Company: RCUS
Filing Date: 2025-10-31
Form Type: 424B5
Source: 0001193125-25-260836
Chunk: 12

Company: Arcus Biosciences, Inc.
Filing Date: 2025-10-31
Form: 424B5
Chunk 12
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 share if the underwriters exercise their option to purchase additional
shares of common stock in full), representing the difference between the public offering price and our as adjusted net tangible book value per share as of September 30, 2025, after giving effect to this offering. Furthermore, if the
underwriters exercise their option to purchase additional shares of common stock, we raise additional capital by issuing equity securities, outstanding options are exercised or additional restricted stock units vest and settle, you could experience
further dilution. See the section below titled “Dilution” for a more detailed illustration of the dilution you would incur if you purchase common stock in this offering.

You may experience further dilution if we issue additional equity securities in future fundraising transactions.

To raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our
common stock at prices that may not be the same as the price per share in this offering. We may sell shares or other securities in any other offering at a price per share that is less than the price per share paid by investors in this offering, and
investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock, or securities convertible or exchangeable into common
stock, in future transactions may be higher or lower than the price per share paid by investors in this offering. Further, we have a significant number of stock options and restricted stock units outstanding. The exercise of outstanding stock
options and the vesting and settlement of restricted stock units may result in further dilution of your investment.

S-9

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS This prospectus supplement and accompanying prospectus, and the documents we have filed with the SEC that are incorporated herein by reference, contain “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Exchange Act. These statements relate to future events or to our future operating or financial performance and involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed or implied by the forward-looking statements. Forward-looking statements may include, but are not limited to, statements about:

| • |     | our expectations regarding our relationship with Gilead; |

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