This study is to evaluate the safety and tolerability of JAB-21822 monotherapy and combination therapy in adult participants with advanced solid tumors harboring KRAS G12C mutation.

The primary objective of this study is to evaluate the safety and tolerability of JAB-21822 monotherapy to determine the MTD and PR2D during Dose Escalation phase; then to evaluate preliminary antitumor activity when JAB-21822 administered alone and combination with cetuximab during Dose Expansion phase in adult participants with advanced solid tumors harboring KRAS G12C mutation.

Inclusion Criteria:

• Participants must be able to provide an archived tumor sample
• Histologically or cytologically confirmed solid tumors with KRAS G12C mutation
• Must have received at least 1 prior standard therapy
• Must have at least 1 measurable lesion per RECIST v1.1
• Must have adequate organ function
• Must be able to swallow and retain orally administered medication

Exclusion Criteria:

• Has brain or spinal metastases, except if treated and no evidence of radiographic progression or hemorrhage for at least 28 days
• Active infection requiring systemic treatment within 7 days
• Active HBV or HCV
• Any severe and/or uncontrolled medical conditions
• LVEF ≤50% assessed by ECHO or QTcF
• QT interval >470 msec
• Experiencing unresolved CTCAE 5.0 Grade >1 toxicities