<HTML><HEAD>
<TITLE>Form 8-K</TITLE>
</HEAD>
 <BODY BGCOLOR="WHITE">

 <P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&nbsp;</P>
<P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P> <P STYLE="margin-top:4pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>UNITED STATES </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>SECURITIES AND EXCHANGE COMMISSION </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>WASHINGTON, D.C. 20549 </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:18pt; font-family:Times New Roman" ALIGN="center"><B>FORM 8-K
</B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>CURRENT REPORT </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>PURSUANT
TO SECTION&nbsp;13 OR 15(D) </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>OF THE SECURITIES EXCHANGE ACT OF 1934 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:12pt; font-family:Times New Roman" ALIGN="center"><B>Date of Report (Date of earliest event reported): November&nbsp;4, 2013 </B></P>
<P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center> <P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:24pt; font-family:Times New Roman" ALIGN="center"><B>Tetraphase Pharmaceuticals, Inc. </B></P>
<P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>(Exact name of registrant as specified in charter) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="34%"></TD>
<TD VALIGN="bottom"></TD>
<TD WIDTH="32%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="32%"></TD></TR>


<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" ALIGN="center"><B>Delaware</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>001-35837</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>20-5276217</B></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top" ALIGN="center"><B>(State or other jurisdiction<BR>of incorporation)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>(Commission<BR>File Number)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>(IRS Employer<BR>Identification No.)</B></TD></TR>
</TABLE> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD WIDTH="50%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="48%"></TD></TR>


<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" ALIGN="center"> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>480 Arsenal Street, Suite 110,</B></P>
<P STYLE="margin-top:0pt; margin-bottom:1pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Watertown, Massachusetts</B></P></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="bottom" ALIGN="center"><B>02472</B></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:8pt">
<TD VALIGN="top" ALIGN="center"><B>(Address of principal executive offices)</B></TD>
<TD VALIGN="bottom">&nbsp;</TD>
<TD VALIGN="top" ALIGN="center"><B>(Zip Code)</B></TD></TR>
</TABLE> <P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Registrant&#146;s telephone number, including area code: (617)&nbsp;715-3600 </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>Not Applicable </B></P> <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>(Former
name or former address, if changed since last report) </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P><center>
<P STYLE="line-height:6.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1.00pt solid #000000;width:21%">&nbsp;</P></center> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Check the
appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (<I>see</I> General Instruction A.2. below): </P>
<P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><FONT STYLE="FONT-FAMILY:WINGDINGS">&#168;</FONT></TD>
<TD ALIGN="left" VALIGN="top">Written communications pursuant to Rule 425 under the Securities Act (17 CFR&nbsp;230.425) </TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><FONT STYLE="FONT-FAMILY:WINGDINGS">&#168;</FONT></TD>
<TD ALIGN="left" VALIGN="top">Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR&nbsp;240.14a-12) </TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><FONT STYLE="FONT-FAMILY:WINGDINGS">&#168;</FONT></TD>
<TD ALIGN="left" VALIGN="top">Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) </TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><FONT STYLE="FONT-FAMILY:WINGDINGS">&#168;</FONT></TD>
<TD ALIGN="left" VALIGN="top">Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) </TD></TR></TABLE> <P STYLE="font-size:10pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<P STYLE="line-height:1.0pt;margin-top:0pt;margin-bottom:0pt;border-bottom:1px solid #000000">&nbsp;</P> <P STYLE="line-height:3.0pt;margin-top:0pt;margin-bottom:2pt;border-bottom:1px solid #000000">&nbsp;</P>

<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman"><B>Item&nbsp;2.02. Results of Operations and Financial Condition. </B></P>
<P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">On November&nbsp;4, 2013, Tetraphase Pharmaceuticals, Inc. (the &#147;Company&#148;) filed with the Securities and Exchange Commission
Amendment #1 to its Registration Statement on Form S-1 (File No.&nbsp;333-191890) (the &#147;Registration Statement&#148;), which contained preliminary estimates of certain of the Company&#146;s financial results for the fiscal quarter ended
September&nbsp;30, 2013 under the heading &#147;Prospectus Summary &#150; Recent Operating Results&#148;. The full text of the section of the Registration Statement containing the preliminary estimates is furnished as Exhibit 99.1 to this Current
Report on Form 8-K. </P> <P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The information in this Current Report on Form 8-K and Exhibit 99.1 attached hereto shall not be deemed
&#147;filed&#148; for purposes of Section&nbsp;18 of the Securities Exchange Act of 1934 (the &#147;Exchange Act&#148;) or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the
Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference in such a filing. </P> <P STYLE="font-size:18pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="10%" VALIGN="top" ALIGN="left"><B>Item&nbsp;9.01.</B></TD>
<TD ALIGN="left" VALIGN="top"><B>Financial Statements and Exhibits. </B></TD></TR></TABLE> <P STYLE="font-size:6pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%">&nbsp;</TD>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><B><I>(d)</I></B></TD>
<TD ALIGN="left" VALIGN="top"><B><I></I></B><B>Exhibits</B> </TD></TR></TABLE> <P STYLE="margin-top:6pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">The following exhibit relating to Item&nbsp;2.02 shall be deemed
to be furnished, and not filed: </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="92%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt" ALIGN="center">


<TR>
<TD></TD>
<TD VALIGN="bottom" WIDTH="3%"></TD>
<TD WIDTH="94%"></TD></TR>


<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>99.1</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;&nbsp;</FONT></TD>
<TD VALIGN="top">Preliminary estimates of certain of the financial results of the registrant for the fiscal quarter ended September&nbsp;30, 2013</TD></TR>
</TABLE>

<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>SIGNATURE </B></P>
<P STYLE="margin-top:12pt; margin-bottom:0pt; text-indent:4%; font-size:10pt; font-family:Times New Roman">Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by
the undersigned hereunto duly authorized. </P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:10pt">


<TR>
<TD WIDTH="46%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="4%"></TD>
<TD VALIGN="bottom"></TD>
<TD WIDTH="2%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="45%"></TD></TR>


<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">By:</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top"> <P STYLE="margin-top:0pt; margin-bottom:1pt; border-bottom:1px solid #000000; font-size:10pt; font-family:Times New Roman">/s/ David C. Lubner</P></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top">Date: November 8, 2013</TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">David C. Lubner</TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT STYLE="font-size:8pt">&nbsp;</FONT></TD>
<TD VALIGN="top">Senior Vice President and Chief Financial Officer</TD></TR>
</TABLE>

<p Style='page-break-before:always'>
<HR  SIZE="3" style="COLOR:#999999" WIDTH="100%" ALIGN="CENTER">

 <P STYLE="margin-top:0pt; margin-bottom:0pt; font-size:10pt; font-family:Times New Roman" ALIGN="center"><B>EXHIBIT INDEX </B></P> <P STYLE="font-size:12pt;margin-top:0pt;margin-bottom:0pt">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" STYLE="BORDER-COLLAPSE:COLLAPSE; font-family:Times New Roman; font-size:8pt" ALIGN="center">


<TR>
<TD></TD>
<TD VALIGN="bottom" WIDTH="5%"></TD>
<TD WIDTH="92%"></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:8pt">
<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE="border-bottom:1.00pt solid #000000; width:25.30pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Exhibit<BR>No.</B></P></TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="bottom" NOWRAP ALIGN="center"> <P STYLE="border-bottom:1.00pt solid #000000; width:39.50pt; font-size:8pt; font-family:Times New Roman" ALIGN="center"><B>Description</B></P></TD></TR>


<TR>
<TD HEIGHT="8"></TD>
<TD HEIGHT="8" COLSPAN="2"></TD></TR>
<TR STYLE="font-family:Times New Roman; font-size:10pt">
<TD VALIGN="top" NOWRAP>99.1</TD>
<TD VALIGN="bottom">&nbsp;&nbsp;</TD>
<TD VALIGN="top">Preliminary estimates of certain of the financial results of the registrant for the fiscal quarter ended September 30, 2013</TD></TR>
</TABLE>
</BODY></HTML>
[{"type": "8-K", "sequence": "1", "filename": "d624567d8k.htm", "description": "FORM 8-K", "secsgml_size_bytes": 14692}]
{"company-data": {"conformed-name": "TETRAPHASE PHARMACEUTICALS INC", "cik": "0001373707", "assigned-sic": "2834", "irs-number": "000000000", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-35837", "film-number": "131205162"}, "business-address": {"street1": "480 ARSENAL STREET", "street2": "SUITE 110", "city": "WATERTOWN", "state": "MA", "zip": "02472", "phone": "617.715.3600"}, "mail-address": {"street1": "480 ARSENAL STREET", "street2": "SUITE 110", "city": "WATERTOWN", "state": "MA", "zip": "02472"}}
Form 8-K
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM 8-K
CURRENT REPORT
PURSUANT
TO SECTION 13 OR 15(D)
OF THE SECURITIES EXCHANGE ACT OF 1934
Date of Report (Date of earliest event reported): November 4, 2013
Tetraphase Pharmaceuticals, Inc.
(Exact name of registrant as specified in charter)
Delaware
001-35837
20-5276217
(State or other jurisdiction
of incorporation)
(Commission
File Number)
(IRS Employer
Identification No.)
480 Arsenal Street, Suite 110,
Watertown, Massachusetts
02472
(Address of principal executive offices)
(Zip Code)
Registrant's telephone number, including area code: (617) 715-3600
Not Applicable
(Former
name or former address, if changed since last report)
Check the
appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (
see
General Instruction A.2. below):
¨
Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
¨
Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
¨
Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
¨
Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))
Item 2.02. Results of Operations and Financial Condition.
On November 4, 2013, Tetraphase Pharmaceuticals, Inc. (the "Company") filed with the Securities and Exchange Commission
Amendment #1 to its Registration Statement on Form S-1 (File No. 333-191890) (the "Registration Statement"), which contained preliminary estimates of certain of the Company's financial results for the fiscal quarter ended
September 30, 2013 under the heading "Prospectus Summary – Recent Operating Results". The full text of the section of the Registration Statement containing the preliminary estimates is furnished as Exhibit 99.1 to this Current
Report on Form 8-K.
The information in this Current Report on Form 8-K and Exhibit 99.1 attached hereto shall not be deemed
"filed" for purposes of Section 18 of the Securities Exchange Act of 1934 (the "Exchange Act") or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the
Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference in such a filing.
Item 9.01.
Financial Statements and Exhibits.
(d)
Exhibits
The following exhibit relating to Item 2.02 shall be deemed
to be furnished, and not filed:
99.1
Preliminary estimates of certain of the financial results of the registrant for the fiscal quarter ended September 30, 2013
SIGNATURE
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by
the undersigned hereunto duly authorized.
By:
/s/ David C. Lubner
Date: November 8, 2013
David C. Lubner
Senior Vice President and Chief Financial Officer
EXHIBIT INDEX
Exhibit
No.
Description
99.1
Preliminary estimates of certain of the financial results of the registrant for the fiscal quarter ended September 30, 2013