X0306 4/A 2016-04-25 2016-04-27 0 0001609809 Seres Therapeutics, Inc. MCRB 0001643756 Aunins John G. C/O SERES THERAPEUTICS, INC. 215 FIRST STREET CAMBRIDGE MA 02142 0 1 0 0 Chief Technology Officer & EVP Common Stock 2016-04-25 4 S 0 18640 31.94 D 56060 D This line item is not new or revised, but is being reported again solely to gain access to the electronic filing system for filing this amendment. This Form 4 when it was initially filed by the Reporting Person on April 27, 2016 and four Forms 4 filed by the Reporting Person after that date incorrectly stated the date the Reporting Person adopted his 10b5-1 trading plan. This amendment is being filed to correct such date. The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on February 26, 2016. The price reported is a weighted average price. These shares were sold in multiple transactions at per share prices ranging from $31.48 to $32.34. The Reporting Person undertakes to provide upon request to the SEC staff, the Issuer, or any stockholder of the Issuer, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. /s/ Thomas J. DesRosier, Attorney-in-fact 2016-08-31