UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE TO

Tender Offer Statement Under Section 14(d)(1) or 13(e)(1)

of the Securities Exchange Act of 1934

(Amendment No. 3)

DECIPHERA PHARMACEUTICALS, INC.

(Name of Subject Company)

TOPAZ MERGER SUB, INC.

a wholly owned subsidiary of

ONO PHARMACEUTICAL CO., LTD.

(Names of Filing Persons – Offeror)

Common Stock, Par Value $0.01 Per Share

(Title of Class of Securities)

24344T101

(CUSIP Number of Class of Securities)

Gyo Sagara

Ono Pharmaceutical Co., Ltd.

8-2, Kyutaromachi 1-chome, Chuo-ku, Osaka 541-8564, Japan

Telephone: +81-6-6263-5670

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications on Behalf of Filing Persons)

Copies to:

Jason T. Simon

Tricia Branker

Greenberg Traurig, LLP

1750 Tysons Boulevard, Suite 1000

McLean, VA 22102

Telephone: (703) 749-1300

Check the appropriate boxes below to designate any transactions to which the statement relates:

Check the following box if the filing is a final amendment reporting the results of the tender offer. ☒

If applicable, check the appropriate box(es) below to designate the appropriate rule provision(s) relied upon:

This Amendment No. 3 (this “Amendment”) amends and supplements the Tender Offer Statement on Schedule TO filed with the Securities and Exchange Commission on May 13, 2024 (together with any subsequent amendments and supplements thereto, the “Schedule TO”) by Topaz Merger Sub, Inc., a Delaware corporation (“Purchaser”) and a wholly owned subsidiary of Ono Pharmaceutical Co., Ltd., a Japanese company (kabushiki kaisha) (“Parent”) and Parent. The Schedule TO relates to the offer by Purchaser to purchase all of the outstanding shares of common stock, par value $0.01 per share (the “Shares”), of Deciphera Pharmaceuticals, Inc., a Delaware corporation (the “Company”), at a price per share of $25.60, net to the seller in cash, without interest and subject to any withholding of taxes required by applicable law, upon the terms and subject to the conditions described in the Offer to Purchase dated May 13, 2024 (as it may be amended from time to time, the “Offer to Purchase”), and in the related Letter of Transmittal (as it may be amended from time to time, the “Letter of Transmittal” and which, together with the Offer to Purchase, constitutes the “Offer”), copies of which are attached to and filed with the Schedule TO as Exhibits (a)(1)(i) and (a)(1)(ii), respectively.

Except as otherwise set forth in this Amendment, the information set forth in the Schedule TO remains unchanged and is incorporated herein by reference to the extent relevant to the items in this Amendment. Capitalized terms used but not defined herein have the meanings ascribed to them in the Schedule TO.

ITEMS 1 THROUGH 9; AND ITEM 11.

The disclosure in the Offer to Purchase and Items 1 through 9 and Item 11 of the Schedule TO, to the extent such items incorporate by reference the information contained in the Offer to Purchase, is hereby amended and supplemented as follows:

“The Offer expired at one minute after 11:59 p.m. New York City Time, on June 10, 2024. Computershare Trust Company, N.A., in its capacity as depositary for the Offer (the “Depositary”), advised that, as of the expiration of the Offer, a total of 76,413,423 Shares were validly tendered and not validly withdrawn pursuant to the Offer, representing approximately 88.25% of the Shares outstanding as of the expiration of the Offer. As of the expiration of the Offer, the number of Shares validly tendered and not validly withdrawn pursuant to the Offer satisfied the Minimum Condition. Promptly after the expiration of the Offer, Merger Sub irrevocably accepted for payment all Shares validly tendered and not validly withdrawn pursuant to the Offer. Merger Sub will promptly pay for all such Shares.

Following the acceptance of such Shares, the Merger was completed on June 11, 2024, in accordance with Section 251(h) of the DGCL without a vote of the Company’s stockholders. At the Effective Time of the Merger, each Share (other than (a) Shares held in the treasury of the Company, (b) Shares that at the commencement of the Offer were owned by Parent or Purchaser or any of their direct or indirect subsidiaries, (c) Shares irrevocably accepted for payment in the Offer, and (d) Shares held by a holder who is entitled to demand and properly demands appraisal of such Shares pursuant to, and who complies in all respects with, Section 262 of the DGCL) were automatically canceled and converted into the right to receive $25.60 in cash, without interest and subject to any withholding of taxes required by applicable law.

As a result of the Merger, the Shares will be delisted and will cease to trade on The Nasdaq Global Select Market. Parent and Purchaser intend to take steps to cause the termination of the registration of the Shares under the Exchange Act and suspend all of the Company’s reporting obligations under the Exchange Act as promptly as practicable.

On June 11, 2024, Parent issued a press release announcing the expiration and results of the Offer. The full text of the press release is attached as Exhibit (a)(5)(iv) hereto and is incorporated herein by reference.”

ITEM 12.

Item 12 is hereby amended and supplemented by adding the following exhibit:

SIGNATURES

After due inquiry and to the best knowledge and belief of the undersigned, each of the undersigned certify that the information set forth in this statement is true, complete and correct.

Exhibit (a)(5)(iv)

Ono Announces Results of Tender Offer to Acquire Deciphera Pharmaceuticals and

Completion of Acquisition of Deciphera (a Wholly Owned Subsidiary of Ono)

Osaka, Japan and Waltham, Massachusetts, June 11, 2024 – Ono Pharmaceutical Co., Ltd. (Chairman and CEO: Gyo Sagara, “Ono”) today announced that it has successfully completed the tender offer, previously announced on April 30, 2024, to acquire all outstanding shares of common stock of a U.S. biopharmaceutical company, Deciphera Pharmaceuticals, Inc. (Nasdaq: DCPH, CEO: Steven L. Hoerter, “Deciphera”) for US$25.60 per share (total amount of approximately US$2.4 billion) net to the seller in cash, without interest thereon and less any applicable withholding taxes, through its wholly owned subsidiary, Topaz Merger Sub, Inc. (“Merger Sub”), established in the State of Delaware, United States, solely for the purpose of engaging in the transactions contemplated in the Merger Agreement.

The tender offer commenced on May 13, 2024, New York City time, and, as set forth below, expired at one minute after 11:59 p.m., New York City time, on June 10, 2024.

On June 11, 2024, following the completion of the tender offer, Merger Sub merged with and into Deciphera with Deciphera continuing as the surviving corporation and a wholly owned subsidiary of Ono. In connection with the acquisition, Deciphera shares ceased to be traded on Nasdaq as of the date of closing of the acquisition and shares of Deciphera’s common stock will be delisted from Nasdaq.

“We are very pleased to welcome Deciphera into the family,” said Gyo Sagara, Chairman and CEO of Ono. “Through this acquisition, we will leverage Deciphera’s excellent research and development capabilities in the oncology field and its sales power in Europe and the United States, and work to further accelerate the expansion of our pipeline and global expansion, which are part of our growth strategies.”

“We are excited to enter a new phase as part of the family of Ono Pharmaceuticals, that has as its mission to contribute to society through the discovery and development of innovative drugs, under the corporate philosophy “Dedicated to the Fight against Disease and Pain,”” said Steven L. Hoerter, President and CEO of Deciphera. “By fully leveraging the research and development capabilities and commercialization platforms of both companies, we look forward to significantly contributing to the growth of the Ono Group as a global specialty pharma company.”

Particulars

Overview of Deciphera (prior to the completion of the acquisition on June 11, 2024):

Financial Impact of the Acquisition

ONO is still reviewing the impact of this acquisition on our business performance. Should there be any events to be disclosed in the future, we will announce them in a timely manner.