Specimen stock certificate evidencing shares of common stock

ZQ|CERT#|COY|CLS|RGSTRY|ACCT#|TRANSTYPE|RUN#|TRANS# . COMMON STOCK PAR VALUE $0.001 COMMON STOCK Certificate Number ZQ00000000 Shares * * 000000 * * * * * * * * * * * * * * * * * * * * * 000000 * * * * * * * * * * * * * * * * * * * * * 000000 * * * * * * * * * * * * * * * * * * * * * 000000 * * * * * * * * * * * * * * * * * * * * * 000000 * * * * * * * * * * * * * * SIGILON THERAPEUTICS, INC. INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE ** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David SEE REVERSE FOR CERTAIN DEFINITIONS THIS CERTIFIES THAT Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander Alexander David SamMple ***R* Mr. A.lexaSnderADavidMSampPle ***L* MrE. Alexan&der DavMid SamRple **S** Mr.. AleSxandeAr DaMvid SamPple *L*** MEr. Alex&ander David Sample **** David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander DavidMSampRle ****.Mr. SAlexaAnderMDavidPSamLple *E*** Mr. &AlexandMer DavRid SaSmple.**** SMr. AAlexanMder DaPvid SLampEle **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Sample **** Mr. Sample is the owner of **000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares*** *000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares**** 000000**Shar*es****0*000Z00**SEhareRs****00O0000**ShHares**U**0000N00**SDhares*R***000E000**DShares**T**000H000**SOhares*U***000S000**AShareNs****00D0000**Shares****0 THIS CERTIFICATE IS TRANSFERABLE IN CITIES DESIGNATED BY THE TRANSFER AGENT, AVAILABLE ONLINE AT www.computershare.com 00000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****00 0000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000 000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****0000 00**Shares****0Z0000E0**ShRares***O*000000*H*ShareUs****0N00000D**SharRes****0E0000D0**ShareAs****0N00000D**SharesZ****00E0000R**SharOes****0*000*00**Shares****00000 0**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000 **Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000* *Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000** Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**Shares****000000**S FULLY-PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK OF Sigilon Therapeutics, Inc. (hereinafter called the “Company”), transferable on the books of the Company in person or by duly authorized attorney, upon surrender of this Certificate properly endorsed. This Certificate and the shares represented hereby, are issued and shall be held subject to all of the provisions of the Certificate of Incorporation, as amended, and the By-Laws, as amended, of the Company (copies of which are on file with the Company and with the Transfer Agent), to all of which each holder, by acceptance hereof, assents. This Certificate is not valid unless countersigned and registered by the Transfer Agent and Registrar. Witness the facsimile seal of the Company and the facsimile signatures of its duly authorized officers. DATED DD-MMM-YYYY COUNTERSIGNED AND REGISTERED: COMPUTERSHARE TRUST COMPANY, N.A. TRANSFERAGENT ANDREGISTRAR, FACSIMILE SIGNATURE TO COME President May 14, 2015 FACSIMILE SIGNATURE TO COME Secretary By AUTHORIZEDSIGNATURE CUSIP/IDENTIFIER Holder ID Insurance Value Number of Shares DTC Certificate Numbers ###-###-#### ###-###-#### ###-###-#### ###-###-#### ###-###-#### ###-###-#### ###-###-#### ###-###-#### ###-###-#### ###-###-#### ###-###-#### ###-###-#### Total Transaction XXXXXX XX X XXXXXXXXXX 1,000,000.00 123456 12345678 123456789012345 PO BOX 505006, Louisville, KY 40233-5006 Num/No. Denom. Total 1 2 3 4 5 6 7 1 2 3 4 5 6 1 2 3 4 5 6 MR A SAMPLE DESIGNATION (IF ANY) ADD 1 ADD 2 ADD 3 ADD 4 CUSIP XXXXXX XX X