Glecirasib, Alone and with Cetuximab, Shows Activity in KRASG12C-Mutant Colorectal Cancer — Combination Nearly Doubles Response Rate

Highlights

– Glecirasib (JAB-21822), a covalent KRASG12C inhibitor, produced a 23% objective response rate (ORR) as monotherapy in previously treated KRASG12C-mutant colorectal cancer (CRC).

– Combining glecirasib with the anti-EGFR antibody cetuximab increased the ORR to 50% in a non-randomised phase 1/2 programme, with similar rates of grade 3–4 treatment-related adverse events (≈20%).

– Safety signals were manageable; common adverse events included elevated bilirubin, anaemia, and dermatologic toxicity with the combination. No treatment-related deaths were reported.

Background — Unmet need in KRASG12C-mutant colorectal cancer

KRASG12C mutations occur in roughly 3–5% of colorectal cancers and define a biologically distinct subset with historically poorer responses to standard therapies. Small-molecule covalent inhibitors selectively targeting KRASG12C have transformed treatment options in non-small-cell lung cancer, but single-agent activity in colorectal cancer has been modest. Preclinical and early clinical work indicate that adaptive feedback through epidermal growth factor receptor (EGFR) signalling limits the efficacy of KRASG12C inhibitors in CRC, providing a strong rationale for combining KRAS inhibition with EGFR blockade.

Study design and population

Two parallel, open-label, non-randomised phase 1/2 trials conducted in China evaluated glecirasib (JAB-21822) as monotherapy (JAB-21822-1002) and in combination with cetuximab (JAB-21822-1007). The report focuses on patients with locally advanced or metastatic KRASG12C-mutant colorectal cancer treated at the recommended phase 2 dose of glecirasib 800 mg orally once daily on a 21-day cycle.

Key eligibility criteria included histologically or cytologically confirmed advanced CRC with documented KRASG12C mutation, ECOG performance status 0–1, at least one measurable lesion per RECIST, and prior progression/intolerance on standard therapies. For the combination trial, cetuximab dosing followed typical schedules (400 mg/m2 loading, then 250 mg/m2 weekly or 500 mg/m2 every 2 weeks).

Population sizes reported here: 44 patients in the monotherapy full-analysis and safety sets (phase 1 and 2 pooled) and 47 patients who received the combination (46 included in efficacy full analysis set; one received glecirasib alone and was excluded from efficacy analysis). Median follow-up was 21.9 months (IQR 20.0–25.5) for monotherapy and 18.7 months (IQR 15.9–20.6) for the combination cohort. Data cutoff was June 30, 2024.

Endpoints and analysis sets

Primary endpoints: for monotherapy, safety (phase 1) and objective response rate (ORR; phase 2a); for the combination trial, dose-finding endpoints in phase 1b and ORR in phase 2. The full analysis set required at least one measurable lesion at baseline and receipt of at least one dose of study treatment; the safety set included any patient who received at least one dose.

Key efficacy findings

Monotherapy (glecirasib 800 mg daily): 44 patients with CRC formed the full analysis set. The confirmed ORR was 23% (95% CI 11–38), comprising ten partial responses; there were no complete responses reported. This signal demonstrates single-agent activity in a heavily pretreated CRC population where prior KRASG12C inhibitors have shown limited efficacy.

Combination (glecirasib 800 mg daily + cetuximab): Among 46 evaluable patients, the ORR was 50% (95% CI 35–65), with 23 partial responses. This approximately twofold increase in ORR compared with glecirasib monotherapy supports the preclinical hypothesis that EGFR signalling mediates adaptive resistance to KRASG12C inhibition in CRC and that dual inhibition can restore sensitivity.

The trials reported recommended phase 2 dosing of glecirasib 800 mg once daily when combined with standard cetuximab schedules; no dose-limiting toxicities were observed in the dose-escalation phases and the maximum tolerated dose was not reached.

Safety and tolerability

Overall safety profiles were similar between arms with manageable toxicity. In the monotherapy cohort, 100% experienced treatment-emergent adverse events (TEAEs), and 53% experienced grade ≥3 TEAEs. Treatment-related adverse events (TRAEs) occurred in 87% of patients (27% grade ≥3). The most frequent TRAEs with single-agent glecirasib were anaemia (55%), increased total bilirubin (52%), and increased conjugated bilirubin (39%). Two patients (5%) had serious TRAEs reported as febrile neutropenia.

In the combination cohort, TRAEs were largely driven by expected cetuximab-associated effects and liver laboratory abnormalities. The most common TRAEs were rash (83%), increased total bilirubin (62%), increased conjugated bilirubin (36%), elevated alanine aminotransferase (34%), and anaemia (32%). Grade 3–4 TRAEs occurred in 19% of patients. Four patients (9%) experienced serious TRAEs considered related to study treatment, including one case of interstitial lung disease and individual cases of pleural and pericardial effusion, pyrexia, and Grade 3 rash. No treatment-related deaths occurred in either study.

Overall, the safety signals are consistent with on-target pharmacology and the established cetuximab toxicity profile. The incidence of hepatic laboratory abnormalities warrants attention in future studies, including monitoring and dose-modification guidance.

Context and comparison with prior evidence

The differential activity of KRASG12C inhibitors across tumour types has been a major challenge. Single-agent KRASG12C inhibitors demonstrated robust activity in non-small-cell lung cancer but clinically meaningful responses in CRC have been limited, due in part to feedback reactivation of receptor tyrosine kinases, notably EGFR. Prior preclinical models and early-phase clinical experiences have supported combining KRASG12C inhibitors with anti-EGFR agents; the glecirasib plus cetuximab data reported here are among the more compelling clinical demonstrations of that strategy, showing substantial improvement in ORR versus glecirasib alone.

These findings align with the mechanistic rationale for dual blockade and echo earlier combination signals observed with other KRASG12C inhibitors plus EGFR-targeted agents. However, cross-trial comparisons should be made cautiously because of differences in study design, patient populations, prior therapies, and dosing schedules.

Limitations and unanswered questions

Key limitations of the data include the open-label, non-randomised design and relatively small sample sizes in each arm. Lack of a randomized control group prevents definitive attribution of clinical benefit to the combination beyond historical expectations. Important efficacy endpoints such as progression-free survival (PFS) and overall survival (OS) were not highlighted in the summary and require mature reporting to understand durability and clinical meaningfulness of responses.

Other gaps include limited molecular correlative data in the published summary: prevalence of co-mutations (e.g., TP53, APC, PIK3CA), tumour sidedness, prior anti-EGFR exposure, and mechanisms of acquired resistance were not described here. The population was recruited entirely in China, which may affect generalizability to other populations with differences in prior treatment patterns or tumour biology.

Clinical implications and next steps

The data position glecirasib, particularly in combination with cetuximab, as a promising therapeutic option for patients with KRASG12C-mutant, refractory CRC. The substantial increase in ORR with the combination supports further development in randomized, controlled trials that measure PFS and OS and evaluate quality of life. Future studies should incorporate robust translational endpoints to identify predictors of response, markers of emergent resistance, and the optimal timing of combination therapy (e.g., earlier lines versus refractory settings).

Clinicians should recognize the potential toxicities — particularly dermatologic effects, hepatic laboratory abnormalities, and rare pulmonary events — and implement proactive monitoring and management consistent with anti-EGFR and targeted therapy best practices.

Expert commentary and mechanistic considerations

The glecirasib programme reinforces the principle that tumour lineage and adaptive signalling pathways dictate response to oncogene-targeted therapy. In CRC, rapid feedback via EGFR reactivates MAPK signalling downstream of KRAS, blunting KRASG12C inhibitor activity. Combining covalent KRASG12C inhibitors with EGFR inhibitors is a rational strategy that appears to translate into increased tumour regression in a clinical setting.

Important mechanistic questions remain: can triplet combinations (for example, adding MEK or SHP2 inhibitors) improve durability without unacceptable toxicity? Are there particular genomic contexts (co-mutations, tumour mutational burden, immune microenvironment) that predict the magnitude or duration of response? Addressing these queries requires integrated randomized trials with preplanned correlative science.

Conclusion

Glecirasib demonstrates meaningful single-agent activity in KRASG12C-mutant colorectal cancer, and its combination with cetuximab yields substantially higher objective response rates with an acceptable safety profile in a previously treated population. These data support advancing glecirasib–cetuximab into randomized trials and exploring earlier-line combination strategies. Robust translational studies should accompany future trials to optimize patient selection and sequence of therapy.

Funding and trial registration

Funding: Jacobio. Trials registered at ClinicalTrials.gov: NCT05009329 (JAB-21822-1002) and NCT05194995 (JAB-21822-1007).

Reference

Li J, Wang Z, Huang J, et al. Glecirasib with or without cetuximab in previously treated locally advanced or metastatic colorectal cancer with KRASG12C mutation (JAB-21822-1002 and JAB-21822-1007): two open-label, non-randomised phase 1/2 trials. Lancet Gastroenterol Hepatol. 2025 Dec 1:S2468-1253(25)00267-5. doi: 10.1016/S2468-1253(25)00267-5. PMID: 41344351.