Introduction: Endometrial cancer is one of the most common gynecological malignancies. Endometrial cancer cells express the gonadotropin-releasing hormone (GnRH) and its receptor (GnRH-R). Among the various therapeutic approaches for the treatment of endometrial cancer is the use of GnRH conjugates, such as the AN-152, created by linking the [D-Lys6] GnRH with the cytotoxic doxorubicin through an ester bond. An undesirable property of these conjugates is their vulnerability to plasma carboxylesterases, which cleave the ester bond to release doxorubicin before reaching the cancer cells. Methods: To overcome this problem, we recently developed the Con-3 and Con-7, which are GnRH analogs conjugated through a disulfide bond with the cytotoxic mitoxantrone. In this study, we determined the cytotoxic properties of the Con-3 and Con-7 on the Ishikawa endometrial cancer cells, assuming that their interaction with the GnRH-R of cells exposes the conjugated mitoxantrone to the cellular thioredoxin. The cellular thioredoxin reduces the disulfide bond of Con-3 & Con-7 to release mitoxantrone, which accumulates in the cancer cells and exerts its cytotoxic actions. Results: Indeed, treatment of Ishikawa cells with Con-3, Con-7, or the free unconjugated mitoxantrone increased their apoptosis and decreased their proliferation in a dose- and time-dependent manner, displaying half-maximal inhibitory concentrations (IC50) of 0.64 - 1.15 μM. In specific, the IC50 values on days 2, 3, and 4 were 1.45, 0.64, and 0.83 μΜ, respectively, for Con-3, 0.91, 0.82 μΜ, and 1.00 μΜ, respectively for Con-7 and 1.15, 0.98, 0.78 μM, respectively for mitoxantrone. Conclusion: In contrast, the free, mitoxantrone-unconjugated peptides did not affect the proliferation of Ishikawa cells. The Con-3 and Con-7 could put the basis for the development of a new class of anticancer drugs for endometrial cancer, which will act as “prodrugs” that deliver the cytotoxic mitoxantrone in a GnRH-R-specific manner.

Chromenes represent a biologically significant family of heterocycles, widely present in pharmaceutical compounds and secondary metabolites. Their importance in synthesis and medicinal chemistry has driven continuous efforts to develop advanced and efficient synthetic methodologies. Over the past decade, photoredox catalysis has revolutionized Organic Synthesis, offering innovative and sustainable strategies for the construction and functionalization of complex molecules. The synthesis of chromene derivatives has greatly benefited from the integration of visible‐light–promoted methodologies, which utilize light as an abundant and non‐toxic energy source, enabling greener chemical transformations. In this review, the latest progress in visible‐light–mediated approaches for the synthesis of chromene derivatives, along with the photochemical reactivity of these relevant frameworks, are summarized.

Gonadotropin-releasing hormone (GnRH) is pivotal in regulating human reproduction and fertility through its specific receptors. Among these, gonadotropin-releasing hormone receptor type I (GnRHR I), which is a member of the G-protein-coupled receptor family, is expressed on the surface of both healthy and malignant cells. Its presence in cancer cells has positioned this receptor as a primary target for the development of novel anti-cancer agents. Moreover, the extensive regulatory functions of GnRH have underscored decapeptide as a prominent vehicle for targeted drug delivery, which is accomplished through the design of appropriate conjugates. On this basis, a rationally designed series of anthraquinone/mitoxantrone–GnRH conjugates (con1–con8) has been synthesized herein. Their in vitro binding affinities range from 0.06 to 3.42 nM, with six of them (con2–con7) demonstrating higher affinities for GnRH than the established drug leuprolide (0.64 nM). Among the mitoxantrone based GnRH conjugates, con3 and con7 show the highest affinities at 0.07 and 0.06 nM, respectively, while the disulfide bond present in the conjugates is found to be readily reduced by the thioredoxin (Trx) system. These findings are promising for further pharmacological evaluation of the synthesized conjugates with the prospect of performing future clinical studies.

The gonadotropin-releasing hormone (GnRH) receptor (GnRH-R) is highly expressed in ovarian cancer cells (OCC), and it is an important molecular target for cancer therapeutics. To develop a new class of drugs targeting OCC, we designed and synthesized Con-3 and Con-7 which are novel high-affinity GnRH-R agonists, covalently coupled through a disulfide bond to the DNA synthesis inhibitor mitoxantrone. We hypothesized that Con-3 and Con-7 binding to the GnRH-R of OCC would expose the conjugated mitoxantrone to the cellular thioredoxin, which reduces the disulfide bond of Con-3 and Con-7. The subsequent release of mitoxantrone leads to its intracellular accumulation, thus exerting its cytotoxic effects. To test this hypothesis, we determined the cytotoxic effects of Con-3 and Con-7 using the SKOV-3 human OCC. Treatment with Con-3 and Con-7, but not with their unconjugated GnRH counterparts, resulted in the accumulation of mitoxantrone within the SKOV-3 cells, increased their apoptosis, and reduced their proliferation, in a dose- and time-dependent manner, with half-maximal inhibitory concentrations of 0.6–0.9 µM. It is concluded that Con-3 and Con-7 act as cytotoxic “prodrugs” in which mitoxantrone is delivered in a GnRH-R-specific manner and constitute a new class of lead compounds for use as anticancer drugs targeting ovarian tumors.

Gonadotropin-Releasing Hormone receptors (GnRHRs) are overexpressed in several hormone-dependent malignancies, making them attractive molecular targets for selective anticancer drug delivery. Peptide–drug conjugates (PDCs) are a promising therapy for cancer and autoimmune diseases with high specificity and reduced toxicity. In this study, the three-dimensional structures of two previously synthesized mitoxantrone–GnRH conjugates, con3 and con7, were elucidated using high-resolution NMR spectroscopy in combination with molecular dynamics (MD) simulations. Complete ¹H and ¹³C resonance assignments were achieved in DMSO-d₆ through two-dimensional NMR experiments. NOESY-derived distance restraints were subsequently used to refine the conformational ensembles obtained from MD simulations performed in water and DMSO. Both conjugates exhibited compact bent conformations with a U-shaped peptide backbone. The mitoxantrone moiety is positioned close to the peptide backbone in water simulations and NMR-refined structures, while it is positioned farther away in DMSO, without affecting the orientation of key residues involved in GnRH receptor binding. Importantly, His², Trp³, and Arg⁸ remain solvent-exposed, whereas the disulfide bond is easily accessible to the solvent, consistent with the proposed drug release mechanism by the thioredoxin system. NMR-restrained molecular modeling confirmed the dominant conformational features predicted by the unconstrained theoretical simulations. Overall, these findings provide better structural understanding of the molecular organization of mitoxantrone–GnRH conjugates, highlighting key receptor-recognition residues and supporting both the proposed thioredoxin-mediated drug release mechanism and their previously reported biological properties. These insights may facilitate the rational design and optimization of improved GnRH peptide–drug conjugates for targeted therapy.

Gonadotropin Releasing Hormone receptors (GnRHRs) are overexpressed in several hormone-dependent malignancies, making them attractive molecular targets for selective anticancer drug delivery. Peptide drug conjugates (PDCs) are a promising therapy for cancer and autoimmune diseases with high specificity and reduced toxicity. In this study, the three-dimensional structures of two previously synthesized mitoxantrone-GnRH conjugates, con3 and con7, were elucidated using high-resolution NMR spectroscopy in combination with molecular dynamics (MD) simulations. Complete ¹H and ¹³C resonance assignments were achieved in DMSO-d₆ through two-dimensional NMR experiments. NOESY-derived distance restraints were subsequently used to refine the conformational ensembles obtained from MD simulations performed in water and DMSO. Both conjugates exhibited compact bent conformations with a U-shaped peptide backbone. The mitoxantrone moiety is positioned close to the peptide backbone in water simulations and NMR-refined structures, while it is positioned farther away in DMSO, without affecting the orientation of key residues involved in GnRH receptor binding. Importantly, His², Trp³, and Arg⁸ remain solvent-exposed, whereas the disulfide bond is easily accessible to the solvent, consistent with the proposed drug release mechanism by the thioredoxin system. NMR-restrained molecular modeling confirmed the dominant conformational features predicted by the unconstrained theoretical simulations. Overall, these findings provide better structural understanding of the molecular organization of mitoxantrone–GnRH conjugates, highlighting key receptor-recognition residues and supporting both the proposed thioredoxin-mediated drug release mechanism and their previously reported biological properties. These insights may facilitate the rational design and optimization of improved GnRH peptide–drug conjugates for targeted therapy.