Company: RCUS
Filing Date: 2025-02-18
Form Type: 424B5
Source: 0001193125-25-028669
Chunk: 13

Company: Arcus Biosciences, Inc.
Filing Date: 2025-02-18
Form: 424B5
Chunk 13
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 capital requirements 
 and our needs for additional financing;                                                                          |

| • |     | our ability to develop, acquire and advance investigational products into, and successfully complete, clinical 
 trials;                                                                                                        |

| • |     | our initiation, timing, progress and results of future research and development programs, preclinical studies and 
 clinical trials;                                                                                                  |

| • |     | our ability to obtain and maintain intellectual property rights covering our investigational products; |

| • |     | our expectations regarding the developments and projections relating to our competitors; |

| • |     | our expectations regarding our industry; and |

| • |     | our expectations as to the effect that geopolitical instability and public health outbreaks will have on our 
 company.                                                                                                     |

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “could,” “would,” “expect,” “plan,” “anticipate,” “believe,” “estimate,” “project,” “predict,” “potential” and similar expressions intended to identify forward-looking statements. These statements reflect our current views with respect to future events and are based on assumptions and are subject to risks and uncertainties. Given these S-9

uncertainties, you should not place undue reliance on these forward-looking statements. We discuss in greater detail many of these risks and uncertainties under the heading “Risk
Factors” contained in this prospectus supplement and accompanying prospectus and in our most recent Quarterly Report on Form 10-Q for the quarter ended September 30, 2024, as updated or superseded by
the risks and uncertainties described under similar headings in our subsequent filings under the Exchange Act, each of which is incorporated by reference into this prospectus supplement and accompanying prospectus in their entirety. Also, these
forward-looking statements represent our estimates and assumptions only as of the date of the document containing the applicable statement. Unless required by law, we undertake no obligation to update or revise any forward-looking statements to
reflect new information or future events or developments. Thus, you should not assume that our silence over time means that actual events are bearing out as expressed or implied in such forward-looking statements. You should read this prospectus
supplement and accompanying prospectus together with the documents we have filed with the SEC that are incorporated by reference and any free writing prospectus that we may authorize for use in connection with this offering completely and with the
understanding that our actual future results may be materially different from what we expect. We qualify all of