Preclinical Development of Seriniquinones as Selective Dermcidin Modulators for the Treatment of Melanoma.

The bioactive natural product seriniquinone was discovered as a potential melanoma drug, which was produced by the as-yet-undescribed marine bacterium of the rare genus Serinicoccus. As part of a long-term research program aimed at the discovery of new agents for the treatment of cancer, seriniquinone revealed remarkable in vitro activity against a diversity of cancer cell lines in the US National Cancer Institute 60-cell line screening. Target deconvolution studies defined the seriniquinones as a new class of melanoma-selective agents that act in part by targeting dermcidin (DCD). The targeted DCD peptide has been recently examined and defined as a "pro-survival peptide" in cancer cells. While DCD was first isolated from human skin and thought to be only an antimicrobial peptide, currently DCD has been also identified as a peptide associated with the survival of cancer cells, through what is believed to be a disulfide-based conjugation with proteins that would normally induce apoptosis. However, the significantly enhanced potency of seriniquinone was of particular interest against the melanoma cell lines assessed in the NCI 60-cell line panel. This observed selectivity provided a driving force that resulted in a multidimensional program for the discovery of a usable drug with a new anticancer target and, therefore, a novel mode of action. Here, we provided an overview of the discovery and development efforts to date.

Seriniquinones as Therapeutic Leads for Treatment of BRAF and NRAS Mutant Melanomas.

Isolated from the marine bacteria Serinicoccus sp., seriniquinone (SQ1) has been characterized by its selective activity in melanoma cell lines marked by its modulation of human dermcidin and induction of autophagy and apoptosis. While an active lead, the lack of solubility of SQ1 in both organic and aqueous media has complicated its preclinical evaluation. In response, our team turned its effort to explore analogues with the goal of returning synthetically accessible materials with comparable selectivity and activity. The analogue SQ2 showed improved solubility and reached a 30-40-fold greater selectivity for melanoma cells. Here, we report a detailed comparison of the activity of SQ1 and SQ2 in SK-MEL-28 and SK-MEL-147 cell lines, carrying the top melanoma-associated mutations, BRAFV600E and NRASQ61R, respectively. These studies provide a definitive report on the activity, viability, clonogenicity, dermcidin expression, autophagy, and apoptosis induction following exposure to SQ1 or SQ2. Overall, these studies showed that SQ1 and SQ2 demonstrated comparable activity and modulation of dermcidin expression. These studies are further supported through the evaluation of a panel of basal expression of key-genes related to autophagy and apoptosis, providing further insight into the role of these mutations. To explore this rather as a survival or death mechanism, autophagy inhibition sensibilized BRAF mutants to SQ1 and SQ2, whereas the opposite happened to NRAS mutants. These data suggest that the seriniquinones remain active, independently of the melanoma mutation, and suggest the future combination of their application with inhibitors of autophagy to treat BRAF-mutated tumors.

Topical delivery of seriniquinone for treatment of skin cancer and fungal infections is enabled by a liquid crystalline lamellar phase.

Seriniquinone (SQ) was initially described by our group as an antimelanoma drug candidate and now also as an antifungal drug candidate. Despite its promising in vitro effects, SQ translation has been hindered by poor water-solubility. In this paper, we described the challenging nanoformulation process of SQ, which culminated in the selection of a phosphatidylcholine-based lamellar phase (PLP1). Liposomes and nanostructured lipid carriers were also evaluated but failed to encapsulate the compound. SQ-loaded PLP1 (PLP1-SQ) was characterized for the presence of sedimented or non-dissolved SQ, rheological and thermal behavior, and irritation potential with hen's egg test on the chorioallantoic membrane (HET-CAM). PLP1 influence on transepidermal water loss (TEWL) and skin penetration of SQ was assessed in a porcine ear skin model, while biological activity was evaluated against melanoma cell lines (SK-MEL-28 and SK-MEL-147) and C. albicans SC5314. Despite the presence of few particles of non-dissolved SQ (observed under the microscope 2 days after formulation obtainment), PLP1 tripled SQ retention in viable skin layers compared to SQ solution at 12 h. This effect did not seem to relate to formulation-induced changes on the barrier function, as no increases in TEWL were observed. No sign of vascular toxicity in the HET-CAM model was observed after cutaneous treatment with PLP1. SQ activity was maintained on melanoma cells after 48 h-treatment (IC50 values of 0.59-0.98 µM) whereas the minimum inhibitory concentration (MIC) against C. albicans after 24 h-treatment was 32-fold higher. These results suggest that a safe formulation for SQ topical administration was developed, enabling further in vivo studies.

Beyond Formulation: Contributions of Nanotechnology for Translation of Anticancer Natural Products into New Drugs.

Nature is the largest pharmacy in the world. Doxorubicin (DOX) and paclitaxel (PTX) are two examples of natural-product-derived drugs employed as first-line treatment of various cancer types due to their broad mechanisms of action. These drugs are marketed as conventional and nanotechnology-based formulations, which is quite curious since the research and development (R&D) course of nanoformulations are even more expensive and prone to failure than the conventional ones. Nonetheless, nanosystems are cost-effective and represent both novel and safer dosage forms with fewer side effects due to modification of pharmacokinetic properties and tissue targeting. In addition, nanotechnology-based drugs can contribute to dose modulation, reversion of multidrug resistance, and protection from degradation and early clearance; can influence the mechanism of action; and can enable drug administration by alternative routes and co-encapsulation of multiple active agents for combined chemotherapy. In this review, we discuss the contribution of nanotechnology as an enabling technology taking the clinical use of DOX and PTX as examples. We also present other nanoformulations approved for clinical practice containing different anticancer natural-product-derived drugs.

Advance of Seriniquinone Analogues as Melanoma Agents.

Seriniquinone, a marine natural product, displayed potent cytotoxicity and selectivity against melanoma cancer cells. This selectivity, combined with a novel mode of action (MOA), prompted studies to translate a pharmacologically relevant lead. Herein, we report on structure-activity relationships (SARs), and provide a strategy to prepare analogues that retain activity and offer an improved water solubility and isomeric purity. From intermediates made on a gram-scale, derivatives were prepared and evaluated for their antiproliferation activity and melanoma selectivity. Overall these studies provide methods to install side chain motifs that demonstrate a common, and yet unique, biological profile.