Molecularly guided therapy in gastrointestinal malignancies: From established targets to resistance and emerging precision strategies

Table 2 Molecularly targeted therapies in colorectal cancer

Molecular target/pathway	Biomarker/alteration	Therapeutic agent(s)	Current clinical role	Evidence grade	Key resistance mechanisms/emerging strategies	Representative sources
EGFR	RAS wild-type mCRC; BRAF status should also be considered for treatment selection and sequencing	Cetuximab; panitumumab	Established therapy in molecularly selected mCRC, used with chemotherapy or as monotherapy in appropriate later-line settings	A	Primary or acquired resistance may involve emergent KRAS/NRAS or BRAF alterations, HER2 or MET amplification, PI3K/PTEN pathway alterations, EGFR extracellular-domain mutations, gene fusions, and intratumoral heterogeneity. ctDNA-guided rechallenge is an emerging strategy in selected patients	Kasi et al[8]; Khelwatty et al[9]; Leite et al[10]; Li et al[14]
VEGF-A	No validated predictive biomarker	Bevacizumab	Established anti-angiogenic therapy, generally combined with chemotherapy in first-line and subsequent-line treatment strategies	A	Adaptive angiogenesis, vascular heterogeneity, hypoxia-driven adaptation, and activation of alternative pro-angiogenic pathways. Biomarker discovery and combinations with immunotherapy remain under investigation	Colombo and Porretto[13]; Li et al[14]; Jacobsen et al[16]
VEGF-A/VEGF-B/PlGF	No validated predictive biomarker	Aflibercept	Established second-line treatment in combination with chemotherapy after progression on an oxaliplatin-containing regimen in appropriate patients	A	Alternative angiogenic pathway activation, vascular remodeling, and endothelial adaptation	Li et al[14]; Fakih[17]
VEGFR-2	No validated predictive biomarker	Ramucirumab	Established second-line treatment in combination with chemotherapy in selected patients previously treated with bevacizumab-, oxaliplatin-, and fluoropyrimidine-based therapy	A	Compensatory angiogenic signaling, vascular remodeling, and microenvironmental adaptation	Li et al[14]
VEGFR1–3 and multiple angiogenic/tumor-signaling kinases	No validated predictive biomarker	Regorafenib	Established later-line treatment for previously treated or refractory mCRC	A	Multikinase pathway escape, adaptive angiogenesis, and tumor–microenvironment interactions. Toxicity and performance status are important treatment considerations	Li et al[14]; Jacobsen et al[16]
VEGFR1–3	No validated predictive biomarker	Fruquintinib	Established later-line treatment for previously treated or refractory mCRC	A	Adaptive angiogenesis and vascular pathway redundancy; combination strategies are under investigation	Li et al[14]; Jiao et al[18]
BRAF/MAPK	BRAF V600E mutation	Encorafenib + cetuximab, with or without binimetinib depending on the treatment context	Established targeted therapy for previously treated BRAF V600E-mutant mCRC	A	MAPK pathway reactivation, feedback signaling, and bypass activation. Combined BRAF/EGFR inhibition, with or without MEK inhibition, is intended to suppress pathway escape	Kopetz et al[24]; Ambrosini et al[22]; Li et al[14]
HER2	HER2 amplification and/or overexpression; assessment requires an appropriate validated assay	Trastuzumab-based dual HER2 blockade; tucatinib-based combinations; trastuzumab deruxtecan and other HER2-directed ADCs	Clinically actionable target in selected HER2-positive mCRC, particularly in RAS wild-type disease and appropriate later-line settings	B	HER2 heterogeneity, HER2 loss, bypass signaling, downstream pathway reactivation, and acquired resistance. Next-generation ADCs and combination HER2-directed strategies are under investigation	Sartore-Bianchi et al[34]; Pizzamiglio et al[33]; Benli et al[38]
KRAS G12C	KRAS G12C mutation	KRAS G12C inhibitor combined with EGFR inhibition	Molecularly selected targeted therapy for KRAS G12C-mutant mCRC, generally in previously treated disease	A	EGFR-mediated feedback, MAPK pathway reactivation, secondary KRAS alterations, and downstream pathway escape. Combination strategies aim to improve pathway suppression and delay resistance	Li et al[14]; Manzi et al[39]
NTRK	NTRK gene fusion	Larotrectinib; entrectinib	Tissue-agnostic targeted therapy for fusion-positive tumors, including rare CRC cases	B	Acquired kinase-domain mutations and bypass signaling may lead to resistance; next-generation TRK inhibitors are being developed for resistant disease	Li et al[40]
RET	RET fusion	Selective RET inhibitors	Rare molecularly selected indication; CRC-specific evidence remains limited	B	Acquired resistance, limited tumor-specific clinical evidence, and uncertainty regarding optimal sequencing; prospective evaluation continues	Li et al[40]
BRAF/MAPK	Non-V600E BRAF alterations	Molecularly matched BRAF-, MEK-, and/or EGFR-directed combinations	Limited clinical evidence in selected patients; not equivalent to the established BRAF V600E treatment pathway	C	Biological heterogeneity and variable sensitivity according to the specific BRAF alteration. Molecularly matched combinations require further clinical validation	Sasaki et al[26]; Ambrosini et al[22]
MET/PI3K/PTEN and related bypass pathways	MET amplification, PIK3CA alterations, PTEN loss, or other putative resistance-associated alterations	Molecularly matched combinations	Investigational strategies aimed at overcoming resistance to EGFR inhibition	C	These alterations may contribute to intrinsic or acquired resistance, although their predictive and therapeutic value is context-dependent. Multi-target inhibition and biomarker-guided approaches remain under investigation	Khelwatty et al[9]; Leite et al[10]

Evidence classification: Evidence levels were assigned according to the maturity and clinical validation of the available data. Established: Supported by prospective randomized trials and/or incorporated into clinical guidelines or routine standard-of-care practice; Clinically supported: Supported by prospective clinical studies, non-randomized comparative studies, or consistent clinical evidence but with more limited validation; Emerging/investigational: Supported by early-phase clinical trials, small prospective or retrospective studies, or preliminary clinical data. Preclinical: Supported primarily by in vitro, animal, organoid, or other laboratory-based studies without sufficient clinical validation. Evidence grades describe the maturity of the evidence and do not necessarily indicate the magnitude of treatment benefit. ADC: Antibody–drug conjugate; BRAF: B-Raf proto-oncogene; EGFR: Epidermal growth factor receptor; FGFR: Fibroblast growth factor receptor; MAPK: Mitogen-activated protein kinase; mCRC: Metastatic colorectal cancer; PDGFR: Platelet-derived growth factor receptor; PI3K: Phosphatidylinositol-3-kinase; PlGF: Placental growth factor; PTEN: Phosphatase and tensin homolog; RET: Rearranged during transfection; T-DXd: Trastuzumab deruxtecan; TRK: Tropomyosin receptor kinase; VEGF: Vascular endothelial growth factor; VEGFR: Vascular endothelial growth factor receptor; ctDNA: Circulating tumor DNA.