Panitumumab Modified with Metal-Chelating Polymers (MCP) Complexed to 111In and 177Lu-An EGFR-Targeted Theranostic for Pancreatic Cancer

Au@109Pd Core-Shell Nanoparticles Conjugated to Panitumumab for the Combined β--Auger Electron Therapy of Triple-Negative Breast Cancer

Apart from HER2-positive, triple-negative breast cancer (TNBC) is the second most highly invasive type of breast cancer. Although TNBC does not overexpress HER2 receptors, it has been observed that EGFR protein expression is present in this specific type of tumor, making it an attractive target for immune and radiopharmaceutical treatments. In our current study, we used 109Pd (T1/2 = 13.7 h) in the form of a 109Pd/109mAg in vivo generator as a source of β- particles and Auger electrons in targeted radionuclide therapy for TNBC. 109Pd, obtained through neutron irradiation of the 108Pd target, was deposited onto 15 nm gold nanoparticles to form Au@109Pd core-shell nanoparticles, which were then conjugated to the panitumumab antibody. Au@109Pd-PEG-panitumumab nanoparticles were bound, internalized, and partially routed to the nucleus in MDA-MB-231 human breast cancer cells overexpressing EGFR receptors. The Au@109Pd-panitumumab radioconjugate significantly reduced the metabolic activity of MDA-MB-231 cells in a dose-dependent manner. In conclusion, we have found that Au@109Pd-PEG-panitumumab nanoparticles show potential as a therapeutic agent for combined β--Auger electron targeted radionuclide therapy of TNBC. The simultaneous emission of β-, conversion, and Auger electrons from the 109Pd/109mAg generator, similar to 161Tb conjugates, significantly enhances the therapeutic effect. The partial localization of these nanoparticles into the cell nucleus, provided by the panitumumab vector, ensures effective therapy with Auger electrons. This is particularly important for the treatment of drug-resistant TNBC cells.

SPECT/CT imaging of EGFR-positive head and neck squamous cell carcinoma patient-derived xenografts with 203Pb-PSC-panitumumab in NRG mice

BACKGROUND

The objective of this research was the development and evaluation of 203Pb-labelled panitumumab (203Pb-PSC-panitumumab) as an immuno-SPECT radioligand for the detection of EGFR + head and neck squamous cell carcinoma (HNSCC) in a patient-derived xenograft (PDX) mouse model. The 51.9 h physical half-life and favourable γ-emission (279 keV; 81%) of 203Pb offer an excellent opportunity for developing immuno-SPECT radioligands. Moreover, 203Pb has a complementary therapeutic radionuclide (212Pb), making 203Pb and 212Pb an ideal matched radiotheranostic pair.

RESULTS

Radiolabeling of panitumumab was performed at a pH of 5.0 and room temperature for 5-10 min with [203Pb]Pb(OAc)2, and the incorporation efficiency was determined using radio-TLC. 203Pb-PSC-panitumumab (~ 10 MBq, 140 μl of saline) was injected into the tail vein of NRG mice bearing subcutaneous (s.c.) HNSCC patient-derived xenografts (PDX). SPECT/CT images were acquired at 48 and 120 h post-injection. For biodistribution studies, mice were euthanized five days after 203Pb-panitumumab injection. The tumour and normal tissues were collected and weighed, and uptake of 203Pb was measured in a γ-counter. The uptake was calculated as the percent injected dose per gram of each tissue (ID%/g). Blocking experiments were performed by pretreating a group of mice (n = 5) with 1 mg of panitumumab 1 h before administering 203Pb-PSC-panitumumab. 4-5 chelators of a new lead-specific chelator (PSC) were attached per antibody; radiolabeling efficiency was 99.2 ± 0.7%. The isolated radiochemical yield of 203Pb-PSC-panitumumab was 41.4 ± 8% (n = 5), and the molar activity was 1.2 ± 0.35 GB/mg. SPECT imaging and biodistribution confirmed high accumulation and retention of 203Pb-PSC-panitumumab in the tumour (26% ID/g) at 120 h post-injection (p.i.), which could be reduced to 6.2%ID/g at 120 h p.i. by predosing with panitumumab (1 mg) confirming EGFR specificity of 203Pb-PSC-panitumumab uptake.

CONCLUSIONS

Panitumumab was successfully and reproducibly labelled with 203Pb in high radiochemical purity using the chelator PSC-NCS. 203Pb-PSC-panitumumab was specifically accumulated and retained in EGFR + tumours in NRG mice with s.c. HNSCC PDX. 203Pb-PSC-panitumumab is a suitable immuno-SPECT radioligand for imaging EGFR + tumours and has great potential for combining with 212Pb-PSC-panitumumab in a radiotheranostic strategy for imaging and treating HNSCC.

Site-specific Conjugation of 6 DOTA Chelators to a CA19-9-targeting scFv-Fc Antibody for Imaging and Therapy

Antibodies conjugated with diagnostic/therapeutic radionuclides are attractive options for inoperable cancers lacking accurate imaging methods and effective therapeutics, such as pancreatic cancer. Hence, we have produced an antibody radionuclide conjugate termed TE-1132 comprising a α-CA19-9 scFv-Fc that is site-specifically conjugated at each C-terminus to 3 DOTA chelators via a cysteine-containing peptide linker. The smaller scFv-Fc size facilitates diffusivity within solid tumors, whereas the chelator-to-antibody ratio of six enabled 177Lu-radiolabeled TE-1132 to exhibit high radioactivity up to 520 MBq/nmol. In mice bearing BxPC3 tumors, immuno-SPECT/CT imaging of [111In]In-TE-1132 and the biodistribution of [177Lu]Lu-TE-1132 showed selective tumor accumulation. Single and multiple doses of [177Lu]Lu-TE-1132 effectively inhibited the BxPC3 tumor growth and prolonged the survival of mice with no irreversible body weight loss or hematopoietic damage. The adequate pharmacokinetic parameters, prominent tumor accumulation, and efficacy with good safety in mice encourage the further investigation of theranostic TE-1132 for treating pancreatic cancer.

Relative Biological Effectiveness (RBE) of [64Cu]Cu and [177Lu]Lu-NOTA-panitumumab F (ab')2 radioimmunotherapeutic agents vs. γ-radiation for decreasing the clonogenic survival in vitro of human pancreatic ductal adenocarcinoma (PDAC) cells

INTRODUCTION

Our objective was to compare [64Cu]Cu-NOTA-panitumumab F(ab')2 and [177Lu]Lu-NOTA-panitumumab F(ab')2 radioimmunotherapy (RIT) agents for decreasing the clonogenic survival fraction (SF) in vitro of EGFR-positive human pancreatic ductal adenocarcinoma (PDAC) cell lines and estimate the relative biological effectiveness (RBE) vs. γ-radiation (XRT).

METHODS

EGFR-positive PDAC cell lines (AsPC-1, PANC-1, MIAPaCa-2, Capan-1) and EGFR-knockout PANC-1 EGFR KO cells were treated in vitro for 18 h with (0-19.65 MBq; 72 nmols/L) of [64Cu]Cu-NOTA-panitumumab F(ab')2 or [177Lu]Lu-NOTA-panitumumab F(ab')2 or XRT (0-8 Gy) followed by clonogenic assay. The SF was determined after culturing single treated cells for 14 d. Cell fractionation studies were performed for cells incubated with 1 MBq (72 nmols/L) of [64Cu]Cu-NOTA-panitumumab F(ab')2 or [177Lu]Lu-NOTA-panitumumab F(ab')2 for 1, 4, or 24 h to estimate the time-integrated activity (Ã) on the cell surface, cytoplasm, nucleus and medium. Radiation absorbed doses in the nucleus were calculated by multiplying à by S-factors calculated by Monte Carlo N Particle (MCNP) modeling using monolayer cell culture geometry. The SF of PDAC cells was plotted vs. dose and fitted to a linear quadratic model to estimate the dose required to decrease the SF to 0.1 (D10). The D10 for RIT agents were compared to XRT to estimate the RBE. DNA double-strand breaks (DSBs) caused by [64Cu]Cu-NOTA-panitumumab F(ab')2 or [177Lu]Lu-NOTA-panitumumab F(ab')2 continuous exposure for 5 h or 20 h were probed by immunofluorescence for γ-H2AX. Relative EGFR expression of PDAC cells was assessed by flow cytometry (scored + to +++) and cell doubling times for untreated cells were determined.

RESULTS

The D10 for [64Cu]Cu-NOTA-panitumumab F(ab')2 ranged from 9.1 Gy (PANC-1) to 39.9 Gy (Capan-1). The D10 for [177Lu]Lu-NOTA-panitumumab F(ab')2 ranged from 11.7 Gy (AsPC-1) to 170.8 Gy (Capan-1). The D10 for XRT ranged from 2.5 Gy (Capan-1) to 6.7 Gy (PANC-1 EGFR KO). D10 values were not correlated with EGFR expression over a relatively narrow range (++ to +++) or with cell doubling times. Based on D10 values, PANC-1 EGFR KO cells were 1.6-fold less sensitive than PANC-1 cells to [64Cu]Cu-NOTA-panitumumab F(ab')2 and 1.9-fold less sensitive to [177Lu]Lu-NOTA-panitumumab F(ab')2. The RBE for [64Cu]Cu-NOTA-panitumumab F(ab')2 ranged from 0.06 for Capan-1 cells to 0.45 for PANC-1 cells. The RBE for [177Lu]Lu-NOTA-panitumumab F(ab')2 ranged from 0.015 for Capan-1 cells to 0.28 for AsPC-1 cells. DNA DSBs were detected in PDAC cells exposed to [64Cu]Cu-NOTA-panitumumab F(ab')2 or [177Lu]Lu-NOTA-panitumumab F(ab')2 but were not correlated with the SF of the cells.

CONCLUSIONS

We conclude that at the same dose delivered to the cell nucleus [64Cu]Cu-NOTA-panitumumab F(ab')2 and [177Lu]Lu-NOTA-panitumumab F(ab')2 were less radiobiologically effective than XRT for decreasing the SF of human PDAC cells, but [64Cu]Cu-NOTA-panitumumab F(ab')2 was more cytotoxic than [177Lu]Lu-NOTA-panitumumab F(ab')2 except for AsPC-1 cells which were more sensitive to [177Lu]Lu-NOTA-panitumumab F(ab')2.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

This study demonstrates that higher radiation doses may be required for RIT than XRT to achieve radiobiologically equivalent effects when used to treat PDAC.

Biodistribution assessment of cationic pullulan nanogel, a nasal vaccine delivery system, in mice and non-human primates

Cationic cholesteryl-group-bearing pullulan nanogel (cCHP-nanogel) is an effective drug-delivery system for nasal vaccines. However, cCHP-nanogel-based nasal vaccines might access the central nervous system due to its close proximity via the olfactory bulb in the nasal cavity. Using real-time quantitative tracking of the nanogel-based nasal botulinum neurotoxin and pneumococcal vaccines, we previously confirmed the lack of deposition of vaccine antigen in the cerebrum or olfactory bulbs of mice and non-human primates (NHPs), rhesus macaques. Here, we used positron emission tomography to investigate the biodistribution of the drug-delivery system itself, cCHP-nanogel after mice and NHPs were nasally administered with ¹⁸F-labeled cCHP nanogel. The results generated by the PET analysis of rhesus macaques were consistent with the direct counting of radioactivity due to ¹⁸F or ¹¹¹In in dissected mouse tissues. Thus, no depositions of cCHP-nanogel were noted in the cerebrum, olfactory bulbs, or eyes of both species after nasal administration of the radiolabeled cCHP-nanogel compound. Our findings confirm the safe biodistribution of the cCHP-nanogel-based nasal vaccine delivery system in mice and NHPs.

Preparation and Catalytic Properties of Carbonic Anhydrase Conjugated to Liposomes through a Bis-Aryl Hydrazone Bond

Liposomes (lipid vesicles) with sizes of about 100-200 nm carrying surface-bound (immobilized) water-soluble enzymes are functionalized molecular compartment systems for possible applications, for example, as therapeutic materials or as catalytic reaction units for running reactions in aqueous media in vitro. One way of covalently attaching enzyme molecules under mild conditions in a controlled way to the surface of preformed liposomes is to apply the spectrophotometrically traceable bis-aryl hydrazone (BAH) bond between the liposome and the enzyme molecules of interest. Using bovine carbonic anhydrase (BCA), an aqueous dispersion of liposome-BAH-BCA - conjugates of defined composition was prepared. The liposomes used consisted of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), N-(methylpolyoxyethylene oxycarbonyl)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE-PEG), and N-(aminopropylpolyoxyethylene oxycarbonyl)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE-PEG-NH₂). The amino group of some of the DSPE-PEG-NH₂ molecules present in the liposomes were converted into an aromatic aldehyde, which (after purification) reacted with (purified) BCA molecules that had on their surface on average one acetone protected aromatic hydrazine. After purification of the liposome-BAH-BCA conjugate dispersion obtained, it was characterized in terms of (i) BCA activity, (ii) overall BCA structure, and (iii) storage stability. For an average liposome of 138 nm diameter, about 1200 BCA molecules were attached to the outer liposome surface. Liposomally bound BCA was found to exhibit (i) similar catalytic activity at 25 °C and (ii) similar storage stability when stored in a dispersed state in aqueous solution at 4 °C as free BCA. Measurements at 5 °C clearly showed that liposome-BAH-BCA is able to catalyze the hydration of carbon dioxide to hydrogen carbonate.

Exploiting active nuclear import for efficient delivery of Auger electron emitters into the cell nucleus

BACKGROUND

The most attractive features of Auger electrons (AEs) in cancer therapy are their extremely short range and sufficiently high linear energy transfer (LET) for a majority of them. The cytotoxic effects of AE emitters can be realized only in close vicinity to sensitive cellular targets and they are negligible if the emitters are located outside the cell. The nucleus is considered the compartment most sensitive to high LET particles. Therefore, the use of AE emitters could be most useful in specific recognition of a cancer cell and delivery of AE emitters into its nucleus.

PURPOSE

This review describes the studies aimed at developing effective anticancer agents for the delivery of AE emitters to the nuclei of target cancer cells. The use of peptide-based conjugates, nanoparticles, recombinant proteins, and other constructs for AE emitter targeted intranuclear delivery as well as their advantages and limitations are discussed.

CONCLUSION

Transport from the cytoplasm to the nucleus along with binding to the cancer cell is one of the key stages in the delivery of AE emitters; therefore, several constructs for exploitation of this transport have been developed. The transport is carried out through a nuclear pore complex (NPC) with the use of specific amino acid nuclear localization sequences (NLS) and carrier proteins named importins, which are located in the cytosol. Therefore, the effectiveness of NLS-containing delivery constructs designed to provide energy-dependent transport of AE emitter into the nuclei of cancer cells also depends on their efficient entry into the cytosol of the target cell.

An Overview of Polymeric Nanoparticles-Based Drug Delivery System in Cancer Treatment

Cancer is recognized as one of the world's deadliest diseases, with more than 10 million new cases each year. Over the past 2 decades, several studies have been performed on cancer to pursue solutions for effective treatment. One of the vital benefits of utilizing nanoparticles (NPs) in cancer treatment is their high adaptability for modification and amalgamation of different physicochemical properties to boost their anti-cancer activity. Various nanomaterials have been designed as nanocarriers attributing nontoxic and biocompatible drug delivery systems with improved bioactivity. The present review article briefly explained various types of nanocarriers, such as organic-inorganic-hybrid NPs, and their targeting mechanisms. Here a special focus is given to the synthesis, benefits, and applications of polymeric NPs (PNPs) involved in various anti-cancer therapeutics. It has also been discussed about the drug delivery approach by the functionalized/encapsulated PNPs (without/with targeting ability) that are being applied in the therapy and diagnostic (theranostics). Overall, this review can give a glimpse into every aspect of PNPs, from their synthesis to drug delivery application for cancer cells.

Panitumumab-DOTA-111In: An Epidermal Growth Factor Receptor Targeted Theranostic for SPECT/CT Imaging and Meitner-Auger Electron Radioimmunotherapy of Triple-Negative Breast Cancer

Epidermal growth factor receptors (EGFR) are overexpressed in triple-negative breast cancer (TNBC) and are an attractive target for the development of theranostic radiopharmaceuticals. We studied anti-EGFR panitumumab labeled with ¹¹¹In (panitumumab-DOTA-¹¹¹In) for SPECT/CT imaging and Meitner-Auger electron (MAE) radioimmunotherapy (RIT) of TNBC. Panitumumab-DOTA-¹¹¹In was bound, internalized, and routed to the nucleus in MCF7, MDA-MB-231/Luc, and MDA-MB-468 human breast cancer (BC) cells dependent on the EGFR expression level (1.5 × 10⁴, 1.7 × 10⁵, or 1.3 × 10⁶ EGFR/cell, respectively). The absorbed dose in the nuclei of MCF7, MDA-MB-231/Luc, and MDA-MB-468 cells incubated with 4.4 MBq of panitumumab-DOTA-¹¹¹In (20 nM) was 1.20 ± 0.02, 2.2 ± 0.1, and 25 ± 2 Gy, respectively. The surviving fraction (SF) of MDA-MB-231/Luc cells treated with panitumumab-DOTA-¹¹¹In (10-300 nM; 1.5 MBq/μg) was reduced as the absorbed dose in the cell increased, with clonogenic survival reduced to an SF = 0.12 ± 0.05 at 300 nM corresponding to 12.7 Gy. The SFs of MDA-MB-468, MDA-MB-231/Luc, and MCF7 cells treated with panitumumab-DOTA-¹¹¹In (20 nM; 1.7 MBq/μg) were <0.01, 0.56 ± 0.05, and 0.67 ± 0.04, respectively. Unlabeled panitumumab had no effect on SF, and irrelevant IgG-DOTA-¹¹¹In only modestly reduced the SF of MDA-MB-231/Luc cells but not MCF7 or MDA-MB-468 cells. The cytotoxicity of panitumumab-DOTA-¹¹¹In was mediated by increased DNA double-strand breaks (DSB), cell cycle arrest at G2/M-phase and apoptosis measured by immunofluorescence detection by flow cytometry. MDA-MB-231/Luc tumors in the mammary fat pad (MFP) of NRG mice were clearly imaged with panitumumab-DOTA-¹¹¹In by microSPECT/CT at 4 days postinjection (p.i.), and biodistribution studies revealed high tumor uptake [18 ± 2% injected dose/g (% ID/g] and lower normal tissue uptake (<10% ID/g). Administration of up to 24 MBq (15 μg) of panitumumab-DOTA-¹¹¹In to healthy NRG mice caused no major hematological, renal, or hepatic toxicity with no decrease in body weight. Treatment of NOD SCID mice with MDA-MB-231 tumors with panitumumab-DOTA-¹¹¹In (22 MBq; 15 μg) slowed tumor growth. The mean time for tumors to reach a volume of ≥500 mm³ was 61 ± 5 days for RIT with panitumumab-DOTA-¹¹¹In compared to 42 ± 6 days for mice treated with irrelevant IgG₂-DOTA-¹¹¹In (P < 0.0001) and 35 ± 3 days for mice receiving 0.9% NaCl (P < 0.0001). However, tumors regrew at later time points. The median survival of mice treated with panitumumab-DOTA-¹¹¹In was 70 days versus 46 days for IgG₂-DOTA-¹¹¹In (P < 0.0001) or 40 days for 0.9% NaCl (P < 0.0001). We conclude that panitumumab-DOTA-¹¹¹In is a promising theranostic agent for TNBC. Increasing the administered amount of panitumumab-DOTA-¹¹¹In and/or combination with radiosensitizing PARP inhibitors used for treatment of patients with TNBC may provide a more durable response to RIT.

Nanomaterials Based on Functional Polymers for Sensitizing Cancer Radiotherapy

Despite being the mainstay treatment for many types of cancer in clinic, radiotherapy is undertaking great challenges in overcoming a series of limitations. Radiosensitizers are promising agents capable of depositing irradiation energy and generating free radicals to enhance the radiosensitivity of tumor cells. Combining radiosensitizers with functional polymer-based nanomaterials holds great potential to improve biodistribution, circulation time, and stability in vivo. The derived polymeric nano-radiosensitizers can significantly improve the efficiency of tumor targeting and radiotherapy, and reduce the side effect to healthy tissues. In this review, we provide an overview of functional polymer-based nanomaterials for radiosensitization in recent years. Particular emphases are given to the action mechanisms, drug loading methods, targeting efficiencies, the impact on therapeutic effects and biocompatibility of various radiosensitizing polymers, which are classified as polymeric micelles, dendrimers, polymeric nanospheres, nanoscale coordination polymers, polymersomes, and nanogels. The challenges and outlooks of polymeric nano-radiosensitizers are also discussed. This article is protected by copyright. All rights reserved.

Multifunctional high-Z nanoradiosensitizers for multimodal synergistic cancer therapy

Radiotherapy (RT) is one of the most common and effective clinical therapies for malignant tumors. However, there are several limitations that undermine the clinical efficacy of cancer RT, including the low X-ray attenuation coefficient of organs, serious damage to normal tissues, and radioresistance in hypoxic tumors. With the rapid development of nanotechnology and nanomedicine, high-Z nanoradiosensitizers provide novel opportunities to overcome radioresistance and improve the efficacy of RT by deposition of radiation energy through photoelectric effects. To date, several types of nanoradiosensitizers have entered clinical trials. Nevertheless, the limitation of the single treatment mode and the unclear mechanism of nanoparticle radiosensitization have hindered the further development of nanoradiosensitizers. In this review, we systematically describe the interaction mechanisms between X-rays and nanomaterials and summarize recent advances in multifunctional high-Z nanomaterials for radiotherapeutic-based multimodal synergistic cancer therapy. Finally, the challenges and prospects are discussed to stimulate the development of nanomedicine-based cancer RT.

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

Background

Epidermal growth factor receptors (EGFR) are overexpressed on many head and neck squamous cell carcinoma (HNSCC). Radioimmunotherapy (RIT) with F(ab')₂ of the anti-EGFR monoclonal antibody panitumumab labeled with the β-particle emitter, ¹⁷⁷Lu may be a promising treatment for HNSCC. Our aim was to assess the feasibility of a theranostic strategy that combines positron emission tomography (PET) with [⁶⁴Cu]Cu-DOTA-panitumumab F(ab')₂ to image HNSCC and predict the radiation equivalent doses to the tumour and normal organs from RIT with [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂.

Results

Panitumumab F(ab')₂ were conjugated to DOTA and complexed to ⁶⁴Cu or ¹⁷⁷Lu in high radiochemical purity (95.6 ± 2.1% and 96.7 ± 3.5%, respectively) and exhibited high affinity EGFR binding (K_d = 2.9 ± 0.7 × 10^− 9 mol/L). Biodistribution (BOD) studies at 6, 24 or 48 h post-injection (p.i.) of [⁶⁴Cu]Cu-DOTA-panitumumab F(ab')₂ (5.5–14.0 MBq; 50 μg) or [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂ (6.5 MBq; 50 μg) in NRG mice with s.c. HNSCC patient-derived xenografts (PDX) overall showed no significant differences in tumour uptake but modest differences in normal organ uptake were noted at certain time points. Tumours were imaged by microPET/CT with [⁶⁴Cu]Cu-DOTA-panitumumab F(ab')₂ or microSPECT/CT with [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂ but not with irrelevant [¹⁷⁷Lu]Lu-DOTA-trastuzumab F(ab')₂. Tumour uptake at 24 h p.i. of [⁶⁴Cu]Cu-DOTA-panitumumab F(ab')₂ [14.9 ± 1.1% injected dose/gram (%ID/g) and [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂ (18.0 ± 0.4%ID/g) were significantly higher (P < 0.05) than [¹⁷⁷Lu]Lu-DOTA-trastuzumab F(ab')₂ (2.6 ± 0.5%ID/g), demonstrating EGFR-mediated tumour uptake. There were no significant differences in the radiation equivalent doses in the tumour and most normal organs estimated for [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂ based on the BOD of [⁶⁴Cu]Cu-DOTA-panitumumab F(ab')₂ compared to those estimated directly from the BOD of [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂ except for the liver and whole body which were modestly underestimated by [⁶⁴Cu]Cu-DOTA-panitumumab F(ab')₂. Region-of-interest (ROI) analysis of microPET/CT images provided dose estimates for the tumour and liver that were not significantly different for the two radioimmunoconjugates. Human doses from administration of [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂ predicted that a 2 cm diameter HNSCC tumour in a patient would receive 1.1–1.5 mSv/MBq and the whole body dose would be 0.15–0.22 mSv/MBq.

Conclusion

A PET theranostic strategy combining [⁶⁴Cu]Cu-DOTA-panitumumab F(ab')₂ to image HNSCC tumours and predict the equivalent radiation doses in the tumour and normal organs from RIT with [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂ is feasible. RIT with [¹⁷⁷Lu]Lu-DOTA-panitumumab F(ab')₂ may be a promising approach to treatment of HNSCC due to frequent overexpression of EGFR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41181-021-00140-1.

Smart magnetic resonance imaging-based theranostics for cancer

Smart theranostics are dynamic platforms that integrate multiple functions, including at least imaging, therapy, and responsiveness, in a single agent. This review showcases a variety of responsive theranostic agents developed specifically for magnetic resonance imaging (MRI), due to the privileged position this non-invasive, non-ionising imaging modality continues to hold within the clinical imaging field. Different MRI smart theranostic designs have been devised in the search for more efficient cancer therapy, and improved diagnostic efficiency, through the increase of the local concentration of therapeutic effectors and MRI signal intensity in pathological tissues. This review explores novel small-molecule and nanosized MRI theranostic agents for cancer that exhibit responsiveness to endogenous (change in pH, redox environment, or enzymes) or exogenous (temperature, ultrasound, or light) stimuli. The challenges and obstacles in the design and in vivo application of responsive theranostics are also discussed to guide future research in this interdisciplinary field towards more controllable, efficient, and diagnostically relevant smart theranostics agents.

The Pharmaceutical Technology Approach on Imaging Innovations from Italian Research

Many modern therapeutic approaches are based on precise diagnostic evidence, where imaging procedures play an essential role. To date, in the diagnostic field, a plethora of agents have been investigated to increase the selectivity and sensitivity of diagnosis. However, the most common drawbacks of conventional imaging agents reside in their non-specificity, short imaging time, instability, and toxicity. Moreover, routinely used diagnostic agents have low molecular weights and consequently a rapid clearance and renal excretion, and this represents a limitation if long-lasting imaging analyses are to be conducted. Thus, the development of new agents for in vivo diagnostics requires not only a deep knowledge of the physical principles of the imaging techniques and of the physiopathological aspects of the disease but also of the relative pharmaceutical and biopharmaceutical requirements. In this scenario, skills in pharmaceutical technology have become highly indispensable in order to respond to these needs. This review specifically aims to collect examples of newly developed diagnostic agents connoting the importance of an appropriate formulation study for the realization of effective products. Within the context of pharmaceutical technology research in Italy, several groups have developed and patented promising agents for fluorescence and radioactive imaging, the most relevant of which are described hereafter.

Targeted Auger electron-emitter therapy: Radiochemical approaches for thallium-201 radiopharmaceuticals

INTRODUCTION

Thallium-201 is a radionuclide that has previously been used clinically for myocardial perfusion scintigraphy. Although in this role it has now been largely replaced by technetium-99 m radiopharmaceuticals, thallium-201 remains attractive in the context of molecular radionuclide therapy for cancer micrometastases or single circulating tumour cells. This is due to its Auger electron (AE) emissions, which are amongst the highest in total energy and number per decay for AE-emitters. Currently, chemical platforms to achieve this potential through developing thallium-201-labelled targeted radiopharmaceuticals are not available. Here, we describe convenient methods to oxidise [201Tl]Tl(I) to chelatable [201Tl]Tl(III) and identify challenges in stable chelation of thallium to support future synthesis of effective [201Tl]-labelled radiopharmaceuticals.

METHODS

A plasmid pBR322 assay was carried out to determine the DNA damaging properties of [201Tl]Tl(III). A range of oxidising agents (ozone, oxygen, hydrogen peroxide, chloramine-T, iodogen, iodobeads, trichloroisocyanuric acid) and conditions (acidity, temperature) were assessed using thin layer chromatography. Chelators EDTA, DTPA and DOTA were investigated for their [201Tl]Tl(III) radiolabelling efficacy and complex stability.

RESULTS

Isolated plasmid studies demonstrated that [201Tl]Tl(III) can induce single and double-stranded DNA breaks. Iodo-beads, iodogen and trichloroisocyanuric acid enabled more than 95% conversion from [201Tl]Tl(I) to [201Tl]Tl(III) under conditions compatible with future biomolecule radiolabelling (mild pH, room temperature and post-oxidation removal of oxidising agent). Although chelation of [201Tl]Tl(III) was possible with EDTA, DTPA and DOTA, only radiolabeled DOTA showed good stability in serum.

CONCLUSIONS

Decay of [201Tl]Tl(III) in proximity to DNA causes DNA damage. Iodobeads provide a simple, mild method to convert thallium-201 from a 1+ to 3+ oxidation state and [201Tl]Tl(III) can be chelated by DOTA with moderate stability. Of the well-established chelators evaluated, DOTA is most promising for future molecular radionuclide therapy using thallium-201; nevertheless, a new generation of chelating agents offering resistance to reduction and dissociation of [201Tl]Tl(III) complexes is required.

Pancreatic Ductal Adenocarcinoma: The Dawn of the Era of Nuclear Medicine?

Pancreatic ductal adenocarcinoma (PDAC), accounting for 90-95% of all pancreatic tumors, is a highly devastating disease associated with poor prognosis. The lack of accurate diagnostic tests and failure of conventional therapies contribute to this pejorative issue. Over the last decade, the advent of theranostics in nuclear medicine has opened great opportunities for the diagnosis and treatment of several solid tumors. Several radiotracers dedicated to PDAC imaging or internal vectorized radiotherapy have been developed and some of them are currently under clinical consideration. The functional information provided by Positron Emission Tomography (PET) or Single Photon Emission Computed Tomography (SPECT) could indeed provide an additive diagnostic value and thus help in the selection of patients for targeted therapies. Moreover, the therapeutic potential of β-- and α-emitter-radiolabeled agents could also overcome the resistance to conventional therapies. This review summarizes the current knowledge concerning the recent developments in the nuclear medicine field for the management of PDAC patients.

Site-Specific Conjugation of Metal-Chelating Polymers to Anti-Frizzled-2 Antibodies via Microbial Transglutaminase

Metal-chelating polymer-based radioimmunoconjugates (RICs) are effective agents for radioimmunotherapy but are currently limited by nonspecific binding and off-target organ uptake. Nonspecific binding appears after conjugation of the polymer to the antibody and may be related to random lysine conjugation since the polymers themselves do not bind to cells. To investigate the role of conjugation sites on nonspecific binding of polymer RICs, we developed a microbial transglutaminase reaction to prepare site-specific antibody-polymer conjugates. The reaction was enabled by introducing a Q-tag (i.e., 7M48) into antibody (i.e., Fab) fragments and synthesizing a polyglutamide-based metal-chelating polymer with a PEG amine block to yield substrates. Mass spectrometric analyses confirmed that the microbial transglutaminase conjugation reaction was site-specific. For comparison, random lysine conjugation analogs with an average of one polymer per Fab were prepared by bis-aryl hydrazone conjugation. Conjugates were prepared from an anti-frizzled-2 Fab to target the Wnt pathway, along with a nonbinding specificity control, anti-Luciferase Fab. Fabs were engineered from a trastuzumab-based IgG1 framework and lack lysines in the antigen-binding site. Conjugates were analyzed for thermal conformational stability by differential scanning fluorimetry, which showed that the site-specific conjugate had a similar melting temperature to the parent Fab. Binding assays by biolayer interferometry showed that the site-specific anti-frizzled-2 conjugate maintained high affinity to the antigen, while the random conjugate showed a 10-fold decrease in affinity, which was largely due to changes in association rates. Radioligand cell-binding assays on frizzled-2+ PANC-1 cells and frizzled-2- CHO cells showed that the site-specific anti-frizzled-2 conjugate had ca. 4-fold lower nonspecific binding compared to the random conjugate. Site-specific conjugation appeared to reduce nonspecific binding associated with random conjugation of the polymer in polymer RICs.

PET and SPECT Imaging of the EGFR Family (RTK Class I) in Oncology

The human epidermal growth factor receptor family (EGFR-family, other designations: HER family, RTK Class I) is strongly linked to oncogenic transformation. Its members are frequently overexpressed in cancer and have become attractive targets for cancer therapy. To ensure effective patient care, potential responders to HER-targeted therapy need to be identified. Radionuclide molecular imaging can be a key asset for the detection of overexpression of EGFR-family members. It meets the need for repeatable whole-body assessment of the molecular disease profile, solving problems of heterogeneity and expression alterations over time. Tracer development is a multifactorial process. The optimal tracer design depends on the application and the particular challenges of the molecular target (target expression in tumors, endogenous expression in healthy tissue, accessibility). We have herein summarized the recent preclinical and clinical data on agents for Positron Emission Tomography (PET) and Single Photon Emission Tomography (SPECT) imaging of EGFR-family receptors in oncology. Antibody-based tracers are still extensively investigated. However, their dominance starts to be challenged by a number of tracers based on different classes of targeting proteins. Among these, engineered scaffold proteins (ESP) and single domain antibodies (sdAb) show highly encouraging results in clinical studies marking a noticeable trend towards the use of smaller sized agents for HER imaging.

Metal-ligand coordination nanomaterials for radiotherapy: emerging synergistic cancer therapy

Radiotherapy (RT) plays a central role in curing malignant tumors. However, the treatment outcome is often impeded by low radiation absorption coefficients and radiation resistance of tumors along with normal tissue radio-toxicity. With the development of nanotechnology, nanomaterials in combination with RT offer the possibility to improve the therapeutic efficacy yet reduce side-effects. Metal-ligand coordination nanomaterials, including nanoscale metal-organic frameworks (NMOFs) and nanoscale coordination polymers (NCPs), formed by coordination interactions between inorganic metal ions/clusters with organic bridging ligands, have shown great potential in the field of radiation oncology in recent years in view of their unique advantages including the porous structure, high surface area, periodic frameworks, and diverse selections of both metal ions/clusters and organic ligands. In this review, we summarize the recent advances in NMOF/NCP-mediated synergistic RT in combination with hypoxia relief, chemotherapy, photodynamic therapy, photothermal therapy, chemodynamic therapy or immunotherapy, which emerged in the last 3 years, and describe cooperative enhancement interactions among these synergistic combinations. Moreover, the potential challenges and future prospects of this rapidly growing direction were also addressed.

Imaging of HER2-Positive Tumors in NOD/SCID Mice with Pertuzumab Fab-Hexahistidine Peptide Immunoconjugates Labeled with [99mTc]-(I)-Tricarbonyl Complex

PURPOSE

Molecular imaging of tumor HER2 expression may allow patient selection for HER2-targeted therapies. Our aim was to introduce hexahistidine (His₆) peptides into pertuzumab Fab to enable labeling with the [^99mTc(CO)₃(H₂O)₃]⁺ complex and study these radioimmunoconjugates for microSPECT/CT imaging of HER2-positive tumor xenografts in mice.

PROCEDURES

Fab were produced by papain digestion of pertuzumab and reacted with sulfo-SMCC for conjugation to His₆-containing peptides (CGYGGHHHHHH). His₆-peptide conjugation was measured by a radiometric assay. His₆-pertuzumab Fab were labeled at 0.4-1.0 MBq/μg with [^99mTc(CO)₃(H₂O)₃]⁺ for 1 h at 37 °C. HER2 immunoreactivity was assessed in a direct (saturation) binding assay using HER2-overexpressing SK-BR-3 human breast cancer (BC) cells. MicroSPECT/CT and biodistribution studies were performed in NOD/SCID mice with HER2-positive s.c. SK-OV-3 human ovarian cancer, or MDA-MB-361 or MDA-MB-231 human BC xenografts at 4 or 24 h post i.v. injection of [^99mTc]His₆-pertuzumab Fab (29-49 MBq, 70 μg). The specificity of tumor uptake was assessed by comparison to irrelevant [^99mTc]Fab 3913 in SK-OV-3 tumor-bearing mice.

RESULTS

SDS-PAGE analysis demonstrated cleavage of pertuzumab to produce Fab, which eluted as a single peak with a retention time of 13.8 min on SE-HPLC. Fab were conjugated to 2.1 ± 0.5 His₆ peptides and labeled with [^99mTc(CO)₃(H₂O)₃]⁺ to a radiochemical purity of 92-97 % at 0.4-0.8 MBq/μg. [^99mTc]His₆-pertuzumab Fab exhibited saturable and specific binding to SK-BR-3 cells with a K_D = 51.3 ± 5.2 × 10^-9 M and B_max = 3.5 ± 0.1 × 10⁶ receptors/cell. SK-OV-3 tumors were imaged at 4 and 24 h p.i [^99mTc]His₆-pertuzumab Fab. Tumor uptake at 24 h p.i. was 4.1 ± 0.6 %ID/g, which was 13-fold significantly greater than [^99mTc]Fab 3913 (0.3 ± 0.0 %ID/g; P < 0.01). MicroSPECT/CT imaged HER2-overexpressing MDA-MB-361 tumors but not MDA-MB-231 tumors with low HER2 expression. Tumor uptake was 5.2-fold significantly greater at 24 h p.i. in MDA-MB-361 than MDA-MB-231 tumors (3.2 ± 0.1 %ID/g vs. 0.8 ± 0.1 %ID/g; P < 0.05).

CONCLUSIONS

MicroSPECT/CT with [^99mTc]His₆-pertuzumab Fab imaged tumors in NOD/SCID mice that exhibited intermediate or high HER2 expression, but not tumors with low HER2. [^99mTc]His₆-pertuzumab Fab is promising for SPECT imaging of tumor HER2 expression.

Nimotuzumab Site-Specifically Labeled with 89Zr and 225Ac Using SpyTag/SpyCatcher for PET Imaging and Alpha Particle Radioimmunotherapy of Epidermal Growth Factor Receptor Positive Cancers

Simple Summary

Monoclonal antibodies (IgG) are excellent probes for targeting cell surface receptors for imaging and therapeutic applications. These theranostic agents are often developed by randomly conjugating radioisotopes/drugs/chelators to the primary amine of lysine or the sulfhydryl groups of cysteine on the antibody. Random conjugation often alters the properties of the antibody. We have site-specifically radiolabeled nimotuzumab an anti-epidermal growth factor receptor (EGFR) monoclonal antibody with 89Zr and 225Ac using SpyTag: ∆N-SpyCatcher for positron emission tomography (PET) imaging and alpha particle radiotherapy, and evaluated these agents in a model of EGFR-positive triple negative breast cancer (TNBC). Nimotuzumab-SpyTag-∆N-SpyCatcher constructs showed improved binding in vitro compared with randomly conjugated constructs. 89Zr-nimotuzumab-SpyTag-∆N-SpyCatcher specifically delineated EGFR-positive xenograft in vivo using microPET/CT imaging. Compared with control treatment groups, 225Ac-nimotuzumab-SpyTag-∆N-SpyCatcher more than doubled the survival of mice bearing EGFR-positive MDA-MB-231 TNBC xenograft. This work highlights a facile method to site-specifically radiolabel antibodies using SpyTag: ∆N-SpyCatcher.

Abstract

To develop imaging and therapeutic agents, antibodies are often conjugated randomly to a chelator/radioisotope or drug using a primary amine (NH₂) of lysine or sulfhydryl (SH) of cysteine. Random conjugation to NH₂ or SH groups can require extreme conditions and may affect target recognition/binding and must therefore be tested. In the present study, nimotuzumab was site-specifically labeled using ∆N-SpyCatcher/SpyTag with different chelators and radiometals. Nimotuzumab is a well-tolerated anti-EGFR antibody with low skin toxicities. First, ΔN-SpyCatcher was reduced using tris(2-carboxyethyl)phosphine (TCEP), which was followed by desferoxamine-maleimide (DFO-mal) conjugation to yield a reactive ΔN-SpyCatcher-DFO. The ΔN-SpyCatcher-DFO was reacted with nimotuzumab-SpyTag to obtain stable nimotuzumab-SpyTag-∆N-SpyCatcher-DFO. Radiolabeling was performed with ⁸⁹Zr, and the conjugate was used for the in vivo microPET imaging of EGFR-positive MDA-MB-468 xenografts. Similarly, ∆N-SpyCatcher was conjugated to an eighteen-membered macrocyclic chelator macropa-maleimide and used to radiolabel nimotuzumab-SpyTag with actinium-225 (²²⁵Ac) for in vivo radiotherapy studies. All constructs were characterized using biolayer interferometry, flow cytometry, radioligand binding assays, HPLC, and bioanalyzer. MicroPET/CT imaging showed a good tumor uptake of ⁸⁹Zr-nimotuzumab-SpyTag-∆N-SpyCatcher with 6.0 ± 0.6%IA/cc (n = 3) at 48 h post injection. The EC₅₀ of ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher and ²²⁵Ac-control-IgG-SpyTag-∆N-SpyCatcher against an EGFR-positive cell-line (MDA-MB-468) was 3.7 ± 3.3 Bq/mL (0.04 ± 0.03 nM) and 18.5 ± 4.4 Bq/mL (0.2 ± 0.04 nM), respectively. In mice bearing MDA-MB-468 EGFR-positive xenografts, ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher significantly (p = 0.0017) prolonged the survival of mice (64 days) compared to ²²⁵Ac-control IgG (28.5 days), nimotuzumab (28.5 days), or PBS-treated mice (30 days). The results showed that the conjugation and labeling using SpyTag/∆N-SpyCatcher to nimotuzumab did not significantly (p > 0.05) alter the receptor binding of nimotuzumab compared with a non-specific conjugation approach. ²²⁵Ac-nimotuzumab-SpyTag-∆N-SpyCatcher was effective in vitro and in an EGFR-positive triple negative breast cancer xenograft model.

Radioimmunotherapy of PANC-1 human pancreatic cancer xenografts in NOD/SCID or NRG mice with Panitumumab labeled with Auger electron emitting, 111In or β-particle emitting, 177Lu

BACKGROUND

Epidermal growth factor receptors (EGFR) are overexpressed on > 90% of pancreatic cancers (PnCa) and represent an attractive target for the development of novel therapies, including radioimmunotherapy (RIT). Our aim was to study RIT of subcutaneous (s.c.) PANC-1 human PnCa xenografts in mice using the anti-EGFR monoclonal antibody, panitumumab labeled with Auger electron (AE)-emitting, 111In or β-particle emitting, 177Lu at amounts that were non-toxic to normal tissues.

RESULTS

Panitumumab was conjugated to DOTA chelators for complexing 111In or 177Lu (panitumumab-DOTA-[111In]In and panitumumab-DOTA-[177Lu]Lu) or to a metal-chelating polymer (MCP) with multiple DOTA to bind 111In (panitumumab-MCP-[111In]In). Panitumumab-DOTA-[177Lu]Lu was more effective per MBq exposure at reducing the clonogenic survival in vitro of PANC-1 cells than panitumumab-DOTA-[111In]In or panitumumab-MCP-[111In]In. Panitumumab-DOTA-[177Lu]Lu caused the greatest density of DNA double-strand breaks (DSBs) in the nucleus measured by immunofluorescence for γ-H2AX. The absorbed dose in the nucleus was 3.9-fold higher for panitumumab-DOTA-[177Lu]Lu than panitumumab-DOTA-[111In]In and 7.7-fold greater than panitumumab-MCP-[111In]In. No normal tissue toxicity was observed in NOD/SCID mice injected intravenously (i.v.) with 10.0 MBq (10 μg; ~ 0.07 nmoles) of panitumumab-DOTA-[111In]In or panitumumab-MCP-[111In]In or in NRG mice injected i.v. with 6.0 MBq (10 μg; ~ 0.07 nmoles) of panitumumab-DOTA-[177Lu]Lu. There was no decrease in complete blood cell counts (CBC) or increased serum alanine aminotransferase (ALT) or creatinine (Cr) or decreased body weight. RIT inhibited the growth of PANC-1 tumours but a 5-fold greater total amount of panitumumab-DOTA-[111In]In or panitumumab-MCP-[111In]In (30 MBq; 30 μg; ~ 0.21 nmoles) administered in three fractionated amounts every three weeks was required to achieve greater or equivalent tumour growth inhibition, respectively, compared to a single amount of panitumumab-DOTA-[177Lu]Lu (6 MBq; 10 μg; ~ 0.07 nmoles). The tumour doubling time (TDT) for NOD/SCID mice with s.c. PANC-1 tumours treated with panitumumab-DOTA-[111In]In or panitumumab-MCP-[111In]In was 51.8 days and 28.1 days, respectively. Panitumumab was ineffective yielding a TDT of 15.3 days vs. 15.6 days for normal saline treated mice. RIT of NRG mice with s.c. PANC-1 tumours with 6.0 MBq (10 μg; ~ 0.07 nmoles) of panitumumab-DOTA-[177Lu]Lu increased the TDT to 20.9 days vs. 11.5 days for panitumumab and 9.1 days for normal saline. The absorbed doses in PANC-1 tumours were 8.8 ± 3.0 Gy and 2.6 ± 0.3 Gy for panitumumab-DOTA-[111In]In and panitumumab-MCP-[111In]In, respectively, and 11.6 ± 4.9 Gy for panitumumab-DOTA-[177Lu]Lu.

CONCLUSION

RIT with panitumumab labeled with Auger electron-emitting, 111In or β-particle-emitting, 177Lu inhibited the growth of s.c. PANC-1 tumours in NOD/SCID or NRG mice, at administered amounts that caused no normal tissue toxicity. We conclude that EGFR-targeted RIT is a promising approach to treatment of PnCa.

Radioimmunotherapy of Pancreatic Ductal Adenocarcinoma: A Review of the Current Status of Literature

Pancreatic ductal adenocarcinoma (PDAC) has long been associated with low survival rates. A lack of accurate diagnostic tests and limited treatment options contribute to the poor prognosis of PDAC. Radioimmunotherapy using α- or β-emitting radionuclides has been identified as a potential treatment for PDAC. By harnessing the cytotoxicity of α or β particles, radioimmunotherapy may overcome the anatomic and physiological factors which traditionally make PDAC resistant to most conventional treatments. Appropriate selection of target receptors and the development of selective and cytotoxic radioimmunoconjugates are needed to achieve the desired results of radioimmunotherapy. The aim of this review is to examine the growing preclinical and clinical trial evidence regarding the application of α and β radioimmunotherapy for the treatment of PDAC. A systematic search of MEDLINE® and Scopus databases was performed to identify 34 relevant studies conducted on α or β radioimmunotherapy of PDAC. Preclinical results demonstrated α and β radioimmunotherapy provided effective tumour control. Clinical studies were limited to investigating β radioimmunotherapy only. Phase I and II trials observed disease control rates of 11.2%-57.9%, with synergistic effects noted for combination therapies. Further developments and optimisation of treatment regimens are needed to improve the clinical relevance of α and β radioimmunotherapy in PDAC.

Radioimmunotherapy of human pancreatic cancer xenografts in NOD-scid mice with [64Cu]Cu-NOTA-panitumumab F(ab')2 alone or combined with radiosensitizing gemcitabine and the PARP inhibitor, rucaparib

INTRODUCTION

Our objective was to determine the feasibility of extending our previously reported PET imaging study of pancreatic cancer (PnCa) with [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ to radioimmunotherapy (RIT) by exploiting the β-particle and Auger electron emissions of ⁶⁴Cu (PET theranostic concept). To enhance the effectiveness of [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂, we further combined RIT with radiosensitizing gemcitabine (GEM) and the poly(ADP)ribose polymerase inhibitor (PARPi), rucaparib.

METHODS

Normal tissue toxicity was assessed in non-tumor-bearing NOD-scid mice injected i.v. with [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ (1.85-9.25 MBq; 10 μg) or [⁶⁴Cu]Cu-NOTA-anti-mouse EGFR Ab30 F(ab')₂ (12.95 MBq). Body weight was monitored, and hematopoietic (CBC), liver (ALT) and kidney [creatinine (SCr)] toxicity were assessed. RIT studies were performed in NOD-scid mice with s.c. OCIP23 human PnCa patient-derived xenografts (PDX) administered [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ (3.7 MBq; 10 μg), unlabeled panitumumab F(ab')₂ (10 μg) or normal saline every two weeks. Subsequent studies evaluated RIT with [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ (12.95 MBq; 10 μg) administered alone or combined with GEM and the PARPi, rucaparib administered on a 14-day treatment cycle for up to 6 cycles in NOD-scid mice with s.c. PANC-1 human PnCa xenografts. The radiation absorbed dose in PANC-1 tumors and normal organs in mice after a single i.v. injection of [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ (12.95 MBq; 10 μg) was estimated based on previously reported biodistribution studies of [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂.

RESULTS

No normal tissue toxicity was observed in non-tumor-bearing NOD-scid mice administered up to 3.7 MBq (10 μg) of [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ but slightly increased ALT was noted at 9.25 MBq. Administration of [⁶⁴Cu]Cu-NOTA-anti-mouse EGFR Ab30 F(ab')₂ (12.95 MBq; 10 μg) caused some hematopoietic toxicity but no increase in ALT or SCr or decreased body weight. A slight tumor growth delay and increased survival was noted in NOD-scid mice with s.c. OCIP23 PDX treated with [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ (3.7 MBq; 10 μg) or unlabeled panitumumab F(ab')₂ (10 μg) compared to normal saline treated mice. RIT with [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ (12.95 MBq; 10 μg) combined with GEM + PARPi for up to 6 cycles was most effective for the treatment of PANC-1 tumors. Tumor doubling time increased to 13.3 ± 0.9 days vs. 7.8 ± 3.7 days for RIT alone and 9.3 ± 2.2 days for normal saline treatment. Median survival was significantly longer (P < 0.05) than in mice treated with normal saline (35 days) for RIT + GEM + PARPi (71 days), GEM + PARPi (44 days) and RIT + GEM (43 days) but not for RIT alone (25 days). RIT + GEM + PARPi provided a longer median survival than RIT (P < 0.01), GEM + PARPi (P = 0.01) but not RIT + GEM (P = 0.23). Nonetheless, PANC-1 tumors grew exponentially in all treatment groups. The absorbed dose in PANC-1 tumors after a single i.v. injection of [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ (12.85 MBq; 10 μg) was 0.8 Gy, while the dose in normal organs ranged from 0.6-1.2 Gy.

CONCLUSIONS

We conclude that RIT with [⁶⁴Cu]Cu-NOTA-panitumumab F(ab')₂ did not cause significant normal tissue toxicity but was not effective when administered alone for treatment of PnCa xenografts in NOD-scid mice. Combining RIT with GEM and the PARPi, rucaparib enhanced its effectiveness but tumors continued to grow exponentially. Our results suggest that ⁶⁴Cu is not feasible for RIT of PnCa due to low tumor absorbed doses. ¹⁷⁷Lu which has a higher abundance of moderate energy β-particle emissions may be more effective than ⁶⁴Cu. The hematopoietic toxicity of [⁶⁴Cu]Cu-NOTA-anti-mouse EGFR Ab30 F(ab')₂ may be mediated by binding to mouse EGFR expressed on some hematopoietic stem cells.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

Direct extension of PET with ⁶⁴Cu(Cu)-NOTA-panitumumab F(ab')₂ to RIT exploiting the β-particle and Auger electron emissions of ⁶⁴Cu is not feasible. Theranostic approaches that combine PET with RIT employing ¹⁷⁷Lu may be more promising and should be explored.

Monoclonal antibody-based molecular imaging strategies and theranostic opportunities

Molecular imaging modalities hold great potential as less invasive techniques for diagnosis and management of various diseases. Molecular imaging combines imaging agents with targeting moieties to specifically image diseased sites in the body. Monoclonal antibodies (mAbs) have become increasingly popular as novel therapeutics against a variety of diseases due to their specificity, affinity and serum stability. Because of the same properties, mAbs are also exploited in molecular imaging to target imaging agents such as radionuclides to the cell of interest in vivo. Many studies investigated the use of mAb-targeted imaging for a variety of purposes, for instance to monitor disease progression and to predict response to a specific therapeutic agent. Herein, we highlighted the application of mAb-targeted imaging in three different types of pathologies: autoimmune diseases, oncology and cardiovascular diseases. We also described the potential of molecular imaging strategies in theranostics and precision medicine. Due to the nearly infinite repertoire of mAbs, molecular imaging can change the future of modern medicine by revolutionizing diagnostics and response prediction in practically any disease.

Delivery systems exploiting natural cell transport processes of macromolecules for intracellular targeting of Auger electron emitters

The presence of Auger electrons (AE) among the decay products of a number of radionuclides makes these radionuclides an attractive means for treating cancer because these short-range electrons can cause significant damage in the immediate vicinity of the decomposition site. Moreover, the extreme locality of the effect provides a potential for selective eradication of cancer cells with minimal damage to adjacent normal cells provided that the delivery of the AE emitter to the most vulnerable parts of the cell can be achieved. Few cellular compartments have been regarded as the desired target site for AE emitters, with the cell nucleus generally recognized as the preferred site for AE decay due to the extreme sensitivity of nuclear DNA to direct damage by radiation of high linear energy transfer. Thus, the advantages of AE emitters for cancer therapy are most likely to be realized by their selective delivery into the nucleus of the malignant cells. To achieve this goal, delivery systems must combine a challenging complex of properties that not only provide cancer cell preferential recognition but also cell entry followed by transport into the cell nucleus. A promising strategy for achieving this is the recruitment of natural cell transport processes of macromolecules, involved in each of the aforementioned steps. To date, a number of constructs exploiting intracellular transport systems have been proposed for AE emitter delivery to the nucleus of a targeted cell. An example of such a multifunctional vehicle that provides smart step-by-step delivery is the so-called modular nanotransporter, which accomplishes selective recognition, binding, internalization, and endosomal escape followed by nuclear import of the delivered radionuclide. The current review will focus on delivery systems utilizing various intracellular transport pathways and their combinations in order to provide efficient targeting of AE to the cancer cell nucleus.

Recent advances in metallopolymer-based drug delivery systems

Metallopolymers (MPs) or metal-containing polymers have shown great potential as new drug delivery systems (DDSs) due to their unique properties, including universal architectures, composition, properties and surface chemistry. Over the past few decades, the exponential growth of many new classes of MPs that deal with these issues has been demonstrated. This review presents and assesses the recent advances and challenges associated with using MPs as DDSs. Among the most widely used MPs for these purposes, metal complexes based on synthetic and natural polymers, coordination polymers, metal-organic frameworks, and metallodendrimers are distinguished. Particular attention is paid to the stimulus- and multistimuli-responsive metallopolymer-based DDSs. Of considerable interest is the use of MPs for combination therapy and multimodal systems. Finally, the problems and future prospects of using metallopolymer-based DDSs are outlined. The bibliography includes articles published over the past five years.

Comprehensive bioinformatics study reveals targets and molecular mechanism of hesperetin in overcoming breast cancer chemoresistance

The effectiveness of chemotherapy in breast cancer treatment can be increased using a combinatorial agent. Hesperetin has been reported to increase the sensitivity of doxorubicin in breast cancer cells; however, the underlying molecular mechanism remains unclear. This present study was conducted to identify the potential target and molecular mechanism of hesperetin in circumventing breast cancer chemoresistance using a bioinformatics approach. Microarray data obtained after hesperetin treatment in the NCI-60 cell line panel collection were retrieved from the COMPARE public library. These data were then compared with the list of the regulatory genes of breast cancer resistance obtained from PubMed and further analyzed for gene ontology and KEGG pathway enrichment, as well as protein-protein interaction network. A Venn diagram of COMPARE microarray data and the gene list from PubMed generated 56 genes (potential therapeutic target genes/PTTGs). These PTTGs participate in the biological process of the JAK-STAT cascade and are located in the nucleus, exert a molecular function in protein serine/threonine kinase activity, and regulate the erbB signaling pathway. Drug association analysis demonstrated that both hesperetin and the erbB receptor inhibitors, i.e., monoclonal antibody and tyrosine kinase inhibitor, target the same mRNA expression. Furthermore, results of the molecular docking study revealed that hesperetin is a promising inhibitor that targets ABL1, DNMT3B, and MLH1 due to the similarity of binding properties with its native ligand. In conclusion, the possible pathways and the regulatory genes identified in this study may offer new insights into the mechanism by which hesperetin overcomes breast cancer chemoresistance. A combinatorial therapy with hesperetin targeting ABL1, DNMT3B, and MLH1 may be effective in circumventing chemoresistance in breast cancer.

Auger electrons for cancer therapy - a review

Background

Auger electrons (AEs) are very low energy electrons that are emitted by radionuclides that decay by electron capture (e.g. ¹¹¹In, ⁶⁷Ga, ^99mTc, ^195mPt, ¹²⁵I and ¹²³I). This energy is deposited over nanometre-micrometre distances, resulting in high linear energy transfer (LET) that is potent for causing lethal damage in cancer cells. Thus, AE-emitting radiotherapeutic agents have great potential for treatment of cancer. In this review, we describe the radiobiological properties of AEs, their radiation dosimetry, radiolabelling methods, and preclinical and clinical studies that have been performed to investigate AEs for cancer treatment.

Results

AEs are most lethal to cancer cells when emitted near the cell nucleus and especially when incorporated into DNA (e.g. ¹²⁵I-IUdR). AEs cause DNA damage both directly and indirectly via water radiolysis. AEs can also kill targeted cancer cells by damaging the cell membrane, and kill non-targeted cells through a cross-dose or bystander effect. The radiation dosimetry of AEs considers both organ doses and cellular doses. The Medical Internal Radiation Dose (MIRD) schema may be applied. Radiolabelling methods for complexing AE-emitters to biomolecules (antibodies and peptides) and nanoparticles include radioiodination (¹²⁵I and ¹²³I) or radiometal chelation (¹¹¹In, ⁶⁷Ga, ^99mTc). Cancer cells exposed in vitro to AE-emitting radiotherapeutic agents exhibit decreased clonogenic survival correlated at least in part with unrepaired DNA double-strand breaks (DSBs) detected by immunofluorescence for γH2AX, and chromosomal aberrations. Preclinical studies of AE-emitting radiotherapeutic agents have shown strong tumour growth inhibition in vivo in tumour xenograft mouse models. Minimal normal tissue toxicity was found due to the restricted toxicity of AEs mostly on tumour cells targeted by the radiotherapeutic agents. Clinical studies of AEs for cancer treatment have been limited but some encouraging results were obtained in early studies using ¹¹¹In-DTPA-octreotide and ¹²⁵I-IUdR, in which tumour remissions were achieved in several patients at administered amounts that caused low normal tissue toxicity, as well as promising improvements in the survival of glioblastoma patients with ¹²⁵I-mAb 425, with minimal normal tissue toxicity.

Conclusions

Proof-of-principle for AE radiotherapy of cancer has been shown preclinically, and clinically in a limited number of studies. The recent introduction of many biologically-targeted therapies for cancer creates new opportunities to design novel AE-emitting agents for cancer treatment. Pierre Auger did not conceive of the application of AEs for targeted cancer treatment, but this is a tremendously exciting future that we and many other scientists in this field envision.

MicroSPECT/CT Imaging of Cell-Line and Patient-Derived EGFR-Positive Tumor Xenografts in Mice with Panitumumab Fab Modified with Hexahistidine Peptides To Enable Labeling with 99mTc(I) Tricarbonyl Complex

We aimed to investigate the feasibility of conjugating synthetic hexahistidine peptides (His₆) peptides to panitumumab Fab (PmFab) to enable labeling with [^99mTc(H₂O)₃(CO)₃]⁺ complex and study these radioimmunoconjugates for imaging EGFR-overexpressing tumor xenografts in mice by microSPECT/CT. Fab were reacted with a 10-fold excess of sulfo-SMCC to introduce maleimide functional groups for reaction with the terminal thiol on peptides [CGYGGHHHHHH] that harbored the His₆ motif. Modification of Fab with His₆ peptides was assessed by SDS-PAGE/Western blot, and the number of His₆ peptides introduced was quantified by a radiometric assay incorporating ¹²³I-labeled peptides into the conjugation reaction. Radiolabeling was achieved by incubation of PmFab-His₆ in PBS, pH 7.0, with [^99mTc(H₂O)₃(CO)₃]⁺ in a 1.4 MBq/μg ratio. The complex was prepared by adding [^99mTcO₄]^- to an Isolink kit (Paul Scherrer Institute). Immunoreactivity was assessed in a direct (saturation) binding assay using MDA-MB-468 human triple-negative breast cancer (TNBC) cells. Tumor and normal tissue uptake and imaging properties of ^99mTc-PmFab-His₆ (70 μg; 35-40 MBq) injected i.v. (tail vein) were compared to irrelevant ^99mTc-Fab 3913 in NOD/SCID mice engrafted subcutaneously (s.c.) with EGFR-overexpressing MDA-MB-468 or PANC-1 human pancreatic ductal carcinoma (PDCa) cell-line derived xenografts (CLX) at 4 and 24 h post injection (p.i.). In addition, tumor imaging studies were performed with ^99mTc-PmFab-His₆ in mice with patient-derived tumor xenografts (PDX) of TNBC, PDCa, and head and neck squamous cell carcinoma (HNSCC). Biodistribution studies in nontumor bearing Balb/c mice were performed to project the radiation absorbed doses for imaging studies in humans with ^99mTc-PmFab-His₆. PmFab was derivatized with 0.80 ± 0.03 His₆ peptides. Western blot and SDS-PAGE confirmed the presence of His₆ peptides. ^99mTc-PmFab-His₆ was labeled to high radiochemical purity (≥95%), and the K_d for binding to EGFR on MDA-MB-468 cells was 5.5 ± 0.4 × 10^-8 mol/L. Tumor uptake of ^99mTc-PmFab-His₆ at 24 h p.i. was significantly (P < 0.05) higher than irrelevant ^99mTc-Fab 3913 in mice with MDA-MB-468 tumors (14.9 ± 3.1%ID/g vs 3.0 ± 0.9%ID/g) and in mice with PANC-1 tumors (5.6 ± 0.6 vs 0.5 ± 0.1%ID/g). In mice implanted orthotopically in the pancreas with the same PDCa PDX, tumor uptake at 24 h p.i. was 4.2 ± 0.2%ID/g. Locoregional metastases of these PDCa tumors in the peritoneum exhibited slightly and significantly lower uptake than the primary tumors (3.1 ± 0.3 vs 4.2 ± 0.3%ID/g; P = 0.02). In mice implanted with different TNBC or HNSCC PDX, tumor uptake at 24 h p.i. was variable and ranged from 3.7 to 11.4%ID/g and 3.8-14.5%ID/g, respectively. MicroSPECT/CT visualized all CLX and PDX tumor xenografts at 4 and 24 h p.i. Dosimetry estimates revealed that in humans, the whole body dose from administration of 740-1110 MBq of ^99mTc-PmFab-His₆ would be 2-3 mSv, which is less than for a ^99mTc-medronate bone scan (4 mSv).

Metallopolymers for advanced sustainable applications

Since the development of metallopolymers, there has been tremendous interest in the applications of this type of materials. The interest in these materials stems from their potential use in industry as catalysts, biomedical agents in healthcare, energy storage and production as well as climate change mitigation. The past two decades have clearly shown exponential growth in the development of many new classes of metallopolymers that address these issues. Today, metallopolymers are considered to be at the forefront for discovering new and sustainable heterogeneous catalysts, therapeutics for drug-resistant diseases, energy storage and photovoltaics, molecular barometers and thermometers, as well as carbon dioxide sequesters. The focus of this review is to highlight the advances in design of metallopolymers with specific sustainable applications.

Radioimmunotherapy of PANC-1 Human Pancreatic Cancer Xenografts in NRG Mice with Panitumumab Modified with Metal-Chelating Polymers Complexed to 177Lu

Our aim was to evaluate the effectiveness and normal tissue toxicity of radioimmunotherapy (RIT) of s.c. PANC-1 human pancreatic cancer (PnCa) xenografts in NRG mice using anti-EGFR panitumumab linked to metal-chelating polymers (MCPs) that present 13 DOTA chelators to complex the β-emitter, ¹⁷⁷Lu. The clonogenic survival (CS) of PANC-1 cells treated in vitro with panitumumab-MCP-¹⁷⁷Lu (0.3-1.2 MBq) and DNA double-strand breaks (DSBs) in the nucleus of these cells were measured by confocal immunofluorescence microscopy for γ-H2AX. Subcellular distribution of radioactivity for panitumumab-MCP-¹⁷⁷Lu was measured, and absorbed doses to the cell nucleus were calculated. Normal tissue toxicity was assessed in non tumor-bearing NRG mice by monitoring body weight, complete blood cell counts (CBC), serum alanine aminotransferase (ALT), and creatinine (Cr) after i.v. injection of 6 MBq (10 μg) of panitumumab-MCP-¹⁷⁷Lu. RIT was performed in NRG mice with s.c. PANC-1 tumors injected i.v. with 6 MBq (10 μg) of panitumumab-MCP-¹⁷⁷Lu. Control mice received nonspecific human IgG-MCP-¹⁷⁷Lu (6 MBq; 10 μg), unlabeled panitumumab (10 μg), or normal saline. The tumor growth index (TGI) was compared. Tumor and normal organ doses were estimated based on biodistribution studies. Panitumumab-MCP-¹⁷⁷Lu reduced the CS of PANC-1 cells in vitro by 7.7-fold at the highest amount tested (1.2 MBq). Unlabeled panitumumab had no effect on the CS of PANC-1 cells. γ-H2AX foci were increased by 3.8-fold by panitumumab-MCP-¹⁷⁷Lu. Panitumumab-MCP-¹⁷⁷Lu deposited 3.84 Gy in the nucleus of PANC-1 cells. Administration of panitumumab-MCP-¹⁷⁷Lu (6 MBq; 10 μg) to NRG mice caused no change in body weight, CBC, or ALT and only a slight increase in Cr compared to NRG mice treated with normal saline. Panitumumab-MCP-¹⁷⁷Lu strongly inhibited tumor growth in NRG mice (TGI = 2.3 ± 0.2) compared to normal saline-treated mice (TGI = 5.8 ± 0.5; P < 0.01). Unlabeled panitumumab had no effect on tumor growth (TGI = 6.0 ± 1.6; P > 0.05). The absorbed dose of PANC-1 tumors was 12.3 Gy. The highest normal organ doses were absorbed by the pancreas, liver, spleen, and kidneys. We conclude that EGFR-targeted RIT with panitumumab-MCP-¹⁷⁷Lu was able to overcome resistance to panitumumab in KRAS mutant PANC-1 tumors in NRG mice and may be a promising approach to treatment of PnCa in humans.

Oridonin-loaded and GPC1-targeted gold nanoparticles for multimodal imaging and therapy in pancreatic cancer

Purpose

Early diagnosis and therapy are critical to improve the prognosis of patients with pancreatic cancer. However, conventional imaging does not significantly increase the capability to detect early stage disease. In this study, we developed a multifunctional theranostic nanoplatform for accurate diagnosis and effective treatment of pancreatic cancer.

Methods

We developed a theranostic nanoparticle (NP) based on gold nanocages (AuNCs) modified with hyaluronic acid (HA) and conjugated with anti-Glypican-1 (anti-GPC1) antibody, oridonin (ORI), gadolinium (Gd), and Cy7 dye. We assessed the characteristics of GPC1-Gd-ORI@HAuNCs-Cy7 NPs (ORI-GPC1-NPs) including morphology, hydrodynamic size, stability, and surface chemicals. We measured the drug loading and release efficiency in vitro. Near-infrared fluorescence (NIRF)/magnetic resonance imaging (MRI) and therapeutic capabilities were tested in vitro and in vivo.

Results

ORI-GPC1-NPs demonstrated long-time stability and fluorescent/MRI properties. Bio-transmission electron microscopy (bio-TEM) imaging showed that ORI-GPC1-NPs were endocytosed into PANC-1 and BXPC-3 (overexpression GPC1) but not in 293 T cells (GPC1- negative). Compared with ORI and ORI-NPs, ORI-GPC1-NPs significantly inhibited the viability and enhanced the apoptosis of pancreatic cancer cells in vitro. Moreover, blood tests suggested that ORI-GPC1-NPs showed negligible toxicity. In vivo studies showed that ORI-GPC1-NPs enabled multimodal imaging and targeted therapy in pancreatic tumor xenografted mice.

Conclusion

ORI-GPC1-NP is a promising theranostic platform for the simultaneous diagnosis and effective treatment of pancreatic cancer.

Dendrimer Scaffold for the Amplification of In Vivo Pretargeting Ligations

The development of immunoconjugates requires a careful balance between preserving the functionality of the antibody and modifying the immunoglobulin with the desired cargo. Herein, we describe the synthesis, development, and in vivo evaluation of a novel bifunctional dendrimeric scaffold and its application in pretargeted PET imaging. The site-specific modification of the huA33 antibody with this dendrimeric scaffold yields an immunoconjugate-^sshuA33-DEN-TCO-decorated with ∼8 trans-cyclooctene (TCO) moieties, a marked increase compared to the ∼2 TCO/mAb of a nondendrimeric control immunoconjugate (^sshuA33-PEG₁₂-TCO). Pretargeted PET imaging and biodistribution experiments were used to compare the in vivo performance of these two immunoconjugates in athymic nude mice bearing subcutaneous SW1222 human colorectal cancer xenografts. To this end, the mice were administered 100 μg of each immunoconjugate followed 120 h later by the injection of a tetrazine-bearing radioligand, [⁶⁴Cu]Cu-SarAr-Tz. Pretargeting with ^sshuA33-DEN-TCO produced excellent tumoral uptake at 24 h (8.9 ± 1.9 %ID/g), more than double that created by ^sshuA33-PEG₁₂-TCO (4.1 ± 1.3 %ID/g). Critically-and somewhat surprisingly-the attachment of the G_0.5 dendrimeric structures did not hamper the in vivo behavior of the immunoconjugate, suggesting that this versatile bifunctional scaffold may have applications beyond pretargeting.