The present disclosure features compounds such as those having the Formulae (IIa), (IIb), (IIc), (IId), (IIIa), and (IIIb), which can increase cystic fibrosis transmembrane conductance regulator (CFTR) activity as measured in human bronchial epithelial (hBE) cells. The present disclosure also features methods of treating a condition associated with decreased CFTR activity or a condition associated with a dysfunction of proteostasis comprising administering to a subject an effective amount of a disclosed compound, such as a compound of Formula (IIa), (IIb), (IIc), (IId), (IIIa), or (IIIb).
