Availability of both [177Lu]Lu-DOTA-TATE and [90Y]Y-DOTATATE as PRRT agents for neuroendocrine tumors: can we evolve a rational sequential duo-PRRT protocol for large volume resistant tumors?

Drug conjugates for the treatment of lung cancer: from drug discovery to clinical practice

A drug conjugate consists of a cytotoxic drug bound via a linker to a targeted ligand, allowing the targeted delivery of the drug to one or more tumor sites. This approach simultaneously reduces drug toxicity and increases efficacy, with a powerful combination of efficient killing and precise targeting. Antibody‒drug conjugates (ADCs) are the best-known type of drug conjugate, combining the specificity of antibodies with the cytotoxicity of chemotherapeutic drugs to reduce adverse reactions by preferentially targeting the payload to the tumor. The structure of ADCs has also provided inspiration for the development of additional drug conjugates. In recent years, drug conjugates such as ADCs, peptide‒drug conjugates (PDCs) and radionuclide drug conjugates (RDCs) have been approved by the Food and Drug Administration (FDA). The scope and application of drug conjugates have been expanding, including combination therapy and precise drug delivery, and a variety of new conjugation technology concepts have emerged. Additionally, new conjugation technology-based drugs have been developed in industry. In addition to chemotherapy, targeted therapy and immunotherapy, drug conjugate therapy has undergone continuous development and made significant progress in treating lung cancer in recent years, offering a promising strategy for the treatment of this disease. In this review, we discuss recent advances in the use of drug conjugates for lung cancer treatment, including structure-based drug design, mechanisms of action, clinical trials, and side effects. Furthermore, challenges, potential approaches and future prospects are presented.

Diagnosis and management of gastroenteropancreatic neuroendocrine neoplasms by nuclear medicine: Update and future perspective

Gastrointestinal (GI) cancers are the second most common cause of cancer related deaths in the World. Neuroendocrine neoplasms (NENs) is a rare tumor that originated from peptidergic neurons and neuroendocrine cells. NENs occurs in all parts of the body, especially in stomach, intestine, pancreas and lung. These rare tumors are challenging to diagnose at earlier stages because of their wide anatomical distribution and complex clinical features. Traditional imaging methods including magnetic resonance imaging (MRI) and computed tomography (CT) are mostly of useful for detection of larger primary tumors that are 1cm in size. A new medical imaging specialty called nuclear medicine uses radioactive substances for both diagnostic and therapeutic purposes. Nuclear medicine imaging relies on the tissue-specific uptake of radiolabeled tracers. Nuclear medicine techniques can easily identify the NENs tissues for their ability to absorb and concentrate amine, precursors, and peptides, whereas the traditional imaging methods are difficult to perform well. The somatostatin receptor (SSTR) is a targetable receptor frequently expressed in the gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs), and is a promising target for tumor-targeted therapies and radiography. SSTR based somatostatin receptor imaging and peptide receptor radionuclide therapy (PRRT) has emerged as a new hot subject in the diagnosis and treatment of GEP-NENs due to the rapid development of somatostatin analogues (SSAs) and radionuclide. This review aims to provide an overview of the current status of nuclear medicine imaging modalities in the imaging of GEP-NENs, and puts them in perspective of clinical practice.

Glucose Metabolism Modification Induced by Radioligand Therapy with [177Lu]Lu/[90Y]Y-DOTATOC in Advanced Neuroendocrine Neoplasms: A Prospective Pilot Study within FENET-2016 Trial

[18F]F-FDG (FDG) PET is emerging as a relevant diagnostic and prognostic tool in neuroendocrine neoplasms (NENs), as a simultaneous decrease in [68Ga]Ga-DOTA peptides and increase in FDG uptake (the “flip-flop” phenomenon) occurs during the natural history of these tumors. The aim of this study was to evaluate the variations on FDG PET in NEN patients treated with two different schemes of radioligand therapy (RLT) and to correlate them with clinical−pathologic variables. A prospective evaluation of 108 lesions in 56 patients (33 males and 23 females; median age, 64.5 years) affected by NENs of various primary origins (28 pancreatic, 13 gastrointestinal, 9 bronchial, 6 unknown primary (CUP-NENs) and 1 pheochromocytoma) and grades (median Ki-67 = 9%) was performed. The patients were treated with RLT within the phase II clinical trial FENET-2016 (CTID: NCT04790708). RLT was offered for 32 patients with the MONO scheme (five cycles of [177Lu]Lu-DOTATOC) and for 24 with the DUO scheme (three cycles of [177Lu]Lu-DOTATOC alternated with two cycles of [90Y]Y-DOTATOC). Variations in terms of the ΔSUVmax of a maximum of three target lesions per patient (58 for MONO and 50 for DUO RLT) were assessed between baseline and 3 months post-RLT FDG PET. In patients with negative baseline FDG PET, the three most relevant lesions on [68Ga]Ga-DOTA-peptide PET were assessed and matched on post-RLT FDG PET, to check for any possible changes in FDG avidity. Thirty-five patients (62.5%) had at least one pathological FDG uptake at the baseline scans, but the number was reduced to 29 (52%) after RLT. In the patients treated with DUO-scheme RLT, 20 out of 50 lesions were FDG positive before therapy, whereas only 14 were confirmed after RLT (p = 0.03). Moreover, none of the 30 FDG-negative lesions showed an increased FDG uptake after RLT. The lesions of patients with pancreatic and CUP-NENs treated with the DUO scheme demonstrated a significant reduction in ΔSUVmax in comparison to those treated with MONO RLT (p = 0.03 and p = 0.04, respectively). Moreover, we found a mild positive correlation between the grading and ΔSUVmax in patients treated with the MONO scheme (r = 0.39, p < 0.02), while no evidence was detected for patients treated with the DUO scheme. Our results suggest that RLT, mostly with the DUO scheme, could be effective in changing NEN lesions’ glycometabolism, in particular, in patients affected by pancreatic and CUP-NENs, regardless of their Ki-67 index. Probably, associating [90Y]Y-labelled peptides, which have high energy emission and a crossfire effect, and [177Lu]Lu ones, characterized by a longer half-life and a safer profile for organs at risk, might represent a valid option in FDG-positive NENs addressed to RLT. Further studies are needed to validate our preliminary findings. In our opinion, FDG PET/CT should represent a potent tool for fully assessing a patient’s disease characteristics, both before and after RLT.

Radiolabeled Nanocarriers as Theranostics-Advancement from Peptides to Nanocarriers

Endogenous targeted radiotherapy is emerging as an integral modality to treat a variety of cancer entities. Nevertheless, despite the positive clinical outcome of the treatment using radiolabeled peptides, small molecules, antibodies, and nanobodies, a high degree of hepatotoxicity and nephrotoxicity still persist. This limits the amount of dose that can be injected. In an attempt to mitigate these side effects, the use of nanocarriers such as nanoparticles (NPs), dendrimers, micelles, liposomes, and nanogels (NGs) is currently being explored. Nanocarriers can prolong circulation time and tumor retention, maximize radiation dosage, and offer multifunctionality for different targeting strategies. In this review, the authors first provide a summary of radiation therapy and imaging and discuss the new radiotracers that are used preclinically and clinically. They then highlight and identify the advantages of radio-nanomedicine and its potential in overcoming the limitations of endogenous radiotherapy. Finally, the review points to the ongoing efforts to maximize the use of radio-nanomedicine for efficient clinical translation.

Peptide-drug conjugate-based novel molecular drug delivery system in cancer

Drug delivery systems are generally believed to comprise drugs and excipients. A peptide-drug conjugate is a single molecule that can simultaneously play multiple roles in a drug delivery system, such as in vivo drug distribution, targeted release, and bioactivity functions. This molecule can be regarded as an integrated drug delivery system, so it is called a molecular drug delivery system. In the context of cancer therapy, a peptide-drug conjugate comprises a tumor-targeting peptide, a payload, and a linker. Tumor-targeting peptides specifically identify membrane receptors on tumor cells, improve drug-targeted therapeutic effects, and reduce toxic and side effects. Payloads with bioactive functions connect to tumor-targeting peptides through linkers. In this review, we explored ongoing clinical work on peptide-drug conjugates targeting various receptors. We discuss the binding mechanisms of tumor-targeting peptides and related receptors, as well as the limiting factors for peptide-drug conjugate-based molecular drug delivery systems.

On the Separation of Yttrium-90 from High-Level Liquid Waste: Purification to Clinical-Grade Radiochemical Precursor, Clinical Translation in Formulation of 90Y-DOTATATE Patient Dose

Introduction: The quality control parameters of in-house-produced ⁹⁰Y-Acetate from high-level liquid waste (HLLW) using supported liquid membrane (SLM) technology were validated and compared with the pharmacopeia standard. The radiolabeling of DOTATATE yielding ⁹⁰Y-DOTATATE in acceptable radiochemical purity (RCP), with expected pharmacological behavior in in vivo models, establish the quality of ⁹⁰Y-Acetate. Clinical translation of ⁹⁰Y-Acetate in formulation of ⁹⁰Y-DOTATATE adds support toward its use as clinical-grade radiochemical. Methods: Quality control parameters of ⁹⁰Y-Acetate, namely radionuclide purity (RNP), were evaluated using β^- spectrometry, γ-spectroscopy, and liquid scintillation counting. RCP and metallic impurities were established using high-performance liquid chromatography and inductively coupled plasma optical emission spectrometry, respectively. The suitability of ⁹⁰Y-Acetate as an active pharmaceutical ingredient radiochemical was ascertained by radiolabeling with DOTATATE. In vivo biodistribution of ⁹⁰Y-DOTATATE was carried out in nude mice bearing AR42J xenografted tumor. Clinical efficacy of ⁹⁰Y-DOTATATE was established after using in patients with large-volume neuroendocrine tumors (NET). Bremsstrahlung imaging was carried out in dual-head gamma camera with a wide energy window setting (100-250 keV). Results: In-house-produced ⁹⁰Y-Acetate was clear, colorless, and radioactive concentration (RAC) in the range of 40-50 mCi/mL. RCP was >98%. ⁹⁰Sr content was <0.85 μCi/Ci of ⁹⁰Y. Gross λ content was <0.8 nCi/Ci of ⁹⁰Y and no γ peak was observed. Fe³⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ contents were <1.7 μg/Ci. The radiolabeling yield (RLY) of ⁹⁰Y-DOTATATE was >94%, RCP was >98%. The in vitro stability of ⁹⁰Y-DOTATATE was up to 72 h postradiolabeling, upon storage at -20°C. Post-therapy (24 h) Bremsstrahlung image of patients with large NET exhibit complete localization of ⁹⁰Y-DOTATATE in tumor region. Conclusions: This study demonstrates that the in-house-produced ⁹⁰Y-Acetate from HLLW can be used for the formulation of various therapeutic ⁹⁰Y-based radiopharmaceuticals. Since ⁹⁰Y is an imported radiochemical precursor available at a high cost in India, this study which demonstrates the suitability of indigenously sourced ⁹⁰Y, ideally exemplifies the recovery of "wealth from waste." The Clinical Trial Registration number: (P17/FEB/2019).

Sequential Duo-Peptide Receptor Radionuclide Therapy With Indigenous 90Y-DOTATATE and 177Lu-DOTATATE in Large-Volume Neuroendocrine Tumors: Posttherapy Bremsstrahlung and PET/CT Imaging Following 90Y-DOTATATE Treatment

The efficacy of Lu-DOTATATE in large neuroendocrine tumors (NETs) is reduced because of the lower energy (Eβmax 0.497 MeV) and shorter range of Lu. The pure β-emitter Y with its longer β range is more effective in larger tumors. This should be balanced with the greater risk of Y-DOTATATE-related nephrotoxicity. Sequential duo-peptide receptor radionuclide therapy may result in a better response with minimal adverse effects in large-volume heterogeneous NETs. A 56-year-old man with large rectal NET liver metastases, treated with Y-DOTATATE and Lu-DOTATATE and sequential duo-peptide receptor radionuclide therapy, presented with post-Y-DOTATATE bremsstrahlung and PET/CT in comparison with Ga-DOTATATE PET/CT and Lu-DOTATATE scans.

Peptide Receptor Radionuclide Therapy of Neuroendocrine Tumors

Peptide receptor radionuclide therapy (PRRT), over the years, has evolved as an important modality in the therapeutic armamentarium of advanced, metastatic or inoperable, progressive Neuroendocrine Neoplasms (NENs). This review deliberates on the basic understanding and applied clinical aspects of PRRT in NENs, with special reference to (1) tumor biology and receptor characteristics, (2) molecular PET-CT imaging (in particular the invaluable role of dual-tracer PET with [68Ga]-DOTA-TATE/NOC and [18F]-FDG for exploring tumor biology in continuum and individualizing treatment decision making) and NEN theranostics, (3) relevant radiochemistry of different therapeutic radionuclides (both beta emitting 177Lu-DOTATATE and 90Y-DOTATATE and alpha emitting 225Ac-DOTATATE), and (4) related dosimetric considerations. Successful clinical management of the NENs would require multifactorial considerations, and all the aforementioned points pertaining to the disease process and available logistics are key considerations for state-of-the-art clinical practice and delivering personalized care in this group of patients. Emphasis has been placed on relatively intriguing areas such as (1) NET grade 3 of WHO 2017 classification (ie, Ki-67>20% but well-differentiation features), (2) "Neoadjuvant PRRT," (3) combining chemotherapy and PRRT, (4) 'Sandwich Chemo-PRRT', (5) duo-PRRT and tandem PRRT, (6) resistant functioning disease with nuances in clinical management and how one can advocate PRRT rationally in such clinical settings and individualize the management in a patient specific manner. Relevant clinical management issues related to some difficult case scenarios, which the Nuclear Medicine attending physician should be aware of to run an efficient clinical PRRT services, are described.

Radiolabelled Peptides for Positron Emission Tomography and Endoradiotherapy in Oncology

This review deals with the development of peptide-based radiopharmaceuticals for the use with positron emission tomography and peptide receptor radiotherapy. It discusses the pros and cons of this class of radiopharmaceuticals as well as the different labelling strategies, and summarises approaches to optimise metabolic stability. Additionally, it presents different target structures and addresses corresponding tracers, which are already used in clinical routine or are being investigated in clinical trials.