KRAS was once the classic example of an “undruggable” cancer target. For decades, its biology seemed to resist therapeutic intervention: the protein had no obvious binding pocket, its affinity for GTP was extremely high, and attempts to block downstream signaling often led to pathway reactivation. In non-small cell lung cancer (NSCLC), this problem was particularly important because KRAS mutations are among the most common oncogenic alterations, and KRAS G12C accounts for approximately 13–14% of NSCLC cases.
That landscape changed with the development of covalent KRAS G12C inhibitors. Sotorasib and adagrasib moved KRAS G12C from a long-standing therapeutic frustration to an actionable biomarker in previously treated NSCLC. Now, the field is entering its next phase: first-line combinations, more selective next-generation inhibitors, CNS-focused strategies, and a deeper confrontation with resistance. The question is no longer whether KRAS G12C can be targeted. The question is how durable, how early, and in which molecular subgroup KRAS G12C inhibitors in NSCLC can deliver the greatest benefit.
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How KRAS G12C Became Targetable
The key breakthrough came from structural biology. In 2013, Ostrem and colleagues identified a previously hidden allosteric pocket near the switch-II region of KRAS G12C. This pocket could be accessed when KRAS was in its inactive GDP-bound state, allowing covalent inhibitors to bind the mutant cysteine at codon 12 while sparing wild-type KRAS (Ostrem et al., 2013).
This approach was important because it created mutation-specific targeting. KRAS G12C contains a reactive cysteine residue that is absent in wild-type KRAS, enabling selective drug binding. The clinical translation of this concept took years of medicinal chemistry optimization, but it ultimately produced the first approved KRAS G12C inhibitors.
For thoracic oncology, this was a major turning point. Before this class emerged, patients with KRAS G12C-mutated NSCLC were generally treated with chemotherapy and immune checkpoint inhibitors, depending on PD-L1 expression and clinical context. Targeted therapy was not part of routine care for this subgroup.
Sotorasib Established The First Clinical Pathway
Sotorasib became the first approved KRAS G12C inhibitor after showing clinical activity in previously treated KRAS G12C-mutated NSCLC. In CodeBreaK 100, sotorasib produced an objective response rate of 37.1% and a median duration of response of 11.1 months in previously treated patients (Hong et al., 2020; Li et al., 2022).
The confirmatory phase III CodeBreaK 200 trial compared sotorasib with docetaxel in 345 patients with previously treated KRAS G12C-mutated NSCLC. Sotorasib significantly improved progression-free survival, with a median PFS of 5.6 months compared with 4.5 months for docetaxel and a hazard ratio of 0.66. Treatment-related grade 3 or higher adverse events occurred in 33% of patients receiving sotorasib and 40% receiving docetaxel, supporting a more favorable tolerability profile for the targeted agent (de Langen et al., 2023).
Overall survival was not significantly different between arms, with median OS of 10.6 months for sotorasib and 11.3 months for docetaxel. This result requires cautious interpretation because crossover was common; 34% of patients assigned to docetaxel later received a KRAS G12C inhibitor, including 26% who crossed over to sotorasib per protocol (de Langen et al., 2023). The trial also became part of a broader discussion about confirmatory endpoints, crossover, and the degree of benefit required for targeted therapies in the post-immunotherapy setting.
Adagrasib Added CNS Activity And Pharmacologic Differentiation
Adagrasib followed as another KRAS G12C inhibitor with important pharmacologic features. In the phase I/II KRYSTAL-1 trial, adagrasib showed an objective response rate of 42.9%, median duration of response of 8.5 months, median PFS of 6.5 months, and median OS of 12.6 months in previously treated KRAS G12C-mutated NSCLC (Jänne et al., 2022).
One clinically relevant distinction is CNS activity. Adagrasib has a longer half-life of approximately 23 hours and demonstrated central nervous system penetration in preclinical studies. In a dedicated KRYSTAL-1 CNS cohort, adagrasib showed intracranial activity in patients with untreated brain metastases (Negrao et al., 2023). This matters because CNS metastases are common in KRAS G12C-mutated NSCLC and can strongly affect survival, neurologic function, and quality of life.
The emergence of two approved agents created the first real targeted therapy framework for KRAS G12C-mutated NSCLC. However, second-line outcomes remain modest in duration, and resistance frequently develops within months. This has pushed the field toward earlier use and rational combinations.
The First-Line Question: KRYSTAL-7 Moves The Field Forward
The most closely watched development is the movement of KRAS G12C inhibition into the first-line setting. The rationale is straightforward. Many patients currently receive immunotherapy-based regimens first and a KRAS G12C inhibitor later, but not all patients remain fit enough to receive targeted therapy after progression. Bringing KRAS inhibition earlier may increase the number of patients exposed to effective targeted treatment.
KRYSTAL-7 is testing this strategy with adagrasib plus pembrolizumab in first-line advanced or metastatic KRAS G12C-mutated NSCLC. Updated phase II results presented at ASCO 2025 reported outcomes in 149 treated patients across PD-L1 expression levels. In patients with PD-L1 TPS ≥50%, adagrasib plus pembrolizumab produced an objective response rate of 59.3%, median duration of response of 26.3 months, and median PFS of 27.7 months (Jänne et al., 2025).
These results are clinically provocative, especially in comparison with historical outcomes for pembrolizumab monotherapy in PD-L1-high NSCLC. However, they should not yet be interpreted as practice-changing. The phase III portion of KRYSTAL-7 is ongoing and is expected to provide the definitive comparison of adagrasib plus pembrolizumab versus pembrolizumab alone in the PD-L1 TPS ≥50% population.
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Safety Will Matter In First-Line Combination Therapy
The safety profile of KRAS G12C inhibitor and immunotherapy combinations will be central to their clinical adoption. In KRYSTAL-7, liver enzyme elevations were among the most important adverse events. Alanine aminotransferase elevations occurred in 39.6% of patients overall, with grade 3/4 elevations in 11.4%. Aspartate aminotransferase elevations occurred in 35.6%, with grade 3/4 events in 14.1% (Jänne et al., 2025).
Treatment discontinuation due to hepatic toxicity occurred in a minority of patients, with 6.7% discontinuing pembrolizumab and 2.0% discontinuing adagrasib. The events were described as largely manageable and reversible, but careful monitoring will be necessary if this approach moves into routine first-line use (Jänne et al., 2025).
This issue is important because first-line therapy is often given to patients with longer expected treatment duration and better performance status. Any new regimen must show not only efficacy but also a safety profile that is acceptable compared with current immunotherapy-based standards.
Resistance Remains The Central Unsolved Problem
Despite major progress, resistance remains the defining limitation of KRAS G12C inhibitors in NSCLC. In the second-line setting, median PFS with sotorasib and adagrasib has generally remained around 6–7 months. Molecular studies at progression have shown that resistance is heterogeneous and can occur through both on-target and off-target mechanisms.
On-target mechanisms include secondary KRAS mutations that affect drug binding or restore KRAS pathway signaling, such as G12D, G12V, Y96D, and H95R/Q/L. Off-target mechanisms include activation of receptor tyrosine kinases such as EGFR, MET, and FGFR; alterations in parallel RAS pathway nodes such as NRAS mutation or BRAF amplification; downstream pathway activation through PI3K/AKT; and histologic or phenotypic transformation including epithelial-to-mesenchymal transition (Awad et al., 2021; Hallin et al., 2022).
This diversity makes resistance difficult to solve with a single strategy. It also explains why combination approaches are increasingly important, including KRAS G12C inhibitors with SHP2 inhibitors, SOS1 inhibitors, MEK inhibitors, EGFR-directed therapy, or other targeted agents.
STK11 And KEAP1 Define A Harder-To-Treat Subgroup
Baseline co-mutations also shape outcomes. STK11 and KEAP1 are among the most clinically important co-alterations in KRAS G12C-mutated NSCLC. STK11 mutations are present in approximately 20% of KRAS G12C-mutated NSCLC, while KEAP1 mutations were present in approximately 26% of patients in the CodeBreaK 200 population (Skoulidis et al., 2023).
These alterations are associated with inferior outcomes with both immunotherapy and KRAS G12C inhibition. STK11 is linked to immune evasion and metabolic reprogramming, while KEAP1 is associated with NRF2 pathway activation, oxidative stress adaptation, and drug resistance biology. Patients with both STK11 and KEAP1 wild-type tumors appear to represent a more responsive subgroup, while co-mutated tumors remain a major unmet need (Skoulidis et al., 2023).
This is why future KRAS G12C trials are increasingly likely to require biomarker stratification beyond KRAS G12C alone. The mutation identifies the target, but co-mutations influence the depth and durability of response.
Next-Generation KRAS G12C Inhibitors Are Advancing
Newer KRAS G12C inhibitors are being developed to improve potency, durability, and resistance coverage. Divarasib demonstrated an objective response rate of 53.4% and median PFS of 13.1 months in a phase I trial of patients with KRAS G12C-mutated NSCLC, suggesting activity that may exceed earlier agents, although cross-trial comparisons must be made cautiously (Sacher et al., 2023).
Divarasib is now being evaluated in phase III studies, including comparisons against approved KRAS G12C inhibitors in previously treated disease. LY3537982 is another next-generation KRAS G12C inhibitor in clinical development, with a distinct binding profile that may provide activity against selected resistance mutations.
The next chapter will likely involve both better drugs and better combinations. KRAS G12C inhibition may need to be paired with upstream blockade, downstream pathway inhibition, or immune-based therapy depending on the resistance mechanism and tumor co-mutation profile.
What This Means For Thoracic Oncology
The KRAS G12C story is one of the most important examples of modern precision oncology. A target considered biologically inaccessible for decades is now part of routine NSCLC treatment. Sotorasib and adagrasib created the first approved pathway. KRYSTAL-7 suggests that first-line adagrasib plus pembrolizumab could become a major strategy if phase III data confirm the phase II signal. Next-generation agents may improve response durability and address some resistance mechanisms.
At the same time, the field should remain cautious. KRAS G12C inhibitors are not curative, resistance is common, and co-mutations such as STK11 and KEAP1 can substantially modify outcomes. The future of KRAS G12C inhibitors in NSCLC will depend on more than target inhibition alone. It will require molecularly informed sequencing, better resistance monitoring, and rational combinations that match the biology of each tumor.
Key Takeaway
KRAS G12C inhibitors have transformed a once-undruggable target into a clinically actionable subtype of NSCLC. Sotorasib and adagrasib established proof of principle in previously treated disease, and first-line adagrasib plus pembrolizumab has produced a strong early signal in PD-L1-high tumors. However, resistance remains the major barrier. The next phase of progress will depend on next-generation inhibitors, biomarker-stratified treatment, and combinations designed to prevent or overcome pathway escape.