Intra-lesional injection of the novel PKC activator EBC-46 rapidly ablates tumors in mouse models

Conversion of Phorbol into Des-D-Ring Tricycle and Crotonianoid B via Peroxidation Reaction

Phorbol (1) has a tetracyclic ABCD-ring and is readily isolable from a natural source. We previously synthesized 1 and 16 structurally related natural products using common ABC-ring intermediate 2. Here we report a new synthetic route to 2 using 1 as a starting material. Key features of the synthesis are chemoselective removal of the D-ring via cyclopropane opening, peroxidation, and retro-aldol reactions. The high utility of the peroxidation was further demonstrated in the first synthesis of crotonianoid B (9).

Tigilanol tiglate is an oncolytic small molecule that induces immunogenic cell death and enhances the response of both target and non-injected tumors to immune checkpoint blockade

BACKGROUND

Tigilanol tiglate (TT) is a protein kinase C (PKC)/C1 domain activator currently being developed as an intralesional agent for the treatment of various (sub)cutaneous malignancies. Previous work has shown that intratumoral (I.T.) injection of TT causes vascular disruption with concomitant tumor ablation in several preclinical models of cancer, in addition to various (sub)cutaneous tumors presenting in the veterinary clinic. TT has completed Phase I dose escalation trials, with some patients showing signs of abscopal effects. However, the exact molecular details underpinning its mechanism of action (MoA), together with its immunotherapeutic potential in oncology remain unclear.

METHODS

A combination of microscopy, luciferase assays, immunofluorescence, immunoblotting, subcellular fractionation, intracellular ATP assays, phagocytosis assays and mixed lymphocyte reactions were used to probe the MoA of TT in vitro. In vivo studies with TT used MM649 xenograft, CT-26 and immune checkpoint inhibitor refractory B16-F10-OVA tumor bearing mice, the latter with or without anti-programmed cell death 1 (PD-1)/anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) mAb treatment. The effect of TT at injected and non-injected tumors was also assessed.

RESULTS

Here, we show that TT induces the death of endothelial and cancer cells at therapeutically relevant concentrations via a caspase/gasdermin E-dependent pyroptopic pathway. At therapeutic doses, our data demonstrate that TT acts as a lipotoxin, binding to and promoting mitochondrial/endoplasmic reticulum (ER) dysfunction (leading to unfolded protein responsemt/ER upregulation) with subsequent ATP depletion, organelle swelling, caspase activation, gasdermin E cleavage and induction of terminal necrosis. Consistent with binding to ER membranes, we found that TT treatment promoted activation of the integrated stress response together with the release/externalization of damage-associated molecular patterns (HMGB1, ATP, calreticulin) from cancer cells in vitro and in vivo, characteristics indicative of immunogenic cell death (ICD). Confirmation of ICD in vivo was obtained through vaccination and rechallenge experiments using CT-26 colon carcinoma tumor bearing mice. Furthermore, TT also reduced tumor volume, induced immune cell infiltration, as well as improved survival in B16-F10-OVA tumor bearing mice when combined with immune checkpoint blockade.

CONCLUSIONS

These data demonstrate that TT is an oncolytic small molecule with multiple targets and confirms that cell death induced by this compound has the potential to augment antitumor responses to immunotherapy.

Total Syntheses of Phorbol and 11 Tigliane Diterpenoids and Their Evaluation as HIV Latency-Reversing Agents

Tigliane diterpenoids possess exceptionally complex structures comprising common 5/7/6/3-membered ABCD-rings and disparate oxygen functionalities. While tiglianes display a wide range of biological activities, compounds with HIV latency-reversing activity can eliminate viral reservoirs, thereby serving as promising leads for new anti-HIV agents. Herein, we report collective total syntheses of phorbol (13) and 11 tiglianes 14-24 with various acylation patterns and oxidation states, and their evaluation as HIV latency-reversing agents. The syntheses were strategically divided into five stages to increase the structural complexity. First, our previously established sequence enabled the expeditious preparation of ABC-tricycle 9 in 15 steps. Second, hydroxylation of 9 and ring-contractive D-ring formation furnished phorbol (13). Third, site-selective attachment of two acyl groups to 13 produced four phorbol diesters 14-17. Fourth, the oxygen functionalities were regio- and stereoselectively installed to yield five tiglianes 18-22. Fifth, further oxidation to the most densely oxygenated acerifolin A (23) and tigilanol tiglate (24) was realized through organizing a 3D shape of the B-ring. Assessment of the HIV latency-reversing activities of the 12 tiglianes revealed seven tiglianes (14-17 and 22-24) with 20- to 300-fold improved efficacy compared with prostratin (12), a representative latency-reversing agent. Therefore, the robust synthetic routes to a variety of tiglianes with promising activities devised in this study provide opportunities for advancing HIV eradication strategies.

Overcoming cold tumors: a combination strategy of immune checkpoint inhibitors

Immune Checkpoint Inhibitors (ICIs) therapy has advanced significantly in treating malignant tumors, though most 'cold' tumors show no response. This resistance mainly arises from the varied immune evasion mechanisms. Hence, understanding the transformation from 'cold' to 'hot' tumors is essential in developing effective cancer treatments. Furthermore, tumor immune profiling is critical, requiring a range of diagnostic techniques and biomarkers for evaluation. The success of immunotherapy relies on T cells' ability to recognize and eliminate tumor cells. In 'cold' tumors, the absence of T cell infiltration leads to the ineffectiveness of ICI therapy. Addressing these challenges, especially the impairment in T cell activation and homing, is crucial to enhance ICI therapy's efficacy. Concurrently, strategies to convert 'cold' tumors into 'hot' ones, including boosting T cell infiltration and adoptive therapies such as T cell-recruiting bispecific antibodies and Chimeric Antigen Receptor (CAR) T cells, are under extensive exploration. Thus, identifying key factors that impact tumor T cell infiltration is vital for creating effective treatments targeting 'cold' tumors.

Tigliane and daphnane diterpenoids from Thymelaeaceae family: chemistry, biological activity, and potential in drug discovery

Tigliane and daphnane diterpenoids are characteristically distributed in plants of the Thymelaeaceae family as well as the Euphorbiaceae family and are structurally diverse due to the presence of polyoxygenated functionalities in the polycyclic skeleton. These diterpenoids are known as toxic components, while they have been shown to exhibit a wide variety of biological activities, such as anti-cancer, anti-HIV, and analgesic activity, and are attracting attention in the field of natural product drug discovery. This review focuses on naturally occurring tigliane and daphnane diterpenoids from plants of the Thymelaeaceae family and provides an overview of their chemical structure, distribution, isolation, structure determination, chemical synthesis, and biological activities, with a prime focus on the recent findings.

Defining in vitro topical antimicrobial and antibiofilm activity of epoxy-tigliane structures against oral pathogens

Background

Peri-implantitis has become an inexorable clinical challenge in implantology. Topical immunomodulatory epoxy-tiglianes (EBCs), derived from the Queensland blushwood tree, which induce remodeling and resolve dermal infection via induction of the inflammasome and biofilm disruption, may offer a novel therapeutic approach.

Design

In vitro antimicrobial activity of EBC structures (EBC-46, EBC-1013 and EBC-147) against Streptococcus mutans, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis in minimum inhibitory concentration, growth curve and permeabilization assays were determined. Antibiofilm activity was assessed using minimum biofilm eradication concentration (MBEC) experiments. Biofilm formation and disruption assays were analyzed using confocal laser scanning microscopy, scanning electron microscopy and direct plate counting.

Results

The observed antimicrobial efficacy of the tested compounds (EBC-1013 > EBC-46 > EBC-147) was directly related to significant membrane permeabilization and growth inhibition (p < 0.05) against planktonic S. mutans and P. gingivalis. Antibiofilm activity was evident in MBEC assays, with S. mutans biofilm formation assays revealing significantly lower biomass volume and increased DEAD:LIVE cell ratio observed for EBC-1013 (p < 0.05). Furthermore, biofilm disruption assays on titanium discs induced significant biofilm disruption in S. mutans and P. gingivalis (p < 0.05).

Conclusions

EBC-1013 is a safe, semi-synthetic, compound, demonstrating clear antimicrobial biofilm disruption potential in peri-implantitis.

From the Bush to the Brain: Preclinical Stages of Ethnobotanical Anti-Inflammatory and Neuroprotective Drug Discovery-An Australian Example

The Australian rainforest is a rich source of medicinal plants that have evolved in the face of dramatic environmental challenges over a million years due to its prolonged geographical isolation from other continents. The rainforest consists of an inherent richness of plant secondary metabolites that are the most intense in the rainforest. The search for more potent and more bioavailable compounds from other plant sources is ongoing, and our short review will outline the pathways from the discovery of bioactive plants to the structural identification of active compounds, testing for potency, and then neuroprotection in a triculture system, and finally, the validation in an appropriate neuro-inflammatory mouse model, using some examples from our current research. We will focus on neuroinflammation as a potential treatment target for neurodegenerative diseases including multiple sclerosis (MS), Parkinson's (PD), and Alzheimer's disease (AD) for these plant-derived, anti-inflammatory molecules and highlight cytokine suppressive anti-inflammatory drugs (CSAIDs) as a better alternative to conventional nonsteroidal anti-inflammatory drugs (NSAIDs) to treat neuroinflammatory disorders.

Tumor microenvironment signaling and therapeutics in cancer progression

Tumor development and metastasis are facilitated by the complex interactions between cancer cells and their microenvironment, which comprises stromal cells and extracellular matrix (ECM) components, among other factors. Stromal cells can adopt new phenotypes to promote tumor cell invasion. A deep understanding of the signaling pathways involved in cell-to-cell and cell-to-ECM interactions is needed to design effective intervention strategies that might interrupt these interactions. In this review, we describe the tumor microenvironment (TME) components and associated therapeutics. We discuss the clinical advances in the prevalent and newly discovered signaling pathways in the TME, the immune checkpoints and immunosuppressive chemokines, and currently used inhibitors targeting these pathways. These include both intrinsic and non-autonomous tumor cell signaling pathways in the TME: protein kinase C (PKC) signaling, Notch, and transforming growth factor (TGF-β) signaling, Endoplasmic Reticulum (ER) stress response, lactate signaling, Metabolic reprogramming, cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) and Siglec signaling pathways. We also discuss the recent advances in Programmed Cell Death Protein 1 (PD-1), Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA4), T-cell immunoglobulin mucin-3 (TIM-3) and Lymphocyte Activating Gene 3 (LAG3) immune checkpoint inhibitors along with the C-C chemokine receptor 4 (CCR4)- C-C class chemokines 22 (CCL22)/ and 17 (CCL17), C-C chemokine receptor type 2 (CCR2)- chemokine (C-C motif) ligand 2 (CCL2), C-C chemokine receptor type 5 (CCR5)- chemokine (C-C motif) ligand 3 (CCL3) chemokine signaling axis in the TME. In addition, this review provides a holistic understanding of the TME as we discuss the three-dimensional and microfluidic models of the TME, which are believed to recapitulate the original characteristics of the patient tumor and hence may be used as a platform to study new mechanisms and screen for various anti-cancer therapies. We further discuss the systemic influences of gut microbiota in TME reprogramming and treatment response. Overall, this review provides a comprehensive analysis of the diverse and most critical signaling pathways in the TME, highlighting the associated newest and critical preclinical and clinical studies along with their underlying biology. We highlight the importance of the most recent technologies of microfluidics and lab-on-chip models for TME research and also present an overview of extrinsic factors, such as the inhabitant human microbiome, which have the potential to modulate TME biology and drug responses.

Evidence for Natural Products as Alternative Wound-Healing Therapies

Chronic, non-healing wounds represent a significant area of unmet medical need and are a growing problem for healthcare systems around the world. They affect the quality of life for patients and are an economic burden, being difficult and time consuming to treat. They are an escalating problem across the developed world due to the increasing incidence of diabetes and the higher prevalence of ageing populations. Effective treatment options are currently lacking, and in some cases chronic wounds can persist for years. Some traditional medicines are believed to contain bioactive small molecules that induce the healing of chronic wounds by reducing excessive inflammation, thereby allowing re-epithelisation to occur. Furthermore, many small molecules found in plants are known to have antibacterial properties and, although they lack the therapeutic selectivity of antibiotics, they are certainly capable of acting as topical antiseptics when applied to infected wounds. As these molecules act through mechanisms of action distinct from those of clinically used antibiotics, they are often active against antibiotic resistant bacteria. Although there are numerous studies highlighting the effects of naturally occurring small molecules in wound-healing assays in vitro, only evidence from well conducted clinical trials can allow these molecules or the remedies that contain them to progress to the clinic. With this in mind, we review wound-healing natural remedies that have entered clinical trials over a twenty-year period to the present. We examine the bioactive small molecules likely to be in involved and, where possible, their mechanisms of action.

Treatment of multiple synchronous canine mast cell tumours using intratumoural tigilanol tiglate

Mast cell tumours (MCTs) are common canine skin neoplasia. While they generally occur as single tumours, multiple synchronous MCTs (msMCTs) of de novo/non-metastatic origin are reported in a proportion of the patient population. Where there is no evidence of metastasis or lymphatic spread, MCTs are effectively controlled by surgery and other local therapies. However, treatment of de novo msMCTs can be more challenging, especially when they occur in surgically difficult locations. Here, we report the use of tigilanol tiglate, a novel small molecule registered as a veterinary pharmaceutical for the local treatment of non-metastatic MCTs, in the treatment of patients with msMCTs presenting at three Australian specialist referral centres. We also present a meta-analysis of the literature to provide a better understanding of the prevalence of canine msMCTs. Notably, nine patients with a total of 32 MCTs were treated during the study. A complete response was recorded in 26 (81%) of the individual MCTs on Day 28 after a single tigilanol tiglate injection. Of the 6 initially non-responsive MCTs, one achieved a complete response after a further tigilanol tiglate treatment. A complete response was reported at 6 months in all 22 of the tumours that were evaluable and that had recorded a complete response at Day 84. For the literature meta-analysis, 22 studies were found with prevalence estimates of msMCTs ranging from 3 to 40%; when combined, these studies yielded 3,745 patients with a prevalence of 13% (95% CI 10; 16). Overall, the results demonstrate the utility of intratumoural tigilanol tiglate as an option for the treatment of multiple MCTs where multiple surgical resections would have been required.

Topical, immunomodulatory epoxy-tiglianes induce biofilm disruption and healing in acute and chronic skin wounds

The management of antibiotic-resistant, bacterial biofilm infections in chronic skin wounds is an increasing clinical challenge. Despite advances in diagnosis, many patients do not derive benefit from current anti-infective/antibiotic therapies. Here, we report a novel class of naturally occurring and semisynthetic epoxy-tiglianes, derived from the Queensland blushwood tree ( Fontainea picrosperma) , and demonstrate their antimicrobial activity (modifying bacterial growth and inducing biofilm disruption), with structure/activity relationships established against important human pathogens. In vitro, the lead candidate EBC-1013 stimulated protein kinase C (PKC)–dependent neutrophil reactive oxygen species (ROS) induction and NETosis and increased expression of wound healing–associated cytokines, chemokines, and antimicrobial peptides in keratinocytes and fibroblasts. In vivo, topical EBC-1013 induced rapid resolution of infection with increased matrix remodeling in acute thermal injuries in calves. In chronically infected diabetic mouse wounds, treatment induced cytokine/chemokine production, inflammatory cell recruitment, and complete healing (in six of seven wounds) with ordered keratinocyte differentiation. These results highlight a nonantibiotic approach involving contrasting, orthogonal mechanisms of action combining targeted biofilm disruption and innate immune induction in the treatment of chronic wounds.

Cryptic Epoxytiglianes from the Kernels of the Blushwood Tree (Fontainea picrosperma)

The kernels of the Australian blushwood tree (Fontainea picrosperma) are the source of the veterinary anticancer drug tigilanol tiglate (2a, Stelfonta) and contain a concentration of phorboids significantly higher than croton oil, the only abundant source of these compounds previously known. The oily matrix of the blushwood kernels is composed of free fatty acids and not by glycerides as found in croton oil. By active partitioning, it was therefore possible to recover and characterize for the first time a cryptic tigliane fraction, that is, the diterpenoid fraction that, because of its lipophilicity, could not be obtained by solvent partition of crude extracts. The cryptic tigliane fraction accounted for ca. 30% of the tigliane kernel titer and was quantified by ¹H NMR spectroscopy and profiled by HPLC-MS. Long-chain (linoleates and/or oleates) 20-acyl derivatives of the epoxytigliane diesters tigilanol tiglate (EBC-46, 2a), EBC-47 (4a), EBC-59 (5a), EBC-83 (6a), and EBC-177 (7a) were identified. By chemoselective acylation of EBC-46 (2a) and EBC-177 (7a) the natural triesters 2b and 7b and a selection of analogues were prepared to assist identification of the natural compounds. The presence of a free C-20 hydroxy group is a critical requirement for PKC activation by phorbol esters. The unexpected activity of 20-linoleoyl triester 2b in a cytotoxicity assay based on PKC activation was found to be related mainly to its hydrolysis to tigilanol tiglate (2a) under the prolonged conditions of the assay, while other esters were inactive. Significant differences between the esterification profile of the epoxytigliane di- and triesters exist in F. picrosperma, suggesting a precise, yet elusive, blueprint of acyl decoration for the tigliane polyol 5-hydroxyepoxyphorbol.

Identification of Gene Biomarkers for Tigilanol Tiglate Content in Fontainea picrosperma

Tigilanol tiglate (EBC-46) is a small-molecule natural product under development for the treatment of cancers in humans and companion animals. The drug is currently produced by purification from the Australian rainforest tree Fontainea picrosperma (Euphorbiaceae). As part of a selective-breeding program to increase EBC-46 yield from F. picrosperma plantations, we investigated potential gene biomarkers associated with biosynthesis of EBC-46. Initially, we identified individual plants that were either high (>0.039%) or low EBC-46 (<0.008%) producers, then assessed their differentially expressed genes within the leaves and roots of these two groups by quantitative RNA sequencing. Compared to low EBC-46 producers, high-EBC-46-producing plants were found to have 145 upregulated genes and 101 downregulated genes in leaves and 53 upregulated genes and 82 downregulated genes in roots. Most of these genes were functionally associated with defence, transport, and biosynthesis. Genes identified as expressed exclusively in either the high or low EBC-46-producing plants were further validated by quantitative PCR, showing that cytochrome P450 94C1 in leaves and early response dehydration 7.1 and 2-alkenal reductase in roots were consistently and significantly upregulated in high-EBC-46 producers. In summary, this study has identified biomarker genes that may be used in the selective breeding of F. picrosperma.

[Successful local treatment of a digital canine mast cell tumour with Tigilanol Tiglate]

Surgical excision is currently the recommended treatment for resectable, nonmetastatic mast cell tumours. Recently, Tigilanol tiglate has become available as a novel intratumoral treatment modality for a subset of cutaneous and subcutaneous mast cell tumours. In the presented case, we document the successful treatment of a 0.445 cm³ subcutaneous digital mast cell tumour in an American Staffordshire Terrier. The resulting wound healed completely and without complications within 4 weeks and the dog was recurrence-free 8 months after treatment. Due to this new intratumoral treatment it was possible to preserve the digit, while a complete surgical resection of the tumour would have required digital amputation.

[New drugs for small animals in 2021]

In 2021, 8 novel pharmaceutical agents for small animals were released on the German market: The specific monoclonal antibodies bedinvetmab (Librela^®) and frunevetmab (Solensia^®), the cyclooxygenase-2 inhibitor enflioxib (Daxocox^®), the ectoparasitic esafoxolaner (NexGard^® Combo) of the isoxazoline group, the anti-haemorrhagic etamsylate (Hemosilate), the antidepressant mirtazapine (Mirataz^®), the alpha-selective sympathomimetic tetryzoline for ophthalmic use (Zolicep^®) and the cytostatic tigilanol tiglate (Stelfonta^®). No active substance received an animal species extension. In addition, for small animals, there were new releases of two agents in a novel pharmaceutical formulation (cefalexin, gentamicin), five drugs with a new content of the active ingredient (metronidazole, pimobendan, thiamazole, tramadol, trilostane), one veterinary drug with a new combination of active ingredients (lotilaner + milbemycin oxime), one drug with a new route of administration (propofol) and furthermore two temporarily non-available active ingredients for certain animal species were reapproved in new drugs (levothyroxine for cats and oxytetracycline for dogs and cats).

Diagnosis, Prognosis and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors

Mast cell tumors (MCTs) are hematopoietic neoplasms composed of mast cells. It is highly common in dogs and is extremely important in the veterinary oncology field. It represents the third most common tumor subtype, and is the most common malignant skin tumor in dogs, corresponding to 11% of skin cancer cases. The objective of this critical review was to present the report of the 2nd Consensus meeting on the Diagnosis, Prognosis, and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors, which was organized by the Brazilian Association of Veterinary Oncology (ABROVET) in August 2021. The most recent information on cutaneous and subcutaneous mast cell tumors in dogs is presented and discussed.

Tigilanol Tiglate-Mediated Margins: A Comparison With Surgical Margins in Successful Treatment of Canine Mast Cell Tumours

Tigilanol tiglate (TT) is a novel small molecule registered as a veterinary pharmaceutical for intratumoural treatment of canine mast cell tumours (MCTs). The drug has a multifactorial mode of action resulting in rapid destruction of the treated tumour by haemorrhagic necrosis and subsequent slough of the necrotic tumour to reveal a tissue deficit that is left to heal by second intention with minimal to no veterinary intervention. Here we introduce the concept of TT-mediated margins, the calculated margin of tissue loss analogous to surgically applied margins to help clinicians conceptualise tissue deficits formed following tumour destruction by TT relative to surgical excision. We used data from 51 dogs that were recurrence-free 12 months after a single administered TT dose into a single target MCT <10 cm³ in volume in a randomised, controlled clinical trial in the USA. We calculated TT-mediated margins based on length of the longest axis of (i) the tumour prior to treatment and (ii) the maximum tissue deficit formed 7–14 days after TT treatment. We compared these TT-mediated margins for each tumour to two surgical approaches to MCT excision in general practise: modified proportional margins (with 2 cm upper limit) and 3 cm fixed margins. For most dogs, TT-mediated margins were less than half the length of the margins calculated for the two surgical approaches in removing the same tumour. There was a trend for TT-mediated margins to increase with increasing tumour volume. Nonetheless, even for the larger tumours in this study (>2 cm³ volume), 50% of TT-mediated margins were less than half the length of the two surgical margins. Eighteen cases were lower limb MCTs, sites often surgically challenging in veterinary practise. On these lower limbs, TT-mediated margins were less than half the length of the corresponding proportional margins in 56% of cases and larger than proportional margins in only two cases. This study suggests that, in many cases, smaller and more targeted margins could be expected when treating MCTs <10 cm³ volume with TT compared with surgical excision. TT-mediated margins are a novel approach to conceptualise tissue deficits after intratumoural TT treatment.

Intratumoural Treatment of 18 Cytologically Diagnosed Canine High-Grade Mast Cell Tumours With Tigilanol Tiglate

Canine high-grade mast cell tumours (HGMCT) are associated with a poor prognosis, are inherently more invasive, and have higher rates of local recurrence. The primary aim of this retrospective study was to assess the efficacy of intratumoural tigilanol tiglate (TT) as a local treatment option. Eighteen dogs with mast cell tumours (MCT) cytologically diagnosed by veterinary pathologists as either high-grade or suspected high-grade MCT were treated with TT. The TT dose was based on tumour volume (0.5 mg TT/cm³ tumour volume) and delivered intratumourally using a Luer lock syringe and a fanning technique to maximise distribution throughout the tumour mass. Efficacy was assessed on the presence/absence of a complete response (CR) to therapy at days 28 and 84 using response evaluation criteria in solid tumours (RECIST). For dogs not achieving a CR after 28 days, the protocol was repeated with a second intratumoural TT injection. Ten out of 18 dogs (56%) in this study achieved and maintained a CR to at least 84 days after their first or second treatment. Six patients were alive and available for evaluation at 2 years, three of those were recurrence free, and a further three patients were recurrence free following a second treatment cycle. Tigilanol tiglate shows efficacy for local treatment of HGMCT, with higher efficacy noted with a second injection if a CR was not achieved following the first treatment. In the event of treatment site recurrence (TSR), the tumour may be controlled with additional treatment cycles. Tigilanol tiglate provides an alternative local treatment approach to dogs with HGMCT that would either pose an unacceptable anaesthetic risk or the tumour location provides a challenge when attempting surgical excision.

Intratumoural administration and tumour tissue targeting of cancer immunotherapies

Immune-checkpoint inhibitors and chimeric antigen receptor (CAR) T cells are revolutionizing oncology and haematology practice. With these and other immunotherapies, however, systemic biodistribution raises safety issues, potentially requiring the use of suboptimal doses or even precluding their clinical development. Delivering or attracting immune cells or immunomodulatory factors directly to the tumour and/or draining lymph nodes might overcome these problems. Hence, intratumoural delivery and tumour tissue-targeted compounds are attractive options to increase the in situ bioavailability and, thus, the efficacy of immunotherapies. In mouse models, intratumoural administration of immunostimulatory monoclonal antibodies, pattern recognition receptor agonists, genetically engineered viruses, bacteria, cytokines or immune cells can exert powerful effects not only against the injected tumours but also often against uninjected lesions (abscopal or anenestic effects). Alternatively, or additionally, biotechnology strategies are being used to achieve higher functional concentrations of immune mediators in tumour tissues, either by targeting locally overexpressed moieties or engineering 'unmaskable' agents to be activated by elements enriched within tumour tissues. Clinical trials evaluating these strategies are ongoing, but their development faces issues relating to the administration methodology, pharmacokinetic parameters, pharmacodynamic end points, and immunobiological and clinical response assessments. Herein, we discuss these approaches in the context of their historical development and describe the current landscape of intratumoural or tumour tissue-targeted immunotherapies.

Floral attraction and flower visitors of a subcanopy, tropical rainforest tree, Fontainea picrosperma

Flowering plants in tropical rainforests rely heavily on pollen vectors for successful reproduction. Research into pollination systems in tropical rainforests is dominated by canopy species, while subcanopy plant-pollinator interactions remain under-represented. The microclimate beneath the rainforest canopy is characterized by low light levels and is markedly different from the canopy environment that receives more light energy.We studied the floral attractants and floral visitors of a dioecious, subcanopy tree, Fontainea picrosperma (Euphorbiaceae), in the Wet Tropics bioregion of northern Queensland, Australia.We found that wind pollination is rare and male and female flowers do not produce nectar. Female flowers are likely pollinated due to their perceptual similarity to pollen-offering male flowers. Female flowers had the same scent profile as male flowers, and floral scent was an important floral attractant that acted to regulate pollinator behavior. The two most abundant scent compounds present in the floral bouquet were benzyl alcohol and 4-oxoisophorone. These compounds are ubiquitous in nature and are known to attract a wide variety of insects. Both day-time and night-time pollinators contributed to successful pollen deposition on the stigma, and diurnal flower visitors were identified from several orders of insects including beetles, flies, predatory wasps, and thrips. Fontainea picrosperma is therefore likely to be pollinated by a diverse array of small insects.Synthesis. Our data indicate that F. picrosperma has a generalist, entomophilous pollination syndrome. The rainforest subcanopy is a distinctive environment characterized by low light levels, low or turbulent wind speeds, and relatively high humidity. Female flowers of F. picrosperma exhibit cost-saving strategies by not producing nectar and mimicking the smell of reward-offering male flowers. Insects opportunistically forage on or inhabit flowers, and pollination occurs from a pool of small insects with low energy requirements that are found beneath the rainforest canopy.

Yuanhuacine Is a Potent and Selective Inhibitor of the Basal-Like 2 Subtype of Triple Negative Breast Cancer with Immunogenic Potential

The heterogeneity of triple negative breast cancer (TNBC) has led to efforts to further subtype this disease with the hope of identifying new molecular liabilities and drug targets. Furthermore, the finding that TNBC is the most inherently immunogenic type of breast cancer provides the potential for effective treatment with immune checkpoint inhibitors and immune adjuvants. Thus, we devised a dual screen to identify compounds from natural product extracts with TNBC subtype selectivity that also promote the expression of cytokines associated with antitumor immunity. These efforts led to the identification of yuanhuacine (1) as a potent and highly selective inhibitor of the basal-like 2 (BL2) subtype of TNBC that also promoted an antitumor associated cytokine signature in immune cells. The mechanism of action of yuanhuacine for both phenotypes depends on activation of protein kinase C (PKC), defining a novel target for the treatment of this clinical TNBC subtype. Yuanhuacine showed potent antitumor efficacy in animals bearing BL2 tumors further demonstrating that PKC could function as a potential pharmacological target for the treatment of the BL2 subtype of TNBC.

The P450 multigene family of Fontainea and insights into diterpenoid synthesis

BACKGROUND

Cytochrome P450s (P450s) are enzymes that play critical roles in the biosynthesis of physiologically important compounds across all organisms. Although they have been characterised in a large number of plant species, no information relating to these enzymes are available from the genus Fontainea (family Euphorbiaceae). Fontainea is significant as the genus includes species that produce medicinally significant epoxy-tigliane natural products, one of which has been approved as an anti-cancer therapeutic.

RESULTS

A comparative species leaf metabolome analysis showed that Fontainea species possess a chemical profile different from various other plant species. The diversity and expression profiles of Fontainea P450s were investigated from leaf and root tissue. A total of 103 and 123 full-length P450 genes in Fontainea picrosperma and Fontainea venosa, respectively (and a further 127/125 partial-length) that were phylogenetically classified into clans, families and subfamilies. The majority of P450 identified are most active within root tissue (66.2% F. picrosperma, 65.0% F. venosa). Representatives within the CYP71D and CYP726A were identified in Fontainea that are excellent candidates for diterpenoid synthesis, of which CYP726A1, CYP726A2 and CYP71D1 appear to be exclusive to Fontainea species and were significantly more highly expressed in root tissue compared to leaf tissue.

CONCLUSION

This study presents a comprehensive overview of the P450 gene family in Fontainea that may provide important insights into the biosynthesis of the medicinally significant epoxy-tigliane diterpenes found within the genus.

Balancing skeleton and functional groups in total syntheses of complex natural products: a case study of tigliane, daphnane and ingenane diterpenoids

Total synthesis of natural products has greatly contributed to natural product research, organic synthesis and drug discovery and development. However, in most cases, the efficiency of total synthesis is far from sufficient for direct practical industrial application. Thus, designing a concise and efficient synthetic route with balanced efforts between building the complex skeleton and introducing functional groups is highly desirable. In this critical review, we first present an introduction of this issue and a philosophical framework that cover possible synthetic approaches. Next, we have chosen the biogenetically closely related, biologically important and synthetically extremely challenging natural products, tiglianes, daphnanes and ingenanes as the particular case for the discussion, since in the past 40 years many synthetic approaches have been reported. The successes and pitfalls included therefore serve as the basis to draw some conclusions that may inspire future development in this area.

Wound formation, wound size, and progression of wound healing after intratumoral treatment of mast cell tumors in dogs with tigilanol tiglate

Background

Tigilanol tiglate (TT) is a novel small molecule for intratumoral treatment of nonmetastatic mast cell tumors (MCTs) in dogs. In a randomized controlled clinical study, 75% of dogs that received a single TT treatment achieved complete resolution of the MCT by 28 days, with no recurrence in 93% of dogs at 84 days. Critical to TT's efficacy was the area of the wound (tissue deficit) after slough of the necrotic tumor relative to pretreatment tumor volume.

Objectives

To analyze data collected during the previous study to (a) describe wounds after slough of treated MCTs and (b) identify determinants of wound area and speed of wound healing.

Methods

Wound presence, condition, and area were determined from clinical records of 117 dogs over 84 days after a single intratumoral TT treatment.

Results

Tumor slough occurred 3 to 14 days after treatment, exposing granulation tissue in the wound bed. Wound area after tumor slough in general was related to pretreatment tumor volume, with maximal recorded wound area fully evident in 89% of dogs by day 7. In dogs achieving complete tumor resolution, all wounds were left to heal by secondary intention. Bandaging and other wound management interventions only were required in 5 dogs. Time to healing (ie, full re‐epithelialization of treatment site) depended on wound area and location on the body, with most wounds being fully healed between 28 and 42 days after treatment.

Conclusions

Wound area and healing after slough of TT‐treated tumors follow a consistent clinical pattern for most dogs.

Activation of PKC supports the anticancer activity of tigilanol tiglate and related epoxytiglianes

The long-standing perception of Protein Kinase C (PKC) as a family of oncoproteins has increasingly been challenged by evidence that some PKC isoforms may act as tumor suppressors. To explore the hypothesis that activation, rather than inhibition, of these isoforms is critical for anticancer activity, we isolated and characterized a family of 16 novel phorboids closely-related to tigilanol tiglate (EBC-46), a PKC-activating epoxytigliane showing promising clinical safety and efficacy for intratumoral treatment of cancers. While alkyl branching features of the C12-ester influenced potency, the 6,7-epoxide structural motif and position was critical to PKC activation in vitro. A subset of the 6,7-epoxytiglianes were efficacious against established tumors in mice; which generally correlated with in vitro activation of PKC. Importantly, epoxytiglianes without evidence of PKC activation showed limited antitumor efficacy. Taken together, these findings provide a strong rationale to reassess the role of PKC isoforms in cancer, and suggest in some situations their activation can be a promising strategy for anticancer drug discovery.

Equivocal, explicit and emergent actions of PKC isoforms in cancer

The maturing mutational landscape of cancer genomes, the development and application of clinical interventions and evolving insights into tumour-associated functions reveal unexpected features of the protein kinase C (PKC) family of serine/threonine protein kinases. These advances include recent work showing gain or loss-of-function mutations relating to driver or bystander roles, how conformational constraints and plasticity impact this class of proteins and how emergent cancer-associated properties may offer opportunities for intervention. The profound impact of the tumour microenvironment, reflected in the efficacy of immune checkpoint interventions, further prompts to incorporate PKC family actions and interventions in this ecosystem, informed by insights into the control of stromal and immune cell functions. Drugging PKC isoforms has offered much promise, but when and how is not obvious.

Recurrence-free interval 12 months after local treatment of mast cell tumors in dogs using intratumoral injection of tigilanol tiglate

Background

Tigilanol tiglate (TT) is a novel small molecule approved by the European Medicines Agency for intratumoral treatment of mast cell tumors (MCTs) in dogs. In a randomized controlled clinical efficacy and safety study in the United States, 85 of 116 dogs that received a single TT injection achieved complete response (CR) of the treated MCT by day 28.

Objective

To evaluate the durability of the TT treatment response achieved at day 28 in the U.S. study by assessing MCT recurrence at the treatment site 6 and 12 months after TT administration.

Animals

Eighty‐five dogs previously treated with TT.

Methods

Dogs that achieved CR at day 28 were assessed retrospectively for the presence or absence of MCT at the treatment site using records from clinical visits and telephone interviews with owners. Dogs unavailable at an assessment time were considered lost‐to‐follow‐up and data for their last assessment used in the final analysis.

Results

By 12 months after TT treatment, 64 dogs remained evaluable, with 21 unavailable. Of evaluable patients, 57 (89%) remained tumor free at the treatment site and 7 (11%) had developed recurrence. All recurrences occurred within the first 6 months, predominantly (5/7, 71%) within the first 12 weeks.

Conclusions and Clinical Importance

Tigilanol tiglate provided a durable long‐term local response for the treatment of MCT in dogs.

The allylic oxidation of tigliane esters

As part of a study on the structure-activity relationships of the anticancer agent tigilanol tiglate (EBC-46, 2), the allylic oxidation of phorbol triacetate (1c) and of the acetonide of its 3αH-dihydroderivative (5) was investigated. The aim was to introduce an oxygen function at C-5 en route to point-like analogues of 2, but functionalization of C-10 was instead observed. This was followed by oxidative fragmentation of ring B to the 9,10-secotigliane derivative 6 and oxidation of the endocyclic Δ⁶ double bond to the C-6/C-10 oxygen bridged 7-oxotigliane 7. Despite the over-functionalization of ring B, these observations suggest the possibility to modify positions overlooked in the oxidase phase of tigliane biosynthesis and explore novel areas of the phorbol chemical space.

Identification of a Noncanonical Necrotic Cell Death Triggered via Enhanced Proteolysis by a Novel Sapogenol Derivative

Small molecules which activate distinct cell death pathways have promising high potential for anticancer drug research. Especially, regulated necrosis draws attention as an alternative cell death mechanism to overcome the drug resistance. Here, we report that a new semisynthetic saponin analogue (AG-08) triggers necrotic cell death with unprecedented pathways. AG-08-mediated necrosis depends on enhanced global proteolysis involving calpains, cathepsins, and caspases. Moreover, AG-08 generates several alterations in lysosomal function and physiology including membrane permeabilization, redistribution toward the perinuclear area, and lastly excessive tubulation. As a consequence of lysosomal impairment, the autophagic process was abolished via AG-08 treatment. Collectively, in addition to its ability to induce necrotic cell death, which makes AG-08 a promising candidate to cope with drug resistance, its unique activity mechanisms including autophagy/lysosome impairment and enhancement of proteolysis leading a strong death capacity emphasizes its potential for anticancer drug research.

Use of the Intratumoural Anticancer Drug Tigilanol Tiglate in Two Horses

Tigilanol tiglate is a novel small molecule approved as a veterinary pharmaceutical in Europe for intratumoural treatment of non-metastatic, non-resectable canine mast cell tumors. The drug has a “tumor agnostic” mode of action associated with induction of an acute inflammatory response at the treatment site, immune cell recruitment, and disruption of tumor vasculature. Consequently, tigilanol tiglate has potential in treating a range of tumor types in humans and companion animals. However, it is likely that species-specific dosing and concomitant medication protocols will be required, especially to manage the drug-induced acute inflammatory response at the treatment site. As an initial step in evaluating tigilanol tiglate for treating cutaneous tumors in horses, we developed an equine-specific protocol involving (a) a 30% reduction in intratumoural tigilanol tiglate dose rate compared to that used in dogs, and (b) a regime of concomitant medications to manage the drug-induced acute inflammatory response at the treatment site. Here we report a preliminary study in two horses using the protocol to treat (i) an aggressive fibroblastic sarcoid that had recurred following surgical excision and (ii) a fast-growing peri-ocular squamous cell carcinoma. Clinical response to tigilanol tiglate treatment in these cases was similar to that observed in canine and human patients. Localized inflammation and bruising developed rapidly at the treatment site with haemorrhagic necrosis of the tumor evident within 24 h. Slough of necrotic tumor mass occurred within 6–16 days followed by infill of the tissue defect and full re-epithelialisation of the treatment site with good functional outcome. Drug-induced inflammation and oedema at the treatment site were well controlled by the concomitant medications and largely resolved within 3 days, while the wound that formed following tumor slough healed uneventfully. Both patients displayed minor lethargy during the first 36 h after treatment and localized treatment-site discomfort was apparent over the first 3–5 days. There was no evidence of recurrence of the sarcoid at 93 days, or the squamous cell carcinoma at 189 days. The results from this study support continued development and evaluation of tigilanol tiglate as a potential future treatment option for cutaneous equine tumors.

Potent Antibacterial Prenylated Acetophenones from the Australian Endemic Plant Acronychia crassipetala

Acronychia crassipetala is an endemic plant species in Australia. Its phytochemistry and therapeutic properties are underexplored. The hexane extract of the fruit A. crassipetala T. G. Hartley was found to inhibit the growth of the Gram-positive bacteria Staphylococcus aureus. Following bio-activity guided fractionation, two prenylated acetophenones, crassipetalonol A (1) and crassipetalone A (2), were isolated. Their structures were determined mainly by NMR and MS spectroscopic analyses. This is the first record of the isolation and structural characterisation of secondary metabolites from the species A. crassipetala. Their antibacterial and cytotoxic assessments indicated that the known compound (2) had more potent antibacterial activity than the antibiotic chloramphenicol, while the new compound (1) showed moderate cytotoxicity.

Use of kinase inhibitors against schistosomes to improve and broaden praziquantel efficacy

Praziquantel (PZQ) is the drug of choice for schistosomiasis. The potential drug resistance necessitates the search for adjunct or alternative therapies to PZQ. Previous functional genomics has shown that RNAi inhibition of Ca2+/calmodulin-dependent protein kinase II (CaMKII) gene in Schistosoma adult worms significantly improved the effectiveness of PZQ. Here we tested the in vitro efficacy of 15 selective and non-selective CaMK inhibitors against Schistosoma mansoni and showed that PZQ efficacy was improved against refractory juvenile parasites when combined with these CaMK inhibitors. By measuring CaMK activity and the mobility of adult S. mansoni, we identified two non-selective CaMK inhibitors, Staurosporine (STSP) and 1Naphthyl PP1 (1NAPP1), as promising candidates for further study. The impact of STSP and 1NAPP1 was investigated in mice infected with S. mansoni in the presence or absence of a sub-lethal dose of PZQ against 2- and 7-day-old schistosomula and adults. Treatment with STSP/PZQ induced a significant (47-68%) liver egg burden reduction compared with mice treated with PZQ alone. The findings indicate that the combination of STSP and PZQ dosages significantly improved anti-schistosomal activity compared to PZQ alone, demonstrating the potential of selective and non-selective CaMK/kinase inhibitors as a combination therapy with PZQ in treating schistosomiasis.

Novel epoxy-tiglianes stimulate skin keratinocyte wound healing responses and re-epithelialization via protein kinase C activation

Epoxy-tiglianes are a novel class of diterpene esters. The prototype epoxy-tigliane, EBC-46 (tigilanol tiglate), possesses potent anti-cancer properties and is currently in clinical development as a local treatment for human and veterinary cutaneous tumors. EBC-46 rapidly destroys treated tumors and consistently promotes wound re-epithelialization at sites of tumor destruction. However, the mechanisms underlying these keratinocyte wound healing responses are not completely understood. Here, we investigated the effects of EBC-46 and an analogue (EBC-211) at 1.51 nM-151 µM concentrations, on wound healing responses in immortalized human skin keratinocytes (HaCaTs). Both EBC-46 and EBC-211 (1.51 nM-15.1 µM) accelerated G0/G1-S and S-G2/M cell cycle transitions and HaCaT proliferation. EBC-46 (1.51-151 nM) and EBC-211 (1.51 nM-15.1 µM) further induced significant HaCaT migration and scratch wound repopulation. Stimulated migration/wound repopulation responses were even induced by EBC-46 (1.51 nM) and EBC-211 (1.51-151 nM) with proliferation inhibitor, mitomycin C (1 μM), suggesting that epoxy-tiglianes can promote migration and wound repopulation independently of proliferation. Expression profiling analyses showed that epoxy-tiglianes modulated keratin, DNA synthesis/replication, cell cycle/proliferation, motility/migration, differentiation, matrix metalloproteinase (MMP) and cytokine/chemokine gene expression, to facilitate enhanced responses. Although epoxy-tiglianes down-regulated established cytokine and chemokine agonists of keratinocyte proliferation and migration, enhanced HaCaT responses were demonstrated to be mediated via protein kinase C (PKC) phosphorylation and significantly abrogated by pan-PKC inhibitor, bisindolylmaleimide-1 (BIM-1, 1 μM). By identifying how epoxy-tiglianes stimulate keratinocyte healing responses and re-epithelialization in treated skin, our findings support the further development of this class of small molecules as potential therapeutics for other clinical situations associated with impaired re-epithelialization, such as non-healing skin wounds.

Randomized controlled clinical study evaluating the efficacy and safety of intratumoral treatment of canine mast cell tumors with tigilanol tiglate (EBC-46)

Objective

To evaluate the efficacy and safety of tigilanol tiglate (TT) for local intratumoral treatment of mast cell tumors (MCTs) in dogs.

Methods

A randomized controlled clinical study in 2 phases involving 123 dogs with cytologically diagnosed MCT. Phase 1 compared 81 TT‐treated dogs with 42 control dogs; phase 2 allowed TT treatment of control dogs and retreatment of dogs that failed to achieve tumor resolution after TT treatment in phase 1. Tigilanol tiglate (1 mg/mL) was injected intratumorally with dose based on tumor volume. Concomitant medications were used to minimize potential for MCT degranulation. Modified response evaluation criteria in solid tumors were used to evaluate treatment response at 28 and 84 days. Adverse events and quality of life were also assessed.

Results

A single TT treatment resulted in 75% complete response (CR) (95% confidence interval [CI] = 61‐86) by 28 days, with no recurrence in 93% (95% CI = 82‐97) of dogs by 84 days. Eight TT‐treated dogs that did not achieve CR in phase 1 achieved CR after retreatment, increasing the overall CR to 88% (95% CI = 77‐93). Control dogs had 5% CR (95% CI = 1‐17) at 28 days. Wound formation after tumor slough and wound size relative to tumor volume were strongly associated with efficacy. Adverse events typically were low grade, transient, and directly associated with TT's mode of action.

Conclusions

Tigilanol tiglate is efficacious and well tolerated, providing a new option for the local treatment of MCTs in dogs.

Phase I dose-escalation study to determine the safety, tolerability, preliminary efficacy and pharmacokinetics of an intratumoral injection of tigilanol tiglate (EBC-46)

BACKGROUND

Tigilanol tiglate, a short-chain diterpene ester, is being developed as intratumoral treatment of a broad range of cancers. We conducted the first-in-human study of intratumoral tigilanol tiglate in patients with solid tumors.

METHODS

Tigilanol tiglate was administered in a multicentre, non randomized, single-arm study, with escalating doses beginning with 0·06 mg/m2 in tumors estimated to be at least twice the volume of injection (dose-escalation cohorts). Patients with smaller tumors were assigned to the local effects cohort and received the appropriate dose for tumor size.

FINDINGS

Twenty-two patients were enrolled. The maximum dose was 3·6 mg/m2 and the maximum tolerated dose was not reached. There was one report of dose-limiting toxicity (upper airway obstruction), two serious adverse events (upper airway obstruction and septicemia), 160 treatment-emergent adverse events, and no deaths. Injection site reactions in all tumors and tumor types occurred even at the lowest dose. Six of the 22 patients experienced a treatment response, with four of the six patients achieving complete response.

INTERPRETATION

Intratumoral tigilanol tiglate was generally well tolerated, the maximum tolerated dose was not reached, and clinical activity was observed in 9 tumor types including complete response in four patients. These results support the continued development of tigilanol tiglate for intratumoral administration.

FUNDING

QBiotics Group Limited Brisbane, Queensland, Australia was the sponsor of the study.

Kunitz type protease inhibitor from the canine tapeworm as a potential therapeutic for melanoma

Modulating the tumor microenvironment to promote an effective immune response is critical in managing any type of tumor. Melanoma is an aggressive skin cancer and the incidence rate is increasing worldwide. Potent protease inhibitors have recently been extensively researched as potential therapeutic agents against various cancers. EgKI-1 is a potent Kunitz type protease inhibitor identified from the canine tapeworm Echinococcus granulosus that has shown anti-cancer activities in vivo. In this study we show that EgKI-1 significantly reduced the growth of melanoma in the B16-F0 mouse model and was not toxic to normal surrounding tissue. Moreover, EgKI-1 treatment significantly reduced survivin expression levels and increased the CD8+ T cell population in draining axillary lymph nodes. Therefore, EgKI-1 potentially reduces tumor growth by inducing apoptosis and modulating the tumor microenvironment, and has potential for development as an intra-lesional treatment for melanoma.

From Petri Dish to Patient: Bioavailability Estimation and Mechanism of Action for Antimicrobial and Immunomodulatory Natural Products

The new era of multidrug resistance of pathogens against frontline antibiotics has compromised the immense therapeutic gains of the 'golden age,' stimulating a resurgence in antimicrobial research focused on antimicrobial and immunomodulatory components of botanical, fungal or microbial origin. While much valuable information has been amassed on the potency of crude extracts and, indeed, purified compounds there are too many reports that uncritically extrapolate observed in vitro activity to presumed ingestive and/or topical therapeutic value, particularly in the discipline of ethnopharmacology. Thus, natural product researchers would benefit from a basic pharmacokinetic and pharmacodynamic understanding. Furthermore, therapeutic success of complex mixtures or single components derived therefrom is not always proportionate to their MIC values, since immunomodulation can be the dominant mechanism of action. Researchers often fail to acknowledge this, particularly when 'null' activity is observed. In this review we introduce the most up to date theories of oral and topical bioavailability including the metabolic processes affecting xenobiotic biotransformation before and after drugs reach the site of their action in the body. We briefly examine the common methodologies employed in antimicrobial, immunomodulatory and pharmacokinetic research. Importantly, we emphasize the contribution of synergies and/or antagonisms in complex mixtures as they affect absorptive processes in the body and sometimes potentiate activity. Strictly in the context of natural product research, it is important to acknowledge the potential for chemotypic variation within important medicinal plants. Furthermore, polar head space and rotatable bonds give a priori indications of the likelihood of bioavailability of active metabolites. Considering this and other relatively simple chemical insights, we hope to provide the basis for a more rigorous scientific assessment, enabling researchers to predict the likelihood that observed in vitro anti-infective activity will translate to in vivo outcomes in a therapeutic context. We give worked examples of tentative pharmacokinetic assessment of some well-known medicinal plants.

An appraisal of natural products active against parasitic nematodes of animals

Here, the scientific and patent literature on the activities of purified natural compounds has been reviewed, with the aim of assessing their suitability as anthelmintic drug discovery starting points. Only compounds described as active against parasitic nematodes of animals or against the model nematode Caenorhabditis elegans have been analysed. Scientific articles published since 2010 and patents granted from 2000, both inclusive, have been included in this analysis. The results show a scarcity of novel chemical structures, a limited follow-up of compounds disclosed before 2010 and a bias towards the screening of plant products, almost to the exclusion of other sources, when microbial extracts have, historically, provided most starting points for anti-infective drugs. All plant products published in this period were previously known, alerting to the high re-discovery rates of a limited number of chemical classes from this source. The most promising compounds described in the literature reviewed here, namely the linear nemadectin-derivatives, are novel and of bacterial origin. Patented but otherwise unpublished spiroketal structures also appear as interesting scaffolds for future development. The patent literature confirmed that it is possible to patent derivatives of previously known products, making them valid starting points for translational research.

Short distance pollen dispersal and low genetic diversity in a subcanopy tropical rainforest tree, Fontainea picrosperma (Euphorbiaceae)

Gene flow via pollen movement affects genetic variation in plant populations and is an important consideration in plant domestication. Fontainea picrosperma is a subcanopy rainforest tree that is of commercial interest because it is the source of tigilanol tiglate, a natural product used for the treatment of solid tumors. We identify patterns of pollen-mediated gene flow within natural populations of F. picrosperma and estimate genetic parameters and genetic structure between adult and juvenile groups using microsatellite markers. Our results show pollination events occur over much shorter distances than reported for tropical canopy species. At least 63% of seeds are sired by male trees located within 30 m of the mother. On average, 27% of the local male population contributed to successful reproduction of F. picrosperma with most fathers siring a single seed, however, the contributions to reproduction were uneven. Larger male trees with more flowers had greater reproductive success than those with less flowers (P < 0.05). There were comparatively low levels of genetic variation across the species (H_E = 0.405 for adult trees and 0.379 for juveniles) and we found no loss of genetic diversity between adult and juvenile trees. Short distance pollen flow and low genetic diversity is theoretically a prelude to genetic impoverishment, however F. picrosperma has persisted through multiple significant climatic oscillations. Nevertheless, the remaining low genetic diversity is of concern for domestication programs which require maximal genetic diversity to facilitate efficient selective breeding and genetic improvement of this commercially significant species.

Dose Characterization of the Investigational Anticancer Drug Tigilanol Tiglate (EBC-46) in the Local Treatment of Canine Mast Cell Tumors

Mast cell tumor (MCT) is the most common cutaneous neoplasm in dogs and wide surgical resection is the current first-line treatment. However, recurrence is common and often requires more specialist and expensive therapies. Tigilanol tiglate is a novel small molecule drug delivered by intratumoral injection that is currently under development to provide a new option for treating MCT. The aim of this study was to characterize a safe and effective dose of tigilanol tiglate for canine MCT and to gather preliminary data on the drug's pharmacokinetics. A multicenter, open-label, uncontrolled, non-randomized, dose de-escalation design was used. Eligibility was MCT stage I/IIa and a tumor size of 0.1–6.0 cm³. Dosing was based on tumor size (50% v/v tumor) and 3 drug concentrations (1.0, 0.5, 0.2 mg/mL) were evaluated. Twenty-seven dogs were treated in 3 dose de-escalation cohorts (10, 10, and 7 dogs, respectively). Efficacy at 21 days was defined using international accepted solid tumor response criteria (RECIST). Greatest efficacy (90% complete response) was observed at the highest drug concentration (1.0 mg/mL) and adverse events were generally low grade, mild and transient, and directly associated with the mode of action of the drug. Hematological and serum biochemistry were generally unremarkable with plasma concentration curves typical of a non-intravenous parenteral medication. Intratumoral treatment of MCT with tigilanol tiglate at a concentration of 1.0 mg/mL was highly efficacious and well-tolerated. These results support the drug's further development for the treatment of MCT and other solid tumors.

Kunitz type protease inhibitor EgKI-1 from the canine tapeworm Echinococcus granulosus as a promising therapeutic against breast cancer

EgKI-1, a member of the Kunitz type protease inhibitor family, is highly expressed by the oncosphere of the canine tapeworm Echinococcus granulosus, the stage that is infectious to humans and ungulates, giving rise to a hydatid cyst localized to the liver and other organs. Larval protoscoleces, which develop within the hydatid cyst, have been shown to possess anti-cancer properties, although the precise molecules involved have not been identified. We show that recombinant EgKI-1 inhibits the growth and migration of a range of human cancers including breast, melanoma and cervical cancer cell lines in a dose-dependent manner in vitro without affecting normal cell growth. Furthermore, EgKI-1 treatment arrested the cancer cell growth by disrupting the cell cycle and induced apoptosis of cancer cells in vitro. An in vivo model of triple negative breast cancer (MDA-MB-231) in BALB/c nude mice showed significant tumor growth reduction in EgKI-1-treated mice compared with controls. These findings indicate that EgKI-1 shows promise for future development as an anti-cancer therapeutic.

Progressive cutaneous viral pigmented plaques in three Hungarian Vizslas and the response of lesions to topical tigilanol tiglate gel

Cutaneous pigmented viral plaques is a disorder of epidermal growth caused by canine papillomavirus type 4 (CPV-4). There is currently no standard of care for managing this condition and it has not been reported in the Hungarian Vizsla. This case series documents the clinical features of canine pigmented viral plaques in Hungarian Vizsla dogs and the treatment of a severe case using a novel topical agent tigilanol tiglate (EBC-46). A 4-year-old spayed Hungarian Vizsla in Australia was presented for multiple cutaneous pigmented plaques extending from the ventral cervical region. Lesions were neither painful nor pruritic. The number and size of these sessile plaques increased over time, with the largest lesions eventually taking on an exophytic (wart-like) appearance. These lesions did not affect the dog's wellbeing. Two much less severe cases in a 5-year-old Vizsla from the UK and a 7-year-old Vizsla from New Zealand were also diagnosed. Histology was consistent with papillomavirus-induced pigmented plaques and CPV-4 DNA sequences were amplified from paraffin-embedded formalin-fixed tissue using the polymerase chain reaction from the most severely affected patient. Topical imiquimod was ineffective although used for only a short time. Two topical applications of novel anti-neoplastic diterpene ester tigilanol tiglate as a gel, 9 days apart, greatly reduced the size and number of lesions in a limited portion of skin treated, over the lateral hock. While CPV-4 has been previously reported to cause pigmented plaques, most commonly on pug dogs, but sporadically on other breeds, this is the first report of this virus causing plaques in Hungarian Vizslas. The cases illustrate some of the difficulties in diagnosing papillomavirus-induced disease in dogs, especially in its early stages. Topical tigilanol tiglate is a potentially useful topical therapy for this viral-induced disorder of cell growth and represents a treatment deserving of further investigation.

An improved preparation of phorbol from croton oil

Background: Croton oil is the only commercial source of the diterpenoid phorbol (1a), the starting material for the semi-synthesis of various diesters extensively used in biomedical research to investigate cell function and to evaluate in vivo anti-inflammatory activity. While efficient chemoselective esterification protocols have been developed for phorbol, its isolation from croton oil is technically complicated, and involves extensive manipulation of very toxic materials like the oil or its native diterpenoid fraction. Results: The preparation of a crude non-irritant phorboid mixture from croton oil was telescoped to only five operational steps, and phorbol could then be purified by gravity column chromatography and crystallization. Evidence is provided that two distinct phorboid chemotypes of croton oil exist, differing in the relative proportion of type-A and type-B esters and showing different stability to deacylation. Conclusion: The isolation of phorbol from croton oil is dangerous because of the toxic properties of the oil, poorly reproducible because of differences in its phorboid profile, and time-consuming because of the capricious final crystallization step. A solution for these issues is provided, suggesting that the poor-reproducibility of croton oil-based anti-inflammatory assays are the result of poor quality and/or inconsistent composition of croton oil.

Anticancer activity test of ethyl acetate extract of endophytic fungi isolated from soursop leaf (Annona muricata L.)

OBJECTIVE

To analyze anticancer activity of an ethyl acetate extract of endophytic fungi isolated from soursop leaf (Annona muricata L.).

METHODS

Anticancer activity of fungal extracts was determined by observing its toxicity against MCF-7 (Michigan Cancer Foundation-7) cells in vitro by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay method. At an extract concentration of 100 μg/mL, 4 isolates out of 12 showed high activity against the cancer cell growth. The four isolates were then selected for further IC₅₀ determination, by measuring the inhibition of cancer cell proliferation at extract concentration of 25 μg/mL, 50 μg/mL, 100 μg/mL, 200 μg/mL and 400 μg/mL.

RESULTS

Results showed that isolate Sir-G5 had the highest anticancer activity with an IC₅₀ of 19.20 μg/mL. The best isolates were screened again using a normal cell (Chang cells) to determine its toxicity against normal cells. Results indicated that the extracts do not affect the proliferation of normal cells. Molecular identification showed that the fungal isolate Sir-G5 has a close relationship with Phomopsis sp.

CONCLUSIONS

The endophytic fungi isolated from soursop leaf has the potential to be used as a source of anticancer agents.

Protein kinase C (PKC) isoforms in cancer, tumor promotion and tumor suppression

The AGC family of serine/threonine kinases (PKA, PKG, PKC) includes more than 60 members that are critical regulators of numerous cellular functions, including cell cycle and differentiation, morphogenesis, and cell survival and death. Mutation and/or dysregulation of AGC kinases can lead to malignant cell transformation and contribute to the pathogenesis of many human diseases. Members of one subgroup of AGC kinases, the protein kinase C (PKC), have been singled out as critical players in carcinogenesis, following their identification as the intracellular receptors of phorbol esters, which exhibit tumor-promoting activities. This observation attracted the attention of researchers worldwide and led to intense investigations on the role of PKC in cell transformation and the potential use of PKC as therapeutic drug targets in cancer diseases. Studies demonstrated that many cancers had altered expression and/or mutation of specific PKC genes. However, the causal relationships between the changes in PKC gene expression and/or mutation and the direct cause of cancer remain elusive. Independent studies in normal cells demonstrated that activation of PKC is essential for the induction of cell activation and proliferation, differentiation, motility, and survival. Based on these observations and the general assumption that PKC isoforms play a positive role in cell transformation and/or cancer progression, many PKC inhibitors have entered clinical trials but the numerous attempts to target PKC in cancer has so far yielded only very limited success. More recent studies demonstrated that PKC function as tumor suppressors, and suggested that future clinical efforts should focus on restoring, rather than inhibiting, PKC activity. The present manuscript provides some historical perspectives on the tumor promoting function of PKC, reviewing some of the observations linking PKC to cancer progression, and discusses the role of PKC in the pathogenesis of cancer diseases and its potential usage as a therapeutic target.