Company: RCUS
Filing Date: 2025-02-18
Form Type: 424B5
Source: 0001193125-25-028669
Chunk: 16

Company: Arcus Biosciences, Inc.
Filing Date: 2025-02-18
Form: 424B5
Chunk 16
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 and settlement of restricted stock units granted after 
 September 30, 2024;                                                                                               |

| • |     | up to an aggregate of 3,361,786 shares of common stock reserved for issuance pursuant to future awards under our                                                                                     
 Equity Incentive Plan, as of September 30, 2024, as well as any annual automatic increases in the number of shares of our common stock reserved for future issuance under the Equity Incentive Plan; |

| • |     | up to an aggregate of 2,694,420 shares of common stock reserved for issuance pursuant to future awards under our 
 Inducement Plan, as of September 30, 2024;                                                                       |

| • |     | up to an aggregate of 2,902,327 shares of common stock reserved for issuance under our Purchase Plan, as of                                                         
 September 30, 2024, as well as any annual automatic increases in the number of shares of our common stock reserved for future issuance under the Purchase Plan; and |

| • |     | any of the shares of our common stock that may be issued and sold to Gilead pursuant to the Stock Purchase 
 Agreement, which, as of September 30, 2024, was up to an aggregate of 3,020,000 shares.                    |

S-12

To the extent that any options are exercised, restricted stock units vest and settle, new options or
restricted stock units are issued under our equity incentive plans or we otherwise issue additional shares of common stock in the future at a price less than the offering price, there may be further dilution to new investors purchasing common stock
in this offering. In addition, we may choose to raise additional capital because of market conditions or strategic considerations, even if we believe that we have sufficient funds for our current or future operating plans. If we raise additional
capital through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders.

S-13

MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS FOR NON-U.S.HOLDERS The following discussion is a summary of the material U.S. federal income tax consequences to Non-U.S.Holders (as defined below) of the purchase, ownership and disposition of our common stock issued pursuant to this offering, but does not purport to be a complete analysis of all potential tax effects. The effects of other U.S. federal tax laws, such as estate and gift tax laws