hematopoietic growth factor consisting of a recombinant human granulocyte-colony stimulating factor (rhG-CSF) analog conjugated to a human IgG4 Fc fragment via a short polyethylene glycol linker. We report results from a second pivotal, randomized, open-label, Phase 3 study comparing the efficacy and safety of eflapegrastim to pegfilgrastim for reducing the risk of chemotherapy-induced neutropenia. Patients with Stage I to IIIA early-stage breast cancer (ESBC) were randomized 1:1 to fixed-dose eflapegrastim 13.2 mg (3.6 mg G-CSF) or pegfilgrastim (6 mg G-CSF) administered one day after standard docetaxel/cyclophosphamide (TC) therapy for four cycles. The primary objective was to demonstrate noninferiority (NI) of eflapegrastim compared to pegfilgrastim in mean duration of severe neutropenia (DSN; Grade 4) in Cycle 1. A total of 237 eligible patients were randomized 1:1 to receive either eflapegrastim (n = 118) or pegfilgrastim (n = 119). Cycle 1 severe neutropenia was observed in 20.3% (n = 24) of patients receiving eflapegrastim and 23.5% (n = 28) receiving pegfilgrastim. The DSN of eflapegrastim in Cycle 1 was noninferior to pegfilgrastim with a mean difference of -0.074 days (NI P-value < .0001). Noninferiority was maintained throughout the four treatment cycles (P < .0001 in all cycles). Other efficacy endpoints results were comparable between treatment arms, and adverse events, irrespective of causality and grade, were comparable between treatment arms. The results demonstrate noninferior efficacy and comparable safety for eflapegrastim, at a lower G-CSF dose, vs pegfilgrastim. The potential for the increased potency of eflapegrastim to deliver improved clinical benefit warrants further clinical study.