Disclosed herein are safe doses of dual-V-region antibody-like binding proteins or fragments thereof, as well as methods for assessing binding of dual-V-region antibody-like proteins or fragments thereof to their targets, and methods of treating idiopathic pulmonary fibrosis (IPF) by administering safe doses of dual-V-region antibody-like binding proteins or fragments thereof. In some embodiments, the dual-V-region antibody-like binding proteins or fragments thereof bind both IL-4 and IL-13.文中係揭示雙-V-區類抗體結合蛋白(dual-V-region antibody-like binding protein)或其片段之安全劑量,以及評估雙-V-區類抗體結合蛋白或其片段與其目標結合之方法,與藉由投予安全劑量之雙-V-區類抗體結合蛋白或其片段治療原發性肺纖維化(IPF)之方法。在某些具體例中,此雙-V-區類抗體結合蛋白或其片段係與IL-4和IL-13二者結合。