<PAGE>
As filed with the Securities and Exchange Commission on September 14, 2000.
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
---------------------------
AMENDMENT NO. 5 TO
SCHEDULE TO
TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) OR 13(e)(1)
OF THE SECURITIES EXCHANGE ACT OF 1934
PATHOGENESIS CORPORATION
(Name of Subject Company (Issuer))
CHIRON CORPORATION
AND PICARD ACQUISITION CORP.,
A WHOLLY OWNED SUBSIDIARY OF
CHIRON CORPORATION
(Name of Filing Person (Offerors))
COMMON STOCK, PAR VALUE $0.001 PER SHARE
(Title of Class of Securities)
70321E104
(CUSIP Number of Class of Securities)
WILLIAM G. GREEN
SENIOR VICE PRESIDENT, GENERAL COUNSEL AND SECRETARY
CHIRON CORPORATION
4560 HORTON STREET
EMERYVILLE, CALIFORNIA 94608
(510) 655-8750
with copies to:
ALISON S. RESSLER, ESQ.
MATTHEW G. HURD, ESQ.
c/o SULLIVAN & CROMWELL
1888 CENTURY PARK EAST
LOS ANGELES, CALIFORNIA 90067-1725
(310) 712-6600
(Name, address, and telephone numbers of
person authorized to receive notices and
communications on behalf of filing persons)
[ ] Check the box if the filing relates solely to preliminary communications
made before the commencement of a tender offer.
<PAGE>
Check the appropriate boxes below to designate any transactions to which the
statement relates:
[x] third-party tender offer subject to Rule 14d-1.
[ ] issuer tender offer subject to Rule 13e-4.
[ ] going-private transaction subject to Rule 13e-3.
[ ] 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: [ ]
This Amendment No. 5 amends and supplements the Tender Offer
Statement on Schedule TO, dated August 21, 2000, relating to the offer by
Picard Acquisition Corp. ("Merger Sub"), a Delaware Corporation and a wholly
owned subsidiary of Chiron Corporation, a Delaware corporation ("Parent"), to
purchase all of the outstanding shares of common stock, par value $0.001 per
share (the "Common Stock"), of PathoGenesis Corporation, a Delaware
corporation (the "Company"), together with the associated rights to purchase
Series A Junior Preferred Stock (the "Rights") issued pursuant to the Rights
Agreement, dated as of June 26, 1997, as amended, between the Company and
Harris Trust and Savings Bank (the Common Stock and the Rights together being
referred to herein as the "Shares"), at a price of $38.50 per Share, net to
the seller in cash, upon the terms and subject to the conditions set forth in
the Offer to Purchase, dated August 21, 2000 (the "Offer to Purchase"), a
copy of which was attached as Exhibit (a)(1) to Schedule TO, and in the
related Letter of Transmittal, a copy of which was attached thereto as
Exhibit (a)(2).
ITEM 12. EXHIBITS
Item 12 is hereby amended to add the following:
(a)(14) Slides shown during a presentation to analysts, dated September
14, 2000.
(a)(15) Question and Answer Communication distributed to PathoGenesis
employees entitled "Questions and Answers for the PathoGenesis
401(k) Plan."
<PAGE>
ITEM 13. INFORMATION REQUIRED BY SCHEDULE 13E-3
Not Applicable.
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.
Date: September 14, 2000
PICARD ACQUISITION CORP.
/s/ William G. Green
--------------------------
Name: William G. Green
Title: Director, Vice
President and Secretary
CHIRON CORPORATION
/s/ William G. Green
--------------------------
Name: William G. Green
Title: Senior Vice President,
Secretary and General
Counsel
