Four novel transporter genes were successfully cloned by screening novel transporter genes based on the human OATP transporter gene sequence. These transporters are useful in the development of drugs by taking advantage of the activity of transporting biological substances and various drugs. It was also found that these transporter genes have single nucleotide polymorphisms (SNP). Gene diagnosis based on the polymorphisms (such as SNP) in these transporter genes enables one to judge, for example, the efficacy of a drug therapy.