QuickLinks -- Click here to rapidly navigate through this document
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, DC 20549
SCHEDULE 14D-9
SOLICITATION/RECOMMENDATION STATEMENT UNDER
SECTION 14(d)(4) OF THE SECURITIES EXCHANGE ACT OF 1934
(AMENDMENT NO. 4)
GENSET
(Name of Subject Company)
GENSET
(Name of Person Filing Statement)
Ordinary Shares, Nominal Value € 3.00 per share
American Depositary Shares, Each Representing One-Third of One Ordinary Share
(Title of Class of Securities)
37244T104
(CUSIP Number of Class of Securities)
Malcolm Bates
General Counsel
Genset
24, rue Royale
75008 Paris, France
(33) 1.55.04.59.00
(Name, Address and Telephone Number of Person Authorized to Receive
Notices and Communications on Behalf of the Person Filing this Statement)
With a copy to:
Manuel A. Orillac, Esq.
Shearman & Sterling
114, avenue des Champs-Elysées
75008 Paris, France
(33) 1.53.89.70.00
o | | Check the box if the filing relates solely to preliminary communications made before the commencement of a tender offer. |
This Amendment No. 4 amends and supplements the Solicitation/Recommendation Statement on Schedule 14D-9 filed by Genset with the Securities and Exchange Commission (the "Commission") on July 16, 2002, as amended by Amendments No. 1, No. 2 and No. 3 filed with the Commission on August 21, 2002, September 3, 2002 and September 23, 2002, respectively, (the "Schedule 14D-9"). The Schedule 14D-9 relates to the tender offer by Serono France Holding S.A. (the "Purchaser"), a wholly-owned subsidiary of Serono S.A. The above-referenced tender offer is disclosed in a Tender Offer Statement on Schedule TO, which was filed by the Purchaser and Serono S.A. with the Commission on July 16, 2002 (as amended, the "Schedule TO"), and is made upon the terms and subject to the conditions set forth in the U.S. Offer to Purchase dated July 16, 2002 and filed as Exhibit 99(a)(1) to the Schedule TO (the "Offer to Purchase") and the related Letter of Transmittal and Forms of Acceptance (which, as they may be amended and supplemented from time to time, constitute, together with the Offer to Purchase, the "U.S. Offer").
Item 9. Exhibits.
Item 9 of the Schedule 14D-9 is hereby amended and supplemented by adding the following exhibit:
(a)(8) Letter from Mr. Marc Vasseur, Chairman of Genset, to security holders, dated October 3, 2002.
2
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.
| | By: | | /s/ MARC VASSEUR Marc Vasseur Chairman and Chief Executive Officer |
Dated: October 3, 2002
3
QuickLinks
SIGNATURE