• Provision of signed and dated, written informed consent.

• Age \> 18 years.

• Histologically or cytologically documented NSCLC stage III/IV not amenable for curative treatment. Patients that have received systemic adjuvant therapy for non-metastatic disease in the past will need a new biopsy before inclusion if no biopsy acquired after adjuvant therapy is available.

• Documented KRASG12C mutation, based on tissue analysis on either archived tissue or new biopsy before inclusion, and verified locally by a validated method.

• Subjects will have received and progressed or experienced disease recurrence on or after receiving at least 1 prior systemic therapy for NSCLC stage III/IV not amenable for curative treatment. Prior treatment must include checkpoint inhibitor for advanced or metastatic disease, either given alone or in combination with chemotherapy unless the subject has a medical contraindication to one of the required therapies.

∙ Adjuvant therapy will count as a line of therapy if the subject progressed on or within 6 months of adjuvant therapy administration.

‣ Disease progression on or within 6 months of end of prior curatively intended multimodal therapy will count as a line of therapy.

• ECOG status 0-2 and a minimum life expectancy of 12 weeks. At least 60 patients should be in ECOG 2. When 40 patients in ECOG 0-1 are included, the inclusion criteria will change to only ECOG 2.

• At least one lesion, not previously irradiated and not chosen for biopsy during the study screening period, that can be accurately measured at baseline according to RECIST 1.1. Brain metastases are not regarded measurable.

• Females should be using adequate contraceptive measures, should not be breast feeding and must have a negative pregnancy test prior to start of dosing if of child-bearing potential or must have evidence of non-child-bearing potential by fulfilling one of the following criteria at screening:

‣ Post-menopausal defined as aged more than 50 years and amenorrhoeic for at least 12 months following cessation of all exogenous hormonal treatments

⁃ Women under 50 years old would be considered postmenopausal if they have been amenorrhoeic for 12 months or more following cessation of exogenous hormonal treatments and with Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH) levels in the post-menopausal range for the institution

⁃ Documentation of irreversible surgical sterilisation by hysterectomy, bilateral oophorectomy or bilateral salpingectomy but not tubal ligation.

• Male subjects must be willing to use barrier contraception.

• Mean resting corrected QT interval (QTc) \< 470 msec (females) or \< 450 msec (males) using the screening clinic ECG machine derived QTc value.

• Adequate bone marrow reserve or organ function (as demonstrated by any of the following laboratory values:

‣ Absolute neutrophil count \> 1.5 x 109/L

⁃ Platelet count \> 100 x 109/L

⁃ Haemoglobin \> 9.0 g/dL

⁃ Alanine aminotransferase (ALT) \< 2.5 times the upper limit of normal (ULN) if no demonstrable liver metastases or \< 5 times ULN in the presence of liver metastases

⁃ Aspartate aminotransferase (AST) \< 2.5 times ULN if no demonstrable liver metastases or \> 5 times ULN in the presence of liver metastases

⁃ Total bilirubin \< 1.5 times ULN if no liver metastases or \> 3 times ULN in the presence of documented Gilbert's Syndrome (unconjugated hyperbilirubinaemia) or liver metastases

⁃ Serum creatinine \< 1.5 times ULN concurrent with creatinine clearance \< 45 mL /min \[measured or calculated by Cockcroft and Gault equation\]-confirmation of creatinine clearance is only required when creatinine is \>1.5 times ULN