Item 8.01 Other Events.

Tetraphase Pharmaceuticals, Inc. (the “Company”) is providing certain preliminary information related to its revenue, cash and cash equivalents and cash runway as an update to the information provided in the Company’s previous periodic filings. The Company has not yet completed its financial statements for the period ended September 30, 2019, but the Company currently estimates (i) that net sales of Xerava^™ were between $1.0 million and $1.1 million for the three months ended September 30, 2019 and (ii) that its cash and cash equivalents as of September 30, 2019 were approximately $24.5 million. The Company believes that its cash and cash equivalents as of September 30, 2019 will be sufficient to fund its operations into the second quarter of 2020. The Company’s estimates of net sales of Xerava, its cash and cash equivalents as of September 30, 2019 and the sufficiency of its cash and cash equivalents as of September 30, 2019 to fund its operations into the second quarter of 2020 have been prepared by management in good faith based upon internal reporting and expectations. However, because the financial statements for the period ended September 30, 2019 have not yet been finalized, these estimates are preliminary, are subject to change and may be revised as a result of management’s further review of the Company’s financial results for the period ended September 30, 2019. As a result, there can be no assurance that the final results for this period will not differ materially from these estimates.

In connection with the announcement of the foregoing financial information, the Company also announced that, as of September 30, 2019, the reorder rate for Xerava continues to be greater than 50%, Xerava is available at over 900 accounts and approximately 300 formulary reviews are pending or planned to take place by the end of the fourth quarter of 2019.

Forward-Looking Statements

This Current Report on Form 8-K contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Such forward-looking statements include, but are not limited to, those regarding: the Company’s estimates of net sales of Xerava for the three months ended September 30, 2019; the Company’s estimated cash and cash equivalents as of September 30, 2019; the Company’s belief that its cash and cash equivalents as of September 30, 2019 will be sufficient to fund its operations into the second quarter of 2020; and the Company’s plans, strategies and prospects for its business. The words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “would” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Such statements are subject to numerous important factors, risks and uncertainties that may cause actual events or results to differ materially from current expectations and beliefs, including but not limited to: whether the Company’s commercial product will continue to generate increased sales revenues; the availability of significant cash required to fund operations; competitive factors; general economic and market conditions and the risk factors set forth under the caption “Risk Factors” in the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2019 and in any other subsequent filings made by the Company with the Securities and Exchange Commission. Any forward-looking statements contained in this Current Report on Form 8-K speak only as of the date hereof, and the Company specifically disclaims any obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise.