TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1)

OF THE SECURITIES EXCHANGE ACT OF 1934

Amendment No. 1

Common Stock, par value $0.001 per share

(Title of Class of Securities)

34962G208

(CUSIP Number of Class of Securities)

Hemamalini (Malini) Moorthy

argenx BV

Industriepark Zwijnaarde 7

9052 Zwijnaarde (Ghent)

Belgium

+31(0)10 70 38 441

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications on Behalf of Filing Persons)

Copies to:

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

If applicable, check the appropriate box(es) below to designate the appropriate rule provision(s) relied upon:

This Amendment No. 1 (this “Amendment”) to Schedule TO amends and supplements the Tender Offer Statement on Schedule TO filed with the Securities and Exchange Commission on August 6, 2026 (together with any subsequent amendments and supplements thereto, the “Schedule TO”), by Avena Merger Sub Inc., a Delaware corporation (“Purchaser”), and wholly owned subsidiary of argenx BV, a private company with limited liability (besloten vennootschap) organized under Belgian law (“Parent”). The Schedule TO relates to the offer by Purchaser to acquire all of the outstanding shares of common stock, par value $0.001 per share (the “Shares”), of Forte Biosciences, Inc., a Delaware corporation (“Forte”), for $77.00 per Share, net to the seller in cash, without interest, subject to any applicable withholding taxes, upon the terms and conditions set forth in the Offer to Purchase, dated August 6, 2026 (as it may be amended or supplemented from time to time, the “Offer to Purchase”) and in the related Letter of Transmittal (as it may be amended or supplemented from time to time, the “Letter of Transmittal” and, together with the Offer to Purchase, the “Offer”), copies of which are attached to the Schedule TO as Exhibits (a)(1)(i) and (a)(1)(ii), respectively.

All information contained in the Offer to Purchase (including Schedule I to the Offer to Purchase) and the accompanying Letter of Transmittal is hereby expressly incorporated herein by reference in response to Items 1 through 9 and Item 11 of the Schedule TO and is supplemented by the information specifically provided in this Amendment. This Amendment should be read together with the Schedule TO. Capitalized terms used and not otherwise defined in this Amendment have the meanings given to such terms in the Offer to Purchase.

The Offer to Purchase and Items 1 through 9 and Item 11 of the Schedule TO, to the extent such Items incorporate by reference the information contained in the Offer to Purchase, are hereby amended and supplemented as follows:

“On August 6, 2026, Parent issued a press release announcing the commencement of the Offer. The full text of the press release is filed as Exhibit (a)(5)(v) to the Schedule TO and is incorporated herein by reference.”

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

After due inquiry and to the best knowledge and belief of the undersigned, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Date: August 6, 2026