Lotilaner - a novel systemic tick and flea control product for dogs

Design, Synthesis, Insecticidal Activity, and SAR of Aryl Isoxazoline Derivatives Containing Pyrazole-5-carboxamide Motif

It is important to develop new insecticides with a new mode of action because of increasing pesticide resistance. In this study, a series of novel aryl isoxazoline derivatives containing the pyrazole-5-carboxamide motif were designed and synthesized. Their structures were confirmed by 1H NMR, 13C NMR, and HRMS. Bioassays indicated that the 24 compounds synthesized possessed excellent insecticidal activity against Mythimna separate and no activity against Aphis craccivora and Tetranychus cinnabarinus. Among these aryl isoxazoline derivatives, 3-(5-(3,5-dichlorophenyl)-5-(trifluoromethyl)-4,5-dihydrozol-3-yl)-N-(4-fluorophenyl)-1-methyl-1H-pyrazole-5-carboxamide (IA-8) had the best insecticidal activity against M. separate, which is comparable with the positive control fluralaner. The molecular docking results of compound IA-8 and fluralaner with the GABA model demonstrated the same docking mode between compound IA-8 and positive control fluralaner in the active site of GABA. Molecular structure comparisons and ADMET analysis can potentially be used to design more active compounds. The structure-activity relationships are also discussed. This work provided an excellent insecticide for further optimization.

Design, synthesis, and insecticidal and fungicidal activities of quaternary ammonium salt derivatives of a triazolyphenyl isoxazoline insecticide

BACKGROUND

Insect pests seriously decrease the yield and quality of agricultural crops. Resistance to commonly used insecticides is increasingly undermining their effectiveness, and therefore the development of agents with novel modes of action is desirable. Isoxazolines are a new class of insecticides that act on γ-aminobutyric acid (GABA) gated chloride channels. In this work, we used the highly active 4-triazolyphenyl isoxazoline DP-9 as a parent structure to design and synthesize a series of quaternary ammonium salt (QAS) derivatives, and we systematically evaluated their insecticidal and antifungal activities.

RESULTS

Many of the synthesized QASs exhibit insecticidal activities equivalent to or higher than that of DP-9. In particular, compounds I-31 (93%, 0.00005 mg/L) and I-34 (80%, 0.00001 mg/L) showed insecticidal activities against diamondback moth larvae that were 2-10 times higher than those of fluralaner (70%, 0.0001 mg/L) and DP-9 (80%, 0.0001 mg/L), in addition to showing excellent activities against oriental armyworm, fall armyworm, cotton bollworm, corn borer, and mosquito larvae. Furthermore, all of the synthesized compounds also showed broad-spectrum fungicidal activities.

CONCLUSION

The insecticidal activities of QAS derivatives of DP-9 were the same as or better than the activity of DP-9. Compounds I-31 and I-34 showed better insecticidal activities against diamondback moth larvae than fluralaner and DP-9, and thus are promising new candidates for insecticide research.

Acaricidal and Repellent Effects of Essential Oils against Ticks: A Review

Tick control is a priority in order to prevent the transmission of vector-borne diseases. Industrial chemical acaricides and repellents have been the most efficient tools against hard ticks for a long time. However, the appearance of resistances has meant the declining effectiveness of the chemicals available on the market. The trend today is to develop alternative control methods using natural products to replace nonefficient pesticides and to preserve the efficient ones, hoping to delay resistance development. Traditional in vitro evaluation of acaricidal activity or resistance to synthetic pesticides have been reviewed and they mainly focus on just one species, the one host tick (Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)). Recent reports have called for the standardization of natural product components, extraction techniques, and experimental design to fully discover their acaricidal potential. This study reviews the main variables used in the bibliography about the efficiency of natural products against ticks, and it proposes a unification of variables relating to ticks, practical development of bioassays, and estimation of ixodicidal activity.

The molecular targets of ivermectin and lotilaner in the human louse Pediculus humanus humanus: New prospects for the treatment of pediculosis

Control of infestation by cosmopolitan lice (Pediculus humanus) is increasingly difficult due to the transmission of parasites resistant to pediculicides. However, since the targets for pediculicides have no been identified in human lice so far, their mechanisms of action remain largely unknown. The macrocyclic lactone ivermectin is active against a broad range of insects including human lice. Isoxazolines are a new chemical class exhibiting a strong insecticidal potential. They preferentially act on the γ-aminobutyric acid (GABA) receptor made of the resistant to dieldrin (RDL) subunit and, to a lesser extent on glutamate-gated chloride channels (GluCls) in some species. Here, we addressed the pediculicidal potential of isoxazolines and deciphered the molecular targets of ivermectin and the ectoparasiticide lotilaner in the human body louse species Pediculus humanus humanus. Using toxicity bioassays, we showed that fipronil, ivermectin and lotilaner are efficient pediculicides on adult lice. The RDL (Phh-RDL) and GluCl (Phh-GluCl) subunits were cloned and characterized by two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes. Phh-RDL and Phh-GluCl formed functional homomeric receptors respectively gated by GABA and L-glutamate with EC₅₀ values of 16.0 μM and 9.3 μM. Importantly, ivermectin displayed a super agonist action on Phh-GluCl, whereas Phh-RDL receptors were weakly affected. Reversally, lotilaner strongly inhibited the GABA-evoked currents in Phh-RDL with an IC₅₀ value of 40.7 nM, whereas it had no effect on Phh-GluCl. We report here for the first time the insecticidal activity of isoxazolines on human ectoparasites and reveal the mode of action of ivermectin and lotilaner on GluCl and RDL channels from human lice. These results emphasize an expected extension of the use of the isoxazoline drug class as new pediculicidal agents to tackle resistant-louse infestations in humans.

Human cosmopolitan lice are responsible for pediculosis, which represent a significant public health concern. Resistant lice against insecticides and lack of safety of the treatments for human and environment is a growing issue worldwide. Here we investigated the efficacy on lice of the classical macrocyclic lactone drug, ivermectin, and of the isoxazoline drug, lotilaner. This study was done to decipher their mode of action at the molecular and functional levels in order to propose new strategies to control lice infestation. Our bioassay results indicate that ivermectin and lotilaner were potent at killing human adult lice, with lotilaner showing a higher efficacy than ivermectin. Furthermore, we identified and pharmacologically characterized the first glutamate- and GABA-gated chloride channels ever described in human lice yet. Mechanistically, our molecular biology and electrophysiology findings demonstrate that ivermectin acted preferentially at glutamate channels, while lotilaner specifically targeted GABA channels. These results provide new insights in the understanding of the insecticide mode of action and highlight the potential of isoxazolines as a new alternative for the treatment of human lice.

Clinical, Parasitological, and Serological Follow-Up of Dogs with Sarcoptic Mange Treated Orally with Lotilaner

Canine sarcoptic mange is a highly pruritic and contagious skin disease caused by the mite Sarcoptes scabiei var. canis. This case series describes the clinical, parasitological, and serological follow-up of a cohort of eight adult Saint Bernard dogs with confirmed sarcoptic mange, treated orally with lotilaner. Dogs were evaluated initially and after 14 days and 1, 2, 3, 4, 6, and 12 months for skin lesions, pruritus severity, presence of parasites, and Sarcoptes-IgG levels. A serological indoor allergy panel (IgE) was obtained for seven dogs at day 0 and repeated 12 months later in five dogs to assess potential cross-reactivity between S. scabiei and environmental allergens. Lotilaner was administered to each dog according to the manufacturer's instructions and was repeated after one and two months without any concurrent therapeutic measure or modification of the husbandry conditions. Pruritus ceased after two weeks. The cutaneous score was reduced by 47%, and skin scrapings were negative for all but three animals. All skin scrapings were negative after one month. Lesions were absent after two months. Serological levels decreased gradually, but more slowly than the skin lesions, and two dogs out of six remained positive in the absence of skin lesions or symptoms. All dogs initially tested positive for dust mites and/or storage mites. The IgE titres remained unchanged 12 months later in the five tested dogs. This case report demonstrates the efficacy of lotilaner on scabies in a cohort of infested dogs under natural conditions and the potential antigenic cross-reaction of S. scabiei with house dust and storage mites.

Controlling phlebotomine sand flies to prevent canine Leishmania infantum infection: A case of knowing your enemy

Leishmaniosis caused by Leishmania infantum is a widespread zoonotic disease that can be transmitted to animals and humans by their vectors, blood-sucking phlebotomine sand flies. To prevent canine leishmaniosis across the whole Mediterranean region, vector control is essential. Because of phlebotomine breeding sites are diverse, environmental larval controls have limited practical value. Control methods of adults are being evaluated, such as selective baits based on sugar feeding of males and females or Attractive Toxic Sugar Baits (ATSB), and the indoor use of Long-Lasting-Insecticidal Nets (LLINs) treated with permethrin to prevent sand fly bites complementing the Indoor Residual Spraying (IRS) approach suggested by WHO. Although several strategies exist, the best control measure to prevent canine Leishmania infantum is to treat dogs using biocidal topical formulations based on legal insecticides (PTs18) or repellents (PTs19) (as collars, spot-ons and/or sprays) during the period when the vectors are active. This means we need to really know the biology and life cycle of the sand fly vector. According to available data, by mapping ambient temperatures we can already predict high risk areas where vector densities will be higher. In ongoing research, new candidates are emerging to fight against sand flies including natural plant extracts with low impacts on the environment and host animal. Other options in the future could be systemic insecticides to help reduce sand fly populations in high density areas. In parallel, health authorities and professionals involved in animal and public health (veterinarians, physicians, entomologists and epidemiologists) must work together in a One Health approach to minimize Leishmania infection. Veterinarians play a crucial role in liaising between key stake holders and dog owners to ensure the latter act responsibly in using repellents as a preventive measure against sand fly bites.

Safety of lotilaner flavoured chewable tablets (CredelioTM) after oral administration in cats

BACKGROUND

Lotilaner is a new member of the isoxazoline class for treatment of flea and tick infestations in cats. This laboratory study with lotilaner vanilla-yeast flavoured chewable tablets (CredelioTM, Elanco) investigated the safety in healthy kittens starting at 8 weeks of age in a randomized, blinded, parallel-group design. Lotilaner tablets were given orally once a month over eight months at one, three and five times the upper level of the maximum recommended dose range (26 mg/kg).

METHODS

The safety of lotilaner flavoured chewable tablets was assessed in healthy kittens when administered orally every 4 weeks for 8 months at the highest recommended dose rates, i.e. 1× (26 mg/kg) and at elevated dose rates, i.e. 3× (78 mg/kg) and 5× (130 mg/kg). Sixteen male and 16 female healthy 8-week-old kittens, with a mean body weight of 0.79 kg and 0.75 kg, respectively, were randomized to an untreated control group or lotilaner groups at dose rates of 26 mg/kg (1×), 78 mg/kg (3×), or 130 mg/kg (5×) every four weeks over eight months. The control group was sham-dosed. All animals were fed within 30 minutes prior to treatment. Safety assessment included general health observations, detailed clinical observations, complete physical/neurological examinations, including ophthalmological examinations, electrocardiographic (ECG) and clinical pathology evaluations (haematology, clinical chemistry and urinalysis), food and water consumption, body weight, pharmacokinetic blood collections, organ macroscopic and microscopic examinations.

RESULTS

Systemic exposure to lotilaner was confirmed during the course of the study in all treated animals with the exception of the control group. No treatment-related effects were seen on daily clinical observations, food consumption (wet), ophthalmoscopic, physical/neurological and microscopic examinations. Statistically significant differences were recorded in some of the clinical pathology parameters, body weights, food consumption (dry), electrocardiograms, and organ weights, but none of the recorded observations was considered to be of clinical relevance.

CONCLUSIONS

Lotilaner, when administered once monthly over eight months at the highest recommended dose and overdoses of three- and five-fold, to 8-week-old healthy kittens, is well tolerated.

Pharmacokinetics of lotilaner following a single oral or intravenous administration in cats

BACKGROUND

CredelioTM (lotilaner) is an oral ectoparasiticide from the isoxazoline class developed for the treatment of flea and tick infestations in cats. It is formulated as a pure S-enantiomer in flavoured chewable tablets. The pharmacokinetics of lotilaner were investigated after intravenous or oral administration and under fed or fasted conditions in cats. Twenty-six adult cats were enrolled in a pharmacokinetic study evaluating either intravenous or oral administration of lotilaner. Following the oral administration at a dosage of 6 mg/kg, under fed or fasted conditions, or intravenous administration of 3 mg/kg, blood samples were collected up to 35 days after treatment. Lotilaner blood concentrations were measured using a validated liquid chromatography/tandem mass spectrometry method. Pharmacokinetic parameters were calculated by non-compartmental analysis. In addition, in vivo enantiomer stability of lotilaner was evaluated in a separate bioanalytical study.

RESULTS

Following oral administration in fed cats, lotilaner was readily absorbed and peak blood concentrations reached within four hours. The terminal half-life was 33.6 days. Food enhanced the absorption, providing close to 100% oral bioavailability and reduced the inter-individual variability. Following intravenous administration, lotilaner had a low clearance of 0.13 l/kg/day, large volumes of distribution Vz and Vss of 5.34 and 5.37 l/kg, respectively and a terminal half-life of 28.7 days. In addition, there was no in vivo racemization of lotilaner.

CONCLUSIONS

The pharmacokinetic properties of lotilaner administered orally as a flavoured chewable tablet (CredelioTM) were studied in detail. With a Tmax of 4 h and a terminal half-life of 33.6 days under fed conditions, lotilaner provides a rapid onset of flea and tick killing activity with consistent and sustained efficacy for at least one month in cats.

Laboratory evaluation of the efficacy and speed of kill of lotilaner (CredelioTM) against Ixodes ricinus ticks on cats

BACKGROUND

Lotilaner, approved for dogs as a chewable tablet formulation, has separately been developed for oral use in cats (CredelioTM chewable tablets for cats), to meet the need for an easy to use, safe and rapidly effective parasiticide. It is a valid cat- and owner-friendly alternative to topical products. This manuscript describes three pivotal laboratory studies assessing the efficacy and speed of kill of lotilaner in cats against Ixodes ricinus ticks following a single oral administration, at a dose rate close to 6 mg/kg.

METHODS

In Studies 1 and 2, efficacy and safety were evaluated 48 h after treatment and post-treatment weekly infestations in 16 cats, against untreated controls, for 35 days. In Study 3, efficacy and safety were assessed in 8 lotilaner-treated cats until Day 35, before and after 24 h incubation of the female live ticks removed from the animals 12, 18 and 24 h after dosing and subsequent weekly infestations.

RESULTS

Efficacy was > 99% on days 23 and 37, and 100% on all other timepoints in Study 1. In Study 2 it was > 98% on Days 9 and 37, and 100% on all other days. In Study 3, on Day 0, lotilaner was > 90% efficacious, pre- and post-incubation at all time-points. On Day 7, at 12 hours after infestation, efficacy was 100%, pre- and post-incubation. On Day 14, there was a 66.5% reduction in geometric mean live tick counts in treated cats compared to controls, increasing, after incubation, to 94.4%. Afterwards, efficacy decreased below 90% while tick counts in the treated groups remained significantly lower compared to controls. At 18 hours, lotilaner was ≥ 90% efficacious through Day 37, increasing to 100% at 24 hours, on all study days, with the exception of Day 28 (98.9 and 99.1% pre- and post-incubation, respectively). There were no treatment-related adverse events.

CONCLUSIONS

At the minimum dose rate of 6 mg/kg, lotilaner was efficacious against I. ricinus ticks. In addition, lotilaner was effective against this tick within 12 hours of treatment, reaching 100% efficacy within 24 hours. Lotilaner sustained a rapid kill of newly infesting I. ricinus through 35 days. By quickly killing ticks that infest cats, lotilaner has the potential to contribute to the reduction of tick-borne pathogens transmission.

A randomized, controlled field study to assess the efficacy and safety of lotilaner (Credelio™) in controlling ticks in client-owned cats in Europe

BACKGROUND

There is a continuing need for novel approaches to tick infestations treatment and control in cats. Lotilaner, an isoxazoline with rapid onset of action, has proven its efficacy against ticks in laboratory studies. A study was undertaken to confirm lotilaner's efficacy and safety in client-owned cats, at the minimum dose of 6.0 mg/kg, against the most common ticks infesting cats in Europe.

METHODS

Twenty clinics in Germany, Hungary and Portugal participated in the study. Households with no more than three cats were randomized 2:1 to a lotilaner or fipronil group. The first household cat with at least three live, attached ticks was the primary cat. Treatments were dispensed on days 0, 28 and 56 for owner administration. Tick counts were performed on days 0, 7, 14, 21, 28, 42, 56, 70 and 84 (primary cats) and supplementary cats were assessed for safety only, on days 28, 56 and 84. Efficacy was assessed by comparing mean day 0 live attached tick counts with subsequent counts.

RESULTS

Most frequently retrieved ticks were Ixodes ricinus, Rhipicephalus sanguineus and Dermacentor reticulatus, with Ixodes hexagonus also present. In the lotilaner group (n = 112) efficacy (based on geometric mean tick counts) was between 98.3-100%. For fipronil (n = 57), efficacy was between 89.6-99.6%, with live attached ticks present on some cats at all time points. Mean tick counts in lotilaner-treated cats were significantly lower than in fipronil-treated cats on days 21, 28, 42 and 56 (P < 0.05). The mean percent efficacy over all post-enrolment visits was 99.6% and 96.4% (lotilaner and fipronil group, respectively), (P < 0.0001). Lotilaner was superior to fipronil for efficacy averaged over all time points (P < 0.0001) and on individual assessment days (day 14 to 70, P < 0.0394); it was non-inferior to fipronil on the other days. Owners successfully administered all treatments, and both products were well tolerated.

CONCLUSIONS

CredelioTM was effective and safe for the treatment of tick infestations in client-owned cats. Efficacy lasted one month and lotilaner was superior to fipronil on most assessment days. Cure rates ranged between 94.5-100% for lotilaner and 68.4-98.2% for fipronil.

Laboratory evaluation of the efficacy and speed of kill of lotilaner (Credelio™) against Ctenocephalides felis on cats

BACKGROUND

Lotilaner is approved for dogs as a chewable tablet formulation. It has separately been developed for oral administration in cats (Credelio™ chewable tablets for cats) to meet the need for an easy to use, safe and rapidly effective parasiticide and as an alternative to topical products. This paper describes two pivotal laboratory studies assessing the efficacy and speed of kill of lotilaner in cats against Ctenocephalides felis fleas following a single oral administration, at the minimum recommended dose rate of 6 mg/kg.

METHODS

Two GCP (Good Clinical Practice), blinded, randomized, negative-controlled, parallel-groups, laboratory studies were performed. In both studies, lotilaner was administered once, per os, at the minimum recommended dose of 6 mg/kg. Study 1 evaluated the efficacy of lotilaner tablets for cats against adult C. felis in experimentally infested cats, 24 h after treatment and after new weekly infestations, until day 35. Study 2 evaluated the speed of kill of lotilaner against C. felis, in cats, 8 and 12 h after treatment and after each subsequent weekly infestation, through day 35. In both studies, for each assessed time point, animals were randomized 1:1 to a lotilaner-treated or a contemporaneous negative control group of 8 cats each.

RESULTS

In both studies, the infestation in the control groups was adequate at all assessment times. In Study 1, efficacy at 24 h was 100% at all time points. In Study 2, efficacy was ≥ 97.4% at the 8 h and ≥ 98.6% at the 12 h time point, through one month. Lotilaner was well tolerated, with no product-related adverse events reported.

CONCLUSIONS

Lotilaner administered orally to cats at the minimum recommended dose rate of 6 mg/kg was effective as early as 8 hours post-administration and at 8 hours after subsequent weekly infestations of adult C. felis for at least one month. The product was well-tolerated.

A single topical fluralaner application to cats and to dogs controls fleas for 12 weeks in a simulated home environment

BACKGROUND

Fluralaner (Bravecto®, Merck Animal Health, Madison, NJ, USA) is a novel isoxazoline that provides up to 12 weeks flea and tick control when administered orally to dogs. Two assessor-blinded studies, one in dogs, the other in cats evaluated the sustained efficacy of a topical fluralaner formulation against fleas in a simulated home environment (SHE).

METHODS

Animals were ranked and blocked into groups of two using flea counts completed 24 hours following Ctenocephalides felis infestations placed on dogs on Day -64, and on cats on Day -36. Within blocks animals were randomized to a treatment group, 10 animals per group, one group to receive fluralaner spot-on (minimum dose rate for dogs, 25 mg/kg; for cats, 40 mg/kg), the other to be a sham-treated control. Animals were then placed into their SHE, one animal per pen or cage and then infested with 100 C. felis at weekly intervals. Dogs were infested from Day -56 through -21 and cats on Days -28 and -21. Fleas were counted and removed from each dog and cat on Day -1. Study animals were then held in clean pens/cages until treatment on Day 0. One day later, after treatment, all animals were returned to their home environment (SHE). Additional 50-flea challenges were placed on each animal on Days 22, 50 and 78. Fleas were counted and replaced on all animals on Day 1 and weekly thereafter for 12 weeks.

RESULTS

Arithmetic mean counts in control-group animals exceeded 10 fleas at all post-treatment assessments except on Days 1, 7 and 14. All control-group animals remained infested at each assessment from Day or 28 through Day 84, thereby validating the challenge methodology. Fluralaner efficacy was 100% on all occasions except for 2 fleas found on 1 dog on Day 1, and 3 fleas on 1 dog on Day 14. One flea was recovered from 1 fluralaner treated cat on Day 1. There were no treatment-related adverse events.

CONCLUSION

A single application of a topical formulation of fluralaner is well tolerated and highly effective in the prevention of flea infestations of dogs and cats throughout the 12 weeks following treatment.