<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>
mstx-8k_20151112.htm
</title>
</head>
<!-- NG Converter v4.0.2.6 -->
<body>
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-size:1pt;">&nbsp;</p>
<p style="text-align:center;line-height:1pt;border-top:Solid 0.75pt #000000;padding-top:0pt;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-size:4pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="text-align:center;margin-top:1pt;line-height:1pt;border-top:Solid 1pt;padding-top:1pt;margin-bottom:0pt;text-indent:0%;font-size:4pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="text-align:center;margin-top:6pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-size:18pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">UNITED STATES</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-weight:bold;font-size:18pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">SECURITIES AND EXCHANGE COMMISSION</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-weight:bold;font-size:12pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">WASHINGTON, D.C. 20549 </p>
<p style="text-align:center;margin-top:9pt;line-height:4pt;border-bottom:Solid 1pt;padding-bottom:1pt;margin-bottom:0pt;margin-left:40%;margin-right:40%;text-indent:0%;font-size:6pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="text-align:center;margin-top:9pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-size:18pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">FORM 8-K </p>
<p style="text-align:center;margin-top:9pt;line-height:4pt;border-bottom:Solid 1pt;padding-bottom:1pt;margin-bottom:0pt;margin-left:40%;margin-right:40%;text-indent:0%;font-size:6pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="text-align:center;margin-top:9pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-size:14pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">CURRENT REPORT </p>
<p style="text-align:center;margin-top:9pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-size:12pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 </p>
<p style="text-align:center;margin-top:9pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">Date of Report (Date of earliest event reported): November 12, 2015</p>
<p style="text-align:center;margin-top:9pt;line-height:4pt;border-bottom:Solid 1pt;padding-bottom:1pt;margin-bottom:0pt;margin-left:40%;margin-right:40%;text-indent:0%;font-size:6pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="text-align:center;margin-top:9pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-size:24pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Mast Therapeutics, Inc.</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">(Exact name of Registrant as Specified in Its Charter) </p>
<p style="text-align:center;margin-top:9pt;line-height:4pt;border-bottom:Solid 1pt;padding-bottom:1pt;margin-bottom:0pt;margin-left:40%;margin-right:40%;text-indent:0%;font-size:6pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-size:9pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<div>
<table border="0" cellspacing="0" cellpadding="0" align="center" style="border-collapse:collapse; width:100%;">
<tr>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">Delaware</p></td>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">001-32157</p></td>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">84-1318182</p></td>
</tr>
<tr>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">(State or Other Jurisdiction</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">of Incorporation)</p></td>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">(Commission File Number)</p></td>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">(IRS Employer</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Identification No.)</p></td>
</tr>
<tr style="height:12pt;">
<td valign="bottom"  style="width:33%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-family:Times New Roman;font-size:10pt;">&nbsp;</p></td>
<td valign="bottom"  style="width:33%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-family:Times New Roman;font-size:10pt;">&nbsp;</p></td>
<td valign="bottom"  style="width:33%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-family:Times New Roman;font-size:10pt;">&nbsp;</p></td>
</tr>
<tr>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">3611 Valley Centre Drive, Suite 500,</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">San Diego, CA</p></td>
<td valign="bottom"  style="padding-left:7.2pt;padding-Right:0pt;padding-Top:0pt;padding-Bottom:0pt;width:33%;">
<p style="line-height:2pt;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-size:4pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p></td>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">92130</p></td>
</tr>
<tr>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">(Address of Principal Executive Offices)</p></td>
<td valign="bottom"  style="padding-left:7.2pt;padding-Right:0pt;padding-Top:0pt;padding-Bottom:0pt;width:33%;">
<p style="line-height:2pt;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-size:4pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p></td>
<td valign="bottom"  style="width:33%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">(Zip Code)</p></td>
</tr>
</table></div>
<p style="text-align:center;margin-top:9pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">Registrant&#8217;s Telephone Number, Including Area Code: (858) 552-0866 </p>
<p style="text-align:center;margin-top:9pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">Not Applicable</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-weight:bold;font-size:7.5pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">(Former Name or Former Address, if Changed Since Last Report) </p>
<p style="text-align:center;margin-top:9pt;line-height:4pt;border-bottom:Solid 1pt;padding-bottom:1pt;margin-bottom:0pt;margin-left:40%;margin-right:40%;text-indent:0%;font-size:6pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="margin-top:9pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">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 Instructions A.2. below): </p>
<div align="left">
<table border="0" cellspacing="0" cellpadding="0"  style="border-collapse:collapse; width:100%;">
<tr>
<td valign="top" style="width:4.54%;white-space:nowrap">
<p style="margin-top:9pt;margin-bottom:0pt;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;font-family:'Wingdings';"><font style="font-size:10pt;font-family:'Wingdings'">&#168;</font></p></td>
<td valign="top">
<p style="margin-top:9pt;margin-bottom:0pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;font-size:10pt;"><font style="font-family:Times New Roman;">Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) </font></p></td></tr></table></div>
<div align="left">
<table border="0" cellspacing="0" cellpadding="0"  style="border-collapse:collapse; width:100%;">
<tr>
<td valign="top" style="width:4.54%;white-space:nowrap">
<p style="margin-top:9pt;margin-bottom:0pt;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;font-family:'Wingdings';"><font style="font-size:10pt;font-family:'Wingdings'">&#168;</font></p></td>
<td valign="top">
<p style="margin-top:9pt;margin-bottom:0pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;font-size:10pt;"><font style="font-family:Times New Roman;">Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) </font></p></td></tr></table></div>
<div align="left">
<table border="0" cellspacing="0" cellpadding="0"  style="border-collapse:collapse; width:100%;">
<tr>
<td valign="top" style="width:4.54%;white-space:nowrap">
<p style="margin-top:9pt;margin-bottom:0pt;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;font-family:'Wingdings';"><font style="font-size:10pt;font-family:'Wingdings'">&#168;</font></p></td>
<td valign="top">
<p style="margin-top:9pt;margin-bottom:0pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;font-size:10pt;"><font style="font-family:Times New Roman;">Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) </font></p></td></tr></table></div>
<div align="left">
<table border="0" cellspacing="0" cellpadding="0"  style="border-collapse:collapse; width:100%;">
<tr>
<td valign="top" style="width:4.54%;white-space:nowrap">
<p style="margin-top:9pt;margin-bottom:0pt;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;font-family:'Wingdings';"><font style="font-size:10pt;font-family:'Wingdings'">&#168;</font></p></td>
<td valign="top">
<p style="margin-top:9pt;margin-bottom:0pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;font-size:10pt;"><font style="font-family:Times New Roman;">Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) </font></p></td></tr></table></div>
<p style="text-align:center;margin-top:4pt;line-height:1pt;border-top:Solid 0.75pt #000000;padding-top:0pt;margin-bottom:0pt;text-indent:0%;font-size:4pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="text-align:center;margin-top:1pt;line-height:1pt;border-top:Solid 1pt;padding-top:1pt;margin-bottom:0pt;text-indent:0%;font-size:4pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&#160;</p>
<p style="margin-top:6pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="text-align:center;margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>

<hr style="page-break-after:always;width:100%;">
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="margin-top:18pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;"><a name="_AEIOULastRenderedPageBreakAEIOU2"></a><font style="font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">Item 2.02 Results of Operations and Financial Condition.</font></p>
<p style="margin-top:6pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">On November 12, 2015, Mast Therapeutics, Inc. issued a press release announcing its financial results for the three and nine months ended September&#160;30, 2015. A copy of the press release is furnished as Exhibit 99.1 hereto.</p>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">Item 9.01 Financial Statements and Exhibits.</p>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">(d) Exhibits. </p>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">The list of exhibits called for by this Item is incorporated by reference to the Exhibit Index immediately following the signature page of this report.</p>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">The information set forth under Item 2.02 and in Exhibit 99.1 is not being filed for purposes of Section 18 of the Securities Exchange Act of 1934 and is not to be incorporated by reference into any filing of the registrant, whether made before or after the date hereof, regardless of any general incorporation language in any such filing.</p>
<p style="text-align:center;margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">2</p>

<hr style="page-break-after:always;width:100%;">
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;"><a name="_AEIOULastRenderedPageBreakAEIOU3"></a><font style="font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">SIG</font><font style="font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">NATURES</font></p>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">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="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-size:12pt;">&nbsp;</p>
<div>
<table border="0" cellspacing="0" cellpadding="0" align="center" style="border-collapse:collapse; width:100%;">
<tr>
<td valign="top"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:45%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:5%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td colspan="2" valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:49%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Mast Therapeutics, Inc.</p></td>
</tr>
<tr>
<td valign="middle"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:45%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:5%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:3%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:45%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:45%; border-bottom:solid 0.75pt transparent;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Date:&nbsp;&nbsp;November 12, 2015</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:5%; border-bottom:solid 0.75pt transparent;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="top"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:3%; border-bottom:solid 0.75pt transparent;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">By:</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:45%; border-bottom:solid 0.75pt #000000;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:16.9pt;;text-indent:0pt;;font-style:italic;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;text-transform:none;font-variant: normal;">/s/&#160;Brandi L. Roberts</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:45%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:5%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="middle"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:3%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:45%; border-top:solid 0.75pt #000000;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:16.9pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Brandi L. Roberts</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:45%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:5%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:3%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:45%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:16.9pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Chief Financial Officer and Senior Vice President</p></td>
</tr>
</table></div>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="text-align:center;margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">3</p>

<hr style="page-break-after:always;width:100%;">
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;"><a name="_Toc403726853"></a><a name="_AEIOULastRenderedPageBreakAEIOU4"></a><font style="font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">Exhibit </font><font style="font-weight:bold;font-family:Times New Roman;font-size:10pt;font-style:normal;text-transform:none;font-variant: normal;">Index</font></p>
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-size:12pt;">&nbsp;</p>
<div>
<table border="0" cellspacing="0" cellpadding="0" align="center" style="border-collapse:collapse; width:100%;">
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%; border-bottom:solid 0.75pt #000000;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Exhibit</p>
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Number</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:2.02%; border-bottom:solid 0.75pt transparent;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:8pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%; border-bottom:solid 0.75pt #000000;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Description</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%; border-top:solid 0.75pt #000000;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-family:Times New Roman;font-size:10pt;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.02%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-family:Times New Roman;font-size:10pt;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%; border-top:solid 0.75pt #000000;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-family:Times New Roman;font-size:10pt;">&nbsp;</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%;">
<p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">99.1</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.02%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> Press release dated November 12, 2015</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.02%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.02%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.02%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.02%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.02%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
</tr>
<tr>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:7.08%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.02%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
<td valign="bottom"  BGCOLOR="#FFFFFF" style="padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:90.9%;">
<p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">&nbsp;</p></td>
</tr>
</table></div>
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;">&nbsp;</p>
<p style="text-align:center;margin-top:12pt;margin-bottom:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">4</p></body>
</html>
[{"type": "8-K", "sequence": "1", "filename": "mstx-8k_20151112.htm", "description": "8-K", "secsgml_size_bytes": 38013}]
{"company-data": {"conformed-name": "Mast Therapeutics, Inc.", "cik": "0001160308", "assigned-sic": "2834", "irs-number": "841318182", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-32157", "film-number": "151224798"}, "business-address": {"street1": "3611 VALLEY CENTRE DRIVE", "street2": "SUITE 500", "city": "SAN DIEGO", "state": "CA", "zip": "92130", "phone": "8585520866"}, "mail-address": {"street1": "3611 VALLEY CENTRE DRIVE", "street2": "SUITE 500", "city": "SAN DIEGO", "state": "CA", "zip": "92130"}, "former-company": [{"former-conformed-name": "ADVENTRX PHARMACEUTICALS INC", "date-changed": "20030613"}, {"former-conformed-name": "BIOKEYS PHARMACEUTICALS INC", "date-changed": "20010928"}]}
mstx-8k_20151112.htm
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 12, 2015
Mast Therapeutics, Inc.
(Exact name of Registrant as Specified in Its Charter)
Delaware
001-32157
84-1318182
(State or Other Jurisdiction
of Incorporation)
(Commission File Number)
(IRS Employer
Identification No.)
3611 Valley Centre Drive, Suite 500,
San Diego, CA
92130
(Address of Principal Executive Offices)
(Zip Code)
Registrant's Telephone Number, Including Area Code: (858) 552-0866
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 Instructions 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 12, 2015, Mast Therapeutics, Inc. issued a press release announcing its financial results for the three and nine months ended September 30, 2015. A copy of the press release is furnished as Exhibit 99.1 hereto.
Item 9.01 Financial Statements and Exhibits.
(d) Exhibits.
The list of exhibits called for by this Item is incorporated by reference to the Exhibit Index immediately following the signature page of this report.
The information set forth under Item 2.02 and in Exhibit 99.1 is not being filed for purposes of Section 18 of the Securities Exchange Act of 1934 and is not to be incorporated by reference into any filing of the registrant, whether made before or after the date hereof, regardless of any general incorporation language in any such filing.
2
SIG
NATURES
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.
Mast Therapeutics, Inc.
Date:  November 12, 2015
By:
/s/ Brandi L. Roberts
Brandi L. Roberts
Chief Financial Officer and Senior Vice President
3
Exhibit
Index
Exhibit
Number
Description
99.1
Press release dated November 12, 2015
4