The invention provides compounds having STimulator of INterferon Genes (STING) agonistic bioactivity that can be used in the treatment of tumors inpatients afflicted therewith. The compounds are of formula (IA), formula (I), and formula (II): wherein the various substituents are as defined herein. Ring A is a 5- or 6-membered heteroaryl comprising 1, 2, or 3 N atoms, unsubstituted or substituted with 1, 2, or 3 groups as defined herein. Compounds for practice of a method of the invention can be delivered via oral delivery for systemic exposure, as well as delivered intratumorally. Antitumor therapy using a compound of formula (I) can further comprise administration of an effective dose of an immunecheckpoint targeting drug.