Dear editorHaving read the original Hoggatt et al article1 and the corrigendum published online on August 27, 2015,2 we do not consider the description of lipegfilgrastim to be entirely accurate, and we would therefore like to clarify what lipegfilgrastim actually is.The description of lipegfilgrastim used in the original article was a “long-acting biosimilar filgrastim”.1 This description was subsequently amended in the corrigendum to “lipegfilgrastim has an active substance that is similar to filgrastim, with similar pharmacokinetics, receptor binding affinity, safety and efficacy as pegfilgrastim”.2It is true that lipegfilgrastim is not a long-acting biosimilar of filgrastim. It is not approved under the biosimilar classification by the European Medicines Agency, and has its own distinct Anatomical Therapeutic Chemical (ATC) code (ATC code L03AA14, lipegfilgrastim; ATC code L03AA02, filgrastim; ATC code L03AA13, pegfilgrastim).3 Further, we believe lipegfilgrastim would be more accurately described as “glycopegylated, long-acting form of recombinant human filgrastim”.Furthermore, the original article does not give the correct indications for either filgrastim or lipegfilgrastim (eg, pages 2,648 and 2,649).1 In August 2013, the European Medicines Agency (EMA) approved lipegfilgrastim to be used for reducing the duration of neutropenia and the incidence of febrile neutropenia in adult patients treated with cytotoxic chemotherapy for malignancy (with the exception of chronic myeloid leukemia and myelodysplastic syndromes).4 Lipegfilgrastim is currently marketed throughout Europe with this indication.