Document and Entity Information - shares
3 Months Ended
Mar. 31, 2019
Jun. 14, 2019
Document and Entity Information [Abstract]    
Document Type 10-Q  
Document Period End Date Mar. 31, 2019  
Entity Registrant Name Applied Therapeutics Inc.  
Entity Central Index Key 0001697532  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   17,052,202