The invention relates to compounds of formula (A) and formula (I): or a salt thereof, wherein R1, R2, R10, R11, R12, R13, R14, R15, R16, q and p are as described herein. Compounds of formula (A), formula (I), and pharmaceutical compositions thereof are a?ß6 integrin inhibitors that are useful for treating fibrosis such as idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP).