Macrofilaricidal Benzimidazole-Benzoxaborole Hybrids as an Approach to the Treatment of River Blindness: Part 2. Ketone Linked Analogs.

The optimization of a series of benzimidazole-benzoxaborole hybrid molecules linked via a ketone that exhibit good activity against Onchocerca volvulus, a filarial nematode responsible for the disease onchocerciasis, also known as river blindness, is described. The lead identified in this series, 21 (AN15470), was found to have acceptable pharmacokinetic properties to enable an evaluation following oral dosing in an animal model of onchocerciasis. Compound 21was effective in killing worms implanted in Mongolian gerbils when dosed orally as a suspension at 100 mg/kg/day for 14 days but not when dosed orally at 100 mg/kg/day for 7 days.

Macrofilaricidal Benzimidazole-Benzoxaborole Hybrids as an Approach to the Treatment of River Blindness: Part 1. Amide Linked Analogs.

A series of benzimidazole-benzoxaborole hybrid molecules linked via an amide linker are described that exhibit good in vitro activity against Onchocerca volvulus, a filarial nematode responsible for the disease onchocerciasis, also known as river blindness. The lead identified in this series, 8a (AN8799), was found to have acceptable pharmacokinetic properties to enable evaluation in animal models of human filariasis. Compound 8a was effective in killing Brugia malayi, B. pahangi, and Litomosoides sigmodontis worms present in Mongolian gerbils when dosed subcutaneously as a suspension at 100 mg/kg/day for 14 days but not when dosed orally at 100 mg/kg/day for 28 days. The measurement of plasma levels of 8a at the end of the dosing period and at the time of sacrifice revealed an interesting dependence of activity on the extended exposure for both 8a and the positive control, flubendazole.

Solid lipid nanoparticle-based dissolving microneedles: A promising intradermal lymph targeting drug delivery system with potential for enhanced treatment of lymphatic filariasis.

Conventional oral therapy of lymphatic filariasis drugs is only effective to kill microfilariae in the bloodstream, but is often ineffective to kill adult filarial (macrofilariae) in the complex anatomy of the lymphatic system. The encapsulation of drugs into lipid-based nanoparticles with sizes of <100nm, and administration intradermally, could be used to enhance lymphatic uptake. Therefore, we developed an innovative approach, using solid lipid nanoparticles (SLNs) and dissolving microneedles (MNs) to deliver antifilariasis drugs, namely doxycycline, diethylcarbamazine and albendazole, intradermally. The SLNs were prepared from Geleol® and Tween®80 as a lipid matrix and stabilizer, respectively. The formulations were optimized using a central composite design, producing SLNs with sizes of <100nm. Drug release was sustained over 48h from SLNs, compared to pure drugs. The SLNs were then incorporated into a polymeric hydrogel which was casted to form SLNs-loaded MNs. SLNs-loaded MNs exhibited sufficient mechanical and insertion properties. Importantly, dermatokinetic studies showed that>40% of drugs were retained in the dermis of excised neonatal porcine skin up to 24h post-MN application, indicating the high possibility of the SLNs to be taken by the lymphatic system. In in vivo studies, the maximal lymph concentrations of the three drugs in rat, achieved following intradermal delivery, ranged between 4- and 7-fold higher than that recorded after oral administration. Additionally, compared to oral administration, despite the lower plasma Cmax and organ-distribution, the AUC and relative bioavailability of the three drugs in rat plasma was also higher using our delivery approach. Accordingly, this delivery approach could maximize the drugs concentrations in the lymph system without essentially increasing their plasma concentrations. This could potentially deliver the drugs efficiently to the bloodstream, where the microfilariae reside, while also targeting drug to the lymph nodes, where filarial nematodes reside in infected patients, leading to an effective therapy for lymphatic filariasis.

Pharmacokinetics, safety, and efficacy of a single co-administered dose of diethylcarbamazine, albendazole and ivermectin in adults with and without Wuchereria bancrofti infection in Côte d'Ivoire.

BACKGROUND: A single co-administered dose of ivermectin (IVM) plus diethylcarbamazine (DEC) plus albendazole (ALB), or triple-drug therapy, was recently found to be more effective for clearing microfilariae (Mf) than standard DEC plus ALB currently used for mass drug administration programs for lymphatic filariasis (LF) outside of sub-Saharan Africa. Triple-drug therapy has not been previously tested in LF-uninfected individuals from Africa. This study evaluated the pharmacokinetics (PK), safety, and efficacy of triple-drug therapy in people with and without Wuchereria bancrofti infection in West Africa. METHODS: In this open-label cohort study, treatment-naïve microfilaremic (>50 mf/mL, n = 32) and uninfected (circulating filarial antigen negative, n = 24) adults residing in Agboville district, Côte d'Ivoire, were treated with a single dose of IVM plus DEC plus ALB, and evaluated for adverse events (AEs) until 7 days post treatment. Drug levels were assessed by liquid chromatography and mass spectrometry. Persons responsible for assessing AEs were blinded to participants' infection status. FINDINGS: There was no difference in AUC0-inf or Cmax between LF-infected and uninfected participants (P>0.05 for all comparisons). All subjects experienced mild AEs; 28% and 25% of infected and uninfected participants experienced grade 2 AEs, respectively. There were no severe or serious adverse events. Only fever (16 of 32 versus 4 of 24, P<0.001) and scrotal pain/swelling in males (6 of 20 versus 0 of 12, P = 0.025) were more frequent in infected than uninfected participants. All LF positive participants were amicrofilaremic at 7 days post-treatment and 27 of 31 (87%) remained amicrofilaremic 12 months after treatment. CONCLUSIONS: Moderate to heavy W. bancrofti infection did not affect PK parameters for IVM, DEC or ALB following a single co-administered dose of these drugs compared to uninfected individuals. The drugs were well tolerated. This study confirmed the efficacy of the triple-drug therapy for clearing W. bancrofti Mf and has added important information to support the use of this regimen in LF elimination programs in areas of Africa without co-endemic onchocerciasis or loiasis. TRIAL REGISTRATION: ClinicalTrials.gov NCT02845713.

Discovery of ABBV-4083, a novel analog of Tylosin A that has potent anti-Wolbachia and anti-filarial activity.

There is a significant need for improved treatments for onchocerciasis and lymphatic filariasis, diseases caused by filarial worm infection. In particular, an agent able to selectively kill adult worms (macrofilaricide) would be expected to substantially augment the benefits of mass drug administration (MDA) with current microfilaricides, and to provide a solution to treatment of onchocerciasis / loiasis co-infection, where MDA is restricted. We have identified a novel macrofilaricidal agent, Tylosin A (TylA), which acts by targeting the worm-symbiont Wolbachia bacterium. Chemical modification of TylA leads to improvements in anti-Wolbachia activity and oral pharmacokinetic properties; an optimized analog (ABBV-4083) has been selected for clinical evaluation.

Boron-Pleuromutilins as Anti- Wolbachia Agents with Potential for Treatment of Onchocerciasis and Lymphatic Filariasis.

A series of pleuromutilins modified by introduction of a boron-containing heterocycle on C(14) of the polycyclic core are described. These analogs were found to be potent anti- Wolbachia antibiotics and, as such, may be useful in the treatment of filarial infections caused by Onchocerca volvulus, resulting in Onchocerciasis or river blindness, or Wuchereria bancrofti and Brugia malayi and related parasitic nematodes resulting in lymphatic filariasis. These two important neglected tropical diseases disproportionately impact patients in the developing world. The lead preclinical candidate compound containing 7-fluoro-6-oxybenzoxaborole (15, AN11251) was shown to have good in vitro anti- Wolbachia activity and physicochemical and pharmacokinetic properties providing high exposure in plasma. The lead was effective in reducing the Wolbachia load in filarial worms following oral administration to mice.

Macrofilaricidal efficacy of single and repeated oral and subcutaneous doses of flubendazole in Litomosoides sigmodontis infected jirds.

Flubendazole (FBZ) is highly efficacious against filarial nematodes after parenteral administration and presents a promising macrofilaricidal drug candidate for the elimination of onchocerciasis and other filariae. In the present study the efficacy of a newly developed bioavailable amorphous solid dispersion (ASD) oral formulation of FBZ was investigated in the Litomosoides sigmodontis jird model. FBZ was administered to chronically infected, microfilariae-positive jirds by single (40mg/kg), repeated (2, 6 or 15mg/kg for 5 or 10 days) oral (OR) doses or single subcutaneous (SC) injections (2 or 10mg/kg). Jirds treated with 5 SC injections at 10mg/kg served as positive controls, with untreated animals used as negative controls. After OR doses, FBZ is rapidly absorbed and cleared and the exposures increased dose proportionally. SC administered FBZ was slowly released from the injection site and plasma levels remained constant up to necropsy eight weeks after treatment end. Increasing single SC doses caused less than dose-proportional exposures. At necropsy, all animals receiving 1x or 5x 10mg/kg SC FBZ had cleared all adult worms and the 1x 2mg/kg SC treatment had reduced the adult worm burden by 98%. 10x 15mg/kg OR FBZ reduced the adult worm burden by 95%, whereas 1x 40mg/kg and 5x 15mg/kg OR reduced the worm burden by 85 and 84%, respectively. Microfilaremia was completely cleared at necropsy in all animals of the SC treatment regimens, while all oral FBZ treatment regimens reduced the microfilaremia by >90% in a dose and duration dependent manner. In accordance, embryograms from female worms revealed a FBZ dose and duration dependent inhibition of embryogenesis. Histological analysis of the remaining female adult worms showed that FBZ had damaged the body wall, intestine and most prominently the uterus and uterine content. Results of this study demonstrate that single and repeated SC injections and repeated oral administrations of FBZ have an excellent macrofilaricidal effect.

Efficacy, Safety, and Pharmacokinetics of Coadministered Diethylcarbamazine, Albendazole, and Ivermectin for Treatment of Bancroftian Filariasis.

BACKGROUND: Available treatments for lymphatic filariasis (LF) are limited in their longterm clearance of microfilaria from the blood. The safety and efficacy of a single-dose triple-drug therapy of the antifilarial drugs diethylcarbamazine (DEC), ivermectin (IVM), and albendazole (ALB) for LF are unknown. METHODS: We performed a pilot study to test the efficacy, safety, and pharmacokinetics of single-dose DEC, IVM, and ALB in Wuchereria bancrofti-infected Papua New Guineans. Adults were randomized into 2 treatment arms, DEC 6 mg/kg + ALB 400 mg (N = 12) or DEC 6 mg/kg + ALB 400 mg + IVM 200 µg/kg (N = 12), and monitored for microfilaria, parasite antigenemia, adverse events (AEs), and serum drug levels. RESULTS: Triple-drug therapy induced >2-log reductions in microfilaria levels at 36 and 168 hours after treatment compared with approximately 1-log reduction with 2 drugs. All 12 individuals who received 3 drugs were microfilaria negative 1 year after treatment, whereas 11 of 12 individuals in the 2-drug regimen were microfilaria positive. In 6 participants followed 2 years after treatment, those who received 3 drugs remained microfilaria negative. AEs, particularly fever, myalgias, pruritus, and proteinuria/hematuria, occurred in 83% vs 50% of those receiving triple-drug compared to 2-drug treatment respectively (P = .021); all resolved within 7 days after treatment. No serious AEs were observed in either group. There was no significant effect of IVM on DEC or ALB drug levels. CONCLUSIONS: Triple-drug therapy is safe and more effective than DEC + ALB for Bancroftian filariasis and has the potential to accelerate elimination of lymphatic filariasis. CLINICAL TRIALS REGISTRATION: NCT01975441.

Perceptive solutions to anti-filarial chemotherapy of lymphatic filariasis from the plethora of nanomedical sciences.

INTRODUCTION: Growing interest in the application of nanotechnology to treat lymphatic filariasis (LF) implies that the imminent medical arsenal of this interesting technology is attractive for health authorities. Currently, they are completely dependent on friendly oral mass drug (anti-filarials) administration to eliminate this morbid disease and are now looking for new alternatives to bring about further improvements. AREAS COVERED: A plethora of issues affecting the oral bioavailability of the mainstay human lymphatic filarial drugs, leading to meager pharmacokinetics and pharmacodynamics issues in anti-filarial chemotherapy are identified. Various important nanomedical drug delivery systems are highlighted and their solutions provided. A conceptual resolution to strictly arrest the transmission of LF in endemic areas is also presented. FUTURE PERSPECTIVES: Unless the solutions for pharmacokinetic tribulations and the measurement of factual pharmacodynamic endpoints for the existing anti-filarial drugs are evaluated using relevant approaches, health authorities will not be able to devise optimal treatment regimens for affected patients. Contemporary therapeutic paradigms need to be shifted toward the upcoming schemes of nanopharmaceutical sciences, which have enormous potential to advance the community-directed management of this tropical disease by improving the pharmacokinetic and pharmacodynamic properties of the filaricidal agents.

Therapeutic efficacy of poly (lactic-co-glycolic acid) nanoparticles encapsulated ivermectin (nano-ivermectin) against brugian filariasis in experimental rodent model.

The present study reports on the antifilarial activity of poly (lactic-co-glycolic acid) nanoparticles encapsulated ivermectin (nano-IVM) against human lymphatic filariid Brugia malayi in rodent host Mastomys coucha. Nano-IVM was prepared and optimized by nanoprecipitation method. The selected nano-IVM (F5) showed a uniform spherical shape with 96 nm diameter and 74.12 % entrapment efficiency, and when used at a suboptimal dose of 100 µg/kg body weight, completely eliminated filarial parasites from systemic circulation on 60 days post-infection in animals inflicted with B. malayi. In contrast, the coadministration of nano-IVM (F5) along with standard filaricide diethylcarbamazine (DEC) was found to be competent enough to suppress microfilarial stage of parasites and successfully eliminated microfilaria at 45 days posttreatment. However, the free form of both the drugs alone or in combination was unable to impart such suppression and followed by recurrence of the infection. Interestingly, nano-IVM (F5) was also found to be effective against adult stage parasites causing 36.67 % worm mortality and 75.89 % in combination with DEC; however, female sterilization remain almost similar. Thus, the combination of entrapped IVM with DEC exhibited enhanced microfilaricidal and marginally better macrofilaricidal efficacy than any of the single formulation or drugs combination.

Improved antifilarial activity of ivermectin in chitosan-alginate nanoparticles against human lymphatic filarial parasite, Brugia malayi.

The current antifilarial treatments are not up to the mark partly due to deep location of filarial parasites in the human lymphatic system. We report here on the improvement in the antifilarial activity of ivermectin (IVM) using chitosan-alginate nanoparticles prepared by modified complex coacervation method. The nanoparticles were spherical having 155 nm size and 4.56 and 75.67% loading and entrapment efficiency respectively for IVM. The delivery system maintained the sustained release and significantly augmented the microfilaricidal (MIF) activity at a single low dose (200 µg/kg body weight, subcutaneously) in contrast to much higher dose of free ivermectin (400 µg/kg body weight, subcutaneously) against human lymphatic filariid, Brugia malayi in rodent host, Mastomys coucha. To substantiate increase in MIF activity, pharmacokinetics study was designed on Wistar rats which revealed a greater peak plasma concentration (45.3 ± 1.79 ng/ml), area under the concentration curve (298 ± 38.7 ng d/ml) and extended mean residence time (23.4 ± 8.56 days)of IVM in chitosan-alginate nanoparticles. Administration of 25 mg/kg of diethylcarbamazine following nanoparticle therapy significantly improved the MIF and macrofilaricidal action of encapsulated drug and was considered superior in this study.

Comparison of the pharmacokinetics of moxidectin and ivermectin after oral administration to beagle dogs.

This study compares plasma disposition kinetics of ivermectin and moxidectin after oral administration to beagle dogs experimentally infected with the filarial parasite, Brugia pahangi. Sixteen dogs were selected and randomly allocated into two groups of eight dogs each. Animals in each group received either ivermectin or moxidectin by oral route at a dose of 250 microg/kg. Blood samples were collected from 0.5 h up to 56 days post-treatment and the plasma was analysed by high performance liquid chromatography (HPLC). The obtained data were analysed by compartmental and non-compartmental pharmacokinetic techniques. Peak plasma concentrations (C(max)) of 234.0 +/- 64.3 ng/ml (mean +/- SD) were obtained for moxidectin and 132.6 +/- 43.0 ng/ml for ivermectin. The terminal elimination half-life was significantly (p<0.01) longer in the moxidectin treated group (621.3 +/- 149.3 h) than for ivermectin treated group (80.3 +/- 29.8 h). A significantly (p< 0.01) larger V(ss)/F was obtained for moxidectin (19.21 +/- 3.61 l/kg) compared with ivermectin (5.35 +/- 1.29 l/kg). The mean estimates of CL/F of moxidectin and ivermectin were 0.0220 +/- 0.00381 and 0.0498 +/- 0.0179 l/h/kg, respectively. The comparative plasma disposition kinetics of ivermectin and moxidectin in dogs is reported for the first time.

Temporary shift of microfilariae of Brugia pahangi from the lungs to muscles in Mongolian jirds, Meriones unguiculatus, after a single injection of diethylcarbamazine.

A single-dose treatment with diethylcarbamazine (DEC) reduced microfilaria (mf) counts of Brugia pahangi by >90% at 30 min post-treatment in Mongolian jirds (Meriones unguiculatus). The reduction was followed by a rapid increase in microfilaremia, with the count reaching pretreatment level in 3 hr. The mechanisms behind this temporary reduction of mf were investigated. Without treatment, mf accumulated in the lungs. At 30 min post-treatment, they had moved from the lungs and accumulated in the muscle. At the same time, electron microscopy revealed many mf in the muscle interstitium. DEC concentrations at 30 min were much lower in the muscle (12.2 microg/g of tissue) than in the lungs, liver, and kidneys (19.8-40.7 microg/g), all of which declined to < 0.6 microg/g by 3 hr. The presence of mf in the muscle would be advantageous for avoiding high DEC concentrations, and their extravascular location could prevent attack by host effector cells.

The co-administration of ivermectin and albendazole--safety, pharmacokinetics and efficacy against Onchocerca volvulus.

A randomized, double-blind, placebo-controlled trial was conducted, to determine whether the co-administration of ivermectin with albendazole is safe and more effective against Onchocerca volvulus than ivermectin alone, and whether a significant pharmacokinetic interaction occurs. Forty-two male onchocerciasis patients received ivermectin (200 mug/kg) alone, albendazole (400 mg) alone or the combination. Safety was determined from the results of detailed clinical and laboratory examinations before treatment, during hospitalization and on day 30. Microfilaricidal efficacy was estimated from the reductions in skin counts between day 0 (pretreatment) and day 30. To determine efficacy against the adult worms, two independent observers examined histology slides prepared from nodules excised on day 180; changes in the skin counts of skin microfilariae between days 30 and 365 provided additional indicators of the level of adulticidal activity. Pharmacokinetic parameters for ivermectin and albendazole sulphoxide were defined over 72 h post-treatment. The co-administration of ivermectin with albendazole did not produce more severe adverse effects than ivermectin alone. Both nodule examiners found that the combination was not macrofilaricidal and that it was not clearly superior to ivermectin alone in the effects on reproductive activity; this was supported by the similar efficacy of the two regimens in the suppression of skin microfilariae. There was no significant pharmacokinetic interaction. Although the co-administration of ivermectin with albendazole appears safe, it offers no advantage over ivermectin alone in the control of onchocerciasis. The combination does not require an alteration in the dosage of either component.

Pharmacokinetics of diethylcarbamazine after single oral dose at two different times of day in human subjects.

In most Wuchereria bancrofti and Brugia malayi infections, the microfilaria are found in the blood in greatest number between 10 p.m. and 2 a.m., indicating that chronotherapy may be beneficial in treating such infections. This study reports the influence of time of administration on the pharmacokinetics of diethylcarbamazine (DEC) in healthy volunteers. The study was conducted in 12 healthy volunteers by administering a 150 mg single oral dose of diethylcarbamazine citrate at 0600 or 1800 h in a balanced crossover design with the approval of an institutional ethics committee. The subjects fasted for about 10 hours before and 3 hours after drug treatment. Blood samples were collected at predetermined time intervals, and the drug content in the serum was estimated using HPLC with an electrochemical detector. Pharmacokinetic analysis was performed using noncompartmental methods employing WinNonlin (version 3.1), and the means of various pharmacokinetic parameters were compared for any dosing time-related changes using a paired t-test at a probability level of 95%. The mean +/- SD values of pharmacokinetic parameters of DEC for the treatments at 0600 versus 1800 h were as follows: Cmax, 500+/-227 versus 637+/-401 ng/ml; tmax, 2.3+/-0.7 versus 2.7+/-1 h; Ka, 2.23+/-0.72 versus 1.96+/-0.97 h(-1); t1/2, 14.6+/-6.7 versus 11.4+/-4.9 h; AUC0-t, 5,334+/-1,853 versus 6,901+/-4,203 ng x h/ml; AUC0-infinity, 5,840+/-1,922 versus 7,220+/-4,205 ng x h/ml; CL/F, 36,058+/-19,011 versus 32,189+/-25,293 ml/h/kg; Vd/F, 570+/-225 versus 533+/-447 L; and MRT 17.7+/-5.9 versus 15.3+/-5.2 h. None of the parameters was significantly changed (p > 0.05) as a function of time of administration.

Effect of activated charcoal on diethylcarbamazine absorption in humans.

We investigated the effect of the oral binder-activated charcoal on the excretion of diethylcarbamazine. Six healthy volunteers were given 150 mg diethylcarbamazine with 350 mL water each. One and 2 weeks later, they received 150 mg diethylcarbamazine plus 7.5 and 15 g activated charcoal, respectively, in 350 mL water as a charcoal slurry. Urinary levels of diethylcarbamazine were measured spectrophotometrically from 1 to 72 hours after ingestion in three different periods. Treatment with activated charcoal led to 5.4% urinary recovery of diethylcarbamazine, decreased excretion rate, and a much lower plateau indicator of reduced absorption. Activated charcoal reduces the absorption and urinary excretion rate of diethylcarbamazine by adsorbing it in the gastrointestinal tract.

Effects of 2-deoxy-D-glucose on Acanthocheilonema viteae: rodent filariids as studied by multinuclear NMR spectroscopyt.

A well known glucose antimetabolite, 2-deoxy glucose (2DG) widely used in chemotherapy of cancer along with radiation, was evaluated as an antifilarial agent by nuclear magnetic resonance. The uptake and metabolism of 2DG in the experimental filarial infection Acanthocheilonema viteae was studied by in vivo multinuclear NMR. An unusually long retention time of 2DG6P within these parasites was observed on continuous 31P NMR monitoring, along with a decrease in ATP levels. These results led to therapeutic investigation in A. viteae infected host Mastomys coucha. 2DG showed a remarkable adulticidal activity (73.6%) with 50% sterilization of surviving female worms at a dose of 250 mg/kg x 5, p.o. NMR observations and activity profile substantiate the findings of one another, directed towards the hitting of bioenergetic machinery of A. viteae by macrofilaricidal agent (2DG).

Acceleration of body clearance of diethylCarbamazine by oral activated charcoal.

The effect of activated charcoal (AC) on body clearance of diethylcarbamazine (DEC) was investigated in six healthy volunteers. On three occasions at weekly intervals, each subject received 150 mg of DEC with 350 ml of water. One and two weeks later, 150 mg of DEC plus 7.5 g and 15 g of AC, respectively, in 350 ml of water as a charcoal slurry. The non-renal clearance of DEC expressed as the total body clearance of DEC was increased after treatment with AC. The 45.2, 79.6 percent and 58.6, 81.6 percent reductions in maximum concentration and area under the concentration-time curve, respectively, suggest an appreciable adsorption of DEC by AC (7.5 and 15 g) in the gut. Serum eliminating half-life was decreased upon treatment with AC (7.5 and 15 g). These results indicate that AC accelerates the body clearance of DEC by increasing non-renal elimination of the drug.

Determination of 6,4'-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]py ridine in plasma and whole blood by high-performance liquid chromatography.

A selective and sensitive HPLC assay for the quantitative determination of a new antifilarial drug, 6,4'-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]pyr idine (CDR 101) is described. After extraction from plasma and blood, CDR 101 was analysed using a C18 Nucleosil ODS column (250x4.6 mm, 5 microm particle size) and mobile phase of acetonitrile-0.05 M ammonium acetate adjusted to pH 3.0, with UV detection at 318 nm. The mean recoveries of CDR 101 in plasma and blood over a concentration range of 25-500 ng/ml were 95.5+/-2.01% and 83.3+/-1.87%, respectively. The within-day and day-to-day coefficient of variations for plasma were 3.23-6.21% and 2.59-9.90%, respectively, those for blood were 2.59-5.92% and 2.89-6.82%, respectively. The minimum detectable concentration for CDR 101 was 1 ng/ml in plasma and 2.5 ng/ml in whole blood. This method was found to be suitable for clinical pharmacokinetic studies.