This study is comparing the efficacy of the study drug RO7198457 versus “watchful waiting” in patients with circulating tumor DNA (ctDNA) positive, surgically resected Stage II/III rectal cancer, or Stage II (high risk)/Stage III colon cancer.

The standard of care beyond surgery and adjuvant chemotherapy, which is one that is applied mostly after surgery with the intention of preventing cancer coming back, is a “watchful waiting” strategy, where patients are observed without further therapeutic interventions unless and until the disease comes back. For patients who experience disease recurrence (cancer coming back), their expected chances of long-term survival are strongly reduced compared to patients diagnosed with the disease for the first time. There is therefore a strong need to develop effective treatments for these patients.

RO7198457 is an immunotherapy known as an autogene cevumeran. It is considered investigational, which means it is not yet approved by the U.S. Food and Drug Adminstration (FDA). 

Participants will be randomized to either receive R07198457 or the “watchful waiting” approach. Randomization is like flipping a coin and there is a 50/50 chance of being assigned to either group. 

All participants will receive treatment via an intravenous (IV) infusion.

Total study participation will last approximately 6 years.