The present invention relates to non-hygroscopic omarigliptin acid addition salts, preferably to non-hygroscopic crystalline omarigliptin acid addition salts such as omarigliptin acid addition salts with an acid selected from the group of hydrochloric acid, fumaric acid, R-mandelic acid, S-mandelic acid and RS-mandelic acid and to methods for their preparation. In addition, the invention is directed to pharmaceutical compositions comprising an effective amount of an omarigliptin acid addition salt of the present invention and at least one pharmaceutically acceptable excipient. The pharmaceutical compositions of the present invention are suitable for the treatment of type 2 diabetes, obesity and high blood pressure, in particular for the treatment of type 2 diabetes.
