The disclosure relates to the use of
phosphodiesterase 1 (PDE1) inhibitors in combination with a Compound of Formula VIII or a Compound of Formula IX, as described herein, or in combination with an antiemetic agent, such as an
antipsychotic agent, e.g.,
olanzapine, for preventing or treating
nausea and / or
vomiting, e.g., CINV (
chemotherapy-induced
nausea and
vomiting). In some embodiments, the Compound of Formula VIII or the Compound of Formula IX is used as mono-therapy (i.e., without a PDE1 inhibitor).