RYZ101 (Ac-225 DOTATATE) Opportunity beyond Gastroenteropancreatic Neuroendocrine Tumors: Preclinical Efficacy in Small-Cell Lung Cancer

Intersection between lung cancer and neuroscience: Opportunities and challenges

Lung cancer, which has the highest morbidity and mortality rates worldwide, involves intricate interactions with the nervous system. Research indicates that the nervous system not only plays a role in the origin of lung cancer, but also engages in complex interactions with cancer cells through neurons, neurotransmitters, and various neuroactive molecules during tumor proliferation, invasion, and metastasis, especially in brain metastases. Cancer and its therapies can remodel the nervous system. Despite advancements in immunotherapy and targeted therapies in recent years, drug resistance of lung cancer cells after treatment limits improvements in patient survival and prognosis. The emergence of neuroscience has created new opportunities for the treatment of lung cancer. However, it also presents challenges. This review emphasizes that a deeper understanding of the interactions between the nervous system and lung cancer, along with the identification of new therapeutic targets, may lead to significant advancements or even a revolution in treatment strategies for patients with lung cancer.

PET- and CT-Based Imaging Criteria for Response Assessment of Gastroenteropancreatic Neuroendocrine Tumors Under Radiopharmaceutical Therapy

Despite well-documented limitations, current guidelines recommend the use of size-based RECIST 1.1 for response assessment of gastroenteropancreatic neuroendocrine tumors (GEP-NETs) under radiopharmaceutical therapy (RPT). We hypothesize that functional criteria are superior to RECIST 1.1 for response assessment and progression-free survival (PFS) prediction, and molecular scores can be used in prognosticating PFS. Methods: This single-center, retrospective study included 178 patients with GEP-NETs (G1 and G2) who were treated with at least 2 consecutive cycles of RPT with [177Lu]Lu-DOTATATE and who underwent somatostatin receptor PET/CT at baseline and after 2 cycles of RPT (follow-up). PFS was defined as the time between baseline and clinical progression, as reported by a GEP-NET multidisciplinary tumor board (MDT) assessment or reported death. The differences in categorization and PFS between RECIST 1.1, Choi (functional criteria), and the MDT were evaluated, and 3-y PFS with MDT defined PFS as the reference. The predictive values of the different scores in somatostatin receptor standardized reporting and data system and Krenning (molecular scores) for PFS were analyzed. Results: Choi criteria classified a higher number of patients as having progressive disease and partial response and a lower number of patients as having stable disease compared with RECIST 1.1 (P < 0.01). The PFS of patients with progressive disease according to RECIST 1.1 and Choi criteria was shorter than that of patients with stable disease and partial response (P < 0.05). Choi criteria showed a nonsignificantly higher concordance with the MDT than with RECIST 1.1. There was a shift in category from a Krenning score of 4 to a score of 3 between baseline and follow-up (P < 0.01). At baseline, a Krenning score of 3 was associated with a shorter median PFS compared with a score of 4 (P < 0.05). Conclusion: In addition to RECIST 1.1, further PET- and CT-based imaging criteria have the potential to assess response and predict PFS in patients with GEP-NETs undergoing RPT. Our data support the assumption to use Choi criteria for prediction of PFS and agreement in response assessment. At baseline, the Krenning score can be used to predict therapy response after 2 cycles of RPT.

Preclinical safety and effectiveness of a long-acting somatostatin analogue [225Ac]Ac-EBTATE against small cell lung cancer and pancreatic neuroendocrine tumors

PURPOSE

We report the preclinical evaluation of potent long-acting [225Ac]Ac-EBTATE against SSTR2-positive small cell lung cancer (SCLC) and pancreatic neuroendocrine tumors (pan-NETs).

METHODS

The pharmacokinetic, biodistribution, and safety studies were evaluated in healthy female and/or male BALB/c mice after intravenous injections of [225Ac]Ac-EBTATE. Further biodistribution and radioligand therapy were investigated in female athymic BALB/c nude mice bearing high or low SSTR2-expressing subcutaneous SCLC models NCI-H524 or NCI-H727, respectively, and in a pan-NET model QGP1.SSTR2.

RESULTS

Pharmacokinetics confirmed a prolonged clearance half-life (40.27 ± 9.23 h) while biodistribution in healthy male and female BALB/c mice was similar, with prolonged blood circulation that peaked at 6 h. Biodistribution in subcutaneous xenograft models of NCI-H524 and NCI-H727 showed consistent tumor-uptake with SSTR2-overexpression while the projected human effective doses for males and females were 61.7 and 83.7 millisievert/megabecquerel, respectively. 2 × 34 kBq of [225Ac]Ac-EBTATE administered 10 days (d) apart, was generally tolerated for 28 days in healthy BALB/c mice as revealed by blood biochemistry, complete blood count, and histopathological examination of H&E-stained organs. Targeted alpha therapy at 2 × 30 kBq of [225Ac]Ac-EBTATE, injected 10 days apart, resulted in 100% survivals and 80% and 20% complete remissions for NCI-H524 and QGP1.SSTR2 models, respectively. Additionally, [225Ac]Ac-EBTATE had a dose-dependent response in the NCI-H727 model, with median survivals for 2 × 30 kBq and 2 × 15 kBq groups being 63 d (p < 0.0007), and 47 d (p = 0.0148), respectively.

CONCLUSIONS

[225Ac]Ac-EBTATE is safe and effective against SCLC and pan-NET and therefore warrants clinical investigation.

Theranostics in Lung Neuroendocrine Tumors

In the last 2 decades, there has been a noticeable increase in the incidence of neuroendocrine tumors, in part due to improved understanding of pathology and/or availability of more sensitive and accurate diagnostic tests. While gastrointestinal tract and pancreas are the most common sites of origin, lung neuroendocrine tumors (LNETs) are also frequently reported and need special considerations from diagnostic as well as therapeutic aspects. Radiopharmaceutical therapy (Theranostics) is a novel approach which utilizes a pair of diagnostic and therapeutic agents that share a common target on tumor sites. Precise treatment of the disease with minimum side effects is the principal aim of Theranostics. It's a known fact that somatostatin receptors (SSTR) are abundantly expressed in neuroendocrine tumors. With the advent of highly specific radiopharmaceuticals targeting SSTR receptors for both diagnosis as well as treatment and other targeted therapies, management of LNETs has become less challenging. Still, there exists significant ambiguity in relation to management of LNETs with a scope of novel diagnostic and therapeutic strategies to pitch in. This review focuses on the role of established evidence for Theranostics strategies in the management of LNETs and highlights the potential future role of newer targets which would be of promising value in addressing such rare and complex tumor biology.

Ac-225 radiochemistry through the lens of [225Ac]Ac-DOTA-TATE

BACKGROUND

Targeted alpha therapy with Ac-225 showed to be effective in treating metastatic cancers. However, the complex decay chain requires optimized radiolabeling and quality control. This study aims to determine critical parameters and establish optimal labeling and accurate measuring techniques for radiochemical yield and purity with DOTA-TATE as a model molecule. Ac-225 sources were analyzed for metals (ΣFe, Zn, Cu) and quantified by UPLC. Optimization of radiolabeling kinetics for clinical conditions was performed in regards to temperature (20-90 °C), heating time (5-60 min), pH (2.5-10, with/without excess of metal ions), buffers, quenchers, volume (0.1-10 mL) and molar activity (90-540 kBq/nmol). The quality control was investigated using radio-TLC/HPLC by changing gradient to evaluate peak separation, radiolysed peptide and impurity separation.

RESULTS

Metal ingrowth was observed in Ac-225 stocks (n = 3), (time of arrival: 17.9, 36.8 and 101.4 nmol per 10 MBq). Optimal radiochemical yields were achieved with > 80 °C (20 min) at pH 8.5 (15 mM TRIS) up to 270 kBq. Labeling at a high pH showed a higher RCY, even in presence of an excess of metals. High stability (RCP > 90%) was achieved after addition of quenchers (cysteine, methionine, ascorbate, histidine, or gentisic acid (35 mM)) up to 24 h. For optimal determination of the radiochemical purity (indirect HPLC) fifty fractions are required.

CONCLUSION

The quality of Ac-225 labeled DOTA-radiopharmaceuticals is highly dependent on the pH and stabilization (buffer/quencher). Within this research it is demonstrated that optimized quality control methods and accurate measurement of the radiolabeling kinetics are crucial to ensure safe implementation for patient treatment.

Open-Flask Protocol for the Removal of Alloc Carbamate and Allyl Ester Protecting Groups. Application to In-solution and On-resin Peptide Synthesis

The standard protocol for Alloc group removal during peptide synthesis still presents limitations, including low reaction yields, N-allylated byproducts, and the use of air-sensitive Pd(PPh3)4. We addressed these challenges by developing a novel protocol using the air-stable Pd(PPh3)2Cl2 catalyst, Meldrum's acid (MA), and triethylsilane (TES-H). This combination ensured high yields, eliminated N-allylated byproducts, and is compatible with automated synthesis. This cost-effective and efficient method shows promise for widespread use in peptide chemistry applications and beyond.

Small Cell Lung Cancer Neuronal Features and Their Implications for Tumor Progression, Metastasis, and Therapy

Small cell lung cancer (SCLC) is an epithelial neuroendocrine form of lung cancer for which survival rates remain dismal and new therapeutic approaches are greatly needed. Key biological features of SCLC tumors include fast growth and widespread metastasis, as well as rapid resistance to treatment. Similar to pulmonary neuroendocrine cells, SCLC cells have traits of both hormone-producing cells and neurons. In this study, we specifically discuss the neuronal features of SCLC. We consider how neuronal G protein-coupled receptors and other neuronal molecules on the surface of SCLC cells can contribute to the growth of SCLC tumors and serve as therapeutic targets in SCLC. We also review recent evidence for the role of neuronal programs expressed by SCLC cells in the fast proliferation, migration, and metastasis of these cells. We further highlight how these neuronal programs may be particularly relevant for the development of brain metastases and how they can assist SCLC cells to functionally interact with neurons and astrocytes. A greater understanding of the molecular and cellular neuronal features of SCLC is likely to uncover new vulnerabilities in SCLC cells, which may help develop novel therapeutic approaches. More generally, the epithelial-to-neuronal transition observed during tumor progression in SCLC and other cancer types can contribute significantly to tumor development and response to therapy.

Peptide Binder to Glypican-3 as a Theranostic Agent for Hepatocellular Carcinoma

Glypican-3 (GPC3) is a membrane-associated glycoprotein that is significantly upregulated in hepatocellular carcinomas (HCC) with minimal to no expression in normal tissues. The differential expression of GPC3 between tumor and normal tissues provides an opportunity for targeted radiopharmaceutical therapy to treat HCC, a leading cause of cancer-related deaths worldwide. Methods: DOTA-RYZ-GPC3 (RAYZ-8009) comprises a novel macrocyclic peptide binder to GPC3, a linker, and a chelator that can be complexed with different radioisotopes. The binding affinity was determined by surface plasma resonance and radioligand binding assays. Target-mediated cellular internalization was radiometrically measured at multiple time points. In vivo biodistribution, monotherapy, and combination treatments with 177Lu or 225Ac were performed on HCC xenografts. Results: RAYZ-8009 showed high binding affinity to GPC3 protein of human, mouse, canine, and cynomolgus monkey origins and no binding to other glypican family members. Potent cellular binding was confirmed in GPC3-positive HepG2 cells and was not affected by isotope switching. RAYZ-8009 achieved efficient internalization on binding to HepG2 cells. Biodistribution study of 177Lu-RAYZ-8009 showed sustained tumor uptake and fast renal clearance, with minimal or no uptake in other normal tissues. Tumor-specific uptake was also demonstrated in orthotopic HCC tumors, with no uptake in surrounding liver tissue. Therapeutically, significant and durable tumor regression and survival benefit were achieved with 177Lu- and 225Ac-labeled RAYZ-8009, as single agents and in combination with lenvatinib, in GPC3-positive HCC xenografts. Conclusion: Preclinical in vitro and in vivo data demonstrate the potential of RAYZ-8009 as a theranostic agent for the treatment of patients with GPC3-positive HCC.