Company: IMRX
Filing Date: 2025-09-25
Form Type: 424B5
Source: 0001104659-25-093438
Chunk: 1

Company: Immuneering Corp
Filing Date: 2025-09-25
Form: 424B5
Chunk 1
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 shares of Class A common stock at the closing of the concurrent private placement. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense. Investing in our securities involves risks. See “Risk Factors” beginning on page S-9of this prospectus supplement and in the documents incorporated by reference in this prospectus supplement concerning factors you should consider before investing in our securities.

| ​                                         | ​ | ​ | Per Share |   |        |   | ​ | ​ | Total |   |             |   | ​ |
|:------------------------------------------|:--|:--|:----------|:--|-------:|:--|:--|:--|:------|:--|------------:|:--|:--|
| Public offering price                     | ​ | ​ | ​         | $ |   9.23 | ​ | ​ | ​ | ​     | $ | 175,000,006 | ​ | ​ |
| Underwriting discounts and commissions(1) | ​ | ​ | ​         | $ | 0.5538 | ​ | ​ | ​ | ​     | $ |  10,500,000 | ​ | ​ |
| Proceeds to us, before expenses           | ​ | ​ | ​         | $ | 8.6762 | ​ | ​ | ​ | ​     | $ | 164,500,006 | ​ | ​ |

(1) We have agreed to reimburse the underwriters for certain of their expenses. See “Underwriting” beginning on page S-22of this prospectus supplement for more information about these arrangements. We have granted the underwriters the option to purchase up to 2,843,987 additional shares of our Class A common stock from us at the public offering price, less underwriting discounts and commissions. The underwriters may exercise this right at any time, in whole or in part, within 30 days following the date of this prospectus supplement. The underwriters expect to deliver the shares of Class A common stock to investors on or about September 26, 2025. The shares of Class A common stock will be delivered in book-entry form through the facilities of The Depository Trust Company on or about September 26, 2025. Joint Bookrunners Leerink Partners Oppenheimer & Co. The date of this prospectus