Disclosed are diamino-pyridine, pyrimidine, and pyridazine compounds of formula (I), wherein the substituents are disclosed within the specification, and a pharmaceutically acceptable salt and/or prodrug thereof. Examples of disclosed compounds of formula (I) include: Bicyclo[2.2.1]hept-2-yl-[4-((3R)-3-methylamino-pyrrolidin-1-yl)-pyridin-2-yl]-amine dihydrochloride； and N-(Cyclopropylmethyl)-4-[(3R)-3-(methylamino)pyrrolidin-1-yl]pyridin-2-amine ditrifluoroacetate； and 4-[(3R)-3-(Methylamino)pyrrolidin-1-yl]-N-[(1S,2S,3S,5R)-2,6,6-trimethylbicyclo[3.1.1]hept-3-yl]pyridin-2-amine； and 4-Piperazin-1-yl-N-propylpyridin-2-amine dihydrochloride. Further disclosed is a composition comprising a compound of formula (I), and the use of a compound of formula (I) in the preparation of a medicament for treating a disease, disorder, or medical condition mediated by histamine H4 receptor activity, such as imflammatory disorders, allergic disorders, dermatological disorders, autoimmune disease, lymphatic disorders, and immunodeficiency disorders.
