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): December 20, 2016

Sucampo Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Delaware

(State or other jurisdiction

of incorporation)

805 King Farm Blvd, Suite 550

Rockville, Maryland 20850

(Address of principal executive offices and zip code)

Registrant’s telephone number, including area code: (301) 961-3400

(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 December 27, 2016, Sucampo Pharmaceuticals, Inc. (the “Company”) issued $300.0 million aggregate principal amount of its 3.25% Convertible Senior Notes due 2021 (the “Notes”) to Leerink Partners LLC (the “Initial Purchaser”), who subsequently resold the Notes to qualified institutional buyers (the “Note Offering”) in reliance on the exemption from registration provided by Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”). The Notes sold in the Note Offering include $40.0 million aggregate principal amount of Notes sold to the Initial Purchaser pursuant to its option to purchase additional Notes, solely to cover over-allotments, which was exercised in full on December 21, 2016.

The Company estimates that the net proceeds from the Note Offering will be $290.4 million, after deducting the Initial Purchaser’s discount and estimated offering expenses. Concurrently with the closing of the Note Offering, the Company intends to use the net proceeds from the Note Offering to repay in full approximately $238.4 million due under the Company’s senior secured credit facility, including all accrued but unpaid interest and a prepayment premium. The Company intends to use the remaining net proceeds for general corporate purposes.

The Notes were issued pursuant to an Indenture, dated as of December 27, 2016 (the “Indenture”), between the Company and U.S. Bank National Association, as trustee. Interest on the Notes will be payable semi-annually in cash in arrears on June 15 and December 15 of each year, beginning on June 15, 2017, at a rate of 3.25% per year. The Notes mature on December 15, 2021 unless earlier converted or repurchased. The Notes are not redeemable prior to the maturity date, and no sinking fund is provided for the Notes.

The Notes are convertible at an initial conversion rate of 60.2637 shares of the Company’s Class A common stock (the “Common Stock”) per $1,000 principal amount of the Notes, subject to adjustment under the Indenture, which is equal to an initial conversion price of approximately $16.59 per share of Common Stock. Upon conversion, the Notes will be settled in shares of the Company’s Common Stock, together with a cash payment in lieu of delivering any fractional share. The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, the Company will increase the conversion rate for a holder who elects to convert its Notes in connection with such a corporate event in certain circumstances.

If the Company undergoes a “fundamental change” (as defined in the Indenture), holders may require the Company to repurchase for cash all or any portion of their Notes at a fundamental change repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

The Indenture includes customary terms and covenants, including certain events of default after which the Notes may be due and payable immediately. The following events are considered “events of default,” which may result in acceleration of the maturity of the Notes:

Subject to certain exceptions, the Company has agreed not to sell or transfer any Common Stock of the Company for 60 days without first obtaining the written consent of the Initial Purchaser. The Company’s directors and executive officers and certain stockholders have also agreed not to sell or transfer any Common Stock of the Company for 60 days, subject to certain exceptions, without first obtaining the written consent of the Initial Purchaser.

The Indenture and form of Note are filed herewith as Exhibit 4.1 and Exhibit 4.2, respectively, and are incorporated by reference herein. The foregoing description of the terms of the Notes and the Indenture does not purport to be complete and is qualified in its entirety by reference to such exhibits.

Item 2.03 Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

See Item 1.01 above, which is incorporated by reference herein.

See Item 1.01 above, which is incorporated by reference herein.

On December 20, 2016, the Company entered into a Purchase Agreement (the “Purchase Agreement”) with the Initial Purchaser relating to the Note Offering. The Company and the Initial Purchaser relied on exemptions from registration based in part on representations made by the Company and the Initial Purchaser, respectively. The Purchase Agreement includes customary representations, warranties and covenants by the Company and the Initial Purchaser. Under the terms of the Purchase Agreement, the Company has agreed to indemnify the Initial Purchaser against certain liabilities under the Securities Act.

On December 21, 2016, the Company issued a press release announcing the pricing of the Note Offering. A copy of the press release is filed herewith as Exhibit 99.1 and incorporated by reference herein.

None of the Notes or the Common Stock issuable upon conversion of the Notes has been registered under the Securities Act or the securities laws of any other jurisdiction, and such securities may not be offered or sold in the United States absent registration or an applicable exemption from registration requirements. This Current Report on Form 8-K does not constitute an offer to sell, or a solicitation of an offer to buy, any security and shall not constitute an offer, solicitation or sale in any jurisdiction in which such offering would be unlawful.

This Current Report on Form 8-K includes forward-looking statements regarding future events. All statements other than statements of historical fact are statements that could be deemed forward-looking statements, including statements regarding the anticipated uses of the proceeds from the Note Offering, any statements of expectation or belief, and any statements of assumptions underlying any of the foregoing. These statements are based on current expectations on the date of this report and involve a number of significant risks and uncertainties that may cause actual results to differ significantly from such estimates. The risks include the satisfaction of the closing conditions of the Note Offering. The Company’s filings with the Securities and Exchange Commission identify many other risks and uncertainties. Any forward-looking statements that the Company makes in this report speak only as of the date of such statement, and the Company undertakes no obligation to update such statements.

(d) Exhibits

SIGNATURES

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.

EXHIBIT INDEX