Provided herein are 2H- and 13C-enriched compounds of formula (I) or (II); wherein R is as defined herein, and wherein at least one hydrogen atom, in certain embodiments, three or more hydrogen atoms, are deuterium atoms or at least one carbon atom is a carbon-13 atom. Also provided are pharmaceutical compositions and methods using the 2H- and 13C-enriched compounds, useful for treating CRTH2-related diseases or disorders such as, for example, asthma, allergic rhinitis, atopic dermatitis, allergic conjuvatitis, Churg-Strauss syndrome, sinusitis, basophilic leukemia, chronic urticaria or basophilic leukocytosis.