anti-EGFR Therapy Research Articles

Efficacy and safety of combination therapy with binimetinib, encorafenib, and cetuximab for BRAF non-V600E mutated metastatic colorectal cancer: Results from a phase 2 BIG BANG trial (EPOC1703).

3585 Background: BRAF mutations which are found in 8-12% of metastatic colorectal cancer (mCRC) can be classified into three groups; Class 1 and 2 tumors do not respond to anti-EGFR antibody therapy because of the RAS independent activity, while previous studies suggested potential anti-tumor activity of anti-EGFR antibody for class 3 tumor. Combination therapy with binimetinib, encorafenib, and cetuximab showed the substantial efficacy for BRAF V600E mutated mCRC in the BEACON CRC trial, however, the clinical activity of these triplet therapy for BRAF non-V600E mutated mCRC is unknown. Here, we conducted a multicenter phase 2 trial to assess the efficacy and safety of combination therapy with binimetinib, encorafenib, and cetuximab in patients with BRAF non-V600E mutated mCRC. Methods: We enrolled patients with RAS wild-type and BRAF non-V600E mutated mCRC, refractory or intolerant to at least one fluoropyrimidine-based chemotherapy, and no prior history of anti-EGFR antibody (primary analysis cohort) or refractory to prior anti-EGFR antibody (anti-EGFR antibody refractory cohort). Enrolled patients receive binimetinib (45 mg BID), encorafenib (300 mg QD), and cetuximab (initially 400 mg/m2 and subsequently 250 mg/m2, weekly) until disease progression or unacceptable toxicity. The primary endpoint was investigator-assessed confirmed objective response rate (ORR) in the primary analysis cohort with sample size of 21 patients. Results: Between May 2018 and March 2023, 12 and 20 patients were enrolled in the primary analysis cohort and the anti-EGFR antibody refractory cohort, respectively (same order in the following abstract). 7 and 19 patients had a history of ≥ 2 lines of previous chemotherapy, respectively. The most frequent mutation overall was BRAF D594G (n=14, 43.8%). There were each 2 responders in both cohorts, resulting in 16.7% (95%CI, 2.1-48.4%) and 10.0% (95%CI, 1.2-31.7%) of confirmed ORR, respectively. Among 7 patients harboring class 1 or 2 tumors in both cohorts combined, there were 2 responders (ORR 28.6%). Median progression-free survival was 3.3 months and 3.0 months, respectively. Grade 3 or higher adverse events occurred in 4 and 10 patients, respectively, and no new safety signals were identified. Conclusions: The combination therapy with binimetinib, encorafenib, and cetuximab showed modest efficacy for BRAF non-V600E mutated mCRC, with a manageable safety profile, although there was not enough statistical power due to slow accrual. Circulating-tumor DNA analyses at the timepoint of before and after treatment are ongoing. Clinical trial information: UMIN000031857. [Table: see text]

Survival benefit with regorafenib and/or trifluridine/tipiracil sequencing to rechallenge with anti-EGFR-based third-line regimens in metastatic colorectal cancer: A multicenter retrospective real-world subgroups comparison.

e15553 Background: Rechallenge with anti-EGFR drugs has recently proven therapeutic activity in a subset of RAS wild type (wt) metastatic colorectal cancer (mCRC) patients who had previously benefited from cetuximab- or panitumumab-based first-line regimen. Regorafenib (R) and Trifluridine/tipiracil (T) have been found to improve survival in patients with refractory mCRC. This real-life subgroup survival analysis focused on treatment with R and T, sequential or not, in patients who had received prior third-line anti-EGFR therapy. Methods: Clinical data of patients diagnosed with mCRC who received R and/or T between July 2012 and March 2022, were retrospectively collected from 13 Italian cancer institutes. The objective of this subgroup analysis was to compare overall survival (OS) and progression-free survival (PFS) in patients who received late-line R and/or T according to prior third-line anti-EGFR-based treatment. Results: The entire study enrolled 866 patients. 146 (16.8%) of them received the T/R sequence (T/R), 116 (13.3%) the reverse sequence (R/T), 325 (37.5%) T, and 279 (32.5%) R. For the purpose of this subgroup analysisi we identified 338 RAS wt patients (39%) who were eligible. Of these, 290/338 patients (85.8%) did not receive the previous third-line anti-EGFR therapy, while 48 patients (14.2%) did it (12 T/R, 10 R/T, 13 T, 13 R). When comparing T/R to R/T in patients who did not previously received third-line anti-EGFR drug rechallenge, we observed a statistically significant and clinically meaningful improvement in PFS. In detail, the median PFS benefit was 67,5% when treating patients with T/R sequence vs. the reverse sequence (11,4 vs. 3,7 months, respectively, ∆ = 7,7 months; p = < 0,0001; HR = 0,17; 95% CI = 0,09-0,32). In patients who received T/R or R/T following rechallenge with anti-EGFR drug, we also observed a comparable, albeit smaller and non-statistically significant, improvement in PFS (8.1 vs. 7.8 months, respectively; p = 0.22; HR 0,51; 95% CI = 0,17-1,50). There were no statistically significant differences in OS between these groups. Anti-EGFR rechallenge data analysis showed that the non-sequential administration of R and T had no statistically significant impact on survival outcomes. Conclusions: With the limit of the sample size, our retrospective subgroup analysis failed to validate the promising beneficial effects of anti-EGFR rechallenge prior to R and/or T treatment. A statistically significant longer PFS was only observed in patients with refractory metastatic colorectal cancer receiving T/R sequence without prior cetuxumab- or panitumumab-based regimens.

Phase IB/II first line panitumumab, irinotecan, trifluridine/tipiracil in RAS wild-type patients with metastatic colorectal cancer: PIT study.

e15532 Background: Trifluridine/tipiracil (TT) is an oral fluoropyrimidine (FP) currently used in later line therapy. Preclinical data have demonstrated synergistic activity when panitumumab (Pmab) or irinotecan (Ir) are combined with TT supporting use in combination schedules in early line protocols. PIT was a phase IB/II study determining the maximum tolerated dose (MTD), safety and tolerability of substituting FP with TT, combined with Pmab and Ir in RAS wild-type mCRC. Methods: Phase IB 3+3 design dose escalation study (Dose level 1: TT 20mg/m2 oral BD, Ir 150mg/m2 IV, Pmab 6mg/m2). Primary objective was MTD of the combination in RAS WT mCRC patients, either 1st or 2nd line. Treatment was administered in 14-day cycles. Pmab and Ir were administered intravenously on day 1 with TT dosed orally, bid, days 1-5. Once MTD was established the phase II expansion study was to enrol 50 previously untreated mCRC patients. Primary endpoint was modified to toxicity. Results: The study closed due to slow recruitment. 14 patients were enrolled from 6/18 to 10/21. Med follow up 23 months. Med age 59 yrs (range 37-74yrs). 60% were male. One patient each was BRAF MT and right sided. ECOG 0/1 50%/50%. Thirteen patients had PIT as first line, 57% had prior adjuvant therapy. There was one DLT in first 3 patients however based on additional toxicity data (Clin Cancer Res. 2020 Apr 1:1555) a decision was made to not dose escalate beyond level 1 and commence phase II. Overall Gd 3 toxicity: Acne/rash 46%, Diarrhoea 31%, Fatigue 8%, neutropenia 15%, hypomagnesaemia 23%. One patient had Gd 4 neutropenia and there was one treatment related death (neutropenic sepsis). 12 patients had evaluable disease, 58% PR, 42% SD. Survival: Med PFS 14.1 mths, Med OS 40.6mths and 12 mth OS 64%. Conclusions: The MTD was deemed TT 20mg/m2, irinotecan 150mg/m2 and panitumumab 6mg/kg. Toxicity was manageable however significant grade 3 diarrhoea and rash was seen. There was one toxic death contributed to therapy. Small numbers do make interpretation difficult however there is a signal of activity. The slow recruitment illustrates difficulty in exploring novel combinations in early lines and potentially the reluctance to consider first line anti-EGFR therapy. Clinical trial information: ACTRN12617001190392.

Early [18F]FDG PET/CT response evaluation after a single dose of anti-EGFR therapy as a predictive biomarker for treatment benefit in patients with advanced colorectal cancer.

Early [¹⁸F]FDG PET/CT response evaluation after a single dose of anti-EGFR therapy as a predictive biomarker for treatment benefit in patients with advanced colorectal cancer.

FDA Approval Summary: Fruquintinib for the Treatment of Refractory Metastatic Colorectal Cancer.

On November 8, 2023, the FDA approved fruquintinib, an inhibitor of vascular endothelial growth factor receptor (VEGFR)-1, -2, and -3, for the treatment of patients with metastatic colorectal cancer (mCRC) who have been previously treated with fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy, an anti-VEGF therapy, and if RAS wild-type and medically appropriate, an anti-EGFR therapy. Approval was based on Study FRESCO-2, a globally conducted, double-blind, placebo-controlled randomized trial. The primary endpoint was overall survival (OS). The key secondary endpoint was progression-free survival. A total of 691 patients were randomly assigned (461 and 230 into the fruquintinib and placebo arms, respectively). Fruquintinib provided a statistically significant improvement in OS with a hazard ratio (HR) of 0.66 [95% confidence interval (CI), 0.55, 0.80; P < 0.001]. The median OS was 7.4 months (95% CI, 6.7, 8.2) in the fruquintinib arm and 4.8 months (95% CI, 4.0, 5.8) for the placebo arm. Adverse events observed were generally consistent with the known safety profile associated with the inhibition of VEGFR. The results of FRESCO-2 were supported by the FRESCO study, a double-blind, single-country, placebo-controlled, randomized trial in patients with refractory mCRC who have been previously treated with fluoropyrimidine-, oxaliplatin-, and irinotecan-based chemotherapy. In FRESCO, the OS HR was 0.65 (95% CI, 0.51, 0.83; P < 0.001). FDA concluded that the totality of the evidence from FRESCO-2 and FRESCO supported an indication for patients with mCRC with prior treatment with fluoropyrimidine, oxaliplatin-, and irinotecan-based chemotherapy, an anti-VEGF biological therapy, and if RAS wild-type and medically appropriate, an anti-EGFR therapy.

Anti‑epidermal growth factor receptor monoclonal antibody therapy in locally advanced head and neck cancer: A systematic review of phase III clinical trials.

The present systematic review evaluated the effectiveness of anti-EGFR therapy in combination with radiotherapy (RT) or with chemoradiation compared with the existing standard of care for the treatment of locally advanced head and neck squamous cell carcinoma (LAHNSCC). The PubMed, SCOPUS, EMBASE and COCHRANE databases were searched and 12 phase III randomized controlled trials were included. The effectiveness of the anti-EGFR monoclonal antibody cetuximab was evaluated in nine trials. Nimotuzumab (one trial), zalutumumab (one trial) and panitumumab (one trial) were the monoclonal antibodies evaluated in the remaining three trials. One study tested the effectiveness of adding cetuximab to radical RT and found that patients with LAHNSCC exhibited improvement in locoregional control (LRC), overall survival (OS) and progression-free survival (PFS) compared with those of patients treated with RT alone. A total of three studies tested the effectiveness of adding an anti-EGFR agent to chemoradiation. Of these, a single institution study in which patients received cisplatin at 30 mg/m2 weekly, instead of the standard doses of 100 mg/m2 every 3 weeks or 40 mg/m2 every week, reported significant improvement in PFS with the addition of nimotuzumab to chemoradiotherapy without an improvement in overall survival. However, the other two studies indicated that, when added to standard chemoradiation, the anti-EGFR monoclonal antibodies cetuximab or zalutumumab did not improve survival outcomes. Two phase III trials evaluated RT plus an anti-EGFR agent compared with chemoradiation alone. Of these, one study reported inferior outcomes with cetuximab-RT in terms of OS and LRC, whereas the other study with panitumumab plus RT failed to prove the non-inferiority. Two trials evaluated induction chemotherapy followed by cetuximab-RT compared with chemoradiotherapy and reported no benefits in terms of OS or PFS. Furthermore, one study evaluated induction chemotherapy followed by cetuximab-RT compared with induction chemotherapy followed by chemoradiotherapy and found no improvement in OS or PFS. Finally, three phase III trials tested the effectiveness of cetuximab plus RT in the treatment of human papillomavirus-positive oropharyngeal carcinoma, and found it to be inferior compared with cisplatin-RT in terms of OS, PFS and failure-free survival. Based on the aforementioned findings, it is difficult to conclude that anti-EGFR therapy in any form has an advantage over conventional chemoradiation in the treatment of LAHNSCC.

Prognostic significance of EGFR, AREG and EREG amplification and gene expression in muscle invasive bladder cancer.

Muscle invasive bladder cancer (MIBC) remains a prevalent cancer with limited therapeutic options, obviating the need for innovative therapies. The epidermal growth factor receptor (EGFR) is a linchpin in tumor progression and presents a potential therapeutic target in MIBC. Additionally, the EGFR ligands AREG and EREG have shown associations with response to anti-EGFR therapy and improved progression-free survival in colorectal carcinoma. We investigated the prognostic significance of EGFR, AREG, and EREG in MIBC. Gene expression and copy number analyses were performed via qRT-PCR on tissue samples from 100 patients with MIBC who underwent radical cystectomy at the University Hospital Mannheim (MA; median age 72, interquartile range [IQR] 64-78 years, 25% female). Results were validated in 361 patients from the 2017 TCGA MIBC cohort (median age 69, IQR 60-77 years, 27% female), in the Chungbuk and MDACC cohort. Gene expressions were correlated with clinicopathologic parameters using the Mann-Whitney test, Kruskal-Wallis- test and Spearman correlation. For overall survival (OS), cancer-specific survival (CSS) and disease-free survival (DFS) gene expression was analyzed with Kaplan-Meier and Cox-proportional hazard models. Significant gene expression differences in EGFR, AREG, and EREG could be detected in all cohorts. In the TCGA cohort, EGFR expression was significantly elevated in patients with EGFR amplification and KRAS wildtype. High AREG expression independently predicted longer OS (HR = 0.35, CI 0.19 - 0.63, p = 0.0004) and CSS (HR = 0.42, CI 0.18 - 0.95, p = 0.0378) in the MA cohort. In the TCGA cohort, high EGFR, AREG, and EREG expression correlated with shorter OS (AREG: HR = 1.57, CI 1.12 - 2.20, p = 0.0090) and DFS (EGFR: HR = 1.91, CI 1.31 - 2.8, p = 0.0008). EGFR amplification was also associated with reduced DFS. High EGFR and EREG indicate worse survival in patients with MIBC. The prognostic role of AREG should further be investigated in large, prospective series. Divergent survival outcomes between the four cohorts should be interpreted cautiously, considering differences in analysis methods and demographics. Further in vitro investigations are necessary to elucidate the functional mechanisms underlying the associations observed in this study.

A consensus molecular subtypes classification strategy for clinical colorectal cancer tissues.

Consensus Molecular Subtype (CMS) classification of colorectal cancer (CRC) tissues is complicated by RNA degradation upon formalin-fixed paraffin-embedded (FFPE) preservation. Here, we present an FFPE-curated CMS classifier. The CMSFFPE classifier was developed using genes with a high transcript integrity in FFPE-derived RNA. We evaluated the classification accuracy in two FFPE-RNA datasets with matched fresh-frozen (FF) RNA data, and an FF-derived RNA set. An FFPE-RNA application cohort of metastatic CRC patients was established, partly treated with anti-EGFR therapy. Key characteristics per CMS were assessed. Cross-referenced with matched benchmark FF CMS calls, the CMSFFPE classifier strongly improved classification accuracy in two FFPE datasets compared with the original CMSClassifier (63.6% versus 40.9% and 83.3% versus 66.7%, respectively). We recovered CMS-specific recurrence-free survival patterns (CMS4 versus CMS2: hazard ratio 1.75, 95% CI 1.24-2.46). Key molecular and clinical associations of the CMSs were confirmed. In particular, we demonstrated the predictive value of CMS2 and CMS3 for anti-EGFR therapy response (CMS2&3: odds ratio 5.48, 95% CI 1.10-27.27). The CMSFFPE classifier is an optimized FFPE-curated research tool for CMS classification of clinical CRC samples.

Exploring the Relationship Between KRAS, NRAS, and BRAF Mutations and Clinical Characteristics in Iranian Colorectal Cancer Patients.

Patients with colorectal cancer can benefit from anti-EGFR (epidermal growth factor receptor) therapy. However, this therapy is not effective for treating colorectal cancers with constitutive activating mutations in the KRAS, NRAS, and BRAF genes. Molecular analysis of tumor tissue frequently informs treatment decisions for colorectal cancer. This study aims to identify KRAS, NRAS, and BRAF mutations in Iranian patients diagnosed with colorectal cancer and to assess the prevalence of these mutations relative to the tumor differentiation stage within these populations. From April 2018 to December 2022, 2000 specimens from patients with colorectal cancer were collected. Data on sex, age, and tumor differentiation stage were recorded for all samples. For mutation detection, the KRAS and NRAS exons (2, 3, and 4) were amplified using the Diatech kit, and a specific primer was used to amplify BRAF exon 15. Pyrosequencing was then performed. Analysis of samples revealed that 1105 specimens (55.3%) contained mutations in at least one of the screened genes. Among the genes studied, the highest occurrence was the KRAS mutation at 47.4%, followed by NRAS at 5.3% and BRAF at 2.7%. Most KRAS mutations were found in exon 2 (89.7%), with the G12D mutation being the most prevalent at 32% of cases. There was a significant difference in the rate of KRAS mutations in women (52.5%) compared to men (43.5%) (P = 0.02). For NRAS, the majority mutations were observed in exon 3 (76.2%), with the Q61H mutation being the most prevalent at 28.5% of cases. There were no significant associations between the clinicopathological parameters and mutations. The study's findings indicate a rising frequency of mutations in these genes in Iran, highlighting the need to screening mutations in the main exons of all three genes for effective colorectal cancer treatment strategies.

Structural and molecular insights from dual inhibitors of EGFR and VEGFR2 as a strategy to improve the efficacy of cancer therapy.

Epidermal growth factor receptor (EGFR) and vascular endothelial growth factor 2 (VEGFR2) are known as valid targets for cancer therapy. Overexpression of EGFR induces uncontrolled cell proliferation and VEGF expression triggering angiogenesis via VEGFR2 signaling. On the other hand, VEGF expression independent of EGFR signaling is already known as one of the mechanisms of resistance to anti-EGFR therapy. Therefore, drugs that act as dual inhibitors of EGFR and VEGFR2 can be a solution to the problem of drug resistance and increase the effectiveness of therapy. In this review, we summarize the relationship between EGFR and VEGFR2 signal transduction in promoting cancer growth and how their kinase domain structures can affect the selectivity of an inhibitor as the basis for designing dual inhibitors. In addition, several recent studies on the development of dual EGFR and VEGFR2 inhibitors involving docking simulations were highlighted in this paper to provide some references such as pharmacophore features of inhibitors and key residues for further research, especially in computer-aided drug design.

Unveiling acquired resistance to anti-EGFR therapies in colorectal cancer: a long and winding road.

Emergence of acquired resistance limits the efficacy of the anti-EGFR therapies cetuximab and panitumumab in metastatic colorectal cancer. In the last decade, preclinical and clinical cohort studies have uncovered genomic alterations that confer a selective advantage to tumor cells under EGFR blockade, mainly downstream re-activation of RAS-MEK signaling and mutations in the extracellular domain of EGFR (EGFR-ECD). Liquid biopsies (genotyping of ctDNA) have been established as an excellent tool to easily monitor the dynamics of genomic alterations resistance in the blood of patients and to select patients for rechallenge with anti-EGFR therapies. Accordingly, several clinical trials have shown clinical benefit of rechallenge with anti-EGFR therapy in genomically-selected patients using ctDNA. However, alternative mechanisms underpinning resistance beyond genomics -mainly related to the tumor microenvironment-have been unveiled, specifically relevant in patients receiving chemotherapy-based multi-drug treatment in first line. This review explores the complexity of the multifaceted mechanisms that mediate secondary resistance to anti-EGFR therapies and potential therapeutic strategies to circumvent acquired resistance.

Single cell lineage tracing reveals clonal dynamics of anti-EGFR therapy resistance in triple negative breast cancer

BackgroundMost primary Triple Negative Breast Cancers (TNBCs) show amplification of the Epidermal Growth Factor Receptor (EGFR) gene, leading to increased protein expression. However, unlike other EGFR-driven cancers, targeting this receptor in TNBC yields inconsistent therapeutic responses.MethodsTo elucidate the underlying mechanisms of this variability, we employ cellular barcoding and single-cell transcriptomics to reconstruct the subclonal dynamics of EGFR-amplified TNBC cells in response to afatinib, a tyrosine kinase inhibitor (TKI) that irreversibly inhibits EGFR.ResultsIntegrated lineage tracing analysis revealed a rare pre-existing subpopulation of cells with distinct biological signature, including elevated expression levels of Insulin-Like Growth Factor Binding Protein 2 (IGFBP2). We show that IGFBP2 overexpression is sufficient to render TNBC cells tolerant to afatinib treatment by activating the compensatory insulin-like growth factor I receptor (IGF1-R) signalling pathway. Finally, based on reconstructed mechanisms of resistance, we employ deep learning techniques to predict the afatinib sensitivity of TNBC cells. ConclusionsOur strategy proved effective in reconstructing the complex signalling network driving EGFR-targeted therapy resistance, offering new insights for the development of individualized treatment strategies in TNBC.

Anti-EGFR Rechallenge in Patients With Refractory ctDNA RAS/BRAF wt Metastatic Colorectal Cancer

The available evidence regarding anti-epidermal growth factor receptor (EGFR) inhibitor rechallenge in patients with refractory circulating tumor DNA (ctDNA) RAS/BRAF wild-type (wt) metastatic colorectal cancer (mCRC) is derived from small retrospective and prospective studies. To evaluate the efficacy of anti-EGFR rechallenge in patients with refractory ctDNA RAS/BRAF wt mCRC. This nonrandomized controlled trial used a pooled analysis of individual patient data from patients with RAS/BRAF wt ctDNA mCRC enrolled in 4 Italian trials (CAVE, VELO, CRICKET, and CHRONOS) and treated with anti-EGFR rechallenge between 2015 and 2022 (median [IQR] follow-up, 28.1 [25.8-35.0] months). Patients received anti-EGFR rechallenge therapy, including cetuximab plus avelumab, trifluridine-tipiracil plus panitumumab, irinotecan plus cetuximab, or panitumumab monotherapy. Overall survival (OS), progression-free survival (PFS), overall response rate (ORR), and disease control rate (DCR) were calculated. Exploratory subgroup analysis evaluating several clinical variables was performed. Safety was reported. Overall, 114 patients with RAS/BRAF wt ctDNA mCRC (median [IQR] age, 61 [29-88] years; 66 men [57.9%]) who received anti-EGFR rechallenge as experimental therapy (48 received cetuximab plus avelumab, 26 received trifluridine-tipiracil plus panitumumab, 13 received irinotecan plus cetuximab, and 27 received panitumumab monotherapy) were included in the current analysis. Eighty-three patients (72.8%) had received 2 previous lines of therapy, and 31 patients (27.2%) had received 3 or more previous lines of therapy. The ORR was 17.5% (20 patients), and the DCR was 72.3% (82 patients). The median PFS was 4.0 months (95% CI, 3.2-4.7 months), and the median OS was 13.1 months (95% CI, 9.5-16.7 months). The subgroup of patients without liver involvement had better clinical outcomes. The median PFS was 5.7 months (95% CI, 4.8-6.7 months) in patients without liver metastasis compared with 3.6 months (95% CI, 3.3-3.9 months) in patients with liver metastasis (hazard ratio, 0.56; 95% CI, 0.37-0.83; P = .004). The median OS was 17.7 months (95% CI, 13-22.4 months) in patients without liver metastasis compared with 11.5 months (95% CI, 9.3-13.9 months) in patients with liver metastasis (hazard ratio, 0.63; 95% CI, 0.41-0.97; P = .04). Treatments showed manageable toxic effects. These findings suggest that anti-EGFR rechallenge therapy has promising antitumor activity in patients with refractory ctDNA RAS/BRAF wt mCRC. Within the limitation of a subgroup analysis, the absence of liver metastases was associated with significant improved survival. ClinicalTrials.gov Identifiers: NCT02296203; NCT04561336; NCT03227926; NCT05468892.

Abstract CT078: Phase 1 study of SGN-EGFRd2 in solid tumors (SGNEGFRd2-001)

Abstract Background: Epidermal growth factor receptor (EGFR) is a cell surface receptor expressed in a variety of solid tumors. Gamma delta (γδ)-T cells represent a conserved T cell subset that can induce cell death in a wide range of malignancies. The presence of γ9δ2-T cells in solid tumors strongly correlates with better patient survival (Gentles 2015; Tosolini 2017). In addition to direct, potent killing by release of cytotoxic molecules, activated γ9δ2-T cells process and present antigen and contribute to a cascade response resulting in downstream activation of innate and adaptive immune cells to mediate further tumor cell killing (Brandes 2005; Devilder 2006; Vantourout 2013). Novel approaches that improve targeting and activation of γ9δ2-T cells may lead to the development of effective and safe cancer treatments. SGN-EGFRd2 is an investigational, bispecific humanized heavy chain-only antibody (HcAb). Advantages of HcAbs include their small size, high solubility, high stability, and excellent tissue penetration in vivo (Bannas 2017). SGN-EGFRd2 simultaneously binds EGFR and the γ9δ2-T cell receptor, resulting in the conditional activation of γ9δ2-T cells. Importantly, full activation of γ9δ2-T cells requires a secondary phosphoantigen stress signal present only in malignant and certain infected cells (Deseke 2020; Herrmann 2020; Rigau 2020; Vantourout 2013), but not normal healthy cells, conferring preferential tumor-directed cytotoxicity. The proposed cytotoxic mechanism of action is independent of KRAS and BRAF mutations (King 2023) known to confer resistance to approved anti-EGFR therapies in colorectal cancer (CRC). This first-in-human study is evaluating the safety, tolerability, and antitumor activity of SGN-EGFRd2 in patients with advanced solid tumors. Methods: SGNEGFRd2-001 (NCT05983133) is an open-label, multicenter, phase 1, dose escalation and expansion study evaluating SGN-EGFRd2 monotherapy in patients with relapsed/refractory (R/R) CRC, head and neck squamous cell cancer, non-small cell lung cancer, and pancreatic ductal adenocarcinoma in 3 parts: dose escalation (Part A; n ~ 75), dose optimization (Part B; optional; up to n = 40), and dose expansion (Part C; up to n = 160). Patients must have R/R disease, or be intolerant to standard of care therapies, with no appropriate standard therapy available. Patients must have measurable disease per RECIST v1.1, an ECOG performance status of 0 or 1, and adequate organ function. Patients are eligible regardless of tumor EGFR expression or EGFR/KRAS/BRAF mutation status. Patients will receive SGN-EGFRd2 as an intravenous infusion. Primary study objectives are safety and tolerability, maximum tolerated dose, and recommended dose and schedule. Secondary objectives include pharmacokinetics, immunogenicity, and antitumor activity. Tumor samples will be analyzed for exploratory biomarkers. Accrual is ongoing in the US. Additional sites in Europe and Canada are planned. Citation Format: Hirva Mamdani, Joel Randolph Hecht, Rachel E. Sanborn, Maria Corinna Palanca-Wessels, Mingjin Yan, Martin Gutierrez, David L. Bajor. Phase 1 study of SGN-EGFRd2 in solid tumors (SGNEGFRd2-001) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT078.

HER2-Positive Metastatic Colorectal Cancer.

Targeted treatment strategies are available for human epidermal growth factor receptor 2 (HER2)-positive (amplified and/or overexpressed) metastatic colorectal cancer (mCRC), and HER2 testing is indicated in patients with mCRC. At present, standard of care first-line treatment for those with HER2-positive mCRC remains chemotherapy in combination with epidermal growth factor receptor (EGFR) inhibitors or bevacizumab, depending on RAS/BRAF mutational status and tumor sidedness. HER2-targeted agents should be considered for those with RAS/BRAF wild-type disease in subsequent-line treatment and in first-line treatment for patients not appropriate for intensive therapy. While the choice of anti-HER2 therapy is empiric given lack of head-to-head comparisons, the combination of trastuzumab plus tucatinib has received FDA accelerated approval for use in this setting and is generally the authors' preference. Trastuzumab plus lapatinib, trastuzumab plus pertuzumab, and trastuzumab deruxtecan (T-DXd) also have evidence of efficacy in this setting. As T-DXd has demonstrated activity following treatment with other HER2-targeted regimens and carries an increased risk of high-grade toxicities, the authors favor reserving it for use after progression on prior anti-HER2 therapy. HER2-targeted therapies that inhibit signal transduction appear to have limited activity in those with RAS mutations, including trastuzumab-containing regimens. However, the antibody drug conjugate T-DXd has some data showing efficacy in this setting, and the authors would consider T-DXd in subsequent-line therapy for HER2-positive, RAS-mutated mCRC. Several areas of uncertainty remain regarding how to best utilize HER2-targeted therapies in mCRC. These include the optimal sequence of anti-HER2 therapies with chemotherapy and anti-EGFR therapies, the optimal combination partners for anti-HER2 therapies, and the incorporation of predictive biomarkers to guide use of anti-HER2 therapies. Results of ongoing studies may thus alter the treatment paradigm above in the coming years.

Abstract 925: Continuing anti-EGFR treatment prolonged survival in mCRC patients receiving conversion liver resection

Abstract Introduction: Anti-EGFR monoclonal antibody plus doublet chemotherapy is the mainstay of first-line treatment of RAS/BRAF wild-type metastatic colorectal cancer (mCRC) patients. Some of these patients might undergo secondary resection. However, there is no standardized suggestion on whether colorectal cancer liver metastasis patients should keep target therapy after secondary resection. NCCN guidelines suggest chemotherapy only in patients receiving primary liver resection. Whether we could spare the use of target therapy after secondary resection is the main aim of our study. Methods: Using Taiwan's National Health Insurance Research Database, we established a cohort of KRAS wild-type mCRC patients treated with first-line anti-EGFR therapy plus doublet chemotherapy between 2013 and 2018. Secondary surgery was defined as either resection of liver metastases or radiofrequency ablation. Results: 5694 stage IV mCRC patients received anti-EGFR MAb plus doublet chemotherapy as a first-line treatment between 2013 and 2018. 174 patients were enrolled in the final analysis, with 153 continuing anti-EGFR MAb after secondary resection and 21 patients without anti-EGFR MAb. Compared with those who without anti-EGFR therapy after secondary resection, patients who continued anti-EGFR MAb exhibited significantly longer overall survival (OS; median, 43.8 vs. 31.9 months, p = 0.031) but not in time to treatment failure (TTF; median, 22.2 vs. 26.6 months, p = 0.841). The OS benefits of continuing anti-EGFR MAb remained regardless of left-sided or right-sided primary tumors (40.9 vs. 43.0 months, p = 0.980). The patient cohort from 2016 to 2018 showed more prolonged survival than from 2012 to 2015 (not reached vs. 40.450, p = 0.0305). TTF has no statistical difference when considering patient cohort or primary tumor location. In multivariate analyses, continuing first-line anti-EGFR MAb therapy after secondary resection remained an independent predictor of longer OS. Conclusion: For mCRC patients who received secondary resection after first-line anti-EGFR and doublet chemotherapy, continuing anti-EGFR MAb after resection was associated with significantly longer OS regardless of primary tumor sidedness. Citation Format: Yao-Yu Hsieh, Chin-Wen Tsai, T-CARE Group, Yi-Hsieh Liang. Continuing anti-EGFR treatment prolonged survival in mCRC patients receiving conversion liver resection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 925.

Abstract 6623: Ala59 mutants of KRAS cooperate with Nf1 loss to enhance colon tumorigenesis

Abstract Understanding the role of KRAS allele heterogeneity in tumor development, and its influence on therapeutic efficacy, is critical for the improvement of cancer treatment. The Kirsten rat sarcoma (KRAS) gene is the most frequently mutated oncogene in colorectal cancer (CRC) and patients with CRC tumors positive for KRAS mutations have poorer outcomes and limited treatment options. Extensive work over the past four decades has shown that common oncogenic alleles of KRAS are associated with hyperactivation of the MAPK signaling pathway (i.e. RAF/MEK/ERK), and it is for this reason that patients with KRAS mutant tumors are excluded from targeted therapies against EGFR. Recently, we characterized two alleles of KRAS, KRASA59T and KRASA59E, that paradoxically promote KRAS activation but are impaired in their ability to promote BRAF dimerization (Johnson et al. Mol Cell. 2022. PMID: 35202574). Consistent with these biochemical functions, KRASA59T and KRASA59E are enriched in CRC tumors that already have genetic alterations in genes that regulate MAPK signaling (e.g. EGFR, BRAF, NRAS, NF1). Further, unlike other described oncogenic alleles of KRAS, clinical data suggest that these KRASA59T and KRASA59E may not confer intrinsic resistance to anti-EGFR therapies at all. While KRASA59T and KRASA59E may not promote BRAF dimers, here we show that KRASA59T and KRASA59E does promote dimerization between ARAF and CRAF, and using an unpublished conditional mouse mode of K-Ras (i.e. LSL-K-RasA59E) we tested (1) whether Ala59 alleles are oncogenic or (2) require cooperation with additional MAPK pathway activating mutations, and (3) whether Ala59 alleles can promote intrinsic resistance to EGFR inhibition. Here, we show that endogenous K-RasA59E can disturb colon homeostasis and decrease mouse survival in an autochthonous colon tumor model, demonstrating that A59E alone is an oncogenic allele of KRAS in the colon. Breeding of LSL-K-RasA59E mice with mice harboring a conditional knockout of Nf1 (i.e. Nf1fl/fl), a GTPase activating protein (GAP) that promotes activation of wildtype RAS, show that combined expression of K-RasA59E and wildtype RAS activation cooperatively perturb colon homeostasis and decrease mouse survival. Thus, while KRASA59E may not require a second genetic alteration to activate the MAPK signaling pathway, it can cooperate with these alterations to increase the severity of disease. Finally, using mouse colon derived organoids, we show that endogenous K-RasA59E neither promotes EGF independence of organoid growth nor confers on these organoids a resistance to EGFR inhibition. Thus, our data support a unique role for RAF dimer function in in KRAS mutant tumors of the colon in both development and sensitivity to drugs, as well as argue for the inclusion of KRASA59T and KRASA59E bearing CRC tumors in anti-EGFR therapies. Citation Format: Christian William Johnson, Elizabeth M. Terrell, Josh Cook, Bing Shui, Eve O'Donoghue, Shannon Hull, Moon Hee Yang, Shikha Sheth, Rona Yaeger, Scott Kopetz, Deborah K. Morrison, Kevin Haigis. Ala59 mutants of KRAS cooperate with Nf1 loss to enhance colon tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6623.

Abstract 1944: Using patient-derived cancer organoids to determine the effects of the anti-EGFR therapy panitumumab in the presence or absence of KRAS mutation

Abstract Introduction: Tumor heterogeneity is a major cause of resistance to therapies in colorectal cancer (CRC). The anti-EGFR (epidermal growth factor receptor) therapies panitumumab (pani) and cetuximab, are now being investigated for the retreatment of patients when resistant subclones could be more abundant in a previously wild-type cancer. Here we utilize patient-derived cancer organoids (PDCOs) to investigate the potential implications of the abundance of resistant subclones on treatment and duration of response. Methods: Two CRC PDCO lines, one pani sensitive (PS) and one pani resistant (PR), were cultured separately and then mixed to determine how different combinations of mutations altered the time for the overall culture to be resistant to pani. NGS was performed on these cells to determine the mutation profile. The two PDCO lines were cultured together with the following concentrations (v/v) of 100% PS; 20% PR+80% PS; 10% PR+90% PS, 5% PR+95% PS, 1% PR+99% PS, and 100% PR using Matrigel and fed with previously published CRC organoid media. Widefield imaging was performed for diameter change analysis at day 0 and day 4 using ImageJ. Upon a median growth of &amp;gt;20% at baseline/untreated, all mixed populations were treated at increments of 20% physiologic Cmax of pani each week. Once select mixed populations reached 100% Cmax and maintained a median growth of &amp;gt;20% for two consecutive weeks, they were determined to have reached complete resistance to the treatment. Results: DNA sequencing of PDCOs showed PR has mutations associated with pani resistance (KRASG12V, PIK3CAH1047R) and the PS line did not. All the conditions except for 100% PS escalated to ≥40% Cmax within 7 weeks and reached complete resistance to pani by week 22. 100% PS remained at 20% Cmax through week 22. The 100% PR population reached complete resistance to pani the quickest at 100% Cmax at week 8. The conditions with the lowest percentages of PR (5% PR+95% PS and 1% PR+99% PS already started to show resistance above the PS line by 8 weeks and reached complete resistance to pani at week 12. Conclusion: PDCO lines containing low concentrations of resistant clones can quickly lead to resistance to pani treatment, even below the typical level for clinical NGS detection. All KRAS mutant conditions (PR) reached resistance quicker than 100% PS condition. Further studies will evaluate even low concentrations of resistance clones across further CRC PDCO models and will evaluate the mechanism by which these clones are leading to resistance. Citation Format: Jordan N. Stoecker, Shirsa Udgata, Amani A. Gillette, Cheri A. Pasch, Melissa C. Skala, Dustin A. Deming. Using patient-derived cancer organoids to determine the effects of the anti-EGFR therapy panitumumab in the presence or absence of KRAS mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1944.

Abstract 2355: SGN-EGFRd2 binding and activity are agnostic to common EGFR extracellular resistance mutations acquired in response to anti-EGFR targeted antibody therapies

Abstract SGN-EGFRd2 is an investigational bispecific antibody comprised of two camelid-derived humanized variable heavy chain only (VHH) domains, one targeting Vγ9Vδ2 (gamma delta) T cells and the other targeting the epidermal growth factor receptor (EGFR). Selective antitumor activity occurs when two conditions are met: 1) the molecule engages both EGFR-expressing tumor cells and gamma delta T cells and 2) butyrophilins, in complex with phosphoantigens (pAgs), are expressed by EGFR-positive tumor cells, resulting in gamma delta T cell directed tumor cell killing by activation, degranulation and secretion of cytolytic molecules. The tumor specific proximity of gamma delta T cells and expression of the butyrophilins/pAgs complex results in the killing of EGFR-expressing tumor cells but not EGFR-expressing normal cells. EGFR is an oncogenic receptor tyrosine kinase and target of several classes of therapeutic modalities, including antibodies. Two antibodies are currently approved for the treatment of EGFR-expressing, KRAS wild-type metastatic colorectal cancer (mCRC): cetuximab (CET) and panitumumab (PAN). Although these anti-EGFR therapies provide significant survival benefits to patients, the duration of response is transient, and most patients progress and develop secondary resistance [1]. One such escape mechanism is the acquisition of mutations in the extracellular domain (ECD) of EGFR, which prevent binding of therapeutic antibodies [2]. Because SGN-EGFRd2 will be tested on patients previously exposed to anti-EGFR therapeutic antibodies, it is paramount to assess its binding to EGFR ECD mutations identified in antibody resistant mCRC patients. EGFR-negative A2058 cells were transduced to express wild type EGFR and a panel of EGFR ECD resistance mutations (N=16). The binding specificity and kinetics of SGN-EGFRd2 were compared to CET and PAN by flow cytometry on engineered cell lines and biolayer interferometry, respectively. Results indicated SGN-EGFRd2 maintained the ability to bind to all tested EGFR ECD mutants, whereas CET and PAN were unable to bind several ECD mutants, as previously described [3,4]. SGN-EGFRd2 binding to EGFR ECD mutant cell lines induced the production of interferon gamma and expression of cell surface CD107a on gamma delta T cells, confirming functional engagement. In contrast to current anti-EGFR therapeutic antibodies, SGN-EGFRd2 binding and activity was unaffected by commonly identified EGFR ECD mutations. These findings highlight SGN-EGFRd2 as a novel molecule targeting wild-type EGFR and common EGFR ECD mutations identified in the mCRC setting. Citation Format: Liem Nguyen, Chun-Shu Wong, Serena Wo, Bryan Grogan, Daniel Diolaiti, Maria Corinna Palanca-Wessels, Astrid Clarke. SGN-EGFRd2 binding and activity are agnostic to common EGFR extracellular resistance mutations acquired in response to anti-EGFR targeted antibody therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2355.

Abstract 4735: Targeting CDK1/2-driven mechanisms of resistance to BRAF and EGFR inhibition in BRAF(V600E) colorectal cancer restores therapeutic response

Abstract Purpose: Metastatic colorectal cancer (mCRC) is the second leading cause of cancer death worldwide. Roughly 8% of mCRC tumors harbor a BRAF(V600E) mutation, associated with the worst prognosis and limited treatment options. Most CRC research and most clinical trials of targeted therapies have narrowly focused on targeting vertical mechanisms of MAPK re-activation (i.e., EGFR-MAPK), with incremental advances for patients. New approaches are needed to address how therapeutic resistance is mediated by coordinated upregulation of multiple signaling pathways. Methods and Recent Advances: Using an innovative high-throughput kinase-activity mapping (HT-KAM) platform and kinase network resource (PhosphoAtlas), we discovered that SRC kinases drive resistance to BRAF ± anti-EGFR therapy independently of ERK signaling by inducing adaptive transcriptional changes via beta-catenin. This compensatory activation of SRC was mediated by an autocrine PGE2-loop that could be blocked with COX2 inhibitors (COX2i). Using patient-derived xenograft (PDX) models established from pre-treatment biopsies in clinical trial participants, we showed that targeting COX2 in combination with standard of care (SOC) BRAFi + EGFRi is an effective drug repurposing strategy to stabilize tumor growth in vivo. New, Unpublished Findings: Building on our drug discovery pipeline to find and target orthogonal modalities of therapeutic resistance, we leveraged our bank of residual PDX tumors collected after 21-day exposure to SOC therapy, and now report that CDK1 and CDK2 are at the center of a stress response program that enables BRAF(V600E) CRC tumor cells to survive under therapeutic pressure. We used HT-KAM to interrogate the activity of 165 kinases and kinase families, and integrated these profiles using computational methods to model signaling pathways. Out of the reprogrammed kinomes of BRAFi + EGFRi resistant tumors, the CDK1/2 kinases and mechanisms of cell cycle checkpoint emerged as critical dependencies. We validated these findings using multiplex immuno-fluorescence in residual tumors, protein/gene expression profile of tissues and cell lines (e.g., upregulation of Cyclins and CDC25s), and cell viability assay using dinaciclib, a CDK1/2 inhibitor. Considering that COX2i has minimal toxicity, yet improved tumor growth inhibition when added to SOC, we evaluated whether jointly blocking inflammatory pathway (COX2) and cell cycle checkpoints (CDK1/2) could overcome resistance. We found that co-targeting CDK1/2 along with BRAFi + EGFRi ± COX2i is well-tolerated in mice and promotes significant, durable suppression of tumor growth in multiple PDX models, including tumor regression, over 9 weeks of treatment. Conclusion: When tumors progress on SOC BRAFi + EGFRi, a therapeutic window remains open to switch to a CDK1/2i-containing regimen and restore cancer control. Citation Format: Jean-Philippe Coppe, Denise P. Muñoz, Chloe E. Atreya, Yeonjoo Hwang, Mehdi Bouhaddou, Louise E. Heinrich, Mohammad Naser, Ons Zakraoui, Roxana Pirker, Rupa Guha, Christina Moelders, Alessandro Scapozza, Cecilia Schwarzer, Layla Phillips, Changjun Wang, Laura van 't Veer, Veronica Steri, Scott R. VandenBerg. Targeting CDK1/2-driven mechanisms of resistance to BRAF and EGFR inhibition in BRAF(V600E) colorectal cancer restores therapeutic response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4735.