SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13D UNDER THE SECURITIES EXCHANGE ACT OF 1934 (AMENDMENT NO. 12)* CHIRON CORPORATION (Name of Issuer) COMMON STOCK, PAR VALUE $0.01 PER SHARE (Title of Class of Securities) 170040109 (CUSIP Number of Class of Securities) WAYNE P. MERKELSON ANDREW R. BROWNSTEIN, ESQ. NOVARTIS CORPORATION TREVOR S. NORWITZ, ESQ. 608 FIFTH AVENUE WACHTELL, LIPTON, ROSEN & KATZ NEW YORK, NEW YORK 10020 51 WEST 52 STREET (212) 307-1122 NEW YORK, NEW YORK 10019 (212) 403-1000 (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications on Behalf of Filing Persons) OCTOBER 30, 2005 (Date of Event Which Requires Filing of this Statement) If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of ss.ss.240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. [ ] NOTE: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See ss.240.13d-7 for other parties to whom copies are to be sent. *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page. The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). CUSIP No. 170040109 -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS: Novartis Biotech Partnership, Inc. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY): 06-1415318 -------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (A) [ ] ------------------------------------------------------------------ (B) [ ] ------------------------------------------------------------------ 3. SEC USE ONLY: -------------------------------------------------------------------------- 4. SOURCE OF FUNDS (SEE INSTRUCTIONS): AF -------------------------------------------------------------------------- 5. CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(D) OR 2(E) [ ] -------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------- Number of 7. SOLE VOTING POWER Shares 0 Beneficially -------------------------------------------------------------- Owned by Each Reporting 8. SHARED VOTING POWER Person 127,206,693 With -------------------------------------------------------------- 9. SOLE DISPOSITIVE POWER 0 -------------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 127,206,693 -------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 127,206,693 ------------------------------------------------------------------------- 12. CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] ------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 53% ------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) CO ------------------------------------------------------------------------- CUSIP No. 170040109 -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS: Novartis Corporation I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY): 13-1834433 -------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (A) [ ] ------------------------------------------------------------------ (B) [ ] ------------------------------------------------------------------ 3. SEC USE ONLY: -------------------------------------------------------------------------- 4. SOURCE OF FUNDS (SEE INSTRUCTIONS): AF -------------------------------------------------------------------------- 5. CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(D) OR 2(E) [ ] -------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION New York -------------------------------------------------------------------------- Number of 7. SOLE VOTING POWER Shares 0 Beneficially -------------------------------------------------------------- Owned by Each Reporting 8. SHARED VOTING POWER Person 127,214,149 With -------------------------------------------------------------- 9. SOLE DISPOSITIVE POWER 0 -------------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 127,214,149 -------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 127,214,149 ------------------------------------------------------------------------- 12. CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] ------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 53% ------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) CO ------------------------------------------------------------------------- CUSIP No. 170040109 -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS: Novartis Pharma AG I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY): -------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (A) [ ] ------------------------------------------------------------------ (B) [ ] ------------------------------------------------------------------ 3. SEC USE ONLY: -------------------------------------------------------------------------- 4. SOURCE OF FUNDS (SEE INSTRUCTIONS): WC -------------------------------------------------------------------------- 5. CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(D) OR 2(E) [ ] -------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Switzerland -------------------------------------------------------------------------- Number of 7. SOLE VOTING POWER Shares 0 Beneficially -------------------------------------------------------------- Owned by Each Reporting 8. SHARED VOTING POWER Person 5,469,770 With -------------------------------------------------------------- 9. SOLE DISPOSITIVE POWER 0 -------------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 5,469,770 -------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 5,469,770 ------------------------------------------------------------------------- 12. CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] ------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 2% ------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) CO ------------------------------------------------------------------------- CUSIP No. 170040109 -------------------------------------------------------------------------------- 1. NAMES OF REPORTING PERSONS: Novartis AG I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY): -------------------------------------------------------------------------- 2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (A) [ ] ------------------------------------------------------------------ (B) [ ] ------------------------------------------------------------------ 3. SEC USE ONLY: -------------------------------------------------------------------------- 4. SOURCE OF FUNDS (SEE INSTRUCTIONS): WC -------------------------------------------------------------------------- 5. CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(D) OR 2(E) [ ] -------------------------------------------------------------------------- 6. CITIZENSHIP OR PLACE OF ORGANIZATION Switzerland -------------------------------------------------------------------------- Number of 7. SOLE VOTING POWER Shares 0 Beneficially -------------------------------------------------------------- Owned by Each Reporting 8. SHARED VOTING POWER Person 132,683,919 With -------------------------------------------------------------- 9. SOLE DISPOSITIVE POWER 0 -------------------------------------------------------------- 10. SHARED DISPOSITIVE POWER 132,683,919 -------------------------------------------------------------- 11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 132,683,919 ------------------------------------------------------------------------- 12. CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [ ] ------------------------------------------------------------------------- 13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 55% ------------------------------------------------------------------------- 14. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) CO ------------------------------------------------------------------------- ITEM 1. SECURITY AND ISSUER This Amendment No. 12 to Schedule 13D relates to Common Stock, par value $0.01 per share (the "Common Stock"), of Chiron Corporation, a Delaware corporation (the "Company"). Novartis AG ("Novartis"), Novartis Corporation, ("Novartis Corp"), Novartis Biotech Partnership, Inc. ("Biotech"), and Novartis Pharma AG ("Novartis Pharma" and, together with Novartis, Novartis Corp and Biotech the "Reporting Persons") hereby amend the Schedule 13D. ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION Item 3 is hereby amended and supplemented by adding the following: Novartis plans to finance the transactions described in Item 4 below with available cash or other liquid assets. ITEM 4. PURPOSE OF TRANSACTION Item 4 is hereby amended and supplemented by adding the following: On October 30, 2005, the Company entered into an Agreement and Plan of Merger (the "Merger Agreement") with Novartis Corp, Biotech and, for certain purposes only, Novartis. On the terms and subject to the conditions of the Merger Agreement, Biotech will be merged with and into the Company (the "Merger"), with the Company continuing as the surviving corporation and as an indirect wholly-owned subsidiary of Novartis. Pursuant to the Merger, each share of Common Stock issued and outstanding at the effective time of the Merger (other than shares of Common Stock (i) owned by the Reporting Persons, the Company, or any of their direct or indirect subsidiaries, except for any such shares held on behalf of third parties, or (ii) owned by stockholders properly exercising appraisal rights) will be converted into the right to receive $45.00 in cash, without interest. Completion of the Merger is subject to approval of (i) the holders of a majority of the outstanding shares of Common Stock and (ii) the holders of a majority of the outstanding shares of Common Stock, excluding shares of Common Stock owned by the Reporting Persons. The Merger Agreement is also subject to the satisfaction of other customary conditions, including governmental and regulatory approvals. Novartis issued a press release on October 31, 2005 announcing the execution of the Merger Agreement. The press release and Merger Agreement are filed as Exhibit 99.1 and Exhibit 99.2 hereto, respectively, and are incorporated by reference herein. The Company also gave Novartis and Novartis AG notice of the exercise of its right, pursuant to the Subscription Agreement, dated as of November 20, 1994 among the Company, Novartis and certain of its affiliates (filed as an exhibit to the Schedule 13D on January 21, 1997), to require Biotech to purchase shares of Common Stock directly from the Company at a price per share equal to fair market value, for an aggregate purchase price of $300 million. "Fair market value" is defined under the Subscription Agreement as the average of the closing sale prices or the closing bid quotations of shares of Common Stock on the Nasdaq National Market during the ten-day period immediately preceding the business day three business days prior to the closing of the purchase, which will occur following satisfaction of all closing conditions set forth in the Subscription Agreement, including governmental and regulatory approvals. ITEM 5. INTEREST IN SECURITIES OF ISSUER Item 5(c) is hereby amended and supplemented by adding the following: (c) The disclosures contained in Item 4 above are incorporated by reference herein. ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO SECURITIES OF THE ISSUER Item 6 is hereby amended and supplemented by adding the following: The disclosure contained in Item 4 above are incorproated by reference herein. ITEM 7. MATERIAL TO BE FILED AS EXHIBITS 99.1 Press Release, dated Octber 31, 2005. 99.2 Agreement and Plan of Merger, dated as of October 30, 2005, by and among Novartis Corporation, Novartis Biotech Partnership, Inc., Chiron Corporation and, for purposes of Section 10.14 thereof only, Novartis AG. 99.3 Joint Filing Agreement, dated as of October 31, 2005, by and among Novartis Biotech Partnership, Inc., Novartis Corporation, Novartis Pharma AG and Novartis AG. SIGNATURES After reasonable 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: October 31, 2005 NOVARTIS BIOTECH PARTNERSHIP, INC. By: /s/ Wayne P. Merkelson -------------------------- Name: Wayne P. Merkelson Title: Vice President NOVARTIS CORPORATION By: /s/ Jeff Benjamin --------------------------- Name: Jeff Benjamin Title: Vice President NOVARTIS PHARMA AG By: /s/ Jorg Reinhardt --------------------------- Name: Jorg Reinhardt Title: Authorized Signatory By: /s/ Martin Henrich --------------------------- Name: Martin Henrich Title: Authorized Signatory NOVARTIS AG By: /s/ Frederic Krohn --------------------------- Name: Frederic Krohn Title: Authorized Signatory Exhibit Index EXHIBIT NUMBER EXHIBIT NAME -------------- ----------------------------------------------------------- 99.1 Press Release, dated October 31, 2005. 99.2 Agreement and Plan of Merger, dated as of October 30, 2005, by and among Novartis Corporation, Novartis Biotech Partnership, Inc., Chiron Corporation and, for purposes of Section 10.14 thereof only, Novartis AG. 99.3 Joint Filing Agreement, dated as of October 31, 2005, by and among Novartis Biotech Partnership, Inc., Novartis Corporation, Novartis Pharma AG and Novartis AG. SCHEDULE I DIRECTORS AND EXECUTIVE OFFICERS OF NOVARTIS, NOVARTIS PHARMA, NOVARTIS CORP AND BIOTECH DIRECTORS AND EXECUTIVE OFFICERS OF NOVARTIS The name, address, citizenship and present principal occupation or employment of each of the directors and executive officers of Novartis are set forth below. Unless otherwise indicated below, each occupation set forth opposite an individual's name refers to employment with Novartis. NAME, FUNCTION AND BUSINESS ADDRESS CITIZENSHIP PRINCIPAL OCCUPATION ----------------------------------- ----------- ---------------------------- Daniel Vasella Switzerland Chairman of the Board of Chairman of the Board of Directors, Directors, Chief Executive Chief Executive Officer Officer c/o Novartis AG Lichtstrasse 35 CH-4002 Basel, Switzerland Hans-Jorg Rudloff Germany Chairman of the Executive Vice Chairman of the Board of Committee of Barclays Directors Capital c/o Novartis AG Lichtstrasse 35 CH-4002 Basel, Switzerland Prof. Dr. Helmut Sihler Austria Retired Vice Chairman of the Board of Directors c/o Novartis AG Lichtstrasse 35 CH-4002 Basel, Switzerland Birgit Breuel Germany Member of the Supervisory Director Board of Gruner + Jahr AG, c/o Novartis AG German Lichtstrasse 35 CH-4002 Basel, Switzerland Prof. Dr. Peter Burckhardt Switzerland Head of Medical Service at Director the University Hospital of c/o Novartis AG Lausanne Lichtstrasse 35 CH-4002 Basel, Switzerland Prof. Srikant Datar, PhD. India Senior Associate Dean for Director Executive Education at c/o Novartis AG Harvard Business School Lichtstrasse 35 CH-4002 Basel, Switzerland William W. George USA Chairman and Chief Executive Director Officer of Medtronic, Inc., c/o Novartis AG Minneapolis Lichtstrasse 35 CH-4002 Basel, Switzerland Alexandre F. Jetzer Switzerland Consultant Director c/o Novartis AG Lichtstrasse 35 CH-4002 Basel, Switzerland Pierre Landoldt Switzerland President of the Sandoz Director Family Foundation c/o Novartis AG Lichtstrasse 35 CH-4002 Basel, Switzerland Prof. Dr. Rolf M. Zinkernagel Switzerland Professor and Director of Director the Institute of c/o Novartis AG Experimental Immunology at Lichtstrasse 35 the University of Zurich CH-4002 Basel, Switzerland Prof. Ulrich Lehner, PhD Germany President and Chief Director Executive Officer of Henkel c/o Novartis AG KGaA Lichtstrasse 35 CH-4002 Basel, Switzerland Dr.-Ing. Wendelin Wiedeking Germany Chairman of Porsche AG Director c/o Novartis AG Lichtstrasse 35 CH-4002 Basel, Switzerland Dr. Raymund Breu Switzerland Chief Financial Officer c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland Dr. Urs Barlocher Switzerland Head of Legal and General c/o Novartis AG Affairs Lichstrasse 35 CH-4002 Basel, Switzerland Jurgen Brokatzky-Geiger Germany Head of Human Resources c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland Dr. Paul Choffat Switzerland Head of Novartis Consumer c/o Novartis AG Health Lichstrasse 35 CH-4002 Basel, Switzerland Thomas Ebeling Germany Head of Pharmaceuticals c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland Mark C. Fishman USA Head of Biomedical Research c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland Steven Kelmar USA Head of Public Affairs and c/o Novartis AG Communications Lichstrasse 35 CH-4002 Basel, Switzerland DIRECTORS AND EXECUTIVE OFFICERS OF NOVARTIS PHARMA The name, address, citizenship and present principal occupation or employment of each of the directors and executive officers of Novartis Pharma are set forth below. Unless otherwise indicated below, each occupation set forth opposite an individual's name refers to employment with Novartis Pharma. NAME, FUNCTION AND BUSINESS ADDRESS CITIZENSHIP PRINCIPAL OCCUPATION ----------------------------------- ----------- ---------------------------- Daniel Vasella Switzerland Chairman of the Board of Chairman of the Board of Directors, Directors, and Chief Chief Executive Officer Executive Officer of c/o Novartis AG Novartis Lichtstrasse 35 CH-4002 Basel, Switzerland Thomas Ebeling Germany Head of Novartis Pharma Director c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland Dr. Raymund Breu Switzerland Chief Financial Officer of Director Novartis c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland Andrin Oswald Switzerland Corporate Secretary c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland DIRECTORS AND EXECUTIVE OFFICERS OF NOVARTIS CORP The name, address, citizenship and present principal occupation or employment of each of the directors and executive officers of Novartis Corp are set forth below. Unless otherwise indicated below, each occupation set forth opposite an individual's name refers to employment with Novartis Corp. NAME, FUNCTION AND BUSINESS ADDRESS CITIZENSHIP PRINCIPAL OCCUPATION ----------------------------------- ----------- ---------------------------- Daniel Vasella Switzerland Chairman of the Board of Chairman of the Board of Directors Directors and Chief c/o Novartis AG Executive Officer of Lichtstrasse 35 Novartis CH-4002 Basel, Switzerland Terence Barnett Great Vice Chairman, President and Vice Chairman of the Board of Britain Chief Executive Officer Directors c/o Novartis Corporation 608 Fifth Avenue New York, NY 10020, USA Dr. Raymund Breu Switzerland Chief Financial Officer of Director Novartis c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland Thomas Ebeling Germany Head of Novartis Pharma Director c/o Novartis AG Lichstrasse 35 CH-4002 Basel, Switzerland Fred Meyer Switzerland Retired Director c/o Omnicom Group, Inc. 437 Madison Avenue New York, NY 10022, USA Urs Naegelin Switzerland Executive Vice President and c/o Novartis Corporation Chief Financial Officer 608 Fifth Avenue New York, NY 10020, USA Dr. Paul Choffat Switzerland Division Head Consumer c/o Novartis AG Health Lichstrasse 35 CH-4002 Basel, Switzerland DIRECTORS AND EXECUTIVE OFFICERS OF BIOTECH The name, address, citizenship and present principal occupation or employment of each of the directors and executive officers of Biotech are set forth below. Unless otherwise indicated below, each occupation set forth opposite an individual's name refers to employment with Biotech. NAME, FUNCTION AND BUSINESS ADDRESS CITIZENSHIP PRINCIPAL OCCUPATION ----------------------------------- ----------- ---------------------------- Urs Naegelin Switzerland Executive Vice President and Chairman of the Board of Directors Chief Financial Officer of c/o Novartis Corporation Novartis Corp 608 Fifth Avenue New York, NY 10020, USA Paulo Costa Brazil Chief Executive Officer of Vice Chairman of the Board of Novartis Pharmaceuticals Directors Corporation c/o Novartis Pharmaceuticals Corporation 59 Route 10 East Hanover, NJ 07936 Terance Barnett Great Vice Chairman, President and Director Britain Chief Executive Officer of c/o Novartis Corporation Novartis Corp 608 Fifth Avenue New York, NY 10020, USA