Cyclooctadepsipeptide PF1022A Research Articles

New Heteroaromatic Derivatives of the Anthelmintic Cyclooctadepsipeptide PF1022A by Click-Chemistry

The cyclooctadepsipeptide PF1022A (1) and its semisynthetic, commercial analogue emodepside (2) have been established as excellent anthelmintics with resistance breaking properties. For a second generation anthelmintic cyclooctadepsipeptide with improved activity for instance against human worm infections new derivatives are required. We detail here for the first time the synthesis of phenylheteroaromatic analogues of PF1022A prepared by efficient click-reactions. Keywords: Anthelmintic, click-chemistry, cyclodep, heteroaromatic analogues, PF1022A, sipeptide.

Semisynthetic routes to PF1022H—A precursor for new derivatives of the anthelmintic cyclooctadepsipeptide PF1022A

The cyclooctadepsipeptide PF1022A and its semisynthetic, commercial analogue emodepside show excellent anthelmintic properties. Bis-hydroxy PF1022 (PF1022H), a minor fermentative side-product represents an interesting precursor for new PF1022 related anthelmintics. We report herein two complementary routes which allow a highly efficient conversion of PF1022A to a regioisomeric mixture consisting mainly of the bis-para isomer PF1022H and the meta–para analogue.

In vivo efficacy of PF1022A and nicotinic acetylcholine receptor agonists alone and in combination against Nippostrongylus brasiliensis

The cyclooctadepsipeptide PF1022A and the aminophenylamidines amidantel, deacylated amidantel (dAMD) and tribendimidine were tested as examples for drug classes potentially interesting for development as anthelmintics against human helminthiases. These compounds and levamisole were tested alone and in combination to determine their efficacy against the rat hookworm Nippostrongylus brasiliensis. After three oral treatments, intestinal worms were counted. Drug effects on parasite morphology were studied using scanning electron microscopy (SEM). Plasma pharmacokinetics were determined for tribendimidine and dAMD. All drugs reduced worm burden in a dose-dependent manner, however amidantel was significantly less active than the other aminophenylamidines. Combinations of tribendimidine and dAMD with levamisole or PF1022A at suboptimal doses revealed additive effects. While PF1022A caused virtually no changes in morphology, levamisole, dAMD and tribendimidine caused severe contraction, particularly in the hind body region. Worms exposed to combinations of PF1022A and aminophenylamidines were indistinguishable from worms exposed only to aminophenylamidines. After oral treatment with tribendimidine, only the active metabolite dAMD was detectable in plasma and concentrations were not significantly different for oral treatment with dAMD. The results support further evaluation of cyclooctadepsipeptides alone and in combination with cholinergic drugs to improve efficacy. Combining these with registered drugs may help to prevent development of resistance.

Anthelmintic cyclooctadepsipeptides: complex in structure and mode of action

The broad-spectrum anthelmintic cyclooctadepsipeptide PF1022A is a fungal metabolite from Rosellinia sp. PF1022, which is a Mycelia sterilia found on the leaves of Camellia japonica. A broad range of structurally related cyclooctadepsipeptides has been characterized and tested for anthelmintic activities. These metabolites have been used as starting points to generate semisynthetic derivatives with varying nematocidal capacity. Predominant among these compounds is emodepside, which exhibits a broad nematocidal potential against gastrointestinal and extraintestinal parasites. Here we review the chemical biology and mode of action of cyclooctadepsides with particular attention to PF1022A and emodepside. We illustrate how they target nematode neuromuscular function, opening up new avenues for antiparasitic treatments with potential capability for important selective toxicity.

Anthelmintic PF1022A: stepwise solid-phase synthesis of a cyclodepsipeptide containing N-methyl amino acids

Cyclodepsipeptides of the enniation-, PF1022-, and verticilide-family represent a diverse class of highly interesting natural products with respect to their manifold biological activities. However, until now no stepwise solid-phase synthesis has been accomplished due to the difficult combination of N-methyl amino acids and hydroxycarboxylic acids. We report here the first stepwise solid-phase synthesis of the anthelmintic cyclooctadepsipeptide PF1022A based on an Fmoc/THP-ether protecting group strategy on Wang-resin. The standard conditions of our synthesis allow an unproblematic adaption to an automated peptide synthesizer.

Efficacy of the cyclooctadepsipeptide PF1022A againstHeligmosomoides bakeri in vitroandin vivo

The cyclooctadepsipeptide PF1022A derived from the fungus, Mycelia sterilia, is characterized by a broad spectrum of activity against different parasitic gastrointestinal nematodes of livestock. In the present work the anthelmintic activity of PF1022A against Heligmosomoides bakeri, a widely used laboratory model was studied. Albendazole, ivermectin and levamisole served as reference. In vitro, PF1022A showed low activity on embryonation but significantly inhibited egg hatch (10 and 100 μg/ml), whereas albendazole (10 and 100 μg/ml) revealed statistically significant inhibitions of both embryonation and egg hatch. PF1022A (1-100 μg/ml) completely inhibited larval movement at most examination points. Comparable significant anthelmintic activity on the larval stages of H. bakeri was observed with levamisole (48-100%), while slightly lower activities were observed with ivermectin (20-92%) and albendazole (0-87%) at 1-100 μg/ml. PF1022A and levamisole significantly inhibited motility and egg release of adult worms, while albendazole and ivermectin failed to demonstrate activity. Significant worm burden reductions were achieved with PF1022A, levamisole and ivermectin in vivo. For example, at 0·125 mg/kg PF1022A a worm burden reduction of 91·8% was observed. The use of drug combinations did not further enhance the in vitro and in vivo activity of PF1022A. In conclusion, further investigations are warranted with PF1022A, as the drug is characterized by significant larvicidal and nematocidal activity in vitro and in vivo.

Effects of the anthelmintic drug PF1022A on mammalian tissue and cells

Nematode infections cause human morbidity and enormous economic loss in livestock. Since resistance against currently available anthelmintics is a worldwide problem, there is a continuous need for new compounds. The cyclooctadepsipeptide PF1022A is a novel anthelmintic that binds to the latrophilin-like transmembrane receptor important for pharyngeal pumping in nematodes. Furthermore, PF1022A binds to GABA receptors, which might contribute to the anthelmintic effect. Like other cyclodepsipeptides, PF1022A acts as an ionophore. However, no correlation between ionophoric activity and anthelmintic properties was found. This is the first study describing the effect of PF1022A on mammalian cells and tissues. While channel-forming activity was observed already at very low concentrations, changes in intracellular ion concentrations and reduction of contractility in isolated guinea pig ileum occurred at multiples of anthelmintically active concentrations. PF1022A did not induce necrotic cell death indicated by complete lack of cellular lactate dehydrogenase release. In contrast, apoptosis induction via the mitochondrial pathway was suggested for long-term drug treatment at high concentrations due to numerous apoptotic morphological changes as well as mitochondrial membrane depolarisation. Short time effects were based on cell cycle blockade in G 0/G 1 phase. Additionally, the cell cycle and apoptosis regulating proteins p53, p21 and bax, but not Bcl-2 were shown to impact on PF1022A-induced cytotoxicity. However, since PF1022A-induced cytotoxicity was found at drug concentrations higher than those used in anthelmintic treatment, it can be suggested that PF1022A intake might not impair human or animal health. Thus, PF1022A seems to be a safe alternative to other anthelmintic drugs.

Influence of the cyclooctadepsipeptides PF1022A and PF1022E as natural products on the design of semi–synthetic anthelmintics such as emodepside

The 24-membered cyclooctadepsipeptide (CODP) PF1022A, the active metabolite of the fungus imperfectus Mycelia sterilia (Rosellinia sp.) isolated from the plant Camellia japonica in Japan, is described as a powerful broad-spectrum anthelmintic natural product with low toxicity in animals. Further CODPs such as PF1022B, C, D and E have been isolated from the same culture and their structures have been established. Both PF1022A and PF1022E serve as valuable starting materials for the synthesis of semi-synthetic CODP derivatives with improved intrinsic anthelmintic potency and broad-spectrum activity. It was found that in most cases the di-substituted PF1022A derivatives showed a greater (or equal) activity by oral application against the gastrointestinal nematode Haemonchus contortus compared to the corresponding mono-substituted PF1022A analogues as exemplified by emodepside. In order to get additional information on the bioactive conformation, emodepside was transformed into its mono- and tetra-thionated derivatives by isosteric replacement. In the light of the increased efficacy of these derivatives against H. contortus or Trichostrongylus colubriformis, it has been suggested that the asymmetric conformation clearly influences the anthelmintic activity of CODPs. Although useful synthetic pathways are available today for the preparation of the semi-synthetic CODP emodepside, the fermentative production of its bis-para-nitro and bis-para-amino precursors could be the process used for its industrial-scale production in the future.

Chimeric Cyclodepsipeptides as Mimetics for the Anthelmintic PF1022A.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Chimeric cyclodepsipeptides as mimetics for the anthelmintic PF1022A

In the anthelmintic cyclooctadepsipeptide PF1022A ( 1) didepsipeptide units have been exchanged for the β-turn mimetics ( d)-Pro-( l)-Pro and BTD ( 7) in order to elucidate the functional role of the depsipeptide backbone. Compounds 12 and 14 are the first PF1022A analogues in which a substantial part of the PF1022A backbone has been replaced with an improvement of anthelmintical activity. Preliminary structure–activity relationships suggest a symmetric conformation to be the biological active one.

GENE MACHINE TRUMPS SYNTHESIS

IN ANOTHER DEMONSTRATION of the power of metabolic engineering, researchers have developed a fungus that produces derivatives of a bioactive natural product that cannot be made efficiently using chemical synthesis. The natural product is the cyclooctadepsipeptide PF1022A. It consists of four residues of N -methyl-L-leucine alternating with two residues each of D-lactate and D-phenyllactate. Its potent activity against nematodes makes it a strong candidate to replace existing agents, to which resistance is increasing. Studies have shown that derivatives of PF1022A in which the para positions of the benzene units are substituted with amino or nitro groups are even more potent against parasitic worms than the original natural product. Chemical methods to introduce substituents at the benzenes' para positions are low yielding and inefficient for industrial-scale production. For this reason, Koji Yanai and coworkers at Meiji Seika Kaisha, in Kanagawa Japan, turned to metabolic engineering. By modifying a filam...

PF1022A and related cyclodepsipeptides - a novel class of anthelmintics.

Parasitic nematodes are a major cause of morbidity and mortality in man and also cause widespread loss of food production by infection of livestock. A milestone in the chemotherapy of nematode infections, especially in animals, was the discovery of the avermectins and milbemycins during the 1970s. Since the discovery of these highly active macrolides, reports of potent new classes of anthelmintics have been scarce. One of the most outstanding recently reported anthelmintics is the cyclooctadepsipeptide PF1022A, the most active member of a novel class of anthelmintic agents. During the past years several total syntheses of PF1022A and manifold structure-activity relationships have been established. Additionally, the biosynthesis of PF1022A has been elucidated and intensive investigations into the mode of action of this novel anthelmintic are underway. Comprehensive studies including cyclodepsipeptides with smaller ring-sizes, such as the enniatins, proved the PF1022 family and related cyclodepsipeptides to be the most promising follow-up candidates for the avermectins and milbemycins, which suffer from increasing nematode resistance.

Azadepsipeptides: Synthesis and Evaluation of a Novel Class of Peptidomimetics

A general route to azadepsipeptides, a new class of pseudopeptides, has been established. The methodology was applied to the synthesis of a bis-aza analogue of the antiparasitic cyclooctadepsipeptide PF1022A. Comparison of the X-ray crystal structures of natural PF1022A (8) and the chimeric aza analogue 9 revealed that the introduction of nitrogen in the backbone of PF1022A results in almost complete conservation of the 3D structure with only minor deviations at the new nitrogen positions.

Synthesis, conformational studies and anthelmintic activity of a constrained PF1022A analogue

A mono-proline analogue of the potent anthelmintic cyclooctadepsipeptide PF1022A has been synthesized. NMR studies in combination with molecular dynamics simulations demonstrate that the confirmation of this analogue is both rigidified and distorted compared with the asymmetric conformation of PF1022A. The backbone conformation is significant with respect to anthelmintic activity.

PF1022A--a novel anthelmintic cyclooctadepsipeptide. Modification and exchange of the N-methyl leucine residues.

The first structure-activity relationships of the anthelmintic cyclooctadepsipeptide PF1022A have been established via a systematic exchange of the leucine residues by a series of related N-alkylated amino acids. The data presented strongly suggest that (L)-N-methyl-leucine is crucial for high in vivo activity.

Solid-phase synthesis of cyclooctadepsipeptide PF1022A analogs using a cyclization-cleavage method with oxime resin

N-Methyloctadepsipeptides attached to an oxime resin were cyclized by heating them in refluxing ethyl acetate for 2 days to give cyclooctadepsipeptide PF1022A analogs.

A highly efficient synthesis of the anthelmintic cyclooctadepsipeptide PF1022A

The potent anthelmintic cyclooctadepsipeptide PF1022A was synthesized by a series of fragment condensations starting from the known ( S)-2-chloropropanoic acid and ( S)-2-chloro-3-phenylpropanoic acid in eleven steps with a total yield of 13%. Noteworthy is the excellent yield of the BOP-Cl mediated lactamization reaction of the linear precursor 17 leading to the 24-membered macrocycle.

Total Synthesis of the Anthelmintic Cyclodepsipeptide, PF1022A

The anthelmintic cyclooctadepsipeptide PF1022A and its antipode were synthesized starting from l-Nα-Boc-leucine (for PF1022A), d-Nα-Boc-leucine (for the antipode), l-lactic acid, and l-phenyllactic acid using Mitsunobu reaction and/or the DCC/HOBt method. The antipode had no anthelmintic efficacy.