Molecular imaging of HER2 expression in breast cancer patients using a novel peptide-based tracer 99mTc-HP-Ark2: a pilot study

Complete preclinical evaluation of the novel antibody mimetic Nanofitin-IRDye800CW for diverse non-invasive diagnostic applications in the management of HER-2 positive tumors

There are well-known limitations associated to the use of antibodies in the non-invasive detection of HER-2 expression. In fact, current procedures recommended for diagnostic purposes of HER-2 status are still invasive techniques. Here, a novel, smaller diagnostic probe, the anti-HER-2 Nanofitin conjugated to the fluorophore IRDye800CW (NF-800), underwent an in vitro/in vivo proof of concept study by Optical Imaging. NF-800 showed high affinity and specificity for the cellular target, and the ability to internalize into HER-2 positive cells. By ex vivo analysis, NF-800 showed a selective tumor accumulation in xenograft tumor models, and also a good tumor targeting efficacy in translational preclinical setups, such as orthotopic and patient-derived xenograft (PDX) models. In the latter, NF-800 was compared to the anti-HER-2 antibody Trastuzumab, displaying a large diagnostic advantage. Interestingly, NF-800 did not seem to share the same binding site with Trastuzumab and Pertuzumab, opening specific theragnostic opportunities for NF-800 in combination with standard-of-care antibodies.

Cancer Targeting Radiopeptidomimetics in Molecular Nuclear Medicine

Peptides are highly receptor-affine molecules exhibiting suitable pharmacokinetics. Additionally, low-cost production, simple protocols allowing easy modifications, and tolerance toward harsh reaction conditions make peptides ideal ligands for preparation of radiopharmaceuticals for cancer detection and treatment. However, natural peptides being substrates for enzymes are susceptible to proteolysis, which limits the in vivo lifetime and the target uptake. Therefore, the majority of peptides are not able to progress beyond preclinical research. Advancement of peptides for clinical analysis needs modification to instill improved features. Continuous increase and further expected rise in cancer cases in the next decade require development of more disease-directed and promising radiopharmaceuticals. Redesigned peptide, mimicking the original peptide with similar or improved affinity and high metabolic stability, shall have significant edge. This review outlines the design of peptidomimetics by incorporation of D-amino acids (inverso); reversal of D-amino acid sequence (retro-inverso), and reversal of L-amino acid sequence (retro). Clinically successful radiopeptidomimetics prepared using the three approaches have been elaborated to elucidate the important role of peptidomimetics in cancer management.

Pharmacokinetic Positron Emission Tomography Imaging of an Optimized CD38-Targeted 68Ga-Labeled Peptide in Multiple Myeloma: A Pilot Study

Multiple myeloma (MM) is an incurable disease characterized by its clinical and prognostic heterogeneity. Despite conventional chemotherapy and autologous hematopoietic stem cell transplantation, the management of relapsed and refractory MM disease poses significant challenges, both medically and socioeconomically. CD38, highly expressed on the surface of MM cells, serves as a distinct tumor biological target in MM. Peptides offer advantages over antibodies, enabling precise tumor imaging and facilitating early tumor diagnosis and dynamic immunotherapy monitoring. In this study, we developed PF381, a CD38-targeted peptide, and investigated its role in diagnosis, biodistribution, and dosimetry through 68Ga-labeling for preclinical evaluation in tumor-bearing models. We screened a microchip-based combinatorial chemistry peptide library to obtain the amino acid sequence of PF381. Affinity for human CD38 was evaluated by SPRi. PF381 was conjugated with DOTA for radiolabeling with 68Ga, and the complex was characterized by HPLC. PET imaging was performed in murine tumor models after the administration of [68Ga]Ga-DOTA-PF381. Biodistribution analysis compared CD38-positive H929 and CD38-negative U266 tumors, and human radiation dosimetry was estimated. Tumor sections were stained for CD38 expression. SPRi showed that PF381 had a high affinity for CD38 with a KD of 2.49 × 10-8 M. HPLC measured a radiolabeling efficiency of 78.45 ± 7.91% for [68Ga]Ga-DOTA-PF381, with >98% radiochemical purity. PET imaging revealed rapid and persistent accumulation of radioactivity in CD38-positive H929 tumors, contrasting with negligible uptake in CD38-negative U266 tumors. Biodistribution confirmed higher uptake in H929 tumors (0.75 ± 0.03%ID/g) vs U266 (0.26 ± 0.08%ID/g, P < 0.001). The kidney received the highest radiation dose (3.57 × 10-02 mSv/MBq), with an effective dose of 1.41 × 10-02 mSv/MBq. Immunofluorescence imaging supported PET and biodistribution findings. We developed a novel peptide targeting CD38 and proved that 68Ga-labeled PF381 had rapid targeting and good tumor penetration capabilities. Therefore, 68Ga-labeled PF381 could achieve high sensitivity in vivo imaging for CD38-positive hematological malignancies.

99mTc-Labeled D-Type PTP as a Plectin-Targeting Single-Photon Emission Computed Tomography Probe for Hepatocellular Carcinoma Imaging

Plectin, a scaffolding protein overexpressed in tumor cells, plays a significant role in hepatocellular carcinoma (HCC) proliferation, invasion, and migration. However, the use of L-type peptides for targeting plectin is hindered by their limited stability and retention. We designed a D-type plectin-targeting peptide (DPTP) and developed a novel single-photon emission computed tomography (SPECT) probe for HCC imaging. The DPTP targeting ability was evaluated in vitro using flow cytometry and ex vivo fluorescence imaging. 99mTc radiolabeling was performed using tricine and ethylenediamine-N,N'-diacetic acid (EDDA) as coligands after modification with 6-hydrazino nicotinamide (HYNIC) at the N termini of DPTP. The radiochemical purity (RCP), in vitro stability, and binding affinity of the prepared 99mTc-HYNIC-DPTP were analyzed. Tumor uptake, metabolic stability, biodistribution, and pharmacokinetics of 99mTc-HYNIC-DPTP were investigated and compared with those of 99mTc-labeled L-type PTP (99mTc-HYNIC-PTP) in HCC tumor-bearing mice. DPTP could be efficiently radiolabeled with 99mTc using the HYNIC/tricine/EDDA system with a high RCP and good in vitro stability. Compared with the L-type PTP, DPTP exhibited improved targeting ability, and 99mTc-HYNIC-DPTP displayed higher tumor uptake, better metabolic stability, longer blood circulation time, and lower kidney retention, resulting in superior imaging performance and biodistribution in vivo. 99mTc-HYNIC-DPTP has great potential as a novel SPECT probe for diagnosing HCC.

Detection of HER2 expression using 99mTc-NM-02 nanobody in patients with breast cancer: a non-randomized, non-blinded clinical trial

BACKGROUND

99mTc radiolabeled nanobody NM-02 (99mTc-NM-02) is a novel single photon emission computed tomography (SPECT) probe with a high affinity and specificity for human epidermal growth factor receptor 2 (HER2). In this study, a clinical imaging trial was conducted to investigate the relationship between 99mTc-NM-02 uptake and HER2 expression in patients with breast cancer.

METHODS

Thirty patients with pathologically confirmed breast cancer were recruited and imaged with both 99mTc-NM-02 SPECT/computed tomography (CT) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT. According to the treatment conditions before recruitment, patients were divided into two groups, the newly diagnosed group (n = 24) and the treated group (n = 6). The maximal standard uptake value (SUVmax) of 18F-FDG and SUVmax and mean SUV (SUVmean) of 99mTc-NM-02 in the lesions were determined to analyze the relationship with HER2 expression.

RESULTS

No meaningful relationship was observed between 18F-FDG uptake and HER2 expression in 30 patients with breast cancer. 99mTc-NM-02 uptake was positively correlated with HER2 expression in the newly diagnosed group, but no correlation was observed in the treated group. 99mTc-NM-02 uptake in HER2-positive lesions was lower in those with effective HER2-targeted therapy compared with the newly diagnosed group. 99mTc-NM-02 SPECT/CT detected brain and bone metastases of breast cancer with a different imaging pattern from 18F-FDG PET/CT. 99mTc-NM-02 showed no non-specific uptake in inflamed tissues and revealed intra- and intertumoral HER2 heterogeneity by SPECT/CT imaging in 9 of the 30 patients with breast cancer.

CONCLUSIONS

99mTc-NM-02 SPECT/CT has the potential for visualizing whole-body HER2 overexpression in untreated patients, making it a promising method for HER2 assessment in patients with breast cancer.

TRIAL REGISTRATION

NCT04674722, Date of registration: December 19, 2020.

From exploring cancer and virus targets to discovering active peptides through mRNA display

During carcinogenesis, neoplastic cells accumulate mutations in genes important for cellular homeostasis, producing defective proteins. Viral infections occur when viral capsid proteins bind to the host cell receptor, allowing the virus to enter the cells. In both cases, proteins play important roles in cancer development and viral infection, so these targets can be exploited to develop alternative treatments. mRNA display technology is a very powerful tool for the development of peptides capable of acting on specific targets in neoplastic cells or on viral capsid proteins. mRNA display technology allows the selection and evolution of peptides with desired functional properties from libraries of many nucleic acid variants. Among other advantages of this technology, the use of flexizymes allows the production of peptides with unnatural amino acid residues, which can enhance the activity of these molecules. From target immobilization, peptides with greater specificity for the targets of interest are generated during the selection rounds. Herein, we will explore the use of mRNA display technology for the development of active peptides after successive rounds of selection, using proteins present in neoplastic cells and viral particles as targets.