UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 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): September 20, 2011

SANTARUS, INC.

(Exact Name of Registrant as Specified in Its Charter)

3721 Valley Centre Drive, Suite 400, San Diego, California 92130

(Address of Principal Executive Offices) (Zip Code)

(858) 314-5700

(Registrant’s Telephone Number, Including Area Code)

N/A

(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:

On September 20, 2011, Santarus, Inc. (“Santarus” or the “Company”) issued a press release announcing that analysis of top-line safety data from a double blind, multicenter 12-month extended use study in patients treated daily with either the investigational drug budesonide MMX^® 6 mg or placebo will be provided as support for the Company’s planned submission in December 2011 of a New Drug Application (“NDA”) for budesonide MMX 9 mg to the U.S. Food and Drug Administration (“FDA”) for the induction of remission of mild or moderate active ulcerative colitis. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

Forward-Looking Statements

Santarus cautions you that statements included in this report that are not a description of historical facts are forward-looking statements. Forward-looking statements include statements regarding the anticipated U.S. NDA submission for budesonide MMX. The inclusion of forward-looking statements should not be regarded as a representation by Santarus that any of its plans or objectives will be achieved. Actual results may differ materially from those set forth in this release due to the risks and uncertainties inherent in Santarus’ business, including, without limitation: Santarus’ ability to successfully develop its budesonide MMX and other product candidates in a timely manner or at all; whether Santarus is able to prepare and submit the NDA for budesonide MMX within its planned timeframe; whether Santarus is able to obtain regulatory approval for budesonide MMX and its other product candidates in a timely manner or at all, including whether the FDA agrees with the statistical analysis plan for the budesonide MMX phase III studies, the clinical interpretation of the results and the conduct of the studies and whether the extended use study, which evaluated budesonide MMX 6 mg, will provide adequate data to support approval of budesonide MMX 9 mg; risks associated with the collaboration with Cosmo Technologies Ltd., a subsidiary of Cosmo Pharmaceuticals, relating to the MMX product candidates, including the potential for termination of the collaboration; competition from other products; unexpected adverse side effects or inadequate therapeutic efficacy of Santarus’ products and product candidates; the scope and validity of patent protection for Santarus’ products and product candidates; other difficulties or delays relating to the development, testing, manufacturing and marketing of, and obtaining and maintaining regulatory approvals for, Santarus’ products and product candidates; and other risks detailed in Santarus’ prior public periodic filings with the Securities and Exchange Commission.

You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and Santarus undertakes no obligation to revise or update this report to reflect events or circumstances after the date hereof. This caution is made under the safe harbor provisions of Section 21E of the Private Securities Litigation Reform Act of 1995.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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