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): November 20, 2015

MB FINANCIAL, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (888) 422-6562

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 (see General Instruction A.2. below):

x                   Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o                     Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o                     Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o                     Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 8.01 Other Events

On November 22, 2015, MB Financial, Inc. (“MB Financial”) issued a press release announcing the execution of an Agreement and Plan of Merger, dated as of November 20, 2015, providing for the merger of American Chartered Bancorp, Inc. (“American Chartered”) with and into MB Financial.  A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.  In addition, MB Financial intends to provide supplemental information regarding the proposed transaction in a presentation to analysts and investors on November 23, 2015.  The slides that will be made available in connection with the presentation are attached hereto as Exhibit 99.2 and are incorporated herein by reference.

Forward-Looking Statements

When used in this Current Report on Form 8-K and in other documents filed with or furnished to the Securities and Exchange Commission (the “SEC”), in press releases or other public shareholder communications, or in oral statements made with the approval of an authorized executive officer, the words or phrases “believe,” “will likely result,” “are expected to,” “will continue,” “is anticipated,” “estimate,” “project,” “plans,” or similar expressions are intended to identify “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995.  You are cautioned not to place undue reliance on any forward-looking statements, which speak only as of the date such statements are made.  These statements may relate to future financial performance, strategic plans or objectives, revenues or earnings projections, or other financial information.  By their nature, these statements are subject to numerous uncertainties that could cause actual results to differ materially from those anticipated in the statements.  Statements about the expected timing, completion and effects of the proposed merger and all other statements in this report other than historical facts constitute forward-looking statements.

Important factors that could cause actual results to differ materially from the results anticipated or projected include, but are not limited to, the following: (1) expected revenues, cost savings, synergies and other benefits from the MB Financial-American Chartered merger might not be realized within the expected time frames or at all and costs or difficulties relating to integration matters, including but not limited to customer and employee retention, might be greater than expected; (2) the requisite regulatory approvals and approval of American Chartered’s stockholders for the MB Financial-American Chartered merger might not be obtained, or may take longer to obtain than expected; (3) the credit risks of lending activities, including changes in the level and direction of loan delinquencies and write-offs and changes in estimates of the adequacy of the allowance for loan losses, which could necessitate additional provisions for loan losses, resulting both from originated loans and loans acquired from other financial institutions; (4) competitive pressures among depository institutions; (5) interest rate movements and their impact on customer behavior, net interest margin and the value of MB Financial’s mortgage servicing rights; (6) the possibility that MB Financial’s mortgage banking business may increase volatility in its revenues and earnings and the possibility that the profitability of MB Financial’s mortgage banking business could be significantly reduced if MB Financial is unable to originate and sell mortgage loans at profitable margins or if changes in interest rates negatively impact the value of MB Financial’s mortgage servicing rights; (7) the impact of repricing and competitors’ pricing initiatives on loan and deposit products; (8) fluctuations in real estate values; (9) the ability to adapt successfully to technological changes to meet customers’ needs and developments in the market place; (10) the possibility that security measures implemented might not be sufficient to mitigate the risk of a cyber attack or cyber theft, and that such security measures might not protect against systems failures or interruptions; (11) MB Financial’s ability to realize the residual values of its direct finance, leveraged and operating leases; (12) the ability to access cost-effective funding; (13) changes in financial markets; (14) changes in economic conditions in general and in the Chicago metropolitan area in particular; (15) the costs, effects and outcomes of litigation; (16) new legislation or regulatory changes, including but not limited to the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 (the “Dodd-Frank Act”) and regulations adopted thereunder, changes in capital requirements pursuant to the Dodd-Frank Act, other governmental initiatives affecting the financial services industry and changes in federal and/or state tax laws or interpretations thereof by taxing authorities; (17) changes in accounting principles, policies or guidelines; (18) future acquisitions by MB Financial of other depository institutions or lines of

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business; and (19) future goodwill impairment due to changes in MB Financial’s business, changes in market conditions, or other factors.

MB Financial does not undertake any obligation to update any forward-looking statement to reflect circumstances or events that occur after the date on which the forward-looking statement is made.

Additional Information

MB Financial will file a registration statement on Form S-4 with the SEC in connection with the proposed transaction.  The registration statement will include a proxy statement/prospectus, which will be sent to the stockholders of American Chartered.  INVESTORS AND STOCKHOLDERS OF AMERICAN CHARTERED ARE ADVISED TO READ THE PROXY STATEMENT/PROSPECTUS WHEN IT BECOMES AVAILABLE BECAUSE IT WILL CONTAIN IMPORTANT INFORMATION ABOUT MB FINANCIAL, AMERICAN CHARTERED AND THE PROPOSED TRANSACTION.  When filed, this document and other documents relating to the merger filed by MB Financial with the SEC can be obtained free of charge from the SEC’s website at www.sec.gov.  These documents also can be obtained free of charge by accessing MB Financial’s website at www.mbfinancial.com under the tab “Investor Relations”.  Alternatively, these documents, when available, can be obtained free of charge from MB Financial upon written request to MB Financial, Inc., Corporate Secretary, 6111 North River Road, Rosemont, Illinois 60018 or by calling (847) 653-1992.

Participants in this Transaction

MB Financial, American Chartered and their respective directors and executive officers and certain other members of management and employees may be deemed to be participants in the solicitation of proxies from American Chartered stockholders in connection with the proposed transaction.  Information about the directors and executive officers of MB Financial is contained in the definitive proxy statement of MB Financial relating to its 2015 Annual Meeting of Stockholders filed by MB Financial with the SEC on April 10, 2015.  Information about the directors and executive officers of American Chartered will be set forth in the proxy statement/prospectus when it is filed with the SEC.

Item 9.01 Financial Statements and Exhibits

(d)              Exhibits:

The following exhibits are filed herewith:

99.1              Press Release dated November 22, 2015

99.2              Investor Presentation

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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.

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EXHIBIT INDEX

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