The goal of this clinical trial is to learn if KQB365 works to treat advanced solid tumor cancer in adults. It will also learn about the safety of KQB365. The main questions it aims to answer are:

• What is the safe dose of KQB365 by itself, in combination with cetuximab, or in combination with KQB198?
• Does KQB365 alone, in combination with cetuximab, or in combination with KQB198 decrease the size of the tumor?
• What happens to KQB365 in the body?

Participants will:

• Receive KQB365 infusion weekly alone, in combination with cetuximab, or in combination with oral KQB198.
• Visit the clinic about 9 times in the first 6 weeks, and then once every week after that.

Inclusion Criteria:

• PART 1 (monotherapy and combo therapy with KQB198): Histologically confirmed diagnosis of a solid tumor malignancy with either a KRAS G12C or KRAS G12S mutation.
• PART 1 (combo therapy with Cetuximab) & PART 2: Histologically confirmed diagnosis of adenocarcinoma of the colon or rectum with either a KRAS G12C or KRAS G12S mutation.
• Unresectable or metastatic disease
• No available treatment with curative intent
• Adequate organ function
• Measurable disease per RECIST v1.1

Exclusion Criteria:

• Active primary central nervous system tumors
• Cardiac abnormalities
• Active interstitial lung disease
• Unable to swallow or GI condition that prevents absorption for patients in KQB198 combination cohorts