Targeting molecules for diagnostics of Head and Neck squamous cell carcinoma

To personalize treatment for cancer, correct staging of the primary tumor, nodal disease and metastatic disease is of essence. By targeting tumor specific receptors with radiolabeled antibodies, specificity and accuracy of imaging may be improved. Radio-immunodiagnostics can potentially detect small volume disease, occult metastasis and recurrent cancer in treated tissue. This thesis focuses on evaluation of radio-immunoconjugates directed towards CD44v6, which is a surface receptor overexpressed in many head and neck squamous cell carcinomas. At the outset, the monoclonal chimeric antibody cMab U36 and its cleavage products Fab’ and F(ab’)2 were labeled with 125I and assessed in vitro and in vivo (paper I). The best distribution pattern and tumor to organ ratio was achieved with F(ab’)2. Due to the immunological responses humans can develop towards chimeric antibodies, they are not optimal for clinical use, and subsequently fully human antibody fragments were developed. AbD15179, which is a monovalent fragment, was labeled with 111In and 125I and evaluated in vitro and in mice bearing CD44v6-expressing tumors. Tumor to organ ratios were improved compared to cMab U36 derived fragments, and 111In-AbD15179 displayed a more favorable distribution compared to 125I-AbD15179 (Paper II). A bivalent Fab-dHXL, AbD19384 derived from AbD15179, was then constructed and labeled with 125I and evaluated in cell- and biodistribution studies. Furthermore, an imaging study in a small animal PET was performed with 124I-AbD19384 (Paper III). Uptake in kidneys was reduced and liver uptake increased compared to AbD15179 reflecting the larger molecule. The high CD44v6 expressing tumor was clearly visualized with maximum uptake at 48 hours post injection.In paper IV human single chain fragments towards CD44v6v were selected, and the top candidates A11 and H12 were further evaluated in vitro and in vivo. Single chain fragments are small molecules exhibiting fast clearance and high affinity to the target. The study proved this by demonstrating superior tumor to blood ratios of radiolabeled A11 and H12 compared to previously studied molecules.

Preclinical evaluation of a novel engineered recombinant human anti-CD44v6 antibody for potential use in radio-immunotherapy

CD44v6 is overexpressed in a variety of cancers, rendering it a promising target for radio-immunotherapy (RIT). In this study, we have characterized a novel engineered recombinant monoclonal anti-CD44v6 antibody, AbN44v6, and assessed its potential for use in RIT using either Lu-177 or I-131 as therapeutic radionuclides. In vitro affinity and specificity assays characterized the binding of the antibody labeled with Lu-177, I-125 or I-131. The therapeutic effects of Lu-177-AbN44v6 and I-131-AbN44v6 were investigated using two in vitro 3D tumor models with different CD44v6 expression. Finally, the normal tissue biodistribution and dosimetry for Lu-177-AbN44v6 and I-125-AbN44v6/I-131-AbN44v6 were assessed in vivo using a mouse model. All AbN44v6 radioconjugates demonstrated CD44v6-specific binding in vitro. In the in vitro 3D tumor models, dose-dependent therapeutic effects were observed with both Lu-177-AbN44v6 and I-131-AbN44v6, with a greater significant therapeutic effect observed on the cells with a higher CD44v6 expression. Biodistribution experiments demonstrated a greater uptake of Lu-177-AbN44v6 in the liver, spleen and bone, compared to I-125-AbN44v6, whereas I-125-AbN44v6 demonstrated a longer circulation time. In dosimetric calculations, the critical organs for Lu-177-AbN44v6 were the liver and spleen, whereas the kidneys and red marrow were considered the critical organs for I-131-AbN44v6. The effective dose was in the order of 0.1 mSv/MBq for both labels. In conclusion, AbN44v6 bound specifically and with high affinity to CD44v6. Furthermore, in vitro RIT demonstrated growth inhibition in a CD44v6-specific activity-dependent manner for both radioconjugates, demonstrating that both Lu-177-AbN44v6 and I-131-AbN44v6 may be promising RIT candidates. Furthermore, biodistribution and dosimetric analysis supported the applicability of both conjugates for RIT. The CD44v6-specific therapeutic effects observed with radiolabeled AbN44v6 in the 3D tumor models in vitro, combined with the beneficial dosimetry in vivo, render AbN44v6 a potential candidate for RIT

In vivo characterization of the novel CD44v6-targeting Fab fragment AbD15179 for molecular imaging of squamous cell carcinoma : a dual-isotope study

BACKGROUND: Patients with squamous cell carcinoma in the head and neck region (HNSCC) offer a diagnostic challenge due to difficulties to detect small tumours and metastases. Imaging methods available are not sufficient, and radio-immunodiagnostics could increase specificity and sensitivity of diagnostics. The objective of this study was to evaluate, for the first time, the in vivo properties of the radiolabelled CD44v6-targeting fragment AbD15179 and to assess its utility as a targeting agent for radio-immunodiagnostics of CD44v6-expressing tumours. METHODS: The fully human CD44v6-targeting Fab fragment AbD15179 was labelled with 111In or 125I, as models for radionuclides suitable for imaging with SPECT or PET. Species specificity, antigen specificity and internalization properties were first assessed in vitro. In vivo specificity and biodistribution were then evaluated in tumour-bearing mice using a dual-tumour and dual-isotope setup. RESULTS: Both species-specific and antigen-specific binding of the conjugates were demonstrated in vitro, with no detectable internalization. The in vivo studies demonstrated specific tumour binding and favourable tumour targeting properties for both conjugates, albeit with higher tumour uptake, slower tumour dissociation, higher tumour-to-blood ratio and higher CD44v6 sensitivity for the 111In-labelled fragment. In contrast, the 125I-Fab demonstrated more favourable tumour-to-organ ratios for liver, spleen and kidneys. CONCLUSIONS: We conclude that AbD15179 efficiently targets CD44v6-expressing squamous cell carcinoma xenografts, and particularly, the 111In-Fab displayed high and specific tumour uptake. CD44v6 emerges as a suitable target for radio-immunodiagnostics, and a fully human antibody fragment such as AbD15179 can enable further clinical imaging studies

Generation and evaluation of antibody agents for molecular imaging of CD44v6-expressing cancers

Aim: The aim of this study was to generate and characterize scFv antibodies directed to human CD44v6, as well as to radiolabel and evaluate top candidates in vitro and in vivo for their potential use in CD44v6-targeted molecular imaging in cancer patients. Materials and methods: Phage display selections were used to isolate CD44v6-specific scFvs. A chain shuffling strategy was employed for affinity maturation based on a set of CD44v6-specific first-generation clones. Two second-generation scFv clones were then chosen for labeling with 111In or 125I and assessed for CD44v6-specific binding on cultured tumor cells. In vivo uptake and distribution was evaluated in tumor-bearing mice using a dual tumor model. Finally, a proof-of-concept small animal PET-CT study was performed on one of the candidates labeled with 124I. Results: Two affinity-matured clones, CD44v6-scFv-A11 and CD44v6-scFv-H12, displayed promising binding kinetics. Seven out of eight radiolabeled conjugates demonstrated CD44v6-specific binding. In vivo studies on selected candidates demonstrated very advantageous tumor-to-organ ratios, in particular for iodinated conjugates, where 125I-labeled scFvs exhibited favorable kinetics and tumor-to-blood ratios above five already at 24 hours p. i.. The small animal PET-CT study using 124I-labeled CD44v6-scFv-H12 was in line with the biodistribution data, clearly visualizing the high CD44v6-expressing tumor. Conclusion: The single chain fragments, CD44v6-scFv-A11 and CD44v6-scFv-H12 specifically bind to CD44v6, and the radiolabeled counterparts provide high tumor-to-blood ratios and fast clearance from organs and blood. We conclude that radioiodinated CD44v6-scFv-A11 and CD44v6-scFv-H12 possess features highly suitable for stringent molecular imaging.Marika Nestor and Ronny Falk shared senior authorship.</p

Mapping impact factors leading to the GLIM diagnosis of malnutrition in patients with head and neck cancer

Background &amp; aims: In head and neck cancer, the combination of weight loss and elevated C-reactive protein levels means that patients have malnutrition as defined by the Global Leadership Initiative on Malnutrition (GLIM). This study aimed to identify impact factors for malnutrition as defined by the GLIM criteria among patients with head and neck cancer at the start of treatment and up to 12 months post-treatment. Methods: In a prospective, observational study, patient, tumour, treatment, and nutritional data from 229 patients with head and neck cancer were collected at the start of treatment and at three follow-ups (7 weeks after the start of treatment and at 3 and 12 months after the termination of treatment). These clinical variables were statistically analysed in relation to malnutrition at each follow-up using univariate and multivariate analyses. Malnutrition was defined according to the two GLIM criteria of &gt;5% body weight loss during the last 6 months and C-reactive protein &gt;5 mg/L. Results: The following factors were predictive for malnutrition in the multivariate analysis performed 7 weeks after the start of treatment: moderate or severe mucositis, chemoradiotherapy ± surgery, and the need for nutritional support (total or partial use of tube feeding/parenteral nutrition). Advanced tumour stage (III-IV) was significant for malnutrition at the start of treatment and at the 7 week and 3 month follow-ups, but not at 12 months. Conclusions: Severe mucositis, chemoradiotherapy ± surgery, and advanced tumour stage were found to be impact factors for the diagnosis of malnutrition using GLIM at different follow-up times from the start of treatment up to 12 months after the end of treatment. Few patients with head and neck cancer are diagnosed with malnutrition according to the GLIM criteria in a long-term perspective after the termination of treatment. Research on the validity of the GLIM criteria is needed to build a comprehensive evidence base of impact factors for malnutrition in head and neck cancer

Evaluation of a novel type of imaging probe based on a recombinant bivalent mini-antibody construct for detection of CD44v6-expressing squamous cell carcinoma

We have developed the CD44v6-targeting human bivalent antibody fragment AbD19384, an engineered recombinant human bivalent Fab antibody formed via dimerization of dHLX (synthetic double helix loop helix motif) domains, for potential use in antibody-based molecular imaging of squamous cell carcinoma in the head and neck region. This is a unique construct that has, to the best of our knowledge, never been assessed for molecular imaging in vivo before. The objective of the present study was to evaluate for the first time the in vitro and in vivo binding properties of radio-iodinated AbD19384, and to assess its utility as a targeting agent for molecular imaging of CD44v6-expressing tumors. Antigen specificity and binding properties were assessed in vitro. In vivo specificity and biodistribution of 125I-AbD19384 were next evaluated in tumor-bearing mice using a dual-tumor setup. Finally, AbD19384 was labeled with 124I, and its imaging properties were assessed by small animal PET/CT in tumor bearing mice, and compared with 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG). In vitro studies demonstrated CD44v6-specific binding with slow off-rate for AbD19384. A favorable biodistribution profile was seen in vivo, with tumor-specific uptake. Small animal PET/CT images of 124I-AbD19384 supported the results through clearly visible high CD44v6-expressing tumors and faintly visible low expressing tumors, with superior imaging properties compared to 18F-FDG. Tumor-to-blood ratios increased with time for the conjugate (assessed up to 72 h p.i.), although 48 h p.i. proved best for imaging. Biodistribution and small-animal PET studies demonstrated that the recombinant Fab-dHLX construct AbD19384 is a promising tracer for imaging of CD44v6 antigen expression in vivo, with the future aim to be used for individualized diagnosis and early detection of squamous cell carcinomas in the head and neck region. Furthermore, this proof-of-concept research established the feasibility of using recombinant Fab-dHLX constructs for in vivo imaging of tumor biomarkers