Relationship Between Cetuximab Target-Mediated Pharmacokinetics and Progression-Free Survival in Metastatic Colorectal Cancer Patients.

BACKGROUND AND OBJECTIVE: Cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal immunoglobulin (Ig)G1 antibody, has been approved for the treatment of metastatic colorectal cancer (mCRC). The influence of target-antigen on cetuximab pharmacokinetics has never been investigated using target-mediated drug disposition (TMDD) modelling. This study aimed to investigate the relationship between cetuximab concentrations, target kinetics and progression-free survival (PFS). METHODS: In this ancillary study (NCT00559741), 91 patients with mCRC treated with cetuximab were assessed. Influence of target levels on cetuximab pharmacokinetics was described using TMDD modelling. The relationship between cetuximab concentrations, target kinetics and time-to-progression (TTP) was described using a joint pharmacokinetic-TTP model, where unbound target levels were assumed to influence hazard of progression by an Emax model. Mitigation strategies of concentration-response relationship, i.e., time-varying endogenous clearance and mutual influences of clearance and time-to-progression were investigated. RESULTS: Cetuximab concentration-time data were satisfactorily described using the TMDD model with quasi-steady-state approximation and time-varying endogenous clearance. Estimated target parameters were baseline target levels (R0 = 43 nM), and complex elimination rate constant (kint = 0.95 day-1). Estimated time-varying clearance parameters were time-invariant component of CL (CL0= 0.38 L/day-1), time-variant component of CL (CL1= 0.058 L/day-1) and first-order rate of CL1 decreasing over time (kdes = 0.049 day-1). Part of concentration-TTP was TTP-driven, where clearance and TTP were inversely correlated. In addition, increased target occupancy was associated with increased TTP. CONCLUSION: This is the first study describing the complex relationship between cetuximab target-mediated pharmacokinetics and PFS in mCRC patients using a joint PK-time-to-progression model. Further studies are needed to provide a more in-depth description of this relationship.

Dynamic Contrast-Enhanced Magnetic Resonance Imaging for the Prediction of Monoclonal Antibody Tumor Disposition.

The prediction of monoclonal antibody (mAb) disposition within solid tumors for individual patients is difficult due to inter-patient variability in tumor physiology. Improved a priori prediction of mAb pharmacokinetics in tumors may facilitate the development of patient-specific dosing protocols and facilitate improved selection of patients for treatment with anti-cancer mAb. Here, we report the use of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), with tumor penetration of the contrast agent gadobutrol used as a surrogate, to improve physiologically based pharmacokinetic model (PBPK) predictions of cetuximab pharmacokinetics in epidermal growth factor receptor (EGFR) positive xenografts. In the initial investigations, mice bearing Panc-1, NCI-N87, and LS174T xenografts underwent DCE-MRI imaging with the contrast agent gadobutrol, followed by intravenous dosing of an 125Iodine-labeled, non-binding mAb (8C2). Tumor concentrations of 8C2 were determined following the euthanasia of mice (3 h-6 days after 8C2 dosing). Potential predictor relationships between DCE-MRI kinetic parameters and 8C2 PBPK parameters were evaluated through covariate modeling. The addition of the DCE-MRI parameter Ktrans alone or Ktrans in combination with the DCE-MRI parameter Vp on the PBPK parameters for tumor blood flow (QTU) and tumor vasculature permeability (σTUV) led to the most significant improvement in the characterization of 8C2 pharmacokinetics in individual tumors. To test the utility of the DCE-MRI covariates on a priori prediction of the disposition of mAb with high-affinity tumor binding, a second group of tumor-bearing mice underwent DCE-MRI imaging with gadobutrol, followed by the administration of 125Iodine-labeled cetuximab (a high-affinity anti-EGFR mAb). The MRI-PBPK covariate relationships, which were established with the untargeted antibody 8C2, were implemented into the PBPK model with considerations for EGFR expression and cetuximab-EGFR interaction to predict the disposition of cetuximab in individual tumors (a priori). The incorporation of the Ktrans MRI parameter as a covariate on the PBPK parameters QTU and σTUV decreased the PBPK model prediction error for cetuximab tumor pharmacokinetics from 223.71 to 65.02%. DCE-MRI may be a useful clinical tool in improving the prediction of antibody pharmacokinetics in solid tumors. Further studies are warranted to evaluate the utility of the DCE-MRI approach to additional mAbs and additional drug modalities.

Semimechanistic Clearance Models of Oncology Biotherapeutics and Impact of Study Design: Cetuximab as a Case Study.

This study aimed to explore the currently competing and new semimechanistic clearance models for monoclonal antibodies and the impact of clearance model misspecification on exposure metrics under different study designs exemplified for cetuximab. Six clearance models were investigated under four different study designs (sampling density and single/multiple-dose levels) using a rich data set from two cetuximab clinical trials (226 patients with metastatic colorectal cancer) and using the nonlinear mixed-effects modeling approach. A two-compartment model with parallel Michaelis-Menten and time-decreasing linear clearance adequately described the data, the latter being related to post-treatment response. With respect to bias in exposure metrics, the simplified time-varying linear clearance (CL) model was the best alternative. Time-variance of the linear CL component should be considered for biotherapeutics if response impacts pharmacokinetics. Rich sampling at steady-state was crucial for unbiased estimation of Michaelis-Menten elimination in case of the reference (parallel Michaelis-Menten and time-varying linear CL) model.

Modeling the dynamics of antibody-target binding in living tumors.

Antibodies have become an attractive class of therapeutic agents for solid tumors, mainly because of their high target selectivity and affinity. The target binding properties of antibodies are critical for their efficacy and toxicity. Our lab has developed a bioluminescence resonance energy transfer (BRET) imaging approach that directly supports the measurement of the binding dynamics between antibodies and their targets in the native tumor environment. In the present study, we have developed a spatially resolved computational model analyzing the longitudinal BRET imaging data of antibody-target binding and exploring the mechanisms of biphasic binding dynamics between a model antibody cetuximab and its target, the epidermal growth factor receptor (EGFR). The model suggested that cetuximab is bound differently to EGFR in the stroma-rich area than in stroma-poor regions, which was confirmed by immunofluorescence staining. Compared to the binding in vitro, cetuximab bound to EGFR to a "slower-but-tighter" degree in the living tumors. These findings have provided spatially resolved characterizations of antibody-target binding in living tumors and have yielded many mechanistic insights into the factors that affect antibody interactions with its targets and treatment efficacy.

Cetuximab Exhibits Sex Differences in Lymphatic Exposure after Intravenous Administration in Rats in the Absence of Differences in Plasma Exposure.

PURPOSE: The aim of this work was to identify whether biochemical and physiological sources of mAb pharmacokinetic sex-effects could be identified in the rat model where target-mediated disposition is avoided. METHODS: Plasma and lymphatic pharmacokinetics of the humanised anti-EGFR antibody cetuximab, along with potential physiological and biochemical drivers of pharmacokinetic sex differences, were examined in male and female rats. Cetuximab was used as a model mAb since plasma clearance is slower in female patients. RESULTS: When plasma concentrations were normalised to dose, female rats displayed slower plasma clearance than males, but no significant differences were observed in liver and spleen biodistribution. Sex differences in apparent plasma clearance, however, were abolished after normalisation to body weight, surface area or fat-free mass. Significant sex differences were observed in plasma testosterone, endogenous IgG and fat free mass, but did not correlate with apparent clearance. Females did, however, show two-fold higher lymphatic exposure compared to males. CONCLUSIONS: These data suggested that mAbs more efficiently access lymph in females, but this does not affect plasma pharmacokinetics or biodistribution. Further, the data suggest that sex differences observed in humans could be a function of antigen density.

Comparison of Various Phase I Combination Therapy Designs in Oncology for Evaluation of Early Tumor Shrinkage Using Simulations.

There is still a lack of efficient designs for identifying the dose response in oncology combination therapies in early clinical trials. The concentration response relationship can be identified using the early tumor shrinkage time course, which has been shown to be a good early response marker of clinical efficacy. The performance of various designs using an exposure-tumor growth inhibition model was explored using simulations. Different combination effects of new drug M and cetuximab (reference therapy) were explored first assuming no effect of M on cetuximab (to investigate the type I error (α)), and subsequently assuming additivity or synergy between cetuximab and M. One-arm, two-arm, and four-arm designs were evaluated. In the one-arm design, 60 patients received cetuximab + M. In the two-arm design, 30 patients received cetuximab and 30 received cetuximab + M. In the four-arm design, in addition to cetuximab and cetuximab + M as standard doses, combination arms with lower doses of cetuximab were evaluated (15 patients/arm). Model-based predictions or "simulated observations" of early tumor shrinkage at week 8 (ETS8) were compared between the different arms. With the same number of individuals, the one-arm design showed better statistical power than other designs but led to strong inflation of α in case of misestimated reference for ETS8 value. The two-arm design protected against this misestimation and, with the same total number of subjects, would provide higher statistical power than a four-arm design. However, a four-arm design would be helpful for exploring more doses of cetuximab in combination with M to better understand the interaction.

A phase 1b study of the MET inhibitor capmatinib combined with cetuximab in patients with MET-positive colorectal cancer who had progressed following anti-EGFR monoclonal antibody treatment.

Background Overcoming resistance to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs) in patients with KRAS wildtype (WT) metastatic colorectal cancer (mCRC) could help meet the needs of patients with limited treatment options. Methods In this phase 1b study, patients with N/KRAS WT, MET-positive mCRC who had progressed following anti-EGFR mAb treatment received escalating oral doses of capmatinib (150, 300, and 400 mg) twice daily plus weekly intravenous cetuximab (at the approved dose). The primary objective was to establish a recommended dose for expansion (RDE) of capmatinib in combination with cetuximab. Safety, preliminary activity, pharmacokinetics, and pharmacodynamics were also explored. Results Thirteen patients were enrolled. No patients experienced a dose-limiting toxicity at investigated doses; the RDE was established as capmatinib 400 mg twice daily plus cetuximab. All patients experienced adverse events (AEs) suspected to be related to the study treatment. Five patients (38.5%) reported study-drug-related AEs of grade 3/4 in severity. No patients achieved a complete or partial response according to RECIST v1.1; however, tumor shrinkage of 29-44% was observed in 4 patients. Conclusions Capmatinib plus cetuximab was well tolerated. Preliminary signs of activity were observed. Further investigation is warranted to obtain efficacy data and refine predictive biomarkers of response. Clinical trial registration NCT02205398.

Evaluation of pharmacokinetics and safety of cetuximab with cisplatin/carboplatin in patients with advanced solid tumor: Result from phase II studies.

The pharmacokinetics and potential drug-drug interactions between cetuximab and cisplatin or carboplatin from two studies (JXBA and JXBB) were evaluated. These studies were multicenter, open-label phase II trials designed to evaluate the drug-drug interactions between cetuximab (400 mg m-2 initial dose) and cisplatin (JXBA; 100 mg m-2) or carboplatin (JXBB; area under the curve [AUC] = 5 mg × min mL-1) with or without 5-fluorouracil (5FU) in patients with advanced solid tumors. Concentrations of cetuximab, cisplatin and carboplatin were determined using analytical methods. The safety and tolerability of cetuximab in combination with cisplatin or carboplatin was also determined in all treated patients. The JXBA study showed that cetuximab serum concentrations were similar when cetuximab was administered alone or in combination with cisplatin. The Cmax, tmax and overall AUC for the cetuximab group (194 µg mL-1, 2.0 hour, 14 900 µg × h mL-1) and the cetuximab and cisplatin combination group (192 µg mL-1, 1.99 hour, 16 300 µg × h mL-1) were similar. The JXBB study showed that mean cetuximab serum concentrations were similar when cetuximab was administered alone or in combination with carboplatin. The Cmax, tmax and overall AUC for the cetuximab group (199 µg mL-1, 1.15 hour, 17 200 µg × h mL-1) and the cetuximab and carboplatin combination group (199 µg mL-1, 3.17 h, 16 800 µg × h mL-1) were similar. Both studies showed that the safety profile was consistent with known side effects of cetuximab, platinum-based therapies and 5-FU. There was no clinically relevant change in cetuximab pharmacokinetics when it was administered in combination with cisplatin or carboplatin.

Removal of interstitial hyaluronan with recombinant human hyaluronidase improves the systemic and lymphatic uptake of cetuximab in rats.

Interstitial, e.g. subcutaneous (SC) or intradermal (ID), administration of monoclonal antibodies (mAb) is less invasive than intravenous administration and leads to mAb uptake into both lymphatic and blood capillaries draining the injection site. Interstitial administration, however, is hindered by the presence of hyaluronan (HA), a glycosaminoglycan that is a major fluid barrier in the interstitial space. The transient removal of HA with recombinant human hyaluronidase (rHuPH20) helps facilitate the interstitial administration of often high therapeutic doses of mAb in the clinic. rHuPH20's impact on the systemic pharmacokinetics of several mAbs has been previously described, however effects on route of absorption (lymph vs blood) are unknown. The current study has therefore explored the lymphatic transport and bioavailability of cetuximab and trastuzumab after SC and ID coadministration in the presence and absence of rHuPH20 in rats. After SC administration cetuximab absolute bioavailability increased from 67 % to 80 % in the presence of rHuPH20. Cetuximab recovery in the lymphatics also increased after SC (35.8 % to 49.4 %) and ID (26.7 % to 58.8 %) administration in the presence of rHuPH20. When the injection volume (and therefore dose) was increased 10-fold in the presence of rHuPH20 cetuximab plasma exposure increased approximately linearly (12- and 8.9-fold respectively after SC and ID administration), although the proportional contribution of cetuximab lymphatic transport reduced slightly (6.2-fold increase for both administration routes). In contrast, co-administration with rHuPH20 did not lead to increases in plasma exposure for trastuzumab after SC or ID administration, most likely reflecting the fact that the reported absolute bioavailability of trastuzumab (in the absence of rHuPH20) is high (∼77-99 %). However, lymphatic transport of trastuzumab did increase when coadministered ID with rHuPH20 in spite of the lack of change to overall bioavailability. The data suggest that co-administration with rHuPH20 is able to increase the volume of mAb that can be administered interstitially, and in some instances can increase the amount absorbed into both the blood and the lymph. In the current studies the ability of rHuPH20 to enhance interstitial bioavailability was higher for cetuximab where intrinsic interstitial bioavailability was low, when compared to trastuzumab where interstitial bioavailability was high.

Development of a Gold Nanoparticle-Functionalized Surface Plasmon Resonance Assay for the Sensitive Detection of Monoclonal Antibodies and Its Application in Pharmacokinetics.

As a prominent human therapeutic, therapeutic monoclonal antibodies (mAbs) have attracted increasing attention in the past decade due to their high-targeting specificity, low toxicity, and prolonged efficacy. Systematic pharmacokinetic analysis of mAbs not only largely facilitates the understanding of their biologic functions but also promotes the development of therapeutic drug discovery, early clinical trial implementation, and therapeutic monitoring. However, the extremely complex nature of biomatrices and the especially low dosages of mAbs make their detection in biomatrices and further pharmacokinetic analysis highly challenging. Therefore, a method capable of reliably, quickly, and sensitively quantifying mAbs in biomatrices is urgently needed. In this work, we developed and evaluated an gold nanoparticle-functionalized surface plasmon resonance assay for cetuximab (C225) detection and pharmacokinetic analysis in rhesus monkeys. Combining its advantages of label-free pretreatment and amplified signal response, the lower limit of quantitation of C225 in monkey serum was reduced to 0.0125 µg/ml, and the linear range had an order of magnitude comparable to that of an ELISA-based method. Furthermore, the pharmacokinetics of C225 in rhesus monkeys was studied after intravenous infusions of single doses at 7.5, 24, and 75 mg/kg. The concentration of C225 in monkey serum was detectable after dosing for 720 hours. We believe that this new strategy will be applicable as a general protocol for mAb quantification, pharmacokinetic characteristic determination, and toxicokinetic analysis during drug development.

Targeting Tumors with IL-10 Prevents Dendritic Cell-Mediated CD8+ T Cell Apoptosis.

Increasing evidence demonstrates that interleukin-10 (IL-10), known as an immunosuppressive cytokine, induces antitumor effects depending on CD8+ T cells. However, it remains elusive how immunosuppressive effects of IL-10 contribute to CD8+ T cell-mediated antitumor immunity. We generated Cetuximab-based IL-10 fusion protein (CmAb-(IL10)2) to prolong its half-life and allow tumor-targeted delivery of IL-10. Our results demonstrated potent antitumor effects of CmAb-(IL10)2 with reduced toxicity. Moreover, we revealed a mechanism of CmAb-(IL10)2 preventing dendritic cell (DC)-mediated CD8+ tumor-infiltrating lymphocyte apoptosis through regulating IFN-γ production. When combined with immune checkpoint blockade, CmAb-(IL10)2 significantly improves antitumor effects in mice with advanced tumors. Our findings reveal a DC-regulating role of IL-10 to potentiate CD8+ T cell-mediated antitumor immunity and provide a potential strategy to improve cancer immunotherapy.

An evaluation of cetuximab dosing strategies using pharmacokinetics and cost analysis.

OBJECTIVES: Cetuximab dosing is based on body surface area (BSA), an approach that is associated with significant wastage due to available vial sizes. NHS England recently introduced an alternative strategy for cetuximab dosing based on dose banding. The aim of this work was to investigate approaches to cetuximab dosing to improve its cost-effectiveness. METHODS: A simulation study using a population pharmacokinetic model was used to assess the performance of dosing strategies using exposure, probability of target attainment and cost. Two dosage regimens (500 and 400/250 mg/m2 ) were investigated; 5% and 10% dose banding, fixed and optimised dosing strategies were evaluated and compared to BSA strategy. KEY FINDINGS: The percentage of the total cost associated with wastage for the 400/250 mg/m2 regimen were 8.75%, 5.13%, 3.61%, 9.2% and 0% for BSA; 5 and 10% bands; fixed and optimal strategies, respectively. Similar results were obtained for 500 mg/m2 regimen. In comparison with BSA strategy, other strategies have comparable or improved performance. Optimised strategy showed consistent performance and ensures equal exposure and probability of target attainment. CONCLUSIONS: Cost-effectiveness of cetuximab treatment can be improved with alternative strategies by reducing wastage without compromising exposure.

A phase 1b study evaluating the safety and pharmacokinetics of regorafenib in combination with cetuximab in patients with advanced solid tumors.

Regorafenib 160 mg orally once daily (QD) 3 weeks on/1 week off is approved in colorectal cancer, gastrointestinal stromal tumors and hepatocellular carcinoma. We established the safety and pharmacokinetics (PK) of regorafenib combined with cetuximab in advanced refractory solid tumors. This was a phase 1, open-label, dose-escalation study (NCT01973868) in patients with advanced/metastatic solid tumors who progressed after standard therapy. Regorafenib was administered at various dose levels QD continuously or intermittently (3 weeks on/1 week off) combined with intravenous cetuximab 250 mg/m2 weekly. The primary objectives were safety, PK and maximum tolerated dose (MTD). The secondary objective was tumor response. Dose-limiting toxicities (DLTs) were evaluated in Cycle 1. Of 42 treated patients, 31 received regorafenib intermittently (120 mg, n = 8; 160 mg, n = 23) and 11 continuously (60 mg, n = 5; 100 mg, n = 6) plus cetuximab. The continuous arm was terminated due to low tolerable dose. In the intermittent arm, one DLT (grade 3 hand-foot skin reaction) was observed at 120 mg but none at 160 mg, therefore 160 mg/day was declared as the MTD in combination with cetuximab. The most common all-grade treatment-emergent adverse events were fatigue (52%), hypophosphatemia (48%) and diarrhea (40%). One grade 3 cetuximab-related dermatitis acneiform was observed. No clinically relevant drug-drug interactions were observed. Five patients (21%) had a partial response. Regorafenib 160 mg QD (3 weeks on/1 week off) plus standard dose of cetuximab was well tolerated with no unexpected toxicities and promising signs of efficacy.

Cetuximab pharmacokinetic/pharmacodynamics relationships in advanced head and neck carcinoma patients.

AIMS: Cetuximab associated with cisplatin and 5-fluorouracil is used to treat patients with inoperable or metastatic head and neck squamous cell carcinomas (HNSCC) up until disease progression or unacceptable toxicities. To date, no biomarkers of efficacy are available to select patients who will benefit from treatment. METHODS: An ancillary pharmacokinetics (PK) exploration was performed in the context of a prospective study investigating circulating-tumour cells vs progression-free survival (PFS). Cetuximab plasma concentrations were analysed according to a population PK model. Individual exposure parameters were confronted with soluble epidermal growth factor receptor (sEGFR) concentrations, tumour response and PFS. RESULTS: PK data (28 patients, 203 observations) were best described by a two-compartment model with linear elimination. Performance status (PS) significantly correlated to both cetuximab clearance and central volume of distribution with both parameters increasing by 33.3% (95% CI 1-65.6) for each 1-point increase of PS compared to PS = 0. Univariate analysis showed that patients with higher trough cetuximab concentrations at Day 7 (Cmin,D7 ) had better tumour response (P = 0.03) and longer PFS (P = 0.035). However, multivariate analysis revealed that only PS and tumour size at baseline remained significantly associated with PFS. Levels of sEGFR increased during cetuximab treatment but were not associated with PFS in the multivariate analysis. CONCLUSIONS: Our study prospectively indicates that PS is likely a confounding factor in the relationship between cetuximab PK and PFS, patients with a poor PS having lower cetuximab plasma exposure and lower PFS.

Synthesis and preclinical investigation of 99mTc-p-SCN-Bzl-DTPA-cetuximab for targeting EGFR using head and neck squamous cell carcinoma (HNSCC) xenografts.

To assess the preclinical potential of technetium-99m labelled conjugated para-isothiocyanato-benzyl diethylene triamine penta-acetic acid cetuximab (99mTc-p-SCN-Bzl-DTPA cetuximab) for imaging EGFR in HNSCC mice and rabbits xenografts. Cetuximab, a chimeric monoclonal antibody targeting EGFR, was conjugated with p-SCN-Bzl-DTPA followed by labelling with 99mTc. The labelled conjugate was evaluated for in vitro stability in L-cysteine at 37 °C. The 99mTc-p-SCN-Bzl-DTPA cetuximab was also investigated for immunoreactivity, internationalization kinetics, dose escalation (up to 300 µg) and biodistribution in HNSCC mice xenograft. The suitability of labelled moiety as a specific EGFR radio-tracer was assessed in HNSCC rabbit xenograft. 99mTc-p-SCN-Bzl-DTPA cetuximab exhibited more than 98% radiochemical purity at room temperature. In excess L-cysteine, it showed a stable behaviour at 37 °C up to 4 h p.l. The labelled conjugate was internalized in vitro in FaDu tumor cells up to 19.55%. Significantly higher uptake in tumor (at 10 µg; 34.75 ± 0.38% ID/g: pi) was seen in HNSCC mice xenograft with dose escalation assay from 1 to 300 µg/mouse. Blocking of EGFR with excess cetuximab consequently decreased the uptake of tumor up to 6.80 ± 1.25%. SPECT images of rabbit xenograft confirmed increase in tumor to background ratio after 4 h pi and validated its potential in preclinical trial as a specific FaDu tumor tracer. Our in vitro and in vivo preclinical findings indicate that the 99mTc-p-SCN-Bzl-DTPA cetuximab prepared at optimal dose of cetuximab could become a useful tool for EGFR imaging in HNSCC using SPECT.

Biodistribution, pharmacokinetics and radioimmunotherapy of 188Re-cetuximab in NCI-H292 human lung tumor-bearing nude mice.

Background Cetuximab is a fully humanized IgG1 subclass monoclonal that binds specifically to the human epidermal growth factor receptor (EGFR). Although EGFR is expressed in normal cells, the overexpression of EGFR is detected in many human cancers, such as colon, rectum and lung tumors. In this study, cetuximab with a combination of radiotherapy nuclear 188Re achieved better therapeutic effect on lung cancer. Methods188Re-cetuximab administered by the i.v. route in human NCI-H292 lung tumor-bearing mice was investigated. NanoSPECT/CT images were taken to evaluate the distribution and tumor targeting of 188Re-cetuximab in mice. The anti-tumor effect of 188Re-cetuximab was assessed by the tumor growth inhibition, survival ratio. Results For nanoSPECT/CT imaging, a significant uptake in tumor was observed at 24 and 48 h following the injection of 188Re-cetuximab. The anti-tumor effect of 188Re-cetuximab was assessed by tumor growth inhibition and the survival ratio. The tumor-bearing mice treated with 188Re-cetuximab showed a better mean tumor growth inhibition rate (MGI = 0.049) and longer median survival time and lifespan (62.50 d; 70.07%) than those treated with 188Re-perrhenate and cetuximab only by single injection. A synergistic effect of tumor growth inhibition was observed with the combination index exceeding one for 188Re-cetuximab (CI = 6.135 and 9.276). Conclusion The tumor targeting and localization of 188Re-cetuximab were confirmed in this study. Synergistic therapeutic efficacy was demonstrated for the radioimmunotherapy of 188Re-cetuximab. The results of this study reveal the potential advantage and benefit obtained from 188Re-cetuximab for diagnosis and therapy of oncology applications in the future.

MET activation confers resistance to cetuximab, and prevents HER2 and HER3 upregulation in head and neck cancer.

An understanding of the mechanisms underlying acquired resistance to cetuximab is urgently needed to improve cetuximab efficacy in patients with head and neck squamous cell carcinoma (HNSCC). Here, we present a clinical observation that MET pathway activation constitutes the mechanism of acquired resistance to cetuximab in a patient with HNSCC. Specifically, RNA sequencing and mass spectrometry analysis of cetuximab-sensitive (CetuxSen ) and cetuximab-resistant (CetuxRes ) tumors indicated MET amplification and overexpression in the CetuxRes tumor compared to the CetuxSen lesion. Stimulation of MET in HNSCC cell lines was sufficient to reactivate the MAPK pathway and to confer resistance to cetuximab in vitro and in vivo. In addition to the direct role of MET in reactivation of the MAPK pathway, MET stimulation abrogates the well-known cetuximab-induced compensatory feedback loop of HER2/HER3 expression. Mechanistically, we showed that the overexpression of HER2 and HER3 following cetuximab treatment is mediated by the ETS homologous transcription factor (EHF), and is suppressed by MET/MAPK pathway activation. Collectively, our findings indicate that evaluation of MET and HER2/HER3 in response to cetuximab in HNSCC patients can provide the rationale of successive line of treatment.

Affibody-Based PET Imaging to Guide EGFR-Targeted Cancer Therapy in Head and Neck Squamous Cell Cancer Models.

In head and neck squamous cell cancer, the human epidermal growth factor receptor 1 (EGFR) is the dominant signaling molecule among all members of the family. So far, cetuximab is the only approved anti-EGFR monoclonal antibody used for the treatment of head and neck squamous cell cancer, but despite the benefits of adding it to standard treatment regimens, attempts to define a predictive biomarker to stratify patients for cetuximab treatment have been unsuccessful. We hypothesized that imaging with EGFR-specific radioligands may facilitate noninvasive measurement of EGFR expression across the entire tumor burden and allow for dynamic monitoring of cetuximab-mediated changes in receptor expression. Methods: EGFR-specific Affibody molecule (ZEGFR:03115) was radiolabeled with 89Zr and 18F. The radioligands were characterized in vitro and in mice bearing subcutaneous tumors with varying levels of EGFR expression. The protein dose for imaging studies was assessed by injecting 89Zr-deferoxamine-ZEGFR:03115 (2.4-3.6 MBq, 2 µg) either together with or 30 min after increasing amounts of unlabeled ZEGFR:03115 (1, 5, 10, 15, and 20 µg). PET images were acquired at 3, 24, and 48 h after injection, and the image quantification data were correlated with the biodistribution results. The EGFR expression and biodistribution of the tracer were assessed ex vivo by immunohistochemistry, Western blot, and autoradiography. To downregulate the EGFR level, treatment with cetuximab was performed, and 18F-aluminium fluoride-NOTA-ZEGFR:03115 (12 µg, 1.5-2 MBq/mouse) was used to monitor receptor changes. Results: In vivo studies demonstrated that coinjecting 10 µg of nonlabeled molecules with 89Zr-deferoxamine-ZEGFR:03115 allows for clear tumor visualization 3 h after injection. The radioconjugate tumor accumulation was EGFR-specific, and PET imaging data showed a clear differentiation between xenografts with varying EGFR expression levels. A strong correlation was observed between PET analysis, ex vivo estimates of tracer concentration, and receptor expression in tumor tissues. Additionally, 18F-aluminium fluoride-NOTA-ZEGFR:03115 could measure receptor downregulation in response to EGFR inhibition. Conclusion: ZEGFR:03115-based radioconjugates can assess different levels of EGFR level in vivo and measure receptor expression changes in response to cetuximab, indicating a potential for assessment of adequate treatment dosing with anti-EGFR antibodies.

Increase in cetuximab-induced skin rash and hypomagnesemia in patients receiving concomitant treatment with proton pump inhibitors (PPIs): a possible drug interaction?

INTRODUCTION: In a previous study, we found that co-administration of proton pump inhibitors (PPIs) with cetuximab was associated with increased skin toxicity. Both these drugs can induce hypomagnesemia. The aim of this study was to retrospectively explore the possible influence of PPI drugs on cetuximab skin toxicity and the potential synergistic effect of hypomagnesemia. PATIENTS AND METHODS: The files of all eligible patients treated with cetuximab during 2015-2016 with metastatic colorectal carcinoma (mCRC) or head and neck (H&N) carcinoma were reviewed. The concomitant use of PPIs was defined if a drug belonging to that class was included in the patient's chronic medications list. RESULTS: One hundred eighteen patients (61 with H&N carcinoma, 57 with mCRC) were included in the study, and 58 of the 118 patients received PPIs concomitantly with cetuximab. Skin toxicity of any grade was reported in 33/58 (56.9%) patients on PPIs compared with 22/60 (36.7%) patients (p = 0.08) with grade 3-4 in 19/58 (32.8%) and 2/60 (3.3%), respectively (p = 0.001). Hypomagnesemia (Mg serum level < 1.2 mg/dL) was reported in 14/58 (25.9%) PPI-treated patients, compared with 5/60 (10.4%) patients not on PPIs (p = 0.08). Grade 3-4 skin toxicity or hypomagnesemia (Mg < 0.9 mg/dL) was reported in 23/58 (39.7%) patients on concomitant treatment with PPIs, compared with 3/60 (5%) patients not on PPIs (p = 0.001). CONCLUSIONS: Both the rate and the severity of cetuximab-induced skin toxicity and hypomagnesemia were increased by chronic concomitant administration of PPIs. A prospective study is needed to confirm the possible interaction between cetuximab and PPIs.

Low intensity focused ultrasound (LIFU) triggered drug release from cetuximab-conjugated phase-changeable nanoparticles for precision theranostics against anaplastic thyroid carcinoma.

Currently, multifunctional nanotechnology is strongly expected to improve the prospect of treatment and diagnosis. In this study, we synthesized epidermal growth factor (EGFR)-targeted phase-changeable polymer nanoparticles (C-HPNs) loaded with two drugs (C225 and 10-HCPT) for specific tumor targeting, synergistic chemotherapy, and ultrasound imaging under low-intensity focused ultrasound (LIFU). Cetuximab (C225), an EGFR-targeted monoclonal antibody, was conjugated on the surface of the nanoparticles, leading to a significantly high binding affinity to EGFR-overexpressing anaplastic thyroid C643 cells both in vitro and in vivo. As expected, an increase of more than 3- to 4-fold in the release rates of 10-HCPT was observed after LIFU irradiation in vitro, demonstrating that LIFU could enhance the release of drugs from the nanoparticles. Combined treatment with C-HPNs and LIFU showed excellent inhibition of cell proliferation in vitro, as well as a remarkable therapeutic effect in vivo. Moreover, the combined treatment simultaneously enhanced ultrasound imaging by LIFU-induced acoustic droplet vaporization (ADV). In conclusion, C225-modified and phase-changeable nanoparticles combined with LIFU exhibited great promise for concurrent targeted ultrasound molecular imaging and effective synergistic antitumor therapy.