The present invention relates to a substituted purine derivative of formula (1):wherein R1is alkoxy, etc., R2is alkyl, etc., Ring Q1is aryl, etc., W1is alkylene, etc., Ring Q2is aromatic carbon ring group, etc., n is 1 to 4, R3is hydrogen atom, etc., X1is single bond, etc., W2is alkylene, etc., R4is hydrogen atom, etc., or a pharmaceutically acceptable salt thereof, which has a potent action inhibiting TLR7 and is useful to treat autoimmune disease.本發明係關於一種顯示出較強之TLR7抑制作用,而對自體免疫疾病之治療等有用之式(1)所表示之經取代嘌呤衍生物或其製藥學上所容許之鹽。 [式中,R1表示烷氧基等,R2表示烷基等,環Q1表示芳基等,W1表示伸烷基等,環Q2表示芳香族碳環基等,n表示1~4,R3表示氫原子等,X1表示單鍵等,W2表示伸烷基等,R4表示氫原子等]。