ABOUT THIS AMENDMENT TO PROSPECTUS SUPPLEMENT
The amendment to the prospectus supplement is part of a registration statement that we have filed with the Securities and Exchange Commission, or the SEC,
utilizing a shelf registration process. Under the shelf registration process, we may offer shares of our common stock having an aggregate offering price of up to $200,000,000. Under the prospectus dated August 30, 2018, as amended
and supplemented, we may offer shares of our common stock having an aggregate offering price of up to $50,000,000 from time to time at prices and on terms to be determined by market conditions at the time of offering. These sales, if any, will be
made pursuant to the terms of a sales agreement dated October 13, 2017 that we entered into with Cowen and Company, LLC, or Cowen, as our sales agent thereunder, a copy of which is incorporated by reference into this amendment.
Before you invest, you should carefully read this amendment, the prospectus supplement, the accompanying prospectus, all information incorporated by reference
herein and the additional information described under Where You Can Find More Information and Incorporation of Documents by Reference. These documents contain information you should consider when making your investment
decision. To the extent that any statement that we make in this amendment, the prospectus supplement and the accompanying prospectus is inconsistent with statements made in the accompanying prospectus or in any documents incorporated by reference,
the statements made in this amendment or the prospectus supplement will be deemed to modify or supersede those made in such documents incorporated by reference; however, if any statement in one of these documents is inconsistent with a statement in
another document having a later date and that is incorporated by reference herein, the statement in the document having the later date modifies or supersedes the earlier statement.
You should rely only on the information contained or incorporated by reference in this amendment, the prospectus supplement, the accompanying prospectus, the
documents incorporated by reference herein and any free writing prospectus we provide you. We have not, and Cowen has not, authorized anyone to provide you with different information. If anyone provides you with different or inconsistent
information, you should not rely on it. We are not, and Cowen is not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this amendment, the
prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and any free writing prospectus we provide you is accurate only as of the date on those respective documents. Our business, financial condition,
results of operations and prospects may have changed since those dates. You should read this amendment, the prospectus supplement, the accompanying prospectus, including the documents incorporated by reference herein, when making your investment
decision. You should also read and consider the information in the documents we have referred you to in the sections of the prospectus supplement and the accompanying prospectus entitled Where You Can Find More Information and
Incorporation of Documents by Reference. The distribution of this amendment, the prospectus supplement and the accompanying prospectus and the offering of the common stock in certain jurisdictions may be restricted by law. Persons
outside the United States, or the U.S., who come into possession of this amendment, the prospectus supplement and the accompanying prospectus must inform themselves about, and observe any restrictions relating to, the offering of the common stock
and the distribution of this amendment, the prospectus supplement and the accompanying prospectus outside the U.S. This amendment, the prospectus supplement and the accompanying prospectus does not constitute, and may not be used in connection with,
an offer to sell, or a solicitation of an offer to buy, any securities offered by this amendment, the prospectus supplement and the accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an
offer or solicitation.
We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any
document that is incorporated by reference in the accompanying prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and
should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be
relied on as accurately representing the current state of our affairs.
Unless the context otherwise requires, Synlogic, SYBX,
the Company, we, us, our and similar terms refer to Synlogic, Inc. and our subsidiaries.
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