The invention relates to 5-HT receptor antagonists. Novel piperidinylamino-thieno [2,3-d]pyrimidine compounds represented by Formula I, and synthesis and uses thereof for treating diseases mediated directly or indirectly by 5-HT receptors, are disclosed. Such conditions include central nervous system disorders such as pulmonary arterial hypertension, migraine, hypertension, disorders of the gastrointestinal tract, restenosis, asthma, obstructive airway disease, prostatic hyperplasia and priapism, anxiety, depression, schizophrenia, neural injury and stroke. Methods of preparation and novel intermediates and pharmaceutical salts thereof are also provided.