UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K/A

(Amendment No. 1)

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 6, 2015

MEDIVATION, INC.

(Exact name of registrant as specified in its charter)

525 Market Street, 36th Floor

San Francisco, California 94105

(Address of principal executive offices and zip code)

Registrant’s telephone number, including area code: (415) 543-3470

(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:

EXPLANATORY NOTE

On August 21, 2015, Medivation, Inc. (“Medivation”) entered into an Asset Purchase Agreement (the “Agreement”) with BioMarin Pharmaceutical Inc. (“BioMarin”) pursuant to which Medivation acquired all rights to talazoparib (“talazoparib research program”) from BioMarin. The acquired talazoparib assets include all patents, data, know-how, third party agreements, regulatory materials, and pre-commercial inventories. Medivation also assumed certain costs related to talazoparib to the extent they arise after the closing, including costs for the ongoing clinical trials of talazoparib, and commitments under certain agreements previously entered into by BioMarin and assigned to Medivation. On October 7, 2015, Medivation filed a Current Report on Form 8-K with the Securities and Exchange Commission (“Initial Form 8-K”) to report the completion of the acquisition.

In connection with the closing of the transaction, Medivation paid BioMarin an upfront cash payment of $410.0 million, and will pay BioMarin up to an additional $160.0 million upon the achievement of defined regulatory and sales-based milestones, and mid-single digit royalties on net sales of products that contain talazoparib during the royalty term specified in the Agreement.

This Current Report on Form 8-K/A is filed as an amendment to the Initial Form 8-K filed by Medivation on October 7, 2015. This Current Report is filed to provide, and amends the Initial Form 8-K to include, the financial statements and pro forma financial information required by Item 9.01 of Form 8-K.

Item 9.01 Financial Statements and Exhibits.

Medivation has concluded that according to the guidance in Financial Accounting Standards Board Accounting Standards Codification Topic No. 805, “Business Combinations,” and Article 11 of Regulation S-X, the transaction meets the definition of a “business” and exceeds the conditions of significance set forth in Rule 1-02(w) of Regulation S-X at the greater than 50% level. The financial statements of the business acquired required by Item 9.01(a) of Form 8-K are included herewith.

The pro forma financial information required by Item 9.01(b) of Form 8-K is included herewith.

SIGNATURE

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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