Benzamide derivative radiotracers targeting melanin for melanoma imaging and therapy: Preclinical/clinical development and combination with other treatments

Navigating the landscape of theranostics in nuclear medicine: current practice and future prospects

Theranostics refers to the combination of diagnostic biomarkers with therapeutic agents that share a specific target expressed by diseased cells and tissues. Nuclear medicine is an exciting component explored for its applicability in theranostic concepts in clinical and research investigations. Nuclear theranostics is based on the employment of radioactive compounds delivering ionizing radiation to diagnose and manage certain diseases employing binding with specifically expressed targets. In the realm of personalized medicine, nuclear theranostics stands as a beacon of potential, potentially revolutionizing disease management. Studies exploring the theranostic profile of radioactive compounds have been presented in this review along with a detailed explanation of radioactive compounds and their theranostic applicability in several diseases. It furnishes insights into their applicability across diverse diseases, elucidating the intricate interplay between these compounds and disease pathologies. Light is shed on the important milestones of nuclear theranostics beginning with radioiodine therapy in thyroid carcinomas, MIBG labelled with iodine in neuroblastoma, and several others. Our perspectives have been put forth regarding the most important theranostic agents along with emerging trends and prospects.

Iodinated 4,4'-Bipyridines with Antiproliferative Activity Against Melanoma Cell Lines

In the last decade, biological processes involving halogen bond (HaB) as a leading interaction attracted great interest. However, although bound iodine atoms are considered powerful HaB donors, few iodinated new drugs were reported so far. Recently, iodinated 4,4'-bipyridines showed interesting properties as HaB donors in solution and in the solid state. In this paper, a study on the inhibition activity of seven halogenated 4,4'-bipyridines against malignant melanoma (MM) cell proliferation is described. Explorative dose/response proliferation assays were first performed with three 4,4'-bipyridines by using four MM cell lines and the normal BJ fibroblast cell line as control. Among them, the A375 MM cell line was the most sensitive, as determined by MTT assays, which was selected to evaluate the antiproliferative activity of all 4,4'-bipyridines. Significantly, the presence of an electrophilic iodine impacted the biological activity of the corresponding compounds. The 3,3',5,5'-tetrachloro-2-iodo-4,4'-bipyridine showed significant antiproliferation activity against the A375 cell line, and lower toxicity on BJ fibroblasts. Through in silico studies, the stereoelectronic features of possible sites determining the bioactivity were explored. These results pave the way for the utilization of iodinated 4,4'-bipyridines as templates to design new promising HaB-enabled inhibitors of MM cell proliferation.

Melanin-targeted [18F]-PFPN PET imaging for prognosticating patients with melanoma

PURPOSE

Positron emission tomography (PET) using [18F]-PFPN, a melanin-targeted imaging tracer, has excellent diagnostic performance in patients with melanoma. This study aimed to investigate its value in prognostication and determine predictors of progression-free survival (PFS) and overall survival (OS).

METHODS

We reviewed melanoma patients who underwent [18F]-PFPN and [18F]-FDG PET from February 2021 to July 2022. Clinical characteristics, follow-up data, and the following [18F]-PFPN PET parameters were recorded: maximum standardized uptake value (SUVmax), whole-body melanotic tumoral volume (WBMTV), and whole-body total lesion melanin (WBTLM). Receiver operating characteristic (ROC), Kaplan-Meier and Cox regression analyses were performed.

RESULTS

Seventy-six patients (47 men and 29 women; mean age, 57.99 ± 10.72 years) were included for analysis. Median follow-up was 12.0 months (range: 1-22 months). Eighteen patients died and 38 experienced progression. Median OS was 17.60 months (95% confidence interval, 15.89-19.31). In the ROC analysis, [18F]-PFPN PET parameters were superior to those of [18F]-FDG PET in prognosticating death and disease progression. PFS and OS were significantly better in patients with lower SUVmax, WBMTV, and WBTLM on [18F]-PFPN PET (log-rank, P < 0.05). In the univariate analyses, distant metastasis, SUVmax, WBMTV, and WBTLM were significantly associated with cumulative incidence of PFS and OS (P < 0.05). In the multivariate analysis, SUVmax was an independent predictor of PFS and OS.

CONCLUSIONS

[18F]-PFPN PET has a role in prognostication of melanoma patients. Patients with higher [18F]-PFPN SUVmax have worse prognosis.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT05645484. Registered 9 December, 2022, https://clinicaltrials.gov/ct2/show/NCT05645484?cond=The+Prognostic+Value+of+18F-PFPN+PET+Imaging+in+Patients+With+Malignant+Melanoma&draw=2&rank=1.

Clinical Advances and Perspectives in Targeted Radionuclide Therapy

Targeted radionuclide therapy has become increasingly prominent as a nuclear medicine subspecialty. For many decades, treatment with radionuclides has been mainly restricted to the use of iodine-131 in thyroid disorders. Currently, radiopharmaceuticals, consisting of a radionuclide coupled to a vector that binds to a desired biological target with high specificity, are being developed. The objective is to be as selective as possible at the tumor level, while limiting the dose received at the healthy tissue level. In recent years, a better understanding of molecular mechanisms of cancer, as well as the appearance of innovative targeting agents (antibodies, peptides, and small molecules) and the availability of new radioisotopes, have enabled considerable advances in the field of vectorized internal radiotherapy with a better therapeutic efficacy, radiation safety and personalized treatments. For instance, targeting the tumor microenvironment, instead of the cancer cells, now appears particularly attractive. Several radiopharmaceuticals for therapeutic targeting have shown clinical value in several types of tumors and have been or will soon be approved and authorized for clinical use. Following their clinical and commercial success, research in that domain is particularly growing, with the clinical pipeline appearing as a promising target. This review aims to provide an overview of current research on targeting radionuclide therapy.

Synthesis and Preclinical Evaluation of a 68Ga-Labeled Pyridine-Based Benzamide Dimer for Malignant Melanoma Imaging

Benzamide (BZA), a small molecule that can freely cross cell membranes and bind to melanin, has served as an effective targeting group for melanoma theranostics. In this study, a novel pyridine-based BZA dimer (denoted as H-2) was labeled with ⁶⁸Ga ([⁶⁸Ga]Ga-H-2) for positron emission tomography (PET) imaging of malignant melanomas. [⁶⁸Ga]Ga-H-2 was obtained with high radiochemical yield (98.0 ± 2.0%) and satisfactory radiochemical purity (>95.0%). The specificity and affinity of [⁶⁸Ga]Ga-H-2 were confirmed in melanoma B16F10 cells and in vivo PET imaging of multiple tumor models (B16F10 tumors, A375 melanoma, and lung metastases). Monomeric [⁶⁸Ga]Ga-H-1 was prepared as a control radiotracer to verify the effects of the molecular structure on pharmacokinetics. The values of the lipid-water partition coefficient of [⁶⁸Ga]Ga-H-2 and [⁶⁸Ga]Ga-H-1 demonstrated hydrophilicity with log P = -2.37 ± 0.07 and -2.02 ± 0.09, respectively. PET imaging and biodistribution showed a higher uptake of [⁶⁸Ga]Ga-H-2 in B16F10 primary and metastatic melanomas than that in A375 melanomas. However, the relatively low uptake of monomeric [⁶⁸Ga]Ga-H-1 in B16F10 tumors and high accumulation in nontarget organs resulted in poor PET imaging quality. This study demonstrates the synthesis and preclinical evaluation of the novel pyridine-based BZA dimer [⁶⁸Ga]Ga-H-2 and indicates that the dimer tracer has promising applications in malignant melanoma-specific PET imaging because of its high uptake and long-time retention in malignant melanoma.

MC1R and melanin-based molecular probes for theranostic of melanoma and beyond

Malignant melanoma is accounting for most of skin cancer-associated mortality. The incidence of melanoma increased every year worldwide especially in western countries. Treatment efficiency is highly related to the stage of melanoma. Therefore, accurate staging and restaging play a pivotal role in the management of melanoma patients. Though 18F-fluorodeoxyglucose (18F-FDG) positron-emission tomography (PET) has been widely used in imaging of tumor metastases, novel radioactive probes for specific targeted imaging of both primary and metastasized melanoma are still desired. Melanocortin receptor 1 (MC1R) and melanin are two promising biomarkers specifically for melanoma, and numerous research groups including us have been actively developing a plethora of radioactive probes based on targeting of MC1R or melanin for over two decades. In this review, some of the MC1R-targeted tracers and melanin-associated molecular imaging probes developed in our research and others have been briefly summarized, and it provides a quick glance of melanoma-targeted probe design and may contribute to further developing novel molecular probes for cancer theranostics.

Targeting Melanin in Melanoma with Radionuclide Therapy

Nearly 100,000 individuals are expected to be diagnosed with melanoma in the United States in 2022. Treatment options for late-stage metastatic disease up until the 2010s were few and offered only slight improvement to the overall survival. The introduction of B-RAF inhibitors and anti-CTLA4 and anti-PD-1/PD-L1 immunotherapies into standard of care brought measurable increases in the overall survival across all stages of melanoma. Despite the improvement in the survival statistics, patients treated with targeted therapies and immunotherapies are subject to very serious side effects, the development of drug resistance, and the high costs of treatment. This leaves room for the development of novel approaches as well as for the exploration of novel combination therapies for the treatment of metastatic melanoma. One such approach is targeting melanin pigment with radionuclide therapy. Advances in melanin-targeting radionuclide therapy of melanoma can be viewed from two spheres: (1) radioimmunotherapy (RIT) and (2) radiolabeled small molecules. The investigation of mechanisms of the action and efficacy of targeting melanin in melanoma treatment by RIT points to the involvement of the immune system such as complement dependent cytotoxicity. The combination of RIT with immunotherapy presents synergistic killing in mouse melanoma models. The field of radiolabeled small molecules is focused on radioiodinated compounds that have the ability to cross the cellular membranes to access intracellular melanin and can be applied in both therapy and imaging as theranostics. Clinical applications of targeting melanin with radionuclide therapies have produced encouraging results and clinical work is on-going. Continued work on targeting melanin with radionuclide therapy as a monotherapy, or possibly in combination with standard of care agents, has the potential to strengthen the current treatment options for melanoma patients.

Vegetable-derived indole enhances the melanoma-treating efficacy of chemotherapeutics

Food-drug interaction is an important but overlooked issue. For example, little is known concerning whether or not the chemotherapy of cancers is affected by the well-defined dietary chemicals such as 2-(indol-3-ylmethyl)-3,3'-diindolylmethane (LTr1) derived from daily consumed cruciferous vegetables. This work, inspired by the described melanogenesis reduction by certain indoles, presents that LTr1 mitigates the melanogenesis and thus potentiates the in vitro and in vivo anti-melanoma effectiveness of different chemotherapeutic agents including dacarbazine, vemurafenib, and sorafenib. In B16 melanoma cells, LTr1 was shown to inhibit the melanogenesis by acting towards the regulatory (R) subunit of protein kinase A (PRKAR1a) associated with the phosphorylation of cAMP-response element binding protein (CREB). This allows LTr1 to reduce the expression of melanogenesis-related enzymes such as tyrosinase (TYR), tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2). Furthermore, LTr1 was addressed to bind to the aryl hydrocarbon receptor (AhR) and up-regulate the expression of CYP1A1 encoding cytochrome P450 1A1, leading to the escalation of reactive oxygen species (ROS) level. The increased ROS generation promotes the cysteine-to-cystine transformation to inhibit the pheomelanogenesis in melanomas. Collectively, the work identifies LTr1 as a new melanogenesis inhibitor that modulates the PKA/CREB/MITF and AhR/CYP1A1/ROS pathways, thereby providing a new option for (re)sensitizing melanomas to chemotherapeutics.

Phase I study of [131I] ICF01012, a targeted radionuclide therapy, in metastatic melanoma: MELRIV-1 protocol

Background

Benzamide-based radioligands targeting melanin were first developed for imaging melanoma and then for therapeutic purpose with targeted radionuclide therapy (TRT).

[¹³¹I]ICF01012 presents a highly favorable pharmacokinetics profile in vivo for therapy. Tumour growth reduction and increase survival have been established in preclinical models of melanoma. According the these preclinical results, we initiate a first-in-human study aimed to determine the recommended dose of [¹³¹I]ICF01012 to administer for the treatment of patients with pigmented metastatic melanoma.

Methods

The MELRIV-1 trial is an open-label, multicentric, dose-escalation phase I trial. The study is divided in 2 steps, a selection part with an IV injection of low activity of [¹³¹I]ICF01012 (185 MBq at D0) to select patients who might benefit from [¹³¹I]ICF01012 TRT in therapeutic part, i.e. patient presenting at least one tumour lesion with [¹³¹I]ICF01012 uptake and an acceptable personalized dosimetry to critical organs (liver, kidney, lung and retina). According to dose escalation scheme driven by a Continual Reassessment Method (CRM) design, a single therapeutic injection of 800 MBq/m², or 1600 MBq/m², or 2700 MBq/m² or 4000 MBq/m² of [¹³¹I]ICF01012 will be administered at D11 (± 4 days). The primary endpoint is the recommended therapeutic dose of [¹³¹I]ICF01012, with DLT defined as any grade 3-4 NCI-CT toxicity during the 6 weeks following therapeutic dose. Safety, pharmacokinetic, biodistribution (using planar whole body and SPECT-CT acquisitions), sensitivity / specificity of [¹³¹I]ICF01012, and therapeutic efficacy will be assessed as secondary objectives. Patients who received therapeutic injection will be followed until 3 months after TRT. Since 6 to 18 patients are needed for the therapeutic part, up to 36 patients will be enrolled in the selection part.

Discussion

This study is a first-in-human trial evaluating the [¹³¹I]ICF01012 TRT in metastatic malignant melanomas with a diagnostic dose of the [¹³¹I]ICF01012 to select the patients who may benefit from a therapeutic dose of [¹³¹I]ICF01012, with at least one tumor lesion with [¹³¹I]ICF01012 uptake and an acceptable AD to healthy organ.

Trial registration

Clinicaltrials.gov: NCT03784625. Registered on December 24, 2018.

Identifier in French National Agency for the Safety of Medicines and Health Products (ANSM): N°EudraCT 2016-002444-17.

Melanin and Melanin-Functionalized Nanoparticles as Promising Tools in Cancer Research-A Review

Cancer poses an ongoing global challenge, despite the substantial progress made in the prevention, diagnosis, and treatment of the disease. The existing therapeutic methods remain limited by undesirable outcomes such as systemic toxicity and lack of specificity or long-term efficacy, although innovative alternatives are being continuously investigated. By offering a means for the targeted delivery of therapeutics, nanotechnology (NT) has emerged as a state-of-the-art solution for augmenting the efficiency of currently available cancer therapies while combating their drawbacks. Melanin, a polymeric pigment of natural origin that is widely spread among many living organisms, became a promising candidate for NT-based cancer treatment owing to its unique physicochemical properties (e.g., high biocompatibility, redox behavior, light absorption, chelating ability) and innate antioxidant, photoprotective, anti-inflammatory, and antitumor effects. The latest research on melanin and melanin-like nanoparticles has extended considerably on many fronts, allowing not only efficient cancer treatments via both traditional and modern methods, but also early disease detection and diagnosis. The current paper provides an updated insight into the applicability of melanin in cancer therapy as antitumor agent, molecular target, and delivery nanoplatform.