Provided is a tryptophan-2,3-dioxygenase (TDO) and/or indoleamine-2,3-dioxygenase (IDO) inhibitor compound for use in medicine, which compound comprises the following formula (I): wherein X1 is selected from C and N； X3 and X5 may be the same or different and each is independently selected from C, N, O and S； Y is selected from N and O； Z is selected from C, N and O； each bond represented by a dotted line may independently be a double bond or a single bond, provided that valencies at each ring atom are maintained and provided that the ring Q contains at least one double bond and provided that the atom N has a double bond； R3 and R5 may be present or absent and may be the same or different and each is independently selected from H and a substituted or unsubstituted organic group, provided that the number of R3 groups present is such that the valency of X3 is maintained, and the number of R5 groups present is such that the valency of X5 is maintained； each R11 and R12 may be present or absent and may be the same or different and each is independently selected from H and a substituted or unsubstituted organic group, provided that the number of R11 and R12 groups present is such that the valency of Z is maintained； R21 is selected from H and a substituted or unsubstituted organic group； R22 may be present or absent and is selected from H and a substituted or unsubstituted organic group； and Cy is a cyclic organic group.
