An IL-13 antagonist for use in improving lung function in a subject with impaired lung function, in which the IL-13 antagonist is a human anti-IL-13 antibody or an IL-binding fragment. 13 thereof, selected from the group consisting of: (a) a human anti-IL-13 antibody or a human IL-13 binding fragment thereof, comprising a VH domain comprising HCDR1, HCDR2 and HCDR3 and a VL domain comprising LCDR1, LCDR2 and LCDR3, in which HCDR1 has the amino acid sequence of SEQ ID NO: 7, HCDR2 has the amino acid sequence of SEQ ID NO: 8, HCDR3 has the amino acid sequence of SEQ ID NO: 9, LCDR1 has the amino acid sequence of SEQ ID NO: 10, LCDR2 has the amino acid sequence of SEQ ID NO: 11 and LCDR3 has the amino acid sequence of SEQ ID NO: 12； (b) a human anti-IL-13 antibody, or a human IL-13 binding fragment thereof, comprising a VH domain having the amino acid sequence of SEQ ID NO: 15 and a VL domain having the sequence of amino acids of SEQ ID NO: 16； and (c) a human anti-IL-13 antibody or a human IL-13 binding fragment thereof according to (a) or (b), further comprising a constant domain of human IgG4； in which the improvement in lung function is an improvement in the forced expiratory volume score in a second (FEV1) of between 5% and 18% with respect to a reference FEV1 measurement taken before administration of the anti-IL antibody -13 human or a human IL-13 binding fragment thereof, and wherein the anti-IL-13 antibody or the IL-13 binding fragment thereof, is administered subcutaneously at a dose between 100 and 600 mg.Un antagonista de IL-13 para su uso en la mejora de la función pulmonar en un sujeto con función pulmonar alterada, en el que el antagonista de IL-13 es un anticuerpo anti-IL-13 humana o un fragmento de unión a IL-13 humana del mismo, seleccionado del grupo que consiste en: (a) un anticuerpo anti-IL-13 humana o un fragmento de unión a IL-13 humana del mismo, que comprende un dominio VH que comprende la HCDR1, HCDR2 y HCDR3 y un dominio VL que comprende la L
