Company: IOBT
Filing Date: 2025-05-23
Form Type: S-3
Source: 0001193125-25-125831
Chunk: 23

Company: IO Biotech, Inc.
Filing Date: 2025-05-23
Form: S-3
Chunk 23
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, modifies or supersedes such earlier statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus or such applicable prospectus supplement. You can obtain any of the filings incorporated by reference into this prospectus or any applicable prospectus supplement through us or from the SEC through the SEC’s website at http://www.sec.gov. Upon written or oral request, we will provide, without charge, a copy of any or all of the reports and documents referred to above which have been incorporated by reference into this prospectus or any applicable prospectus supplement. Prospective and current investors may obtain documents incorporated by reference in this prospectus or any 19

applicable prospectus supplement by requesting them in writing or by telephone from us at our executive offices at:

IO Biotech, Inc.

Ole
Maaløes Vej 3

DK-2200 Copenhagen N

Denmark

Our reports and documents incorporated
by reference herein may also be found in the “Investors” section of our website at www.iobiotech.com. The content of our website and any information that is linked to or accessible from our website (other than our filings with the SEC that
are incorporated by reference, as set forth under “Incorporation of Certain Documents by Reference”) is not incorporated by reference into this prospectus or any applicable prospectus supplement and you should not consider it a part of
this prospectus, any applicable prospectus supplement, or the registration statement.

20

Up to 5,623,664 Shares of Common Stock Offered by the Selling Stockholders

PROSPECTUS

, 2025

We have not authorized any dealer, salesperson or other person to give any information or represent anything not contained in this prospectus. You must not
rely on any unauthorized information. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus does not offer to sell any securities in any jurisdiction where it is unlawful. Neither the delivery
of this prospectus, nor any sale made hereunder, shall create any implication that the information in this prospectus is correct after the date hereof.

PART II INFORMATION NOT REQUIRED IN PROSPECTUS Item 14. Other Expenses of Issuance and Distribution. The fees and expenses payable by us in connection with this registration statement are estimated as follows:

| SEC Registration Fee            |     | $ |      878 |
| Accounting Fees and Expenses