A new monoclonal antibody for detection of EGF-receptors in western blots and paraffin-embedded tissue sections

Structure-Directed and Tailored Diversity Synthetic Antibody Libraries Yield Novel Anti-EGFR Antagonists

We tested whether grafting an interaction domain into the hypervariable loop of a combinatorial antibody library could promote targeting to a specific epitope. Formation of the epidermal growth factor receptor (EGFR) signaling heterodimer involves extensive contacts mediated by a "dimerization loop." We grafted the dimerization loop into the third hypervariable loop of a synthetic antigen-binding fragment (Fab) library and diversified other loops using a tailored diversity strategy. This structure-directed Fab library and a naı̈ve synthetic Fab library were used to select Fabs against EGFR. Both libraries yielded high affinity Fabs that bound to overlapping epitopes on cell-surface EGFR, inhibited receptor activation, and targeted epitopes distinct from those of cetuximab and panitumumab. Epitope mapping experiments revealed complex sites of interaction, comprised of domains I and II but not exclusively localized to the receptor dimerization loop. These results validate the grafting approach for designing Fab libraries and also underscore the versatility of naı̈ve synthetic libraries.

Frequent co-expression of EGFR and NeuGcGM3 ganglioside in cancer: it's potential therapeutic implications

Interaction between epidermal growth factor receptor (EGFR) signaling with GM3 ganglioside expression has been previously described. However, little is known about EGFR and NeuGcGM3 co-expression in cancer patients and their therapeutic implications. In this paper, we evaluate the co-expression of EGFR and NeuGcGM3 ganglioside in tumors from 92 patients and in two spontaneous lung metastasis models of mice (Lewis lung carcinoma (3LL-D122) in C57BL/6 and mammary carcinoma (4T1) in BALB/c). As results, co-expression of EGFR and NeuGcGM3 ganglioside was frequently observed in 63 of 92 patients (68 %), independently of histological subtype. Moreover, EGFR is co-expressed with NeuGcGM3 ganglioside in the metastasis of 3LL-D122 and 4T1 murine models. Such dual expression appears to be therapeutically relevant, since combined therapy with mAbs against these two molecules synergistically increase the survival of mice treated. Overall, our results suggest that NeuGcGM3 and EGFR may coordinately contribute to the tumor cell biology and that therapeutic combinations against these two targets might be a valid strategy to explore.

Multiple dose toxicity study of the humanized anti-epidermal growth factor receptor monoclonal antibody h-R3 intravenously administered to Cercopithecus aethiops sabaeus monkeys

The h-R3 is a humanized growth factor receptor monoclonal antibody (mAb) in development for the treatment of head and neck tumours in which malignant cells overexpress the Epidermal Growth Factor receptor. The present study was designed to evaluate the toxicity of repeated intravenous doses of the h-R3 mAb in a relevant species demonstrated by the avidin-biotin-peroxidase immunohistochemical (IHC) technique in skin biopsy samples from three Cercopithecus aethiops sabaeus monkeys (green monkeys). Additionally, 18 green monkeys were daily intravenously treated during 14 consecutive days. Monkeys were distributed into three experimental groups with three animals of each sex in each group. Group I received saline solution and served as control group; group II received 2.85 mg/kg of h-R3 mAb; and group III received 11.4 mg/kg of the h-R3 mAb. During the study there were no deaths, neither pathological clinical signs, or variations in the corporal weight curve. The electroneurophysiological and sanguine chemistry results did not evidence alterations related to the assay substance. Areas of haematomas, haemorrhages and inflammation, probably related with the administration procedure, were observed at the administration zones of all animals; this fact could also explain the increase in the neutrophil count of all animals at the end of the study. The electrocardiography study showed that in the 14 days of the study one female monkey, from the higher dose group, shifted its cardiac axis from +60° to +120°; this finding could be interpreted as a right ventricular elongation due to the relative high daily administered volume.

It is concluded that doses up to 11.4 mg/kg of h-R3, intravenously administered during 14 consecutive days to Cercopithecus aethiops sabaeus monkeys do not produce considerable toxic effects in the studied system.

Prospective phase II trial of nimotuzumab in combination with radiotherapy and concurrent capecitabine in locally advanced rectal cancer

PURPOSE

The aim of the study was to evaluate the safety and efficacy of adding concurrent nimotuzumab to preoperative radiotherapy with concurrent capecitabine in locally advanced rectal cancer.

METHODS AND MATERIALS

Patients with rectal cancer (clinical stage T3/4 or N+) were scheduled to receive weekly nimotuzumab (400 mg; days -6, 1, 8, 15, 22, and 29). Capecitabine (825 mg/m(2)) was delivered orally twice daily for the duration of radiotherapy. Radiotherapy was administered at 50.4 Gy (45 + 5.4 Gy). The main endpoint was the pathologic complete response (pCR) rate.

RESULTS

Twenty-one patients with T3 or T4 disease were enrolled; 66.7 % were nodal-positive; the median distance from the anal verge was 5.5 cm. A pCR was achieved in four patients (19.0 %); 71.4 % patients obtained moderate or good tumor regression (Grade 2 and 3). Downstaging occurred in 15/21 (71.4 %) patients by T stage and 11/14 (78.6 %) by N stage. The actual dose intensities (median/mean, %) were nimotuzumab (100, 100) and capecitabine (100, 99.5). The most frequent Grade 1/2 toxicities were radiation dermatitis (57.1 %), nausea/vomiting (52.4 %), leukocytopenia (47.6 %), diarrhea (47.6 %), and proctitis (38.1 %). Grade 3 diarrhea was observed in 9.5 % of patients and Grade 3 leukocytopenia in 4.8 %.

CONCLUSION

These preliminary results indicate that nimotuzumab can be safely combined with radiotherapy plus concurrent capecitabine. The efficacy of this regimen (pCR = 19.0 %) was significantly higher than that observed in previous phase II trials of preoperative radiotherapy with concurrent capecitabine and cetuximab in rectal cancer. Further investigation of concurrent nimotuzumab with radiotherapy plus capecitabine is warranted.

Delineating the functional map of the interaction between nimotuzumab and the epidermal growth factor receptor

Molecular details of epidermal growth factor receptor (EGFR) targeting by nimotuzumab, a therapeutic anti-cancer antibody, have been largely unknown. The current study delineated a functional map of their interface, based on phage display and extensive mutagenesis of both the target antigen and the Fv antibody fragment. Five residues in EGFR domain III (R353, S356, F357, T358, and H359T) and the third hypervariable region of nimotuzumab heavy chain were shown to be major functional contributors to the interaction. Fine specificity differences between nimotuzumab and other anti-EGFR antibodies were revealed. Mapping information guided the generation of a plausible in silico binding model. Knowledge about the epitope/paratope interface opens new avenues for the study of tumor sensitivity/resistance to nimotuzumab and for further engineering of its binding site. The developed mapping platform, also validated with the well-known cetuximab epitope, allows a comprehensive exploration of antigenic regions and could be expanded to map other anti-EGFR antibodies.

Nimotuzumab in combination with radiotherapy in high grade glioma patients: a single institution experience

Nimotuzumab, a humanized antibody targeting epidermal growth factor receptor, has potent anti-proliferative, anti-angiogenic, and pro-apoptotic effects in vitro and in vivo. It also reduces the number of radio-resistant CD133(+) glioma stem cells. The antibody has been extensively evaluated in patients with advanced head and neck, glioma, lung, esophageal, pancreatic, and gastric cancer. In this single institution experience, 35 patients with anaplastic astrocytoma (AA) or glioblastoma multiforme (GBM) were treated with irradiation and 200 mg doses of nimotuzumab. The first 6 doses were administered weekly, together with radiotherapy, and then treatment continued every 21 days until 1 year. The median number of doses was 12, and the median cumulative dose was thus 2400 mg of nimotuzumab. The most frequent treatment-related toxicities were increase in liver function tests, fever, nausea, anorexia, asthenia, dizziness, and tremors. These adverse reactions were classified as mild and moderate. The median survival time was 12.4 mo or 27.0 mo for patients with GBM or AA patients, respectively, who received curative-intent radiotherapy in combination with the antibody. The survival time of a matched population treated at the same hospital with irradiation alone was decreased (median 8.0 and 12.2 mo for GBM and AA patients, respectively) compared with that of the patients who received nimotuzumab and curative-intent radiotherapy. We have thus confirmed that nimotuzumab is a very well-tolerated drug, lacking cumulative toxicity after maintenance doses. This study, in a poor prognosis population, validates the previous data of survival gain after combining nimotuzumab and radiotherapy, in newly diagnosed high-grade glioma patients.

A phase I, pharmacokinetic and pharmacodynamic study of nimotuzumab in Japanese patients with advanced solid tumors

PURPOSE

Nimotuzumab is a humanized IgG₁ monoclonal antibody to the epidermal growth factor receptor (EGFR) and has demonstrated the absence of severe dermatological toxicity commonly caused by other EGFR-targeting antibodies. We conducted a phase I study to assess toxicities, pharmacokinetics, pharmacodynamics, and predictive biomarkers of nimotuzumab administered in Japanese patients with advanced solid tumors.

METHODS

Three dose levels, 100, 200, and 400 mg, of weekly i.v. nimotuzumab were given until disease progression or drug intolerability. Four patients with solid tumors were enrolled in each dose level. The expression and gene copy number of EGFR or its downstream transducers were investigated using skin biopsy samples and tumor specimens.

RESULTS

Planned dose escalation was completed without dose-limiting toxicity, and maximum tolerated dose was not reached. No allergic reaction and hypomagnesaemia were observed, and grade 3 or 4 toxicity did not occur. The common toxicity was skin rash (58 %); however, all of them were grade 1 or 2. In skin biopsies, no correlation was shown between doses and the phosphorylation of EGFR or its downstream signal transducers. Of 11 evaluable patients, no objective response was obtained, while 8 patients had stable disease (73 %). Patients with a higher-EGFR gene copy number level measured by FISH showed a longer time to progression.

CONCLUSIONS

Nimotuzumab administered weekly was feasible and well tolerated up to 400 mg in Japanese patients. A low dermatological toxicity could be a notable advantage as anti-EGFR mAb, and further evaluation is warranted.

Radiotherapy plus nimotuzumab or placebo in the treatment of high grade glioma patients: results from a randomized, double blind trial

Background

The prognosis of patients bearing high grade glioma remains dismal. Epidermal Growth Factor Receptor (EGFR) is well validated as a primary contributor of glioma initiation and progression. Nimotuzumab is a humanized monoclonal antibody that recognizes the EGFR extracellular domain and reaches Central Nervous System tumors, in nonclinical and clinical setting. While it has similar activity when compared to other anti-EGFR antibodies, it does not induce skin toxicity or hypomagnesemia.

Methods

A randomized, double blind, multicentric clinical trial was conducted in high grade glioma patients (41 anaplastic astrocytoma and 29 glioblastoma multiforme) that received radiotherapy plus nimotuzumab or placebo. Treatment and placebo groups were well-balanced for the most important prognostic variables. Patients received 6 weekly doses of 200 mg nimotuzumab or placebo together with irradiation as induction therapy. Maintenance treatment was given for 1 year with subsequent doses administered every 3 weeks. The objectives of this study were to assess the comparative overall survival, progression free survival, response rate, immunogenicity and safety.

Results

The median cumulative dose was 3200 mg of nimotuzumab given over a median number of 16 doses. The combination of nimotuzumab and RT was well-tolerated. The most prevalent related adverse reactions included nausea, fever, tremors, anorexia and hepatic test alteration. No anti-idiotypic response was detected, confirming the antibody low immunogenicity. The mean and median survival time for subjects treated with nimotuzumab was 31.06 and 17.76 vs. 21.07 and 12.63 months for the control group.

Conclusions

In this randomized trial, nimotuzumab showed an excellent safety profile and significant survival benefit in combination with irradiation.

Trial registration

Cuban National Register for clinical trials (No. 1745) (http://registroclinico.sld.cu/ensayos).

Protein-based tumor molecular imaging probes

Molecular imaging is an emerging discipline which plays critical roles in diagnosis and therapeutics. It visualizes and quantifies markers that are aberrantly expressed during the disease origin and development. Protein molecules remain to be one major class of imaging probes, and the option has been widely diversified due to the recent advances in protein engineering techniques. Antibodies are part of the immunosystem which interact with target antigens with high specificity and affinity. They have long been investigated as imaging probes and were coupled with imaging motifs such as radioisotopes for that purpose. However, the relatively large size of antibodies leads to a half-life that is too long for common imaging purposes. Besides, it may also cause a poor tissue penetration rate and thus compromise some medical applications. It is under this context that various engineered protein probes, essentially antibody fragments, protein scaffolds, and natural ligands have been developed. Compared to intact antibodies, they possess more compact size, shorter clearance time, and better tumor penetration. One major challenge of using protein probes in molecular imaging is the affected biological activity resulted from random labeling. Site-specific modification, however, allows conjugation happening in a stoichiometric fashion with little perturbation of protein activity. The present review will discuss protein-based probes with focus on their application and related site-specific conjugation strategies in tumor imaging.

Pharmacodynamic trial of nimotuzumab in unresectable squamous cell carcinoma of the head and neck: a SENDO Foundation study

PURPOSE

To assess the pharmacodynamic effects of nimotuzumab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody with intermediate affinity for the receptor, in skin and tumor tissues from head and neck cancer patients.

EXPERIMENTAL DESIGN

Pharmacodynamic study in patients with advanced squamous cell carcinoma of the head and neck, unsuitable for chemoradiotherapy, enrolled in a single-center trial. Patients received 8 weekly infusions of nimotuzumab. The first nimotuzumab infusion was administered 1 week before starting radiation, whereas the remaining doses were administered concomitantly with irradiation. Paired biopsies were taken from skin and primary tumors, before (pretherapy) and 1 week (on single-agent therapy) after first infusion. Immunohistochemistry was conducted to assay the effects of nimotuzumab on total and phosphorylated EGFR, phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), p-AKT, and proliferation (Ki-67).

RESULTS

Nimotuzumab was well tolerated and there was no evidence of skin rash. Objective response was achieved in 9 of 10 patients. The pharmacodynamic assays showed inhibition of p-EGFR in both skin and tumor (P = 0.042 in skin and P = 0.034 in tumor). No significant changes in p-ERK1/2, p-AKT, or Ki-67 were detected in skin. In addition, lymphocytic infiltrates, folliculitis, or perifolliculitis were not observed. In tumor samples, there was an upregulation of p-AKT (P = 0.043), a reduction in proliferation index (P = 0.012), and a nonsignificant trend toward a decrease of p-ERK1/2 (P = 0.091).

CONCLUSIONS

The pharmacodynamic data confirmed the ability of nimotuzumab to decrease EGFR phosphorylation. Downstream effects were observed in tumor cells but not in skin, a finding that may help to explain the lack of skin rash in patients treated with nimotuzumab.

Nimotuzumab, a promising therapeutic monoclonal for treatment of tumors of epithelial origin

Nimotuzumab is a humanized therapeutic monoclonal antibody against epidermal growth factor receptor (EGFR). Clinical trials are ongoing globally to evaluate nimotuzumab in different indications. Nimotuzumab has been granted approval for use in squamous cell carcinoma of head and neck (SCCHN), glioma and nasopharyngeal cancer in different countries. This review focuses on the unique functional characteristics of nimotuzumab. Also, it discusses the safety and efficacy data obtained from the Phase IIb clinical trial conducted in India in SCCHN. Post marketing surveillance data from Cuba for the use of nimotuzumab in pediatric and adult glioma is also discussed. Overall, nimotuzumab has immense therapeutic potential in cancers of epithelial origin.

Interaction of antibodies with ErbB receptor extracellular regions

Antibodies to the extracellular region of the ErbB receptors have played key roles in the development of a mechanistic understanding of this family of receptor tyrosine kinases. An extensively studied class of such antibodies inhibits activation of ErbB receptors, and these antibodies have been the focus of intense development as anti-cancer agents. In this review we consider the properties of ErbB receptors antibodies in light of the current structure-based model for ErbB receptor homo- and hetero-dimerization and activation. Crystal structures of the Fab fragments from five different inhibitory antibodies in complex with the extracellular regions of EGFR and ErbB2 have been determined. These structures highlight several different modes of binding and mechanisms of receptor inhibition. Information about antibody interactions with the structurally well-characterized soluble extracellular regions of ErbB receptors can be combined with the rich knowledge of the effects of these antibodies in cultured cells, and in vivo, to provide insights into the conformation and activation of ErbB receptors at the cell surface.

Biological activity in vitro of anti-epidermal growth factor receptor monoclonal antibodies with different affinities

Epidermal growth factor receptor (EGFR) is frequently overexpressed in epithelial tumors and is associated with a poor prognosis. An increasing interest in developing anti-EGFR therapies has resulted in the evaluation of monoclonal antibodies with the capacity to bind to the EGFR, inhibiting EGFR-dependent cellular transformation. A differential toxicity and therapeutic effect in vivo are associated with the affinity and isotype of the molecule. In this study, we examined the biological activities of three monoclonal antibodies (MAbs) -- Ior egf/r3 (mouse IgG2a, 10(-9) M), Nimotuzumab (humanized IgG1, 10(-9) M), and Cetuximab (human/mouse chimeric IgG1, 10(-10) M) -- considering inhibition of cell proliferation, apoptosis, and complement-mediated cell death in squamous cell carcinoma A431 in vitro. All the antibodies bound to the EGFR on these cells, inhibiting the receptor phosphorylation, as measured by flow cytometry, inmunocytochemistry, and Western blot. Exposure to the different antibodies inhibited cell proliferation in culture in a range from 50 to 80% compared to controls. Furthermore, similar capabilities to induce either complement-mediated cytotoxicity (ranging between 70 and 90%) or a two-fold increase in the rate of apoptotic cells were found when tumor cells were exposed to the antibodies. These results suggest that the affinity between specific anti-EGFR antibodies and its receptor could affect, but not determine their biological activity at least in those cell lines that exhibit high sensitivity to withheld EGFR. Our findings also confirm previous evidences that blocking EGFR in A431 cells by means of antibodies significantly changes tumor cell biology by promoting apoptosis while decreasing tumor cell proliferation.

Multimodality imaging of the HER-kinase axis in cancer

The human epidermal growth factor receptor (HER) family of receptor tyrosine kinases controls critical pathways involved in epithelial cell differentiation, growth, division, and motility. Alterations and disruptions in the function of the HER-kinase axis can lead to malignancy. Many therapeutic agents targeting the HER-kinase axis are approved for clinical use or are in preclinical/clinical development. The ability to quantitatively image the HER-kinase axis in a noninvasive manner can aid in lesion detection, patient stratification, new drug development/validation, dose optimization, and treatment monitoring. This review summarizes the current status in multimodality imaging of the HER-kinase axis using PET, SPECT, optical, and MR imaging. The targeting ligands used include small-molecule tyrosine kinase inhibitors, peptides, proteins, antibodies, and engineered antibody fragments. EGFR and HER2 imaging have been well documented in the past, and imaging of HER3, HER4, HER heterodimers, and HER-kinase mutants deserves significant research effort in the future. Successful development of new HER-kinase-targeted imaging agents with optimal in vivo stability, targeting efficacy, and desirable pharmacokinetics for clinical translation will enable maximum benefit in cancer patient management.

Targeted cancer therapies based on antibodies directed against epidermal growth factor receptor: status and perspectives

Compelling experimental and clinical evidence suggests that epidermal growth factor receptor (EGFR) plays an important role in the pathogenesis of a variety of human cancers; thus, providing a strong rationale for the development of receptor antagonists as effective and specific therapeutic strategies for the treatment of EGFR-expressing cancers. Monoclonal antibodies (mAb), owing to their high specificity towards a given target, represent a unique class of novel cancer therapeutics. A number of anti-EGFR mAb are currently being developed in our clinic, including two that have been approved by the United States Food and Drug Administration for the treatment of refractory metastatic colorectal cancer (mCRC) and squamous cell carcinomas of the head and neck (SCCHN). Cetuximab (Erbitux, IMC-C225), an IgG1 mAb, has demonstrated significant antitumor activity, both as a single agent and in combination with chemotherapeutics and radiation, in patients with refractory mCRC and SCCHN, respectively. Panitumumab (Vectibix), an IgG2 mAb, has been approved as a single agent for the treatment of patients with refractory mCRC. These mAb, via blocking ligand/receptor interactions, exert their biological activity via multiple mechanisms, including inhibition of cell cycle progression, potentiation of cell apoptosis, inhibition of DNA repair, inhibition of angiogenesis, tumor cell invasion and metastasis and, potentially, induction of immunological effector mechanisms. Anti-EGFR antibodies have demonstrated good safety profiles and potent anticancer activity in our clinic and may prove to be efficacious agents in the treatment of a variety of human malignancies.

Immunohistochemical Evaluation of H-R3 a Novel Humanized Monoclonal Antibody That Neutralizes the EGF-receptor

The epidermal growth factor receptor (EGF-R) is an important growth regulator of epithelial cancer cells, overexpressed by several human tumors and scantly detectable in most normal tissues. The introduction of monoclonal antibodies (Mabs) and more recently engineered humanized Mabs have greatly expanded the therapeutic potential of this modality of cancer treatment. The present study was designed to compare the specificity of the murine and humanized anti-EGF-R Mabs. Biotinylated Mabs were tested in samples of fetal and adult normal and neoplastic tissues by ABC peroxidase method. All fetal tissues studied were positive for both Mabs, showing 2 different staining patterns, one homogeneous and finely granular in cytoplasm and another grosser with intense labeling in both membrane and cytoplasm. A similar recognition pattern was exhibited in adult normal tissues, where an intense reactivity was also evidenced in skin, tongue, gastrointestinal tract, renal tubules, and breast gland epithelium. In tissues from genitourinary and central nervous system, a faint staining was demonstrate, whereas those from cardiovascular and lymphoid tissues proved to be negative. These Mabs exhibited a heterogeneous and strong membrane and cytoplasm staining in neoplastic cells from lung, breast, and head and neck cancer. On the basis of these results, we conclude that the humanized (h-R3) and murine (egf/r3) anti-EGF-R Mabs show a very similar immunohistochemical pattern of recognition of fetal, adult, and neoplastic tissues. Also h-R3 Mab is a novel candidate for the development of an immunotherapeutic approach suitable for the treatment of tumors with EGF-R overexpression.

Local and systemic toxicity of h-R3, an anti-epidermal growth factor receptor monoclonal antibody, labeled with 188osmiun after the intracerebral administration in rats

h-R3 is a humanized anti-epidermal growth factor receptor (EGFR) monoclonal antibody (MAb). This receptor is over-expressed in the majority of tumors of epithelial origin, including glioblastomas. 188Rhenium (188Re) constitutes an ideal radionuclide for imagining and radioimmunotherapy, and its toxicity is known, nevertheless, it is unknown if 188Os, as 188Re's daughter, has any local or systemic toxicity effect when it is administered intracerebrally for treating intracranial tumors. For this reason we decided to assess the toxicity of stable 188Os once the complete decay of 188Re has occurred, by administering intracerebrally to rats the h-R3 labeled with 188Os. Forty rats (20 each sex) were distributed randomly into four experimental groups (ten per group): control group received 5microL of glucoheptonate solution vehicle; two other groups were treated with unlabeled or labeled h-R3 with 188Os. The remaining group served as a non-treated control group. A single 5 microL dose (2.5 microL into each lateral ventricle) of neutral solution containing 50 microg of h-R3 labeled initially with 13.25 microCi of 188Re was stereotactically administered into lateral ventricles 8 days after the conjugation with the radionuclide was done. Each animal was observed daily for detection of toxicity signs. Body weights were recorded on days 0, 7 and 14. Blood samples for analysis of hematological and clinical chemistry parameters were taken on days 0 and 14. Necropsy and histopathological studies were carried out at the end of the study. All animals gained weight by day 14. There were no changes in hematological and clinical chemistry, but minimal histopathological changes were observed at the application sites. This study shows that single doses of 188Os-h-R3 is tolerable and causes minimal local and no systemic toxicity effects in rats.

7A7 MAb: a new tool for the pre-clinical evaluation of EGFR-based therapies

The epidermal growth factor receptor (EGFR) is highly expressed in many types of epithelial tumors. EGFR overexpression has been associated with an advanced stage of the disease, with resistance to standard therapies, and, for certain tumors, with poor patient prognosis. As a result, EGFR has been considered a meaningful target in anti-tumor strategies. Active and passive immunotherapies blocking EGFR and its ligands have been explored. But for successful pre-clinical evaluation of these approaches, well-established murine tumor models are not available and highly desirable. We described, for the first time, the generation and characterization of an anti-murine EGFR extracellular domain monoclonal antibody (7A7 MAb) (IgG1). 7A7 was generated by immunization of Balb/c mice with the recombinant extracellular domain of murine EGFR (rECD-mEGFR). 7A7 recognized an epitope present in the amino acidic core of the antigen and is cross-reactive with the human EGFR. Interestingly, this MAb was able to specifically bind EGFR at the cell surface, allowing the assessment of its differential expression in a panel of murine cells. Noteworthy, in a preliminary immunohistochemical study with 7A7 MAb, recognition of Balb/c mice skin sections and EGFR-positive tumors were observed. We concluded that 7A7 MAb is a valuable tool for EGFR-based therapeutic pre-clinical studies.

Immunohistochemical Recognition of the Epidermal Growth Factor Receptor by the h-R3 Antibody in the Skin of Experimental Animals

The h-R3 is a humanized monoclonal antibody (Mab) that binds to the external domain of the human epidermal growth factor receptor (EGF-R). It has being used for the treatment of head and neck tumors. Since it is known that different animal species have different EGF-R amino acid sequences, it raises the handicap that, a priori, the animal species relevant for the pharmacodynamic, pharmacokinetic, and toxicologic studies of this Mab are unknown. To elucidate relevant laboratory animal species, the authors investigated the immunohistochemical recognition by h-R3 Mab of EGF-R in small skin biopsy samples obtained from NMRI nu/nu, C57Bl/6, and OF-1 mice; Sprague-Dawley rats; Hartley guinea pigs; New Zealand rabbits; and Cercopithecus aethiops and Macaca fascicularis monkeys. Additionally, three human skin biopsies were obtained from trauma victims. The immunolocalization of EGF-R in different tissue sections was performed using the avidin-biotin peroxidase complex (ABC) technique. The skin sections from different tissues were tested with the biotinylated h-R3 Mab or with a biotinylated irrelevant Mab, used as negative control. The staining intensity was qualified as:-, no staining; +, weak staining; ++, moderate staining; +++, strong staining. Macaca fascicularis monkey, New Zealand rabbit, and OF-1 mouse skins had a strong staining intensity; Cercopithecus aethiops monkey and Sprague-Dawley rat skins showed a moderate to strong staining intensity; C57Bl/6 mouse skins showed a moderate staining intensity. No staining was observed in the skins from Hartley guinea pigs and MNRI nu/nu mice. The fact that h-R3 Mab recognizes other animal EGF receptors in addition to the human EGF-R makes it possible to perform relevant pharmacodynamic, pharmacokinetic, and toxicologic studies in some laboratory animals.

Use of the humanized anti-epidermal growth factor receptor monoclonal antibody h-R3 in combination with radiotherapy in the treatment of locally advanced head and neck cancer patients

PURPOSE

To evaluate safety and preliminary efficacy of the humanized anti-epidermal growth factor receptor monoclonal antibody h-R3 in combination with radiotherapy (RT) in unresectable head and neck cancer patients. Secondary end points were the measurement of h-R3 serum levels and the assessment of the potential mechanisms of antitumor effect on patient biopsies. Anti-idiotypic response to h-R3 was assessed. To predict pharmacologic effect, a mathematical model for antibodies recognizing antigens expressed in tumors and normal tissues was built.

PATIENTS AND METHODS

Twenty-four patients with advanced carcinomas of the head and neck received six once-weekly infusions of h-R3 at four dose levels in combination with RT. Pretreatment tumor biopsies were obtained to evaluate epidermal growth factor receptor expression as an enrollment criterion. Second biopsies were taken to evaluate the proliferative activity and angiogenesis in comparison with the pretreatment samples. Patient serum samples were collected to measure h-R3 levels and anti-idiotypic response.

RESULTS

The combination of h-R3 and RT was well tolerated. Antibody-related adverse events consisted in infusion reactions. No skin or allergic toxicity appeared. Overall survival significantly increased after the use of the higher antibody doses. Immunohistochemistry studies of tumor specimens before and after treatment revealed that antitumor response correlated with antiproliferative and antiangiogenic effect. One patient developed antibodies to h-R3. The mathematical model predicted that the maximum difference between the area under the curve in tumors and normal tissues is reached when the antibody has intermediate affinity.

CONCLUSION

h-R3 is a well-tolerated drug that may enhance radiocurability of unresectable head and neck neoplasms.

Pharmacological evaluation of humanized anti-epidermal growth factor receptor, monoclonal antibody h-R3, in patients with advanced epithelial-derived cancer

Epidermal growth factor receptor (EGFR) overexpression has been detected in many tumors of epithelial origin, and it is often associated with tumor growth advantages and poor prognosis. h-R3 is a genetically engineered humanized antibody (mAb) that recognizes an epitope located in the extracellular domain of human EGFR. The antibody exhibited potent in vitro and in vivo antitumor effect on EGFR overexpressing cell lines. To study safety, pharmacokinetics, and biodistribution, 12 patients with advanced epithelial-derived tumors received single intravenous infusion of h-R3 at four dose levels. Safety evaluation was made according to World Health Organization toxicity criteria. For biodistribution, 3 mg of the total dose were labeled with Technetium and then pooled with the rest of the dose. Anterior and posterior whole-body images were acquired using a gamma camera. Blood samples were taken for pharmacokinetics, antiidiotypic response, and for soluble EGFR detection. After hR3 administration, no evidence of severe toxicity was observed. Secondary reactions were mild and moderate and mainly consisted of tremors, fever, and vomiting. No anaphylactic or skin reactions were detected. Qualitative analysis of whole-body images showed that the liver had the highest mAb uptake. Pharmacokinetic analysis revealed that elimination half-lives and the AUC increased linearly with dose, while total body clearance decreased when increasing doses of h-R3. No relation between shed EGFR and mAb clearance was found. No antiidiotypic response against h-R3 was detected. Several phase II trials are now underway to evaluate the efficacy of h-R3 in the treatment of advanced cancer patients.

A phase I study of 99mTc-hR3 (DiaCIM), a humanized immunoconjugate directed towards the epidermal growth factor receptor

A phase I trial was conducted to evaluate the safety, tumour and normal tissue localization, pharmacokinetics and radiation dosimetry of Tc-hR3, a humanized monoclonal antibody directed towards the epidermal growth factor receptor, in 12 patients with recurrent or metastatic epithelial malignancies. Patients were injected intravenously with 3.0 mg or 6.0 mg (1010 MBq) of Tc-hR3. Blood and plasma concentrations of radioactivity were measured and a complete 24 h urine collection was obtained. Whole-body images were acquired up to 24 h post-injection and normal organ uptake quantified. Radiation dosimetry was estimated using MIRDose. Safety was evaluated by clinical observation, biochemical/haematological testing and by measuring immune response to Tc-hR3. There were no adverse effects, no changes in biochemical/haematological indices and no immune response to Tc-hR3. Tc-hR3 was rapidly cleared from the blood with a distribution half-life of 10.8+/-3.8 min. The volume of distribution, and clearance, were 180+/-37 ml.kg and 14+/-3 ml.kg.min, respectively. The elimination phase could not be discerned due to increasing blood radioactivity at later times. About 19-24% was excreted in the urine. Normal tissue uptake was mainly in the liver (44-50%), spleen (3-4%) and kidneys (3%). Imaging was positive in one patient with squamous cell carcinoma of the mouth and an involved cervical lymph node. The whole-body radiation dose from Tc-hR3 was 1.34+/-0.02x10 mSv.Bq. We conclude that Tc-hR3 exhibited an excellent safety profile. Future studies to determine the sensitivity and specificity of imaging with Tc-hR3 in a larger group of patients with pre-selection for epidermal growth factor receptor positivity are planned.

Antiproliferative, antiangiogenic and proapoptotic activity of h-R3: A humanized anti-EGFR antibody

The epidermal growth factor receptor (EGFR) proto-oncogene is frequently overexpressed in tumors of epithelial origin. This event is thought to be causative for tumor development and progression and henceforth associated with poor prognosis. The recent considerable interest in developing EGFR-targeting agents resulted in derivation of the monoclonal, humanized, neutralizing antibody h-R3, which binds to the extracellular domain of EGFR with high affinity and strongly inhibits EGFR-dependent cellular transformation. Thus, treatment of A431 squamous cell carcinoma cells with h-R3 in either 2-dimensional or 3-dimensional culture resulted in appreciable antimitotic effects through induction of the G1 arrest. Although h-R3 does not appear to have a direct proapoptotic activity in this setting, it inhibits production of the vascular endothelial growth factor (VEGF) by A431 cells both in vitro and in vivo. In the latter case, h-R3 treatment (0.25-1 mg/mouse; every other day per 2 weeks) not only significantly reduced VEGF mRNA expression of A431 tumors growing subcutaneously in SCID mice but also resulted in reduction of the overall microvascular density (MVD), disappearance of dilated "mother vessels," as well as in suppression of tumor growth followed by regression of established tumors. This apparent antiangiogenic activity of h-R3 was associated with reduction in Ki67-positive tumor cell fraction and (unlike in vitro) also with an elevated apoptotic index, the latter indicative of a cytotoxic mode of action in vivo. Taken together, h-R3 is a promising new antagonist of the EGFR oncogene, the anticancer properties of which are associated with combined and potent antiproliferative, antiangiogenic and proapoptotic activity.

Phase I clinical evaluation of a neutralizing monoclonal antibody against epidermal growth factor receptor in advanced brain tumor patients: preliminary study

High levels of growth factors and their receptors have been demonstrated in human tumors. Gliomas and meningiomas are characterized by overexpression of epidermal growth factor receptor (EGF-R). Ior egf/r3, is a neutralizing murine monoclonal antibody (MAb) against EGF-R, and was generated at the Cuban Institute of Oncology. The antibody recognizes EGF-R with high affinity, inhibiting tyrosine kinase activation. A clinical trial was conducted in brain tumor patients to evaluate toxicity, immunogenicity, and clinical benefit of escalating doses of the antibody. Nine patients with histologically confirmed gliomas or meningiomas, who had active or recurrent disease after receiving conventional treatment, received four intravenous doses of ior egf/r3. Total dosages ranged from 160 to 480 mg. As inclusion criteria, radioimmunoscintigraphy with the same MAb labeled with 99mTechnetium (99mTc) was performed. Immune response against the murine antibody was also evaluated. After four doses of ior egf/r3 MAb, no significant toxicity was found, except in one patient who developed a grade 4 allergic adverse event. This reaction was probably related with previous sensitization to the same MAb and the development of human anti-mouse antibodies (HAMA) response. Despite no major objective antitumor responses, eight patients had stable disease on the 6-month evaluation, and two patients remain alive after four years of MAb therapy.

Characterization of a recombinant monoclonal antibody by mass spectrometry combined with liquid chromatography

In this report, we present the characterization of a humanized monoclonal antibody specific for the human epidermal growth factor receptor (hEGFR). Direct analysis by matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) of peptide mixtures and chromatographically isolated fractions allowed identification of 94.0% and 85.4% of the amino acid sequence of light and heavy chains, respectively. Microheterogeneity sources were identified in light and heavy chains and a previously unreported posttranslational modification for immunoglobulins was found. One N-glycosylation site was identified in the heavy chain with non-sialylated bianntenary fucosylated structures. This study is one of the first to assess the potential of MALDI-MS in combination with more conventional protein chemistry techniques for the characterization of monoclonal antibodies.

Phase I clinical evaluation of a neutralizing monoclonal antibody against epidermal growth factor receptor

Ior egf/r3, a neutralizing monoclonal antibody (mAb) against Epidermal Growth Factor Receptor (EGFR) was generated at the Cuban Institute of Oncology. Immunoscintigraphic studies in 148 patients with this 99-m Technetium (99Tc) labeled mAb, showed a high sensitivity and specificity for in vivo detection of epithelial tumors. To study safety, pharmacokinetic and immunogenicity of ior egf/r3 at high doses, a phase I clinical trial was conducted. Nineteen patients with advanced epithelial tumors received 4 mAb intravenous infusions at 6 dose levels: from 50 to 500 mg. Previously, immunoscintigraphic images using the same mAb labeled with 99Tc were acquired. Blood samples were collected for pharmacokinetic analysis and HAMA response. After mAb therapy, objective response was classified according to WHO criteria. Ior egf/r3 was well tolerated in spite of the high-administered doses. Only a severe adverse reaction consisting of hypotension and lethargy was observed. In 13 patients, selective accumulation of 99Tc-labeled mAb was observed at the site of the primary tumor or the metastasis. Pharmacokinetic analysis revealed that elimination half-life and the area under the time-concentration curve increased linearly with dose. HAMA response was detected in 17 patients. After 6 months of mAb therapy, 4 patients had stable disease. One patient had a tumor partial remission after 3 cycles of ior egf/r3.

Radiotoxicity of h-R3 monoclonal antibody labeled with 188Re administered intracerebrally in rats

Brain tumors are often incurable despite current aggressive treatment modalities. Regional intracerebral administration of labeled monoclonal antibodies (Mabs) can maximize the radioisotope and Mab concentration to tumor sites while reducing systemic toxicity. h-R3 is a humanized antiepidermal growth factor receptor Mab that successfully targets the epidermal growth factor receptor, which is overexpressed in glioblastomas. We studied the acute local and systemic toxicity effects of intraventricular 188Re-h-R3 in rats. Forty rats were distributed into four groups with five animals of each sex in each group. A single 5 -microl dose (2.5 microl into the left and 2.5 microl into the right lateral ventricles) of neutral solution containing 50 microg of h- R3 labeled with 49.5 +/- 1.7,284 +/- 13.7 or 579 +/- 23.7 muCi of 188Re were stereotactically administered to each animal. Control animals received vehicle alone. Each animal was observed twice daily for detection of toxicity signs. Body weights were recorded on days 0, 7 and 14. Blood samples for analysis of hematological and clinical chemistry parameters were taken on days 0 and 14. Necropsy and histopathological studies were carried out after completion of the study. All animals, but one, remained clinically stable. Toxicities included local radionecrosis, discrete increase in ALAT and creatinine blood values at higher dose level. We concluded that a single intraventricular administration of relatively large doses of 188Re-h-R3 is tolerable and causes minimal local and systemic toxicity effects in rats. Nevertheless, further studies are necessary to discard learning and behavioral problems.

Humanized versus murine anti-human epidermal growth factor receptor monoclonal antibodies for immunoscintigraphic studies

The anti-human epidermal growth factor receptor (EGF-R) humanized antibody h-R3 (IgG(1)), which binds to an extracellular domain of EGF-R, was used to evaluate the biodistribution on nude mice xenografted with A431 epidermoid carcinoma cell line. Results are compared with its murine version ior egf/r3 monoclonal antibody (mAb). Twenty-one athymic female 4NMRI nu/nu mice were injected intravenously with 10 microg/100 microCi of (99m)Tc-labeled mAbs. The mAb ior C5 that recognizes an antigen expressed preferentially on the surface of malignant and cytoplasm of normal colorectal cells was used as negative control. Immunoreactivity of (99m)Tc-labeled mAbs was measured by enzyme linked immunosorbent assay on A431 cell line and the immunoreactive fractions determined by Lindmo method. Among all organs significative accumulation was found in tumor (6.14 +/- 2.50 %ID/g, 5.06 +/- 2.61 %ID/g for murine and humanized mAbs, respectively) 4 h after injection. The immunoreactive fractions were found to be 0.88 and 0.81 for murine and humanized mAb, respectively. Thus, we expect better results using the humanized mAb h-R3 for diagnostic immunoscintigraphy.

Freeze-dried formulation for direct 99mTc-labeling ior-egf/r3 MAb: additives, biodistribution, and stability

Monoclonal antibodies (MAbs) have been useful for immunoscintigraphic applications in clinical diagnosis since they were introduced in nuclear medicine practice. The MAb ior egf/r3 developed at the Center of Molecular Immunology (Havana, Cuba) is a murine antibody that recognizes the human epidermal growth factor receptor (EGF-R) and has been used widely in the radioimmunodiagnosis of tumors of epithelial origin. Based on the direct Schwarz method, the present report describes the preparation of a freeze-dried formulation for radiolabeling the MAb ior egf/r3 with 99mTc for immunoscintigraphic applications. Radiolabeling efficiency, effects on immunoreactivity, biodistribution, pharmacokinetic, and stability of the formulation are reported. The study demonstrated that the freeze-dried formulation can be labeled with 99mTc at high yield. The resulting 99mTc-labeled ior egf/r3 MAb can be used to visualize in vivo human tumors of epithelial origin by immunoscintigraphy studies. The kit does not need any other addition or purification at the time of tagging other than the requisite amount of pertechnetate (40-50 mCi). Because the contents of the kit are lyophilized, no special storage or transportation is required.

188Re-direct labeling of monoclonal antibodies for radioimmunotherapy of solid tumors: biodistribution, normal organ dosimetry, and toxicology

The increased interest in the availability of radionuclides for therapy has resulted from the recent success and potential importance of radiolabeled antibodies for both diagnosis and therapy. There is a widespread interest in the availability of 188Re for various therapeutic applications, particularly for attachment to tumor-specific monoclonal antibodies for radioimmunotherapy. This review provides a perspective of 188Re-direct labeled MAbs for radioimmunotherapy of solid tumors, normal organ biodistribution, absorbed radiation doses to normal organs and tumors, and the toxicity to bone marrow and normal tissues. Methods for calculation of mean absorbed radiation doses to the whole body, various normal organs, and tumors have been developed using source-organ residence times and the methods developed by the Medical Internal Radiation Dose (MIRD) committee. The toxicity for 188Re-labeled antibodies is predominantly hematopoietic, with platelets and white blood cells being most sensitive to the effects of radiation. Rhenium-188 would be the isotope of choice for radioimmunotherapeutic applications because of cost, availability, and favorable radiation characteristics. Rhenium-188 has a half-life of 16.9 h and maximum beta energy of 2.118 MeV. This isotope is particularly attractive because it can be supplied conveniently from 188W/188Re-radionuclide generator system.

Estrogen regulation of transforming growth factor-alpha in ovarian cancer

Transforming growth factor alpha (TGFalpha) may be induced by estrogen in estrogen responsive systems and can contribute to the growth-modulatory effects of this hormone. To test whether TGFalpha contributes to estrogen-regulated growth in ovarian cancers, we have compared the effects of 17beta-estradiol (E2) and TGFalpha in a range of ovarian carcinoma cell lines. Addition of E2 to the estrogen receptor (ER)-positive cell lines (PE01, PE04 and PE01CDDP) produced a 2-4 fold increase in TGFalpha protein concentrations in media conditioned by the cells. Both E2 and TGFalpha stimulated the growth of the PE01 and PE04 lines and inhibited the growth of the PE01CDDP line. Furthermore, the E2-mediated growth effects could be reversed by an epidermal growth factor (EGF) receptor-targeted antibody. E2 also down-regulated EGF receptor expression in ER-positive cell lines. In a series of primary ovarian tumors, higher concentrations of ER were associated with an increased percentage of tumors expressing TGFalpha mRNA and a decreased percentage expressing EGF receptor protein. All these data are consistent with E2 increasing production of TGFalpha in ER-positive ovarian cancer and this in turn acting through the EGF receptor to modulate growth in an autocrine manner.

Pharmacokinetics, biodistribution and dosimetry of 99mTc-labeled anti-human epidermal growth factor receptor humanized monoclonal antibody R3 in rats

The pharmacokinetics, biodistribution and dosimetry of 99mTc-labeled anti-human epidermal growth factor receptor (anti-hEGF-r) humanized monoclonal antibody (MAb) R3 was investigated following intravenous injection in normal Wistar rats. Serum disappearance curves were best fit by a two-compartment model having a mean distribution half-life (t 1/2alpha) of 0.250 h and a mean elimination (t 1/2beta) of 13.89 h. Among the various organs, a little accumulation of the radiolabeled antibody was found only in kidneys. Biodistribution and dosimetry studies in humans were performed by extrapolation of the animal data to humans. Absorbed dose to normal organs and the remainder of the whole body were estimated using the medical internal radiation dose formula, and dose contributions from radioactivity in transit through the gastrointestinal tract were estimated using a compartment model. Extrapolated values of radiation absorbed dose to normal organs in rads per millicurie administered were whole body, 0.0085; lower large intestine wall, 0.0898; small intestine, 0.0530; upper large intestine wall, 0.0731; and kidneys, 0.0455. The effective dose equivalent predicted was 0.0162 rem/mCi and the effective dose was found to be 0.015 rem/mCi. On the basis of the pharmacokinetics, biodistribution and internal radiation dosimetry information obtained in this study, a diagnostic phase I clinical trial with 99mTc-labeled humanized MAb R3 conjugate in patients should be supported.

Humanization of a mouse monoclonal antibody that blocks the epidermal growth factor receptor: recovery of antagonistic activity

BACKGROUND

Antibody humanization by transplanting the complementarity determining regions (CDRs) of a murine antibody to a human framework aims to reduce the response of the human immune system against a foreign molecule. Frequently, however, some murine amino acids from the framework have to be retained to recover binding affinity.

OBJECTIVES

To redesign R3, a mouse monoclonal antibody (mAb) that binds the human epidermal growth factor (EGF)-receptor and inhibits the binding of EGF, to be a human IgG1.

STUDY DESIGN

The light and heavy chains of REI and Eu, respectively, were selected as human immunoglobulin (Ig) frameworks for CDR-grafting based on their high homology with the corresponding sequences of murine R3. Molecular modeling was used to analyze the possible effects of mutating murine residues that underlie the CDRs.

RESULTS

CDR-grafting dramatically reduced the binding capability of the antibody. Molecular modeling suggested that two amino acids (Thr 76 and Thr 93), among five immunoglobulin heavy chain variable region (VH) residues underlying the CDRs, were critical for antigen binding. The five residues were mutated back to the original murine amino acids in different combinations contained in six variants of humanized antibodies. In agreement with molecular modeling analysis. The variant in which three murine residues were retained (Ser 75, Thr 76 and Thr 93) exhibited a similar capacity to inhibit the binding of 125I-labeled EGF to its receptor as compared with the original antibody. This humanized antibody was at least 2-fold less immunogenic in African Green monkeys than the chimeric antibody.

CONCLUSIONS

Only very few mutations in the frameworks may be necessary to recover the binding capability of a humanized antibody. Molecular modeling can serve as a powerful tool to identify residues critical for binding.

Growth inhibition of human lung adenocarcinoma cells by antibodies against epidermal growth factor receptor and by ganglioside GM3: involvement of receptor-directed protein tyrosine phosphatase(s)

Growth of the EGF receptor-expressing non-small-cell lung carcinoma cell line H125 seems to be at least partially driven by autocrine activation of the resident EGF receptors. Thus, the possibility of an EGF receptor-directed antiproliferative treatment was investigated in vitro using a monoclonal antibody (alpha EGFR ior egf/r3) against the human EGF receptor and gangliosides which are known to possess antiproliferative and anti-tyrosine kinase activity. The moderate growth-inhibitory effect of alpha EGFR ior egf/r3 was strongly potentiated by the addition of monosialoganglioside GM3. Likewise, the combination of alpha EGFR ior egf/r3 and GM3 inhibited EGF receptor autophosphorylation activity in H125 cells more strongly than either agent alone. A synergistic inhibition of EGF receptor autophosphorylation by alpha EGFR ior egf/r3 and GM3 was also observed in the human epidermoid carcinoma cell line A431. In both cell lines, the inhibition of EGF receptor autophosphorylation by GM3 was prevented by pretreatment of the cells with pervanadate, a potent inhibitor of protein tyrosine phosphatases (PTPases). Also, GM3 accelerated EGF receptor dephosphorylation in isolated A431 cell membranes. These findings indicate that GM3 has the capacity to activate EGF receptor-directed PTPase activity and suggest a novel possible mechanism for the regulation of cellular PTPases.