Characterization of NVX-207, a novel betulinic acid-derived anti-cancer compound

Antitumor activity and transcriptome sequencing (RNA-seq) analyses of hepatocellular carcinoma cells in response to exposure triterpene-nucleoside conjugates

Fifteen betulonic/betulinic acid conjugated with nucleoside derivatives were synthesized to enhance antitumor potency and water solubility. Among these, the methylated betulonic acid-azidothymidine compound (8c) exhibited a broad-spectrum of antitumor activity against three tested tumor cell lines, including SMMC-7721 (IC50 = 5.02 μM), KYSE-150 (IC50 = 5.68 μM), and SW620 (IC50 = 4.61 μM) and along with lower toxicity (TC50 > 100 μM) estimated by zebrafish embryos assay. Compared to betulinic acid (<0.05 μg/mL), compound 8c showed approximately 40-fold higher water solubility (1.98 μg/mL). In SMMC-7721 cells, compound 8c induced autophagy and apoptosis as its concentration increased. Transcriptomic sequencing analysis was used to understand the potential impacts of the underlying mechanism of 8c on SMMC-7721 cells. Transcriptomic studies indicated that compound 8c could activate autophagy by inhibiting the PI3K/AKT pathway in SMMC-7721 cells. Furthermore, in the xenograft mice study, compound 8c significantly slowed down the tumor growth, as potent as paclitaxel treated group. In conclusion, methylated betulonic acid-azidothymidine compound (8c) not only increases water solubility, but also enhances the potency against hepatocellular carcinoma cells by inducing autophagy and apoptosis, and suppressing the PI3K/Akt/mTOR signaling pathway.

Potent drug delivery enhancement of betulinic acid and NVX-207 into equine skin in vitro - a comparison between a novel oxygen flow-assisted transdermal application device and microemulsion gels

BACKGROUND

Gray horses are predisposed to equine malignant melanoma (EMM) with advancing age. Depending on the tumor's location and size, they can cause severe problems (e.g., defaecation, urination, feeding). A feasible therapy for EMM has not yet been established and surgical excision can be difficult depending on the location of the melanoma. Thus, an effective and safe therapy is needed. Naturally occurring betulinic acid (BA), a pentacyclic triterpene and its synthetic derivate, NVX-207 (3-acetyl-betulinic acid-2-amino-3-hydroxy-2-hydroxymethyl-propanoate) are known for their cytotoxic properties against melanomas and other tumors and have already shown good safety and tolerability in vivo. In this study, BA and NVX-207 were tested for their permeation potential into equine skin in vitro in Franz-type diffusion cell (FDC) experiments after incubation of 5 min, 30 min and 24 h, aiming to use these formulations for prospective in vivo studies as a treatment for early melanoma stages. Potent permeation was defined as reaching or exceeding the half maximal inhibitory concentrations (IC50) of BA or NVX-207 for equine melanoma cells in equine skin samples. The active ingredients were either dissolved in a microemulsion (ME) or in a microemulsion gel (MEG). All of the formulations were transdermally applied but the oil-in-water microemulsion was administered with a novel oxygen flow-assisted (OFA) applicator (DERMADROP TDA).

RESULTS

All tested formulations exceeded the IC50 values for equine melanoma cells for BA and NVX-207 in equine skin samples, independently of the incubation time NVX-207 applied with the OFA applicator showed a significant time-dependent accumulation and depot-effect in the skin after 30 min and 24 h (P < 0.05).

CONCLUSIONS

All tested substances showed promising results. Additionally, OFA administration showed a significant accumulation of NVX-207 after 30 min and 24 h of incubation. Further in vivo trials with OFA application are recommended.

Betulinic Acid for Glioblastoma Treatment: Reality, Challenges and Perspectives

Betulinic acid is a naturally occurring compound that can be obtained through methanolic or ethanolic extraction from plant sources, as well as through chemical synthesis or microbial biotransformation. Betulinic acid has been investigated for its potential therapeutic properties, and exhibits anti-inflammatory, antiviral, antimalarial, and antioxidant activities. Notably, its ability to cross the blood-brain barrier addresses a significant challenge in treating neurological pathologies. This review aims to compile information about the impact of betulinic acid as an antitumor agent, particularly in the context of glioblastoma. Importantly, betulinic acid demonstrates selective antitumor activity against glioblastoma cells by inhibiting proliferation and inducing apoptosis, consistent with observations in other cancer types. Compelling evidence published highlights the acid's therapeutic action in suppressing the Akt/NFκB-p65 signaling cascade and enhancing the cytotoxic effects of the chemotherapeutic agent temozolomide. Interesting findings with betulinic acid also suggest a focus on researching the reduction of glioblastoma's invasiveness and aggressiveness profile. This involves modulation of extracellular matrix components, remodeling of the cytoskeleton, and secretion of proteolytic proteins. Drawing from a comprehensive review, we conclude that betulinic acid formulations as nanoparticles and/or ionic liquids are promising drug delivery approaches with the potential for translation into clinical applications for the treatment and management of glioblastoma.

Substances of Natural Origin in Medicine: Plants vs. Cancer

Continuous monitoring of the population's health is the main method of learning about disease prevalence. National and international data draw attention to the persistently high rates of cancer incidence. This necessitates the intensification of efforts aimed at developing new, more effective chemotherapeutic and chemopreventive drugs. Plants represent an invaluable source of natural substances with versatile medicinal properties. Multidirectional activities exhibited by natural substances and their ability to modulate key signaling pathways, mainly related to cancer cell death, make these substances an important research direction. This review summarizes the information regarding plant-derived chemotherapeutic drugs, including their mechanisms of action, with a special focus on selected anti-cancer drugs (paclitaxel, irinotecan) approved in clinical practice. It also presents promising plant-based drug candidates currently being tested in clinical and preclinical trials (betulinic acid, resveratrol, and roburic acid).

Synthesis of Novel Pentacyclic Triterpenoid Derivatives that Induce Apoptosis in Cancer Cells through a ROS-dependent, Mitochondrial-Mediated Pathway

Betulinic acid (BA) and oleanolic acid (OA) are plant-derived conjugates found in various medicinal plants that have emerged as potential antitumor agents. Herein, a series of novel BA and OA derivatives were synthesized by conjugation with per-O-methylated-β-cyclodextrin (PM-β-CD), and their anticancer properties against a panel of three human cancer cell lines were evaluated. Two OA-PM-β-CD conjugates (48 and 50) were observed to be the most potent conjugates against the three cell lines (MCF-7, BGC-823, and HL-60), with a 15- to 20-fold decrease in the IC₅₀ values (IC₅₀: 6.06-8.47 μM) compared with their parental conjugate (OA). Annexin V-FITC/propidium iodide staining and Western blot analysis revealed that both conjugates induced apoptosis in HL-60 cells. Additionally, in the representative conjugate 48-treated HL-60 cells, a decrease in mitochondrial membrane potential and subsequent release of cytochrome c into the cytosol were observed, indicating the activation of the intrinsic apoptosis pathway. Furthermore, 48 dramatically induced the generation of reactive oxygen species (ROS) in HL-60 cells, and the corresponding effect could be reversed using the ROS scavenger N-acetylcysteine. Collectively, these results suggest that the novel pentacyclic triterpenoid derivatives trigger the intrinsic apoptotic pathways via the ROS-mediated activation of caspase-3 signaling, inducing cell death in human cancer cells.

Advances in the Semi-Synthesis of Triterpenoids

Recent achievements in triterpenoid semi-synthesis are discussed in this short review, which is divided into three parts according to the type of synthetic strategy being employed. These strategies include functionalization, modification of the carbon skeleton, and glycosylation. In the section on functionalization strategies, both functional group interconversions and new functional group installations on triterpenoid starting materials are described. The section on modification of the carbon skeleton is divided into three parts according to the tactic being applied, and incorporates rearrangement of the carbon skeleton, ring scission, and introduction of an additional heterocyclic ring. Meanwhile, in the section on glycosylation, notable achievements in the semi-synthesis of both natural and artificial triterpene saponins are discussed. Overall, the pivotal transformations that have brought about striking chemical structure variations of triterpenoid starting materials are highlighted herein, and it is hoped that this short review will provide inspiration to both established and new investigators engaged in this field of research.

1 Introduction

2 Semi-Synthesis of Triterpenoids via Functionalization Strategies

2.1 Functionalization of Rings with Functional Groups

2.2 Functionalization of a Side Chain

2.3 Functionalization of Rings without Existing Functional Groups

2.4 Functionalization of Angular Methyl Groups

2.5 Functionalization of Angular Methyl Groups and Functional-Group-Free Rings

2.6 Multisite Modifications

3 Semi-Synthesis of Triterpenoids via C-Skeleton Modification Strategies

3.1 Rearrangement Tactics

3.2 Ring-Opening Tactics

3.3 Additional Ring Introduction Tactics

4 emi-Synthesis of Triterpenoids via a Glycosylation Strategy

5 Conclusions and Outlook

Effects of Topically Applied Betulinic Acid and NVX-207 on Melanocytic Tumors in 18 Horses

Simple Summary

Melanomas are skin tumors of the pigment-producing melanocytes. Equine melanomas are among the most frequently diagnosed tumors affecting grey horses. The melanocytic tumors progress to malignancy in more than two-thirds of cases. Previous laboratory experiments and studies with horses utilizing the naturally occurring betulinic acid (BA) and its derivative NVX-207 showed promising results with respect to the topical (epicutaneous) treatment of equine melanoma. Therefore, the aim of this feasibility study was to gain first insights into the effect and safety of BA and NVX-207 in eighteen horses with early-stage melanocytic tumors after a 13-week-long topical application. The topical treatment was convenient and safe. Compared to a placebo, the data suggest a positive treatment effect from topical application of BA and NVX-207 on equine melanomas toward the end of the treatment period. However, the time period studied was too short to conclusively prove this. Further advancement of the investigational medicinal products studied herein could lead to an effective, topical and marketable novel drug which helps to relieve suffering and, consequently, improve the welfare of equine skin cancer patients.

Abstract

The naturally occurring betulinic acid (BA) and its derivative NVX-207 induce apoptosis in equine melanoma cells in vitro. After topical application, high concentrations of the substances can be reached in healthy equine skin. With the aim to investigate the effect and safety of topically applied BA and NVX-207 in horses with melanocytic tumors, the longitudinal, prospective, randomized, double-blind, placebo-controlled study protocol included eighteen Lipizzaner mares with early-stage cutaneous melanoma assigned to three groups. Melanocytic lesions were topically treated either with a placebo, 1% BA or 1% NVX-207 twice a day for 91 days. Caliper measurements, clinical examinations and blood tests were performed to assess the effects and safety of the medication. The topical treatment was convenient and safe. The volumes of tumors treated with BA were significantly reduced over time as compared to tumors treated with the placebo from day 80 of the study. Although treatment with NVX-207 seemed to decrease tumor volume, these results did not reach statistical significance. The findings must be regarded as preliminary due to the limited group size and need to be replicated in a larger cohort with modified pharmaceutical test formulations. Accordingly, the treatment protocol cannot yet be recommended in its current form.

Betulin Sulfonamides as Carbonic Anhydrase Inhibitors and Anticancer Agents in Breast Cancer Cells

Hypoxia-regulated protein carbonic anhydrase IX (CA IX) is up-regulated in different tumor entities and correlated with poor prognosis in breast cancer patients. Due to the radio- and chemotherapy resistance of solid hypoxic tumors, derivatives of betulinic acid (BA), a natural compound with anticancer properties, seem to be promising to benefit these cancer patients. We synthesized new betulin sulfonamides and determined their cytotoxicity in different breast cancer cell lines. Additionally, we investigated their effects on clonogenic survival, cell death, extracellular pH, HIF-1α, CA IX and CA XII protein levels and radiosensitivity. Our study revealed that cytotoxicity increased after treatment with the betulin sulfonamides compared to BA or their precursors, especially in triple-negative breast cancer (TNBC) cells. CA IX activity as well as CA IX and CA XII protein levels were reduced by the betulin sulfonamides. We observed elevated inhibitory efficiency against protumorigenic processes such as proliferation and clonogenic survival and the promotion of cell death and radiosensitivity compared to the precursor derivatives. In particular, TNBC cells showed benefit from the addition of sulfonamides onto BA and revealed that betulin sulfonamides are promising compounds to treat more aggressive breast cancers, or are at the same level against less aggressive breast cancer cells.

In vitro assessment of triterpenoids NVX-207 and betulinyl-bis-sulfamate as a topical treatment for equine skin cancer

Equine sarcoid (ES) is the most prevalent skin tumor in equids worldwide. Additionally, aging grey horses frequently suffer from equine malignant melanoma (EMM). Current local therapies targeting these skin tumors remain challenging. Therefore, more feasible topical treatment options should be considered. In order to develop a topical therapy against ES and EMM, betulinyl-bis-sulfamate and NVX-207, derivatives of the naturally occurring betulin and betulinic acid, respectively, were evaluated for their antiproliferative (crystal violet staining assay), cytotoxic (MTS assay) and apoptotic (AnnexinV staining, cell cycle investigations) effects on primary ES cells, EMM cells and equine dermal fibroblasts in vitro. The more potent derivative was assessed for its in vitro penetration and permeation on isolated equine skin within 30 min and 24 h using Franz-type diffusion cells and HPLC analysis. Betulinyl-bis-sulfamate and NVX-207 inhibited the proliferation and metabolism in ES cells, EMM cells and fibroblasts significantly (p < 0.001) in a time- and dose-dependent manner. NVX-207 had superior anticancer effects compared to betulinyl-bis-sulfamate. Both compounds led to the externalization of phosphatidylserines on the cell membrane and DNA fragmentation, demonstrating that the effective mode of action was apoptosis. After 48 h of treatment with NVX-207, the number of necrotic cells was less than 2% in all cell types. Detected amounts of NVX-207 in the different skin layers exceeded the half-maximal inhibitory concentrations calculated by far. Even though data obtained in vitro are auspicious, the results are not unconditionally applicable to the clinical situation. Consequently, in vivo studies are required to address the antitumoral effects of topically applied NVX-207 in ES and EMM patients.

Concentration profiles and safety of topically applied betulinic acid and NVX-207 in eight healthy horses-A randomized, blinded, placebo-controlled, crossover pilot study

The naturally occurring betulinic acid (BA) and its derivative NVX-207 show anticancer effects against equine malignant melanoma (EMM) cells and a potent permeation in isolated equine skin in vitro. The aim of the study was to determine the in vivo concentration profiles of BA and NVX-207 in equine skin and assess the compounds' local and systemic tolerability with the intent of developing a topical therapy against EMM. Eight horses were treated percutaneously in a crossover design with 1% BA, 1% NVX-207 or a placebo in a respective vehicle twice a day for seven consecutive days with a seven-day washout period between each formulation. Horses were treated at the neck and underneath the tail. Concentration profiles of the compounds were assessed by high-performance liquid chromatography in the cervical skin. Clinical and histopathological examinations and blood analyses were performed. Higher concentrations of NVX-207 were found in the skin compared to BA. Good systemic tolerability and only mild local adverse effects were observed in all three groups. This study substantiates the topical application of BA and NVX-207 in further clinical trials with horses suffering from EMM; however, penetration and permeation of the compounds may be altered in skin affected by tumors.

Recent Achievements in Medicinal and Supramolecular Chemistry of Betulinic Acid and Its Derivatives ‡

The subject of this review article refers to the recent achievements in the investigation of pharmacological activity and supramolecular characteristics of betulinic acid and its diverse derivatives, with special focus on their cytotoxic effect, antitumor activity, and antiviral effect, and mostly covers a period 2015–2018. Literature sources published earlier are referred to in required coherences or from historical points of view. Relationships between pharmacological activity and supramolecular characteristics are included if such investigation has been done in the original literature sources. A wide practical applicability of betulinic acid and its derivatives demonstrated in the literature sources is also included in this review article. Several literature sources also focused on in silico calculation of physicochemical and ADME parameters of the developed compounds, and on a comparison between the experimental and calculated data.

Design, synthesis and evaluation of antiproliferative activity of fluorinated betulinic acid

Betulinic acid (BA), a pentacyclic triterpenoid, exhibits broad spectrum antiproliferative activity, but generally with only modest potency. To improve BA's pharmacological properties, fluorine was introduced as a single atom at C-2, creating two diastereomers, or in a trifluoromethyl group at C-3. We evaluated the impact of these groups on antiproliferative activity against five human tumor cell lines. A racemic 2-F-BA (compound 6) showed significantly improved antiproliferative activity, while each diastereomer exhibited similar effects. We also demonstrated that 2-F-BA is a topoisomerase (Topo) I and IIα dual inhibitor in cell-based and cell-free assays. A hypothetical mode of binding to the Topo I-DNA suggested a difference between the hydrogen bonding of BA and 2-F-BA to DNA, which may account for the difference in bioactivity against Topo I.

Betulin and its derivatives as novel compounds with different pharmacological effects

Betulin (B) and Betulinic acid (BA) are natural pentacyclic lupane-structure triterpenoids which possess a wide range of pharmacological activities. Recent evidence indicates that B and BA have several properties useful for the treatment of metabolic disorders, infectious diseases, cardiovascular disorders, and neurological disorders. In the current review, we discuss B and BA structures and derivatives and then comprehensively explain their pharmacological effects in relation to various diseases. We also explain antiviral, antibacterial and anti-cancer effects of B and BA. Finally, we discuss the delivery methods, in which these compounds most effectively target different systems.

Synthesis and Evaluation of Anticancer Activities of Novel C-28 Guanidine-Functionalized Triterpene Acid Derivatives

Triterpene acids, namely, 20,29-dihydrobetulinic acid (BA), ursolic acid (UA) and oleanolic acid (OA) were converted into C-28-amino-functionalized triterpenoids 4–7, 8a, 15, 18 and 20. These compounds served as precursors for the synthesis of novel guanidine-functionalized triterpene acid derivatives 9b–12b, 15c, 18c and 20c. The influence of the guanidine group on the antitumor properties of triterpenoids was investigated. The cytotoxicity was tested on five human tumor cell lines (Jurkat, K562, U937, HEK, and Hela), and compared with the tests on normal human fibroblasts. The antitumor activities of the most tested guanidine derivatives was lower, than that of corresponding amines, but triterpenoids with the guanidine group were less toxic towards human fibroblasts. The introduction of the tris(hydroxymethyl)aminomethane moiety into the molecules of triterpene acids markedly enhanced the cytotoxic activity of the resulting conjugates 15, 15c, 18b,c and 20b,c irrespective of the triterpene skeleton type. The dihydrobetulinic acid amine 15, its guanidinium derivative 15c and guanidinium derivatives of ursolic and oleanolic acids 18c and 20c were selected for extended biological investigations in Jurkat cells, which demonstrated that the antitumor activity of these compounds is mediated by induction of cell cycle arrest at the S-phase and apoptosis.

Triterpenic azines, a new class of compounds with selective cytotoxicity to leukemia cells CCRF-CEM

Aim: From betulinic acid (1a), we synthesized 30-oxobetulinic acid (2a) that is highly cytotoxic against many cancer cell lines; however, its generic toxicity is the main obstacle in further development as cytostatic. Methodology & results: From 2a, we prepared a new class of compounds – nonsymmetrical azines and tested their in vitro cytotoxicity. All new azines with a free 28-COOH group (4a–4e) were highly and selectively cytotoxic against the T-lymphoblastic leukemia cell line CCRF-CEM and exhibited dose-dependent inhibition of RNA and DNA synthesis and other cell-cycle alterations, including the M-phase block. Conclusion: The potential use of azines (4a–4e) in drug development focused on hematological cancers is significantly higher than that of previously studied acids 1a and 2a.

Synthesis and antiproliferative properties of new hydrophilic esters of triterpenic acids

To improve the properties of cytotoxic triterpenoid acids 1-5, a large set of hydrophilic esters was synthesized. We choose betulinic acid (1), dihydrobetulinic acid (2), 21-oxoacid 3 along with highly active des-E lupane acids 4 and 5 as a model set of compounds for esterification of which the properties needed to be improved. As ester moieties were used - methoxyethanol and 2-(2-methoxyethoxy)ethanol and glycolic unit (type a-d), pyrrolidinoethanol, piperidinoethanol and morpholinoethanol (type f-h), and monosaccharide groups (type i-l). As a result, 56 triterpenic esters (49 new compounds) were obtained and their cytotoxicity on four cancer cell lines and normal human fibroblasts was tested. All new compounds were fully soluble at all tested concentrations, which used to be a problem of the parent compounds 1 and 2. 16 compounds had IC₅₀ < 10 μM on at least one cancer cell line, 12 compounds had cytotoxicity of <10 μM against at least three of four tested cancer cell lines. The highest activity was found for compound 3c (1.8 μM on MCF7, 2.8 μM on HeLa, and 1.6 μM on G-361 cells) which also had no toxicity on non-cancerous BJ fibroblasts at the highest tested concentration (50 μM). High selective cytotoxicity was also found in compounds 1k, 2k, 3c, and 3i that are ideal candidates for drug development. Therefore, more studies to identify the mechanism of action were performed in case of 1k, 3c, and 3g such as effects on cell cycle and apoptosis. It was found that compounds 3c and 3g can induce apoptosis via caspase-3 activation and modulation of protein Bcl-2 in G-361 cells. In conclusion, compounds 1k, 3c, and 3g show high and selective cytotoxicity, therefore they are significantly better candidates for anti-cancer drug development than the parent acids 1-5.

Betulinic acid derivative BA5, a dual NF-kB/calcineurin inhibitor, alleviates experimental shock and delayed hypersensitivity

Betulinic acid (BA) is a naturally occurring triterpenoid with several biological properties already described, including immunomodulatory activity. Here we investigated the immunomodulatory activity of eight semi-synthetic amide derivatives of betulinic acid. Screening of derivatives BA1-BA8 led to the identification of compounds with superior immunomodulatory activity than BA on activated macrophages and lymphocytes. BA5, the most potent derivative, inhibited nitric oxide and TNFα production in a concentration-dependent manner, and decreased NF-κB activation in Raw 264.7 cells. Additionally, BA5 inhibited the proliferation of activated lymphocytes and the secretion of IL-2, IL-4 IL-6, IL-10, IL-17A and IFNɣ, in a concentration-dependent manner. Flow cytometry analysis in lymphocyte cultures showed that treatment with BA5 induces cell cycle arrest in pre-G1 phase followed by cell death by apoptosis. Moreover, BA5 also inhibited the activity of calcineurin, an enzyme that plays a critical role in the progression of cell cycle and T lymphocyte activation. BA5 has a synergistic inhibitory effect with dexamethasone on lymphoproliferation, showing a promising profile for drug combination. Finally, we observed immunosuppressive effects of BA5 in vivo in mouse models of lethal endotoxemia and delayed type hypersensitivity. Our results reinforce the potential use of betulinic acid and its derivatives in the search for potent immunomodulatory drugs.

Cytotoxic conjugates of betulinic acid and substituted triazoles prepared by Huisgen Cycloaddition from 30-azidoderivatives

In this work, we describe synthesis of conjugates of betulinic acid with substituted triazoles prepared via Huisgen 1,3-cycloaddition. All compounds contain free 28-COOH group. Allylic bromination of protected betulinic acid by NBS gave corresponding 30-bromoderivatives, their substitution with sodium azides produced 30-azidoderivatives and these azides were subjected to CuI catalysed Huisgen 1,3-cycloaddition to give the final conjugates. Reactions had moderate to high yields. All new compounds were tested for their in vitro cytotoxic activities on eight cancer and two non-cancer cell lines. The most active compounds were conjugates of 3β-O-acetylbetulinic acid and among them, conjugate with triazole substituted by benzaldehyde 9b was the best with IC50 of 3.3 μM and therapeutic index of 9.1. Five compounds in this study had IC50 below 10 μM and inhibited DNA and RNA synthesis and caused block in G0/G1 cell cycle phase which is highly similar to actinomycin D. It is unusual that here prepared 3β-O-acetates were more active than compounds with the free 3-OH group and this suggests that this set may have common mechanism of action that is different from the mechanism of action of previously known 3β-O-acetoxybetulinic acid derivatives. Benzaldehyde type conjugate 9b is the best candidate for further drug development.

Synthesis of novel lupane triterpenoid-indazolone hybrids with oxime ester linkage

An efficient protocol for the synthesis of novel lupane triterpenoid-indazolone hybrids with oxime ester linkage has been developed from naturally accessible precursor betulin. For the first time a series of betulonic acid-indazolone hybrids have been synthesized via an acylation of corresponding 6,7-dihydro-1H-indazol-4(5H)-one oximes with betulonic acid chloride. Diastereoselective reduction of the obtained betulonic acid conjugates with NaBH₄ resulted in a formation of betulinic acid-indazolone hybrids in excellent yields. The configuration of the key compounds has been fully established by X-ray and 2D NMR analysis.

In vitro anticancer activity of Betulinic acid and derivatives thereof on equine melanoma cell lines from grey horses and in vivo safety assessment of the compound NVX-207 in two horses

Betulinic acid, a pentacyclic triterpene, and its derivatives are promising compounds for cancer treatment in humans. Melanoma is not only a problem for humans but also for grey horses as they have a high potential of developing melanoma lesions coupled to the mutation causing their phenotype. Current chemotherapeutic treatment carries the risk of adverse health effects for the horse owner or the treating veterinarian by exposure to antineoplastic compounds. Most treatments have low prospects for systemic tumor regression. Thus, a new therapy is needed. In this in vitro study, Betulinic acid and its two derivatives B10 and NVX-207, both with an improved water solubility compared to Betulinic acid, were tested on two equine melanoma cell lines (MelDuWi and MellJess/HoMelZh) and human melanoma (A375) cell line. We could demonstrate that all three compounds especially NVX-207 show high cytotoxicity on both equine melanoma cell lines. The treatment with these compounds lead to externalization of phosphatidylserines on the cell membrane (AnnexinV-staining), DNA-fragmentation (cell cycle analysis) and activation of initiator and effector caspases (Caspase assays). Our results indicate that the apoptosis is induced in the equine melanoma cells by all three compounds. Furthermore, we succeed in encapsulating the most active compound NVX-207 in 2-Hydroxyprolyl-β-cyclodextrine without a loss of its activity. This formulation can be used as a promising antitumor agent for treating grey horse melanoma. In a first tolerability evaluation in vivo the formulation was administered every one week for 19 consecutive weeks and well tolerated in two adult melanoma affected horses.

Betulinic Acid: Recent Advances in Chemical Modifications, Effective Delivery, and Molecular Mechanisms of a Promising Anticancer Therapy

An important method of drug discovery is examination of diverse life forms, including medicinal plants and natural products or bioactive compounds isolated from these sources. In cancer research, lead structures of compounds from natural sources can be used to design novel chemotherapies with enhanced biological properties. Betulinic acid (3β-hydroxy-lup-20(29)-en-28-oic acid or BetA) is a naturally occurring pentacyclic triterpene with a wide variety of biological activities, including potent antitumor properties. Non-malignant cells and normal tissues are not affected by BetA. Because BetA exerts its effects directly on the mitochondrion and triggers death of cancerous cells, it is an important alternative when certain chemotherapy drugs fail. Mitochondrion-targeted agents such as BetA hold great promise to circumvent drug resistance in human cancers. BetA is being developed by a large network of clinical trial groups with the support of the U.S. National Cancer Institute. This article discusses recent advances in research into anticancer activity of BetA, relevant modes of delivery, and the agent's therapeutic efficacy, mechanism of action, and future perspective as a pipeline anticancer drug. BetA is a potentially important agent in cancer therapeutics.

Betulinyl Sulfamates as Anticancer Agents and Radiosensitizers in Human Breast Cancer Cells

Betulinic acid (BA), a natural compound of birch bark, is cytotoxic for many tumors. Recently, a betulinyl sulfamate was described that inhibits carbonic anhydrases (CA), such as CAIX, an attractive target for tumor-selective therapy strategies in hypoxic cancer cells. Data on combined CAIX inhibition with radiotherapy are rare. In the human breast cancer cell lines MDA-MB231 and MCF7, the effects of BA and betulinyl sulfamates on cellular and radiobiological behavior under normoxia and hypoxia were evaluated. The two most effective betulinyl sulfamates CAI 1 and CAI 3 demonstrated a 1.8–2.8-fold higher cytotoxicity than BA under normoxia in breast cancer cells, with IC₅₀ values between 11.1 and 18.1 µM. BA exhibits its strongest cytotoxicity with IC₅₀ values of 8.2 and 16.4 µM under hypoxia. All three substances show a dose-dependent increase in apoptosis, inhibition of migration, and inhibition of hypoxia-induced gene expression. In combination with irradiation, betulinyl sulfamates act as radiosensitizers, with DMF10 values of 1.47 (CAI 1) and 1.75 (CAI 3) under hypoxia in MDA-MB231 cells. BA showed additive effects in combination with irradiation. Taken together; our results suggest that BA and betulinyl sulfamates seem to be attractive substances to combine with radiotherapy; particularly for hypoxic breast cancer.

Betulinic Acid and its Derivatives as Potential Antitumor Agents

Betulinic acid (BA) is a lupane-type pentacyclic triterpene, distributed ubiquitously throughout the plant kingdom. BA and its derivatives demonstrate multiple bioactivities, particularly an antitumor effect. This review critically describes the recent research on isolation, synthesis, and derivatization of BA and its natural analogs betulin and 23-hydroxybetulinic acid. The subsequent part of the review focuses on the current knowledge of antitumor properties, combination treatments, and pharmacological mechanisms of these compounds. A 3D-QSAR analysis of 62 BA derivatives against human ovarian cancer A2780 is also included to provide information concerning the structure-cytotoxicity relationships of these compounds.

Betulinic acid derivatives NVX-207 and B10 for treatment of glioblastoma--an in vitro study of cytotoxicity and radiosensitization

Betulinic acid (BA), a pentacyclic triterpene, represents a new therapeutic substance that has potential benefits for treating glioblastoma. Recently, new strategies for producing BA derivatives with improved properties have evolved. However, few studies have examined the combination of BA or BA derivatives using radiotherapy. The effects of two BA derivatives, NVX-207 and B10, on cellular and radiobiological behavior were analyzed using glioblastoma cell lines (U251MG, U343MG and LN229). Based on IC50 values under normoxic conditions, we detected a 1.3-2.9-fold higher cytotoxicity of the BA derivatives B10 and NVX-207, respectively, compared to BA. Incubation using both BA derivatives led to decreased cell migration, cleavage of PARP and decreased protein expression levels of Survivin. Weak radiation sensitivity enhancement was observed in U251MG cells after treatment with both BA derivatives. The enhancement factors at an irradiation dose of 6 Gy after treatment with 5 µM NVX-207 and 5 µM B10 were 1.32 (p=0.029) and 1.55 (p=0.002), respectively. In contrast to BA, neither NVX-207 nor B10 had additional effects under hypoxic conditions. Our results suggest that the BA derivatives NVX-207 and B10 improve the effects of radiotherapy on human malignant glioma cells, particularly under normoxic conditions.

New horizons for old drugs and drug leads

There is mounting urgency to find new drugs for the treatment of serious infectious diseases and cancer that are rapidly developing resistance to previously effective drugs. One approach to addressing this need is through drug repurposing, which refers to the discovery of new useful activities for "old" clinically used drugs through screening them against relevant disease targets. A large number of potential drug that, for various reasons, have failed to advance to clinical and commercial use can be added to the candidates available for such purposes. The application of new techniques and methodology developed through the impressive progress made in multidisciplinary, natural product-related research in recent years should aid substantially in expediting the discovery and development process. This review briefly outlines some of these developments as applied to a number of selected natural product examples, which may also include advances in chemical synthesis of derivatives with extended biological activities.

Approaches to improve the oral bioavailability and effects of novel anticancer drugs berberine and betulinic acid

BACKGROUND

The poor bioavailability of Berberine (BBR) and Betulinic acid (BA) limits the development of these promising anticancer agents for clinical use. In the current study, BBR and BA in spray dried (SD) mucoadhesive microparticle formulations were prepared.

METHODS

A patented dual channel spray gun technology established in our laboratory was used for both formulations. Gastrointestinal (GI) permeability studies were carried out using Caco-2 cell monolayer grown in in-vitro system. The oral bioavailability and pharmacokinetic profile of SD formulations were studied in Sprague Dawley rats. A549 orthotopic and H1650 metastatic NSCLC models were utilized for the anticancer evaluations.

RESULTS

Pharmacokinetic studies demonstrated that BBR and BA SD formulations resulted in 3.46 and 3.90 fold respectively, significant increase in plasma Cmax concentrations. AUC levels were increased by 6.98 and 7.41 fold in BBR and BA SD formulations, respectively. Compared to untreated controls groups, 49.8 & 53.4% decrease in the tumor volumes was observed in SD formulation groups of BBR and BA, respectively. Molecular studies done on excised tumor (A549) tissue suggested that BBR in SD form resulted in a significant decrease in the survivin, Bcl-2, cyclin D1, MMP-9, HIF-1α, VEGF and CD31 expressions. Cleaved caspase 3, p53 and TUNEL expressions were increased in SD formulations. The RT-PCR analysis on H1650 tumor tissue suggested that p38, Phospho-JNK, Bax, BAD, cleaved caspase 3&8 mRNA expressions were significantly increased in BA SD formulations. Chronic administration of BBR and BA SD formulations did not show any toxicity.

CONCLUSIONS

Due to significant increase in oral bioavailability and superior anticancer effects, our results suggest that spray drying is a superior alternative formulation approach for oral delivery of BBR and BA.

Synthesis and studies of anticancer properties of lupane-type triterpenoid derivatives containing a cisplatin fragment

Both betulinic acid 1 and cisplatin are promising antitumor agents, which induce apoptotic cell death of cancer cells. In the present investigation a new series of betulinic acid-cisplatin conjugates were synthesized and cytotoxicity and selectivity were assessed against five different tumor cell lines. The aim was to combine two structural units, both related with apoptosis induction. The derivatives exerted a dose-dependent antiproliferative action at micromolar concentrations and the effect of these structural variations on anticancer activity was studied and discussed. Several compounds revealed significant antitumor activity, as the most active substance 3-O-acetylbetulinic (2-(2-aminoethyl)aminoethyl)amide (IC50=1.30-2.24 μM). Interestingly, Betulinic acid-cisplatin conjugates were less cytotoxic than the precursors.

The chemical and biological potential of C ring modified triterpenoids

A convenient and elegant route has been developed to separate the natural regioisomers triterpenoids ursolic acid (UA) and oleanolic acid (OA) as well as derivatives thereof. Eleven unknown derivatives of OA were designed, synthesized, and their cytotoxicity was investigated. Further sixteen compounds were prepared to correlate all compounds in a SAR study. It could be shown that C-ring modifications of OA and UA have only a moderate influence onto the cytotoxic activity of the compounds but a significant impact onto the ability to trigger apoptosis in ovarian cancer cells (cell line A2780).

Targeted inhibition of tumor proliferation, survival, and metastasis by pentacyclic triterpenoids: potential role in prevention and therapy of cancer

Over the last two decades, extensive research on plant-based medicinal compounds has revealed exciting and important pharmacological properties and activities of triterpenoids. Fruits, vegetables, cereals, pulses, herbs and medicinal plants are all considered to be biological sources of these triterpenoids, which have attracted great attention especially for their potent anti-inflammatory and anti-cancer activities. Published reports in the past have described the molecular mechanism(s) underlying the various biological activities of triterpenoids which range from inhibition of acute and chronic inflammation, inhibition of tumor cell proliferation, induction of apoptosis, suppression of angiogenesis and metastasis. However systematic analysis of various pharmacological properties of these important classes of compounds has not been done. In this review, we describe in detail the pre-clinical chemopreventive and therapeutic properties of selected triterpenoids that inhibit multiple intracellular signaling molecules and transcription factors involved in the initiation, progression and promotion of various cancers. Molecular targets modulated by these triterpenoids comprise, cytokines, chemokines, reactive oxygen intermediates, oncogenes, inflammatory enzymes such as COX-2, 5-LOX and MMPs, anti-apoptotic proteins, transcription factors such as NF-κB, STAT3, AP-1, CREB, and Nrf2 (nuclear factor erythroid 2-related factor) that regulate tumor cell proliferation, transformation, survival, invasion, angiogenesis, metastasis, chemoresistance and radioresistance. Finally, this review also analyzes the potential role of novel synthetic triterpenoids identified recently which mimic natural triterpenoids in physical and chemical properties and are moving rapidly from bench to bedside research.

Impairment of lysosomal integrity by B10, a glycosylated derivative of betulinic acid, leads to lysosomal cell death and converts autophagy into a detrimental process

In this study, we report a novel mechanism of action for a cytotoxic derivative of betulinic acid (BA). B10 is a semi-synthetic glycosylated derivative of BA selected for its enhanced cytotoxic activity. Interestingly, although B10 induces apoptosis, caspase-3 downregulation incompletely prevents B10-induced cell death, Bcl-2 overexpression fails to protect cells and DNA fragmentation rates do not reflect cell death rates in contrast to cytoplasmic membrane permeabilization. These results implicate that apoptotic and non-apoptotic cell death coexist upon B10 treatment. Unexpectedly, we found that B10 induces autophagy and also abrogates the autophagic flux. B10 destabilizes lysosomes as shown by Lysotracker Red staining and by cathepsin Z and B release from lysosomes into the cytoplasm. Consistently, the cathepsin inhibitor Ca074Me significantly decreases B10-induced cell death, further supporting the fact that the release of lysosomal enzymes contributes to B10-triggered cell death. Downregulation of ATG7, ATG5 or BECN1 by RNAi significantly decreases caspase-3 activation, lysosomal permeabilization and cell death. Thus, by concomitant induction of autophagy and inhibition of the autophagic flux, B10 turns autophagy into a cell death mechanism. These findings have important implications for the therapeutic exploitation of BA derivatives, particularly in apoptosis-resistant cancers.

Screening of filamentous fungi to identify biocatalysts for lupeol biotransformation

The goal of the study was to evaluate the ability of filamentous fungi to biotransform the pentacyclic triterpene lupeol. The microbial transformations were carried out in shake flasks in different media. Experiments were also run with control flasks. Samples of each culture were taken every 24 hours, extracted with ethyl acetate, and analyzed by GC-MS. The biotransformation of lupeol by Aspergillus ochraceus and Mucor rouxii afforded two compounds in each culture, which were detected in the cultures developed for more than seven days only in the Koch’s K1 medium. The obtained data demonstrated that A. ochraceus is a good biocatalyst to introduce double bonds in the lupeol structure, whereas M. rouxii exhibits ability to biocatalyze oxygen insertions in that pentacyclic triterpene. Mass spectrometry was demonstrated to be an efficient analytical method to select promising biocatalysts for the compound investigated in this study. The biotransformation processes were influenced by the culture medium and incubation period. The obtained results open the perspective of using A. ochraceus and M. rouxii in pentacyclic triterpene biotransformations.

Betulinic acid, a natural compound with potent anticancer effects

New therapies using novel mechanisms to induce tumor cell death are needed with plants playing a crucial role as a source for potential anticancer compounds. One highly promising class of natural compounds are the triterpenoids with betulinic acid (BetA) as the most prominent representative. In-vitro studies have identified this agent as potently effective against a wide variety of cancer cells, also those derived from therapy-resistant and refractory tumors, whereas it has been found to be relatively nontoxic for healthy cells. In-vivo preclinically applied BetA showed some remarkable anticancer effects and a complete absence of systemic toxicity in rodents. BetA also cooperated with other therapies to induce tumor cell death and several potent derivatives have been discovered. Its antitumor activity has been related to its direct effects on mitochondria where it induces Bax/Bak-independent cytochrome-c release.