Therapeutically active heteroaryl carboxylic acid derivatives of Formula (I) wherein R.sup.1, R.sup.2, W, X, Y and Z are as defined in the specification, processes for the preparation of said derivatives, pharmaceutical formulations containing the active compounds and the use of the compounds in therapy, particularly in the treatment of diseases in which under-activation of the HM74A receptor contributes to the disease or in which activation of the receptor will be beneficial, are disclosed.