Bayer Schering Pharma Aktiengesellschaft (SHR) SC TO-T/A Third party tender offer statement (amended)

QuickLinks -- Click here to rapidly navigate through this document

As filed with the Securities and Exchange Commission on April 14, 2006

SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

SCHEDULE TO
(Rule 14d-100)
Tender Offer Statement under Section 14(d)(1) of the Securities
Exchange Act of 1934
(Amendment No. 1)

Schering Aktiengesellschaft
(Name of Subject Company (issuer))

Dritte BV GmbH
Bayer Aktiengesellschaft
(Name of Filing Persons (offerors))

Ordinary Shares,
no par value
(Title of Class of Securities)
DE0007172009
(CUSIP Number of Class of Securities)

American Depositary Shares
(each representing one Ordinary Share)
(Title of Class of Securities)
806585204
(CUSIP Number of Class of Securities)

Dr. Roland Hartwig
Bayerwerk, Gebaeude W11
Kaiser-Wilhelm-Allee
51368 Leverkusen
Germany
+49 (214) 3081195

(Name, Address and Telephone Number of Person Authorized to Receive
Notices and Communications on Behalf of the Person(s) Filing Statement)
With copies to:

Charles Nathan, Esq.
John E. Sorkin, Esq.
Latham & Watkins LLP
885 Third Avenue
New York, New York 10022
(212) 906-1200 Dr. Joachim von Falkenhausen
Stefan Widder
Latham & Watkins LLP
Warburgstrasse 50
20354 Hamburg, Germany
+49 (40) 414030

CALCULATION OF FILING FEE

Transaction Valuation*	Amount of Filing Fee*
$19,860,767,584.80	$2,125,102.13

*

Estimated for purposes of calculating the amount of the filing fee only. The calculation of the transaction valuation assumes the purchase of 191,000,875 bearer shares, no par value per share ("Shares"), of Schering Aktiengesellschaft ("Schering") (including those Shares represented by American Depositary Shares ("ADSs")), at a purchase price of EUR 86.00 per Share in cash, converted into U.S. dollars at the noon buying rate as published by the Federal Reserve Bank of New York on April 10, 2006 of EUR 1 = $1.2091. Such number of Shares represents the number of Shares (including Shares represented by ADSs) issued and outstanding as of April 11, 2006 and excludes Shares held by Schering in treasury.

ý

Check the box if any part of the filing fee is offset as provided by Rule 0-11(a)(2) and identify the filing with which the offsetting fee was previously paid. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

Amount Previously Paid:	$2,125,102.13
Form or Registration No.:	Schedule TO
Filing Party:	Dritte BV GmbH Bayer Aktiengesellschaft
Date Filed:	April 13, 2006

o

Check the box if the filing relates solely to preliminary communications made before the commencement of a tender offer.

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

ý

third-party tender offer subject to Rule 14d-1.

o

issuer tender offer subject to Rule 13e-4.

o

going-private transaction subject to Rule 13e-3.

o

amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results of the tender offer: o

This Amendment No. 1 to Schedule TO (this "Statement") relates to the offer by Dritte BV GmbH, a limited liability company organized under the laws of the Federal Republic of Germany (the "Bidder") and a wholly-owned subsidiary of Bayer Aktiengesellschaft, a stock corporation organized under the laws of the Federal Republic of Germany ("Bayer"), to purchase all of the issued and outstanding bearer shares, no par value (the "Shares"), including those Shares represented by American Depositary Shares ("ADSs"), of Schering Aktiengesellschaft, a stock corporation organized under the laws of the Federal Republic of Germany ("Schering"), at a purchase price of EUR 86.00 per Share in cash. The terms and conditions of the offer (as it may be amended or supplemented from time to time, the "Offer") are described in the Offer Document, published April 13, 2006 (the "Offer Document"), a copy of which was orginally filed as Exhibit (a)(1)(A), and, where applicable, the related U.S. Declaration of Acceptance and ADS Letter of Transmittal and the instructions thereto, copies of which were originally filed as Exhibits (a)(1)(B) and (C), to the Schedule TO filed on April 14, 2006. Except as otherwise indicated, the information set forth in the Schedule TO remains unchanged. Capitalized terms used but not defined herein have the meanings ascribed to them in the Schedule TO.

ITEM 12. EXHIBITS

        Item 12 of the Schedule TO is hereby amended and supplemented by adding the following thereto:

(a)(1)(N) Pamphlet distributed to Schering shareholders regarding tender offer.

SIGNATURE

        After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this Statement is true, complete and correct.

        Dated: April 14, 2006

Bayer Aktiengesellschaft
By:	/s/  DR. ROLAND HARTWIG      Name: Dr. Roland Hartwig Title: General Counsel
By:	/s/  DR. ALEXANDER ROSAR      Name: Dr. Alexander Rosar Title: Head of Investor Relations
Dritte BV GmbH
By:	/s/  DR. ARMIN BUCHMEIER      Name: Dr. Armin Buchmeier Title: Managing Director

QuickLinks

ITEM 12. EXHIBITS

SIGNATURE