Company: RCUS
Filing Date: 2025-10-31
Form Type: 424B5
Source: 0001193125-25-260836
Chunk: 6

Company: Arcus Biosciences, Inc.
Filing Date: 2025-10-31
Form: 424B5
Chunk 6
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| • |     | No unexpected safety signals were observed at the time of data cut off. The safety profile of domvanalimab plus        
 zimberelimab and chemotherapy was generally well tolerated and is consistent with that of anti-PD-1 plus chemotherapy. |

Concurrent with our first presentation of this data at European Society for Medical Oncology (“ESMO”) congress in October 2025, these data were published in Nature Medicine. Adenosine-Pathway Program (quemliclustat) In October 2025, we completed enrollment of PRISM-1,a Phase 3 trial of quemliclustat combined with gemcitabine/nab-paclitaxelversus gemcitabine/nab-paclitaxelin first-line metastatic pancreatic ductal adenocarcinoma, within 12 months of study initiation.

S-3

Risks Associated with our Business Our business is subject to numerous risks. You should read these risks before you invest in our common stock. In particular, our risks include, but are not limited to, the following:

| • |     | We have a history of operating losses, have never generated any revenue from product sales and anticipate that we 
 will continue to incur significant losses for the foreseeable future.                                             |

| • |     | We may need to obtain additional funding. If we do not receive or are unable to raise additional capital when       
 needed, we may be forced to restrict our operations or delay, reduce or eliminate our product development programs. |

| • |     | If we are unable to obtain regulatory approval for our investigational products, or experience significant delays 
 in doing so, our business will be materially harmed.                                                              |

| • |     | Preliminary, topline and interim data from our clinical studies that we announce or publish from time to time are                                          
 subject to audit and verification procedures that could result in material changes in the final data and may change as more patient data become available. |

| • |     | Enrollment and retention of subjects in clinical trials is expensive and time consuming and can be made more                                                                                                                                        
 difficult or rendered impossible by competing treatments, clinical trials of competing investigational products, geopolitical instability and public health epidemics, each of which could result in significant delays and additional costs in our 
 product development activities, or in the failure of such activities.                                                                                                                                                                               |

| • |     | Serious adverse events, undesirable side effects or other unexpected properties of our investigational products                                                                                                                                  
 may be identified during development