Monoclonal Antibodies Panitumumab Research Articles

Immuno-PET Imaging of EGFR with 64Cu-NOTA Panitumumab in Subcutaneous and Metastatic Nonsmall Cell Lung Cancer Xenografts.

Objective: About 65-90% of nonsmall cell lung cancer (NSCLC) express the epithelial growth factor receptor (EGFR) as a transmembrane protein that is activated by binding of specific ligands, including epidermal growth factor and transforming growth factor α (TGFα). Identifying EGFR as an oncogene has led to the development of anticancer therapeutics directed against EGFR, including the full-length human IgG2 monoclonal antibody panitumumab. The main goal of the present study was to investigate 64Cu-labeled panitumumab with immuno-PET in subcutaneous and metastatic EGFR-positive NSCLC xenografts. Methods: Bifunctional chelating agent 2-S-(4-isothiocyanatobenzyl)-1,4,7-triazacyclo-nonane-1,4,7-triacetic acid (NOTA-NCS) was attached to panitumumab. The number of chelators per panitumumab was determined using matrix-assisted laser desorption/ionization (MALDI) mass spectroscopy. The incorporation efficiency of 64Cu into NOTA-panitumumab was measured by using radio-TLC. EGFR-expressing epithelial-like H1299-luc+ NSCLC cells were used for in vitro and in vivo experiments. Cell uptake of [64Cu]Cu-NOTA-panitumumab was measured in the presence and absence of panitumumab. Subcutaneous and metastatic H1299-luc tumor models were grown in male NSG mice. The presence of tumors at lung and metastatic sites was analyzed by [18F]FLT PET. Immuno-PET with [64Cu]Cu-NOTA-panitumumab was performed as static PET imaging at 2, 24, and 48 h postinjection in both tumor models. Proof-of-target was confirmed by blocking experiments with panitumumab. Detailed ex vivo biodistribution experiments were performed in both animal tumor models to confirm biodistribution profiles obtained by immuno-PET imaging. Results: MALDI analysis confirmed the attachment of ∼1.5 NOTA per antibody. Radiolabeling efficiency with [64Cu]CuCl2 was 93.8 ± 5.7% and a molar activity of 0.65 MBq/μg. Cellular uptake studies with [64Cu]Cu-NOTA-panitumumab in H1299 cells demonstrated increasing uptake over time, reaching 29.1 ± 2.9% radioactivity(Bq)/mg protein (n = 3) and plateauing at 45 min. Addition of 25 μg of panitumumab reduced radioligand uptake to 1.22 ± 0.06% radioactivity/mg protein (n = 3). PET imaging revealed high uptake of [64Cu]Cu-NOTA-panitumumab in subcutaneous tumors: Standardized uptake values (SUV)mean reached 4.70 ± 0.42 and 5.37 ± 0.40 (n = 5) after 24 and 48 h postinjection, respectively. Administration of 1 mg panitumumab reduced tumor uptake significantly to 1.94 ± 0.22 and 1.66 ± 0.08 (n = 4; p < 0.001). In the metastatic model, the following SUVmean were analyzed from liver and lung lesions: 5.55 ± 0.34 and 6.28 ± 0.46 (both n = 23 lesions from 6 mice) after 24 and 48 h postinjection, which was also significantly reduced to 2.53 ± 0.39 and 2.31 ± 0.15 (both n = 16 lesions from 4 mice; p < 0.001) after injection of 1 mg panitumumab. Detailed ex vivo biodistribution confirmed immuno-PET analysis in both models. Panitumumab reduced radioactivity uptake into subcutaneous tumors from 11.01 ± 0.72 (n = 4) to 3.67 ± 0.33% ID/g (n = 5; p < 0.001), and in metastatic liver lesions from 29.44 ± 8.14 (n = 4) to 8.35 ± 1.30% ID/g (n = 5; p < 0.001), respectively. Conclusions: [64Cu]Cu-NOTA-panitumumab was successfully used for immuno-PET imaging of EGFR-expressing subcutaneous and metastatic NSCLC tumors. This result represents the basis for developing radiotheranostics for targeting EGFR in cancers and for selecting the right patients for the right treatment at the right time.

Efficacy and Safety of Panitumumab in Patients With RAF/RAS-Wild-Type Glioblastoma: Results From the Drug Rediscovery Protocol.

The prognosis of malignant primary high-grade brain tumors, predominantly glioblastomas, is poor despite intensive multimodality treatment options. In more than 50% of patients with glioblastomas, potentially targetable mutations are present, including rearrangements, altered splicing, and/or focal amplifications of epidermal growth factor receptor (EGFR) by signaling through the RAF/RAS pathway. We studied whether treatment with the clinically available anti-EGFR monoclonal antibody panitumumab provides clinical benefit for patients with RAF/RAS-wild-type (wt) glioblastomas in the Drug Rediscovery Protocol (DRUP). Patients with progression of treatment refractory RAF/RASwt glioblastoma were included for treatment with panitumumab in DRUP when measurable according to RANO criteria. The primary endpoints of this study are clinical benefit (CB: defined as confirmed objective response [OR] or stable disease [SD] ≥ 16 weeks) and safety. Patients were enrolled using a Simon-like 2-stage model, with 8 patients in stage 1 and up to 24 patients in stage 2 if at least 1 in 8 patients had CB in stage 1. Between 03-2018 and 02-2022, 24 evaluable patients were treated. CB was observed in 5 patients (21%), including 2 patients with partial response (8.3%) and 3 patients with SD ≥ 16 weeks (12.5%). After median follow-up of 15 months, median progression-free survival and overall survival were 1.7 months (95% CI 1.6-2.1 months) and 4.5 months (95% CI 2.9-8.6 months), respectively. No unexpected toxicities were observed. Panitumumab treatment provides limited CB in patients with recurrent RAF/RASwt glioblastoma precluding further development of this therapeutic strategy.

Prolonging the stability of cetuximab (Erbitux®) and panitumumab (Vectibix®): An orthogonal assessment of physicochemical, biological and microbiological properties of original opened glass vials and diluted saline preparations

The two anti-epidermal growth factor receptor monoclonal antibodies (mAbs) cetuximab and panitumumab are the pillars for the treatment of EGFR-positive, KRAS wild-type metastatic colorectal cancers. However, stability data of these mAbs are generally missing or incomplete. Here, we report for the first time an orthogonal analysis of the stability of cetuximab (Erbitux®) and panitumumab (Vectibix®), either undiluted vial leftovers or saline dilutions in polyolefin/polyamide infusion bags. All samples were stored at 2–8 °C protected from light, according to their summary of product characteristics (SmPCs). Alternatively, opened vials and preparations were maintained at 25 °C for 15 h, and then stored again at 2–8 °C protected from light to mimic a temporary interruption of the cold chain. Vial leftovers proved stable up to 180 days when stored according to their SmPCs, while compounded preparations in infusion bags maintained their physiochemical, biological and microbiological stability up to 30 days. Additionally, no changes were detected up to 30 days for the same samples undergoing a thermal excursion. Our results provide additional rationale to the SmPCs, crucial especially in the case of reassignment and pre-preparation of bags. This information will allow hospitals to achieve significant cost savings, and better organization of the entire therapeutic process.

Exploring proteoforms of the IgG2 monoclonal antibody panitumumab using microchip capillary electrophoresis-mass spectrometry

The IgG2 type monoclonal antibody panitumumab is an anti-epidermal growth factor receptor (EGFR) drug used for the treatment of EGFR-expressing, chemotherapy resistant, metastatic colorectal carcinoma. In this study, panitumumab drug product was first analysed using size exclusion chromatography coupled to mass spectrometry for rapid identity testing. The experimental data led to the identification of two panitumumab isoforms with several prominent forms remaining unidentified, despite apparently low sample complexity. Microchip capillary electrophoresis-mass spectrometry (CE-MS) was subsequently utilised for a more detailed characterization. It was observed that panitumumab is subject to partial N-terminal pyroglutamate formation. Incomplete conversion is uncharacteristic for N-terminally exposed glutamines and in case of panitumumab gives rise to forms which show successive mass offsets of 17 Da, respectively. If not separated before mass spectrometric analysis, e.g. by capillary electrophoresis, such near isobaric species coalesce into single MS peaks, which subsequently hampers or prevents their assignment. With a total of 42 panitumumab isoforms assigned by CE-MS, these observations highlight a potential pitfall of commonly applied rapid identity testing workflows and demonstrate that even low complexity biopharmaceuticals can require separation strategies which offer high separation selectivity for species close in mass.

Panitumumab plus trifluridine/tipiracil as third-line anti-EGFR rechallenge therapy in chemo-refractory RAS WT metastatic colorectal cancer: The VELO randomized phase II clinical trial.

129 Background: Rechallenge therapy with epidermal growth factor receptor (EGFR) inhibitors in chemo-refractory metastatic colorectal cancer (mCRC) is an emerging therapeutic approach. Trifluridine-tipiracil is approved for treatment of chemo-refractory mCRC patients. Methods: Chemo-refractory RAS WT mCRC patients, that had a major response (partial or complete response) to first-line chemotherapy plus an anti-EGFR monoclonal antibody and had an-anti-EGFR drug-free interval during second-line therapy of four or more months were randomized in a phase II trial to assess the addition of the anti-EGFR monoclonal antibody panitumumab to trifluridine-tipiracil as third-line rechallenge therapy. The primary endpoint was progression free survival (PFS). Baseline plasma was analyzed for circulating free tumor (ct) DNA by using Biocartis Idylla platform to detect mutations in KRAS, NRAS, BRAF ( V600E) and EGFRextracellular domain ( S492R). In 24 patients with baseline RAS/BRAF wild type (WT) ctDNA, Foundation One liquid CDx (324 gene profiling) was also performed before treatment and at disease progression. Results: 62 patients were treated with trifluridine-tipiracil (31 patients, arm A) or with trifluridine-tipiracil plus panitumumab (31 patients, arm B). As of September 16, 2022, 1 patient in arm A and 2 patients in arm B were on treatment. The primary endpoint was met. Median PFS (mPFS) was 4 months in arm B versus 2.5 months in arm A [hazard ratio (HR): 0.48; 95% CI 0.28-0.82; P = 0.007]. Baseline plasma RAS/BRAF WT ctDNA was found in 23/31 patients in Arm A and in 26/31 patients in Arm B. In this group, mPFS was 4.5 months in Arm B versus 2.6 months in Arm A (HR: 0.48; 95% CI 0.26-0.89; P = 0.019). Disease control (major responses plus stable disease) was higher for patients in Arm B compared to Arm A (81% versus 48%), whereas disease progression was the best response in 19% versus 52% patients, respectively. PFS rates at 6 and 12 months were 38.5% and 15.4% in arm B versus 13% and 0% in arm A. At disease progression, Foundation One liquid CDx detected several mutations within the EGFR pathway, which could correlate with cancer cell resistance to panitumumab. Conclusions: This is the first prospective randomized trial which evaluated anti-EGFR monoclonal antibody (panitumumab) in addition to standard of care (trifluridine-tipiracil) as third-line rechallenge therapy in chemo-refractory RASWT mCRC patients. Baseline liquid biopsy allows selection of RAS/BRAF WT ctDNA patients who could have a relevant clinical benefit. Clinical trial information: NCT05468892 .

First-line anti-EGFR or anti-VEGF therapy, tumour sidedness, and survival: Results from the South Australian (SA) Metastatic Colorectal Cancer (mCRC) Registry.

42 Background: The anti-EGFR monoclonal antibodies panitumumab (Pmab) and cetuximab (Cmab) and the anti-VEGF antibody bevacizumab (bev) have demonstrated clinical efficacy in mCRC in combination with first-line chemotherapy. Clinical and molecular characteristics, such as primary tumour sidedness, RAS, BRAF and MMR status are prognostic and predictive biomarkers for response to treatment. Our aim was to compare the survival and tumour characteristics of patients receiving first-line chemotherapy and antibody combinations using the SA mCRC Registry. Methods: This real-world registry has collected data from all patients diagnosed with mCRC in SA prospectively since 2006. We identified patients who had received first-line Pmab, Cmab or bev. Survival was analysed using the Kaplan-Meier method and log-rank test to compare outcomes based on primary tumour location. Results: Of the 5537 patients currently entered onto the registry, 1313 with RAS results available had received first-line anti-EGFR/VEGF antibodies and had colon tumour side recorded. The table summarises median overall survival (mOS) and patient characteristics. Survival was significantly shorter for those with right colon cancers (P &lt; 0.001). There were more high-grade (P &lt; 0.001), KRAS mutant (P = 0.004) and BRAF mutant (P = 0.036) tumours in those with right colon cancers, and a trend towards fewer curative liver resections (P = 0.059). There was no significant difference in mOS seen between Pmab, Cmab or bev for both left (P = 0.14) and right-sided (P = 0.88) primary tumours. Conclusions: There were more high-grade, BRAF and KRAS mutant patients with right colon tumours, and lower rates of liver resection, which may explain the significantly shorter mOS. The survival seen for Pmab and Cmab was almost identical for both right and left primary tumours. When comparing Pmab, Cmab and bev as first-line therapy, there was no significant difference in mOS for both left- and right-sided CRC. [Table: see text]

An Update on the Role of Anti-EGFR in the Treatment of Older Patients with Metastatic Colorectal Cancer

Although colorectal cancer is increasingly being diagnosed in older patients, their number is largely underrepresented in phase II or III clinical trials. Consequently, guidelines and the SIOG recommendations are not sufficiently clear regarding the treatment of these patients, particularly when chemotherapy is combined with monoclonal antibodies (bevacizumab, cetuximab, and panitumumab). Targeted therapy based on the use of anti-epidermal growth factor receptors (EGFRs) is conditioned by the potential for increased toxicity, making it more difficult to treat an older, rat sarcoma virus (RAS) and B rapidly accelerated fibrosarcoma (BRAF) wild-type patient. In light of a more detailed characterization of the older population, modernly differentiable between fit, vulnerable, or frail patients on the basis of the comprehensive geriatric assessment, and of the analysis of more recent studies, this review fully collects data from the literature, differentiating the results on functional status patients.

Pharmacophore-based virtual screening approaches to identify novel molecular candidates against EGFR through comprehensive computational approaches and in-vitro studies.

Alterations to the EGFR (epidermal growth factor receptor) gene, which primarily occur in the axon 18-21 position, have been linked to a variety of cancers, including ovarian, breast, colon, and lung cancer. The use of TK inhibitors (gefitinib, erlotinib, lapatinib, and afatinib) and monoclonal antibodies (cetuximab, panitumumab, and matuzumab) in the treatment of advanced-stage cancer is very common. These drugs are becoming less effective in EGFR targeted cancer treatment and developing resistance to cancer cell eradication, which sometimes necessitates stopping treatment due to the side effects. One in silico study has been conducted to identify EGFR antagonists using other compounds, databases without providing the toxicity profile, comparative analyses, or morphological cell death pattern. The goal of our study was to identify potential lead compounds, and we identified seven compounds based on the docking score and four compounds that were chosen for our study, utilizing toxicity analysis. Molecular docking, virtual screening, dynamic simulation, and in-vitro screening indicated that these compounds' effects were superior to those of already marketed medication (gefitinib). The four compounds obtained, ZINC96937394, ZINC14611940, ZINC103239230, and ZINC96933670, demonstrated improved binding affinity (-9.9kcal/mol, -9.6kcal/mol, -9.5kcal/mol, and -9.2kcal/mol, respectively), interaction stability, and a lower toxicity profile. In silico toxicity analysis showed that our compounds have a lower toxicity profile and a higher LD50 value. At the same time, a selected compound, i.e., ZINC103239230, was revealed to attach to a particular active site and bind more tightly to the protein, as well as show better in-vitro results when compared to our selected gefitinib medication. MTT assay, gene expression analysis (BAX, BCL-2, and β-catenin), apoptosis analysis, TEM, cell cycle assay, ELISA, and cell migration assays were conducted to perform the cell death analysis of lung cancer and breast cancer, compared to the marketed product. The MTT assay exhibited 80% cell death for 75µM and 100µM; however, flow cytometry analysis with the IC50 value demonstrated that the selected compound induced higher apoptosis in MCF-7 (30.8%) than in A549.

With metastatic colorectal cancer: A single center experience use of monoclonal antibodies (Bevacizumab, Cetuximab, and Panitumumab) in patients

With metastatic colorectal cancer: A single center experience use of monoclonal antibodies (Bevacizumab, Cetuximab, and Panitumumab) in patients

Modified FOLFOXIRI plus panitumumab (mFOLFOXIRI/PAN) versus mFOLFOX6/PAN as initial treatment of patients with unresectable RAS and BRAF wild-type metastatic colorectal cancer (mCRC): Results of the phase III randomized TRIPLETE study by GONO.

LBA3505 Background: The association of a chemotherapy doublet (FOLFOX/FOLFIRI) with an anti-EGFR monoclonal antibody (cetuximab or panitumumab) is an upfront option for the treatment of RAS and BRAF wt mCRC patients. Phase II studies investigating the combination of the triplet FOLFOXIRI with an anti-EGFR reported promising activity results and an acceptable safety profile when lower doses of 5FU and irinotecan were adopted. The added value of intensifying the upfront chemotherapy when combined with a targeted agent in a molecularly selected population is not established. Methods: TRIPLETE is a prospective, open label, phase III trial in which previously untreated patients with unresectable RAS and BRAF wt mCRC were randomized to receive mFOLFOX6/pan (arm A) or mFOLFOXIRI (irinotecan 150 mg/sqm, oxaliplatin 85 mg/sqm, L-leucovorin 200 mg/sqm, 5-fluoruracil 2400 mg/sqm 48 h infusion)/pan (arm B) up to 12 cycles, followed by 5FU/LV/pan until disease progression. The primary endpoint is overall response rate (ORR) according to RECIST 1.1 criteria. Secondary endpoints include safety profile, R0 resection rate, PFS and OS. Under the assumption of an ORR of 60% in arm A, to detect an increase of at least 15% in arm B, a sample size of 432 cases provided approximately 90% power to a two-sided chi square test for heterogeneity at the 0.05 significance level. Results: From September 2017 to September 2021, 435 pts were enrolled (arm A/B: 217/218) in 67 Italian sites. Main pts’ characteristics were (arm A/B): median age 59/59, ECOG PS 0 80%/84%, left-sided 88%/88%, synchronous metastases 88%/87%, prior adjuvant 2%/6%, resected primary 43%/51%, liver-only 37%/39%. Main grade &gt; 2 adverse events were diarrhoea 7%/23%, stomatitis 7%/7%, neutropenia 20%/32%, febrile neutropenia 3%/6%, fatigue 2%/7%, skin rash 29%/19%. 160 (73%) out of 218 patients in arm B and 165 (76%) out of 217 patients in arm A achieved RECIST response (OR 0.87, 95%CI 0.56-1.34, p=0.526). No interaction effect between treatment arm and disease spread (liver-limited vs not-liver limited) was evident. No differences in early tumor shrinkage (arm A/B 58%/57%, p=0.878) and deepness of response (median arm A/B: 47%/48%, p=0.845) were reported, nor in R0 resection rate (arm A/B 29%/25%, p=0.317). At a median follow up of 26.5 mos, 305 (arm A/B: 157/148) PFS events were collected, with no significant difference between arms (median PFS: 12.7 vs 12.3 months, HR: 0.88, 95%CI 0.70-1.11, p=0.277). Conclusions: The intensification of the upfront chemotherapy backbone in combination with panitumumab in molecularly selected and mostly (88%) left-sided mCRC patients does not provide any benefit in terms of treatment activity at the price of a non-negligible increase in gastrointestinal toxicity. Clinical trial information: NCT03231722.

O-6 Modified FOLFOXIRI plus panitumumab (mFOLFOXIRI/PAN) versus mFOLFOX6/PAN as initial treatment of unresectable RAS/BRAF wild-type metastatic colorectal cancer (mCRC) patients: Results of the phase III randomized TRIPLETE study by GONO

The association of a chemotherapy doublet (FOLFOX/FOLFIRI) with an anti-EGFR monoclonal antibody (cetuximab or panitumumab) is an upfront option for the treatment of RAS and BRAF wt mCRC patients. Phase II studies investigating the combination of the triplet FOLFOXIRI with an anti-EGFR reported promising activity results and an acceptable safety profile when lower doses of 5FU and irinotecan were adopted. The added value of intensifying the upfront chemotherapy when combined with a targeted agent in a molecularly selected population is not established.

O-7 Evidence of therapeutic effectiveness of third-line cetuximab rechallenge in appropriately selected patients: Findings from long-term follow-up of CRICKET and CAVE trials

Rechallenge strategy is based on the concept that a subset of patients with RAS wild type (WT) metastatic colorectal cancer (mCRC) could still benefit of epidermal growth factor receptor (EGFR) blockade, even after progression to an anti-EGFR based chemotherapy. In fact, after an anti-EGFR free window, that reduces the number of resistant cancer cell clones, re-treatment with the anti-EGFR monoclonal antibodies cetuximab or panitumumab may have antitumor activity. Here we performed a pooled and comparative analysis of two phase II prospective trials in rechallenge setting.

Dose predictions for [177Lu]Lu-DOTA-panitumumab F(ab\u2032)2 in NRG mice with HNSCC patient-derived tumour xenografts based on [64Cu]Cu-DOTA-panitumumab F(ab\u2032)2 \u2013 implications for a PET theranostic strategy

BackgroundEpidermal growth factor receptors (EGFR) are overexpressed on many head and neck squamous cell carcinoma (HNSCC). Radioimmunotherapy (RIT) with F(ab')2 of the anti-EGFR monoclonal antibody panitumumab labeled with the β-particle emitter, 177Lu may be a promising treatment for HNSCC. Our aim was to assess the feasibility of a theranostic strategy that combines positron emission tomography (PET) with [64Cu]Cu-DOTA-panitumumab F(ab')2 to image HNSCC and predict the radiation equivalent doses to the tumour and normal organs from RIT with [177Lu]Lu-DOTA-panitumumab F(ab')2.ResultsPanitumumab F(ab')2 were conjugated to DOTA and complexed to 64Cu or 177Lu in high radiochemical purity (95.6 ± 2.1% and 96.7 ± 3.5%, respectively) and exhibited high affinity EGFR binding (Kd = 2.9 ± 0.7 × 10− 9 mol/L). Biodistribution (BOD) studies at 6, 24 or 48 h post-injection (p.i.) of [64Cu]Cu-DOTA-panitumumab F(ab')2 (5.5–14.0 MBq; 50 μg) or [177Lu]Lu-DOTA-panitumumab F(ab')2 (6.5 MBq; 50 μg) in NRG mice with s.c. HNSCC patient-derived xenografts (PDX) overall showed no significant differences in tumour uptake but modest differences in normal organ uptake were noted at certain time points. Tumours were imaged by microPET/CT with [64Cu]Cu-DOTA-panitumumab F(ab')2 or microSPECT/CT with [177Lu]Lu-DOTA-panitumumab F(ab')2 but not with irrelevant [177Lu]Lu-DOTA-trastuzumab F(ab')2. Tumour uptake at 24 h p.i. of [64Cu]Cu-DOTA-panitumumab F(ab')2 [14.9 ± 1.1% injected dose/gram (%ID/g) and [177Lu]Lu-DOTA-panitumumab F(ab')2 (18.0 ± 0.4%ID/g) were significantly higher (P < 0.05) than [177Lu]Lu-DOTA-trastuzumab F(ab')2 (2.6 ± 0.5%ID/g), demonstrating EGFR-mediated tumour uptake. There were no significant differences in the radiation equivalent doses in the tumour and most normal organs estimated for [177Lu]Lu-DOTA-panitumumab F(ab')2 based on the BOD of [64Cu]Cu-DOTA-panitumumab F(ab')2 compared to those estimated directly from the BOD of [177Lu]Lu-DOTA-panitumumab F(ab')2 except for the liver and whole body which were modestly underestimated by [64Cu]Cu-DOTA-panitumumab F(ab')2. Region-of-interest (ROI) analysis of microPET/CT images provided dose estimates for the tumour and liver that were not significantly different for the two radioimmunoconjugates. Human doses from administration of [177Lu]Lu-DOTA-panitumumab F(ab')2 predicted that a 2 cm diameter HNSCC tumour in a patient would receive 1.1–1.5 mSv/MBq and the whole body dose would be 0.15–0.22 mSv/MBq.ConclusionA PET theranostic strategy combining [64Cu]Cu-DOTA-panitumumab F(ab')2 to image HNSCC tumours and predict the equivalent radiation doses in the tumour and normal organs from RIT with [177Lu]Lu-DOTA-panitumumab F(ab')2 is feasible. RIT with [177Lu]Lu-DOTA-panitumumab F(ab')2 may be a promising approach to treatment of HNSCC due to frequent overexpression of EGFR.

Colorectal Cancer: From Genetic Landscape to Targeted Therapy.

Colorectal cancer (CRC) is the third most common cancer type and the second cause of death worldwide. The advancement in understanding molecular pathways involved in CRC has led to new classifications based on the molecular characteristics of each tumor and also improved CRC management through the integration of targeted therapy into clinical practice. In this review, we will present the main molecular pathways involved in CRC carcinogenesis, the molecular classifications. The anti-VEGF and anti-EGFR therapies currently used in CRC treatment and those under clinical investigation will also be outlined, as well as the mechanisms of primary and acquired resistance to anti-EGFR monoclonal antibodies (cetuximab and panitumumab). Targeted therapy has led to great improvement in the treatment of metastatic CRC. However, there has been variability in CRC treatment outcomes due to molecular heterogeneity in colorectal tumors, which underscores the need for identifying prognostic and predictive biomarkers for CRC-targeted drugs.

Abstract 1057: Combination of the KRASG12C inhibitor sotorasib with targeted agents improves anti-tumor efficacy in KRAS p.G12C cancer models

Abstract KRAS is the most frequently mutated oncogene in cancer and encodes a key signaling protein in tumors. The p.G12C mutation of KRAS is present in approximately 13% of lung adenocarcinoma, 3% of colorectal cancer, and 2% of other solid tumors. Sotorasib (formerly known as AMG 510), the first KRASG12C inhibitor to reach clinical testing in humans, has demonstrated evidence of clinical activity as a single agent in patients with non-small cell lung (NSCLC), colorectal (CRC), endometrial, and appendiceal carcinoma. Preclinically, sotorasib has shown significant tumor growth inhibition as a single agent in multiple CDX and PDX models. The clinically-validated strategy of combining multiple inhibitors in the MAPK pathway suggests that combination strategies could yield even better outcomes for patients. Specifically, the combination of sotorasib and other inhibitors in the MAPK and AKT signaling pathways might further enhance tumor cell killing and overcome potential resistance. To test this hypothesis, in vitro combination experiments were conducted in multiple KRAS p.G12C cell lines with combination matrices of sotorasib and inhibitors of HER kinases, EGFR, SOS1, SHP2, MEK, PI3K, or mTOR, as well as an inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6). The combination of sotorasib with multiple agents resulted in robust synergistic cell killing of KRAS p.G12C tumor cells in vitro. To understand whether these observations translated in vivo, we assessed combinations of sotorasib with a SHP-2 inhibitor or a HER kinase inhibitor in pharmacodynamic assays and efficacy models in tumor xenografts. Consistent with the synergy observed in vitro, sotorasib in combination with a HER kinase inhibitor (afatinib) or a SHP2 inhibitor (RMC-4550) in vivo resulted in enhanced inhibition of MAPK signaling as measured by p-ERK in NCI-H358 tumors. In efficacy studies using the NCI-H358 xenograft model, significantly enhanced anti-tumor activity was observed with a minimally efficacious dose of sotorasib in combination with afatinib, RMC-4550, or a CDK4/6 inhibitor (palbociclib). Furthermore, enhanced anti-tumor activity was observed with sotorasib in combination with a MEK inhibitor or with the anti-EGFR monoclonal antibody panitumumab in a CRC KRAS p.G12C PDX model. Taken together, these data support the clinical evaluation of combination treatment of sotorasib with analogous agents in patients with KRAS p.G12C tumors. Citation Format: Karen Rex, Anne Y. Saiki, Tyler Holt, Alla Verlinsky, Patricia L. McElroy, Tao Osgood, Ji-Rong Sun, Marwan G. Fakih, Upendra P. Dahal, Bernd Bruenner, Victor J. Cee, Brian A. Lanman, Jude Canon, J. Russell Lipford. Combination of the KRASG12C inhibitor sotorasib with targeted agents improves anti-tumor efficacy in KRAS p.G12C cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1057.

Combined treatment of patients with liver colorectal cancer metastases

The literature review is devoted to the analysis of the main methods of treatment of patients with colorectal cancer liver metastases. The analysis of the clinical trials results over the past 10 years has been carried out. Colorectal cancer is the common malignant neoplasm. About 20% of patients have distant metastases in the diagnosing. Liver is the most frequent targeted organ, liver metastases are detected in 14,5% of patients with colorectal cancer. Despite the encouraging results of treatment of certain groups of patients with metastatic colorectal cancer, the treatment tactics for most patients is limited to palliative chemotherapy. In recent years, the survival of patients with metastatic colorectal cancer has significantly improved due to the success of systemic therapy. The median overall survival has reached for 2 years due to combination chemotherapy based on fluoropyrimidines, oxaliplatin, irinotecan in combination with monoclonal antibodies (bevacizumab, cetuximab and panitumumab). The optimal combination and sequence of using these anticancer agents in the treatment of metastatic colorectal cancer has not yet been determined. Surgery is the standard of care for this category of patients. At the same time, until nowdays there are no clear and generally accepted criteria for choosing the optimal volume of surgical intervention, prescribing first-line chemotherapy and using other methods of antitumor treatment.

Determination of the Serum Concentrations of the Monoclonal Antibodies Bevacizumab, Rituximab, and Panitumumab Using Porous Membranes Containing Immobilized Peptide Mimotopes.

Effective monoclonal antibody (mAb) therapies require a threshold mAb concentration in patient serum. Moreover, the serum concentration of the mAb Bevacizumab should reside in a specific range to avoid side effects. Methods for conveniently determining the levels of mAbs in patient sera could allow for personalized dosage schedules that lead to more successful treatments. This work utilizes microporous nylon membranes functionalized with antibody-binding peptides to capture Bevacizumab, Rituximab, or Panitumumab from diluted (25%) serum. Modification of the capture-peptide terminus is often crucial to creating the affinity necessary for effective binding. The high purity of eluted mAbs allows for their quantitation using native fluorescence, and membranes are effective in spin devices that can be used in any laboratory. The technique is effective over the therapeutic range of Bevacizumab concentrations. Future work aims at further modifications to develop rapid point-of-care devices and decrease detection limits.

Dose-Dense Methotrexate, Vinblastine, Doxorubicin, and Cisplatin With or Without Panitumumab in Patients With Advanced Urothelial Carcinoma: Multicenter, Randomized, French Unicancer GETUG/AFU 19 Study

Epidermal growth factor receptor (EGFR) overexpression is frequent and associated with poor outcome in urothelial carcinoma. EGFR inhibition could improve the antitumor activity of chemotherapy. Patients with advanced, treatment-naïve, histologically confirmed advanced urothelial carcinoma and no HRAS or KRAS mutation in the primary tumor received dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin (dd-MVAC) without or with the anti-EGFR monoclonal antibody panitumumab (Pmab). A randomized (1:2) phase II design was used with progression-free survival (PFS) as the primary endpoint. Ninety-seven eligible patients were randomized; 96 patients were evaluable for toxicity and 87 for efficacy. The median PFS were 6.8 months (95% confidence interval [CI], 6.3-9.2) for dd-MVAC and 5.7 months (95% CI, 4.6-6.4 months) for dd-MVAC+Pmab. For both immunohistochemical and molecular definition of basal/squamous-like (BASQ) tumors, no difference was observed in objective response rates or PFS between the two arms in BASQ and non-BASQ tumors. dd-MVAC+Pmab was associated with more serious adverse events and no improvement in efficacy outcomes.

Effect of Cetuximab-Conjugated Gold Nanoparticles on the Cytotoxicity and Phenotypic Evolution of Colorectal Cancer Cells.

Epidermal growth factor receptor (EGFR) is estimated to be overexpressed in 60~80% of colorectal cancer (CRC), which is associated with a poor prognosis. Anti-EGFR targeted monoclonal antibodies (cetuximab and panitumumab) have played an important role in the treatment of metastatic CRC. However, the therapeutic response of anti-EGFR monoclonal antibodies is limited due to multiple resistance mechanisms. With the discovery of new functions for gold nanoparticles (AuNPs), we hypothesize that cetuximab-conjugated AuNPs (cetuximab-AuNPs) will not only improve the cytotoxicity for cancer cells, but also introduce expression change of the related biomarkers on cancer cell surface. In this contribution, we investigated the size-dependent cytotoxicity of cetuximab-AuNPs to CRC cell line (HT-29), while also monitored the expression of cell surface biomarkers in response to treatment with cetuximab and cetuximab-AuNPs. AuNPs with the size of 60 nm showed the highest impact for cell cytotoxicity, which was tested by cell counting kit-8 (CCK-8) assay. Three cell surface biomarkers including epithelial cell adhesion molecule (EpCAM), melanoma cell adhesion molecule (MCAM), and human epidermal growth factor receptor-3 (HER-3) were found to be expressed at higher heterogeneity when cetuximab was conjugated to AuNPs. Both surface-enhanced Raman scattering/spectroscopy (SERS) and flow cytometry demonstrated the correlation of cell surface biomarkers in response to the drug treatment. We thus believe this study provides powerful potential for drug-conjugated AuNPs to enhance cancer prognosis and therapy.

PULSE: A randomized phase II open label study of panitumumab rechallenge versus standard therapy after progression on anti-EGFR therapy in patients with RAS wild-type metastatic colorectal cancer (mCRC).

TPS143 Background: Patients with KRAS and NRAS ( RAS) wild-type mCRC benefit from the epidermal growth factor receptor (EGFR) monoclonal antibodies (Abs) panitumumab and cetuximab, but nearly all patients experience resistance. Blood-based profiling of cell free DNA (cfDNA) can identify genomic alterations that drive acquired EGFR Ab resistance. After discontinuation of anti-EGFR Abs, acquired genomic alterations decay over time to undetectable levels. Some studies have suggested clinical benefit from EGFR Ab rechallenge, but there is limited evidence that EGFR Ab rechallenge improves survival compared to standard of care (SOC) therapies. We hypothesize that cfDNA profiling will identify patients appropriate for panitumumab rechallenge, and that these molecularly selected patients will have improved survival compared to current SOC therapies. Methods: This is a randomized phase II, open label study designed to compare the overall survival (OS) of panitumumab rechallenge versus SOC (investigator choice TAS-102 or regorafenib). Secondary objectives include comparisons of progression free survival, objective response rate, clinical benefit rate, and quality of life as measured by the linear analogue self-assessment (LASA) questionnaire. Eligible patients have radiographically measurable KRAS, NRAS, and BRAF codon 600 wild-type mCRC based on tumor tissue testing, and must have experienced progression or intolerance to treatment with a fluoropyrimidine, oxaliplatin, irinotecan, an anti-VEGF Ab, and an anti-PD-1 Ab if the tumor has mismatch repair deficiency or is MSI-H. Progression after at least 4 months treatment with an anti-EGFR Ab is required. All patients must be enrolled in the COLOMATE cfDNA screening protocol (NCT03765736) and meet molecular eligibility based on Guardant360 cfDNA profiling (absence of amplification of ERBB2, KRAS, NRAS, and MET; absence of mutations of BRAF, EGFR, ERBB2, KRAS, NRAS, and MET [mutant allele frequency &gt; 0.5%]). Greater than 90 days must have elapsed between the most recent treatment with an anti-EGFR Ab and cfDNA profiling. Dosing for all study drugs is according to clinical SOC. 120 patients will be randomized 1:1 to panitumumab rechallenge or SOC. With 83 OS events, this study will have 80% power to detect an improvement in median OS from 6.5 to 10 months (HR=0.65; 1-sided α= 0.15). This study began enrollment in 6/2020. Recruitment is ongoing at 16 sites in the Academic and Community Cancer Research United (ACCRU) network (ACCRU-GI-1623). Clinical trial information: NCT03992456.