v3.26.3
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2026
Nov. 02, 2026
Cover [Abstract]    
Entity Registrant Name Korsana Biosciences, Inc.  
Document Type 10-Q  
Document Period End Date Sep. 30, 2026  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   45,541,358
Entity Central Index Key 0001755237  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Document Quarterly Report true  
Document Transition Report false  
Entity Tax Identification Number 83-1895370  
Entity File Number 001-38787  
Entity Incorporation, State or Country Code MA  
Entity Address, Address Line One 203 Crescent Street  
Entity Address, Address Line Two Bldgs. #3/3A/4  
Entity Address, Address Line Three Suite 503  
Entity Address, City or Town Waltham  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02453  
City Area Code 781  
Local Phone Number 516-2325  
Title of 12(b) Security Common Stock, no par value per share  
Trading Symbol KRSA  
Security Exchange Name NASDAQ