Blanca Ocampo-García

The management of rheumatoid arthritis and related inflammatory arthropathies is evolving from late structural assessment toward early molecular phenotyping of synovitis. Target-specific radiopharmaceuticals for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) now permit non-invasive detection of activated fibroblast-like synoviocytes, inflammatory macrophages, chemokine-driven immune-cell trafficking, angiogenesis, and mitochondrial stromal activation. This review analyzes the radiochemical basis of synovitis imaging, beginning with the radionuclide-dependent behavior of ¹¹C, ⁶⁸Ga, ⁶⁴Cu, [Al¹⁸F]²⁺, and ^99mTc, and then linking these properties to chelator selection, covalent radiolabeling, labeling conditions, and pharmacokinetics. The review further examines the development of radioligands targeting fibroblast activation protein (FAP), integrin α_vβ₃, folate receptor beta (β-FR), CXCR4, and the 18 kDa translocator protein (TSPO). It covers FAP-inhibitor scaffolds, RGD-based integrin probes, pteroyl-glutamate folate conjugates, CXCR4 antagonists, and TSPO heteroaromatic ligands. Clinical and translational datasets are discussed in relation to disease-activity evolution, treatment-response monitoring, and differentiation of stromal activation, macrophage infiltration, angiogenesis, and immune-cell recruitment. Finally, the review integrates kinetic modeling and dosimetric translation, emphasizing absorbed-dose estimation as a perspective on therapeutic optimization and safety constraints for emerging β-emitting and α-emitting synovial theranostics, ¹⁷⁷Lu and ²²⁵Ac. Collectively, these developments define a bench-to-bedside framework for rheumatology precision medicine, in which radiopharmaceutical chemistry, molecular imaging, clinical trial evidence, and patient-specific dosimetry converge to guide diagnosis, therapeutic selection, and future targeted synovial micro-radioresection.

Prostate-specific membrane antigen (PSMA) is a validated theranostic target with clinical relevance extending beyond prostate cancer to PSMA-expressing neovasculature in solid tumors. Despite the success of ¹⁷⁷Lu-PSMA therapy, a significant proportion of patients experience disease recurrence or partial responses, motivating the development of targeted alpha therapy (TAT) approaches. In this study, novel monomeric and dimeric ²²⁵Ac-labeled PSMA inhibitors, [²²⁵Ac]Ac-DOTA-iPSMA ([²²⁵Ac]Ac-D-iPSMA) and [²²⁵Ac]Ac-MACROPA-iPSMA ([²²⁵Ac]Ac-M-iPSMA), were designed through receptor-based computational screening, synthesized, radiolabeled, and evaluated in vitro and in vivo. Radiolabeling achieved high radiochemical purities (>96%), and saturation binding assays using lanthanum(III) surrogates confirmed cooperative nanomolar PSMA affinity. The binding affinities were Kd = 8.28 ± 0.51 nM (La-D-iPSMA) and Kd = 16.76 ± 2.51 nM (La-M-iPSMA). PSMA-specific uptake was validated in 4T1 breast cancer and HCT116 colorectal cancer cells. D-iPSMA induced superior late apoptosis (41.74% at 2 Gy), associated with reductions in GSK-3 α/β (Glycogen Synthase Kinase-3) and WNK1 (With No Lysine Kinase 1) phosphorylation, β-catenin downregulation, and dose-dependent DNA double-strand breaks (72.08% γ-H2AX [γ-phosphorylated histone]-positive cells at 6 Gy). [²²⁵Ac]Ac-M-iPSMA biodistribution in 4T1 tumor-bearing BALB/c mice revealed rapid blood clearance, a tumor-to-kidney dose ratio of 54:1, and a high tumor-absorbed dose. A combination of [¹⁷⁷Lu]Lu-D-iPSMA with [²²⁵Ac]Ac-M-iPSMA maximized reactive oxygen species generation. These findings support both conjugates as promising TAT candidates for PSMA-expressing tumors.

Copper-64 is increasingly recognized for its advantages in positron emission tomography (PET) imaging and theranostic applications due to its favorable half-life, decay profile, and high spatial resolution. This research addresses the need for reliable, high-purity PET radiotracers by developing GMP-grade lyophilized kits for one-step preparation of ⁶⁴Cu-NOTA-peptides using gelatin as a chelating agent for metallic impurities and NOTA for selective copper binding. The approach was applied to five peptide analogs formulated for fast ⁶⁴Cu labeling: NOTA-iPSMA, NOTA-TOC, NOTA-iPD-L1, NOTA-iFAP, and NOTA-UBI 29–41, which were preclinically evaluated to enable the precise molecular imaging of cancer and infection. Each multidose kit included 0.5 μmol of the NOTA-peptide and 25 mg of gelatin, labeled with 925 MBq of ⁶⁴Cu. The radiochemical purity of the ⁶⁴Cu-NOTA-peptides exceeded 98% (mean 99.2% ± 0.3%) without the need for additional purification. The ⁶⁴Cu-radiotracers remained stable for at least 24 h at room temperature and showed high stability in human serum. In preclinical studies, saturation-binding assays demonstrated that affinity (Kd) was less than 10 nM in all ⁶⁴Cu-NOTA-peptides, with tumor-to-lung ratios ranging from 14 to 290 at 2 h post-injection and low liver uptake (2.95% ± 1.36% ID/g). The research demonstrated that these formulations, which include peptides specific to PSMA, SSTR2, PD-L1, FAP, and infection sites, offer excellent in vivo performance and high PET imaging quality in mice with induced tumors or infection sites. The findings support the use of gelatin-NOTA-peptide kits as a standardized and practical solution for producing ⁶⁴Cu-labeled peptides, facilitating routine clinical PET imaging, and advancing personalized molecular diagnostics.

Castration-resistant prostate cancer presents radiotherapeutic challenges, especially in optimizing the cytosolic internalization of therapeutic radiopharmaceuticals. This research aimed to design and evaluate in vitro, a new dimeric radiopharmaceutical, [¹⁷⁷Lu]Lu–iPSMA–iGRP78, which combines PSMA and GRP78 inhibitors in a heterodimeric radioligand to improve the radionuclide internalization and cytotoxicity efficacy. Molecular docking showed that the dimer iPSMA–iGRP78 presents a higher affinity for GRP78 (CNN-docking score: −14.0 kcal·mol⁻¹, pKi: 10) and for PSMA (CNN-docking score: −17.0 kcal·mol⁻¹, pKi: 11.5) compared to the monomers iGRP78 (CNN-docking score: −11.0 kcal·mol⁻¹, pKi: 9.4) and iPSMA (CNN-docking score: −13.9 kcal·mol⁻¹, pKi: 10.2). The saturation binding assay using LNCaP cells (PSMA+, CS-GRP78+) showed an affinity (K_d) of 1.883 nM for [¹⁷⁷Lu]Lu–iPSMA–iGRP78 and 2.245 nM for [¹⁷⁷Lu]Lu–iPSMA. The dimeric radiopharmaceutical achieved 10.44 ± 2.43% cytosolic internalization and 4.81 ± 0.94% nuclear internalization, while the [¹⁷⁷Lu]Lu–iPSMA monomer showed 6.45 ± 0.60% cytosolic internalization and no uptake in the cell nucleus. In PC3 cells (PSMA–, CS-GRP78–), [¹⁷⁷Lu]Lu–iPSMA–iGRP78 uptake was negligible, demonstrating specificity. Treatment with the dimeric radiopharmaceutical reduced cell viability (69.93 ± 4.85% of dead cells) significantly more than [¹⁷⁷Lu]Lu–iPSMA (38.63 ± 6.13% of dead cells). In conclusion, conjugation of a GRP78 inhibitor to [¹⁷⁷Lu]Lu–iPSMA improves the radionuclide internalization and cytotoxicity in prostate cancer cells, suggesting that the bispecific radiopharmaceutical is a promising strategy in prostate cancer treatment.

Introduction: Gene therapy using siRNA is a current area of research in oncology. Although siRNA formulations have not yet been approved for cancer therapy, numerous studies have demonstrated their therapeutic potential for tumor remission. Objective: To provide an overview of the formulations designed and developed to date based on synthetic siRNA for systemic administration to silence cancer genes. Methodology: A thorough search was conducted using the keywords “siRNA”, “therapy”, and “cancer”, with further classification of the resulting works into the various topics addressed in this review. Results: This review encompasses a wide range of aspects, from the design of siRNA using bioinformatics tools to the primary cellular signals and mechanisms targeted for inhibition in cancer therapy. It describes the primary chemical modifications made to siRNA chains to enhance stability, improve bioavailability, and ensure their binding to nanocarrier systems. siRNA formulations ranging from simple conjugates with biomolecules and small molecules to organic, inorganic, and hybrid nanoparticles, which are examined focusing on their advantages and disadvantages. The significance of nanosystems in dual therapy, including siRNA, for developing personalized treatments that achieve better outcomes is emphasized. Conclusions: Personalized cancer therapy appears to be the preferred approach for oncological treatments. To progress, strategies need to be tailored to the patient’s genetic profile. siRNA therapies provide a flexible platform for targeting and inhibiting critical oncogenes, enhancing the prospects of genomics-guided, patient-specific therapies.

Rhodamine-6G, rhodamine-123, and rhodamine-B undergo type I charge transfer reactions with folic acid under irradiation at 532 nm. Therefore, these compounds are potential therapeutic agents for photodynamic therapy in hypoxic media. As 532 nm light penetrates poorly into tissues, an alternative is to use biphotonic absorption at 1064 nm as an excitation source. In this study, the ability of rhodamine-6G, rhodamine-123, and rhodamine-B to induce charge transfer reactions with folic acid by biphotonic absorption at 1064 nm was evaluated via fluorescence. If the reaction takes place, folic acid breaks up and fluorescence is increased. The cytotoxicity induced by these rhodamines in breast cancer cells upon irradiation at 1064 nm after passive internalization and internalization via reconstituted high-density lipoprotein nanoparticles was also studied. Rhodamine-123 did not undergo a type I reaction at 1064 nm in solution; rhodamine-6G and rhodamine-B did so to a similar extent. Irradiation of cancer cells after 1 h of incubation with rhodamine/(folic acid) solutions and 24 h of incubation post-treatment revealed rhodamine-6G- and rhodamine-B-induced toxicity via the production of reactive oxygen species. Such species damage mitochondria and induce apoptosis and necrosis. The cell internalization of rhodamines via rHDL nanoparticles did not compromise the cytotoxic effect previously exhibited. Rhodamine-6G and rhodamine-B transported in nanoparticles are potential candidates for biphotonic photodynamic therapy at 1064 nm.

Targeted radionuclide therapy (TRT) utilizes radiopharmaceuticals to deliver radiation directly to cancer cells while sparing healthy tissues. Beyond the absorbed dose of ablative radiation, TRT induces non-targeted effects (NTEs) that significantly enhance its therapeutic efficacy. These effects include radiation-induced bystander effects (RIBEs), abscopal effects (AEs), radiation-induced genomic instability (RIGI), and adaptive responses, which collectively influence the behavior of cancer cells and the tumor microenvironment (TME). TRT also modulates immune responses, promoting immune-mediated cell death and enhancing the efficacy of combination therapies, such as the use of immune checkpoint inhibitors. The molecular mechanisms underlying TRT involve DNA damage, oxidative stress, and apoptosis, with repair pathways like homologous recombination (HR) and non-homologous end joining (NHEJ) playing critical roles. However, challenges such as tumor heterogeneity, hypoxia, and radioresistance limit the effectiveness of this approach. Advances in theranostics, which integrate diagnostic imaging with TRT, have enabled personalized treatment approaches, while artificial intelligence and improved dosimetry offer potential for treatment optimization. Despite the significant survival benefits of TRT in prostate cancer and neuroendocrine tumors, 30–40% of patients remain unresponsive, which highlights the need for further research into molecular pathways, long-term effects, and combined therapies. This review outlines the dual mechanisms of TRT, direct toxicity and NTEs, and discusses strategies to enhance its efficacy and expand its use in oncology.

Background/Objective: Programmed cell death ligand-1 (PD-L1), which is overexpressed in certain tumors, inhibits the body’s natural immune response by providing an “off” signal that enables cancer cells to evade the immune system. It has been demonstrated that [¹⁷⁷Lu]Lu-DOTA-iPD-L1 (PD-L1 inhibitor cyclic peptide) promotes immune responses. This study aimed to synthesize and evaluate [¹⁸F]AlF-NOTA-iPD-L1 as a novel radiotracer for PD-L1 positron emission tomography (PET) imaging and as a potential theranostic pair for [¹⁷⁷Lu]Lu-DOTA-iPD-L1. Methods: The NOTA-iPD-L1 peptide conjugate was synthesized and characterized by U.V.-vis, I.R.-FT, and UPLC-mass spectroscopies. Radiolabeling was performed using [¹⁸F]AlF as the precursor, and the radiochemical purity (HPLC), partition coefficient, and serum stability were assessed. Cellular uptake and internalization (in 4T1 triple-negative breast cancer cells), binding competition, immunofluorescence, and Western blot assays were applied for the radiotracer in vitro characterization. Biodistribution in mice bearing 4T1 tumors was performed, and molecular imaging (Cerenkov images) of [¹⁸F]AlF-NOTA-iPD-L1 and [¹⁷⁷Lu]Lu-DOTA-iPD-L1 in the same mouse was obtained. Results: [¹⁸F]AlF-NOTA-iPD-L1 was prepared with a radiochemical purity greater than 97%, and it demonstrated high in vitro and in vivo stability, as well as specific recognition by the PD-L1 protein (IC₅₀ = 9.27 ± 2.69 nM). Biodistribution studies indicated a tumor uptake of 6.4% ± 0.9% ID/g at 1-hour post-administration, and Cerenkov images showed a high tumor uptake of both [¹⁸F]AlF-NOTA-iPD-L1 and ¹⁷⁷Lu-iPD-L1 in the same mouse. Conclusions: These results warrant further studies to evaluate the clinical usefulness of [¹⁸F]AlF-NOTA-iPD-L1/[¹⁷⁷Lu]Lu-DOTA-iPD-L1 as a radiotheranostic pair in combination with anti-PD-L1/PD1 immunotherapy.

Background/Objectives: Prostate cancer (PC) represents the second most diagnosed form of cancer in men on a global scale. Despite the theranostic efficacy of prostate-specific membrane antigen (PSMA) radioligands, there is a spectrum of PC disease in which PSMA expression is low or absent. The gastrin-releasing peptide receptor (GRPR), also known as the bombesin type 2 receptor, has been identified as a target in both the early and advanced stages of PC. The objective of this study was to prepare and preclinically evaluate [^99mTc]Tc-iPSMA-Bombesin ([^99mTc]Tc-iPSMA-BN), estimate dosimetry in healthy subjects, and assess the diagnostic efficacy of the radiotracer in patients with metastatic PC, with the hypothesis of non-inferiority to one of the gold standards, [¹⁸F]-PSMA-1007. Moreover, the potential of [^99mTc]Tc-iPSMA-BN as a theranostic pair with [¹⁷⁷Lu]Lu-iPSMA-BN was investigated. Methods: [^99mTc]Tc-iPSMA-BN was prepared under GMP conditions with radiochemical purities > 95%, showing specific recognition by PSMA and GRP receptors in prostate cancer cells and mice bearing PC tumors. Six healthy volunteers were enrolled, and [^99mTc]Tc-iPSMA-BN SPECT/CT imaging (740 MBq) was performed to estimate the dosimetry. The pilot clinical study included seven mCRPC and four mCSPC patients with prior androgen deprivation therapy. All patients had a recent [¹⁸F]-PSMA-PET/CT scan and were enrolled in this prospective study on their own signed behalf. Volumetric lesion target-to-background ratios (TBRs) were obtained from PET/CT and SPECT/CT images. Results: [^99mTc]Tc-iPSMA-BN effective radiation dose was 1.94 ± 0.39 mSv/740 MBq. A total of 178 lesions were detected via CT, 162 via [¹⁸F]-PSMA-1007 PET, and 155 via [^99mTc]Tc-iPSMA-BN SPECT. Three patients with mCRPC had higher TBR values on SPECT than on PET. [^99mTc]Tc-iPSMA-BN appears to have better lesion detection in patients with aggressive histologic transformation. Two-way ANOVA analysis revealed a significant difference in TBR values between patients with mCRPC and mCSPC (p < 0.05) but no difference between [¹⁸F]-PSMA-1007 and [^99mTc]Tc-iPSMA-BN (p > 0.05). In one patient, [¹⁷⁷Lu]Lu-iPSMA-BN showed a high correlation with [^99mTc]Tc-iPSMA-BN for lesions that concentrated radioactivity. Conclusions: [^99mTc]Tc-iPSMA-BN SPECT/CT is a promising alternative not only for diagnostic purposes but also for broadening the spectrum of PC patients who may benefit from radionuclide theranostics. The results justify the development of a clinical trial involving a significant number of patients with PC.