Background The parasitic filariae responsible for onchocerciasis and lymphatic filariasis are host to an endosymbiotic bacterium, Wolbachia , which is essential to the fertility and development of the parasites. We performed a Phase-I pharmacokinetic, safety and food-effect study on single and multiple ascending doses of flubentylosin (ABBV-4083), a macrolide antibacterial with activity against Wolbachia , intended to sterilize and eliminate the parasites. Methods Seventy-eight healthy adults were exposed to flubentylosin; 36 were exposed to single ascending 40, 100, 200, 400 or 1000 mg doses; 12 received 1000 mg in the food-effect part; and 30 received multiple ascending daily doses of 100 mg for 7 days, 200 mg for 7 or 14 days, or 400 mg for 7 or 14 days. Twenty-two subjects received placebo. Results Maximum concentrations (C max ) of flubentylosin were reached after 1–2 hours, with a half-life < 4 hours at doses ≤ 400 mg. C max and AUC increased in a more than dose-proportional manner, with similar exposure after multiple dose administration. The most frequently reported adverse events were nausea (8/78, 10%) and headache (6/78, 8%). Two subjects given a single dose of flubentylosin 1000 mg in the food-effect part experienced reversible asymptomatic ALT and AST elevations at Grade 2 or Grade 4, with no elevation in bilirubin, deemed related to study drug. The effect of food on exposure parameters was minimal. No treatment-related serious adverse events were reported. Discussion Flubentylosin 400 mg for 14 days was the maximum tolerated dose in this first-in-human, Phase-I study in healthy adults. Based on preclinical pharmacokinetic/pharmacodynamic modeling, flubentylosin 400 mg once daily for 7 or 14 days is expected to be an effective dose. A Phase-II, proof-of-concept study with flubentylosin using these regimens is currently ongoing in patients with onchocerciasis in Africa.

ObjectiveThe aim was to demonstrate that continuous s.c. infusion of a soluble levodopa (LD)/carbidopa (CD) phosphate prodrug combination effectively delivers stable LD exposure via a minimally invasive and convenient mode and has the potential to treat Parkinson's disease (PD) patients who are not well controlled on oral medication.MethodsFoslevodopa and foscarbidopa were prepared and the equilibrium solubility and chemical stability examined in aqueous media with different values of pH. Solutions of foslevodopa/foscarbidopa (ratios ranging from 4:1 to 20:1) were prepared by dissolving pH‐adjusted lyophilized materials in water and infused s.c. in healthy volunteers for ≤72 hours. Frequent blood samples were collected to measure LD and CD exposure, and safety was monitored throughout the study.ResultsFoslevodopa/foscarbidopa (ABBV‐951) demonstrates high water solubility and excellent chemical stability near physiological pH, enabling continuous s.c. infusion therapy. After s.c. infusion, a stable LD pharmacokinetic (PK) profile was maintained for ≤72 hours, and the infusion was well tolerated.InterpretationPreparation of foslevodopa and foscarbidopa enables preclinical and clinical PK, safety, and tolerability studies in support of their advancement for the treatment of PD. In phase 1 clinical trials, foslevodopa/foscarbidopa demonstrates consistent and stable LD plasma exposure, supporting further studies of this treatment as a potentially transformational option for those suffering from PD. ANN NEUROL 2021;90:52–61

Oral drug absorption is a complex process depending on many factors, including the physicochemical properties of the drug, formulation characteristics and their interplay with gastrointestinal physiology and biology. Physiological-based pharmacokinetic (PBPK) models integrate all available information on gastro-intestinal system with drug and formulation data to predict oral drug absorption. The latter together with in vitro-in vivo extrapolation and other preclinical data on drug disposition can be used to predict plasma concentration-time profiles in silico. Despite recent successes of PBPK in many areas of drug development, an improvement in their utility for evaluating oral absorption is much needed. Current status of predictive performance, within the confinement of commonly available in vitro data on drugs and formulations alongside systems information, were tested using 3 PBPK software packages (GI -Sim (ver.4.1), Simcyp (R) Simulator (ver.15.0.86.0), and GastroPlus (TM) (ver.9.0.00xx)). This was part of the Innovative Medicines Initiative (IMI) Oral Biopharmaceutics Tools (OrBiTo) project. Fifty eight active pharmaceutical ingredients (APIs) were qualified from the OrBiTo database to be part of the investigation based on a priori set criteria on availability of minimum necessary information to allow modelling exercise. The set entailed over 200 human clinical studies with over 700 study arms. These were simulated using input parameters which had been harmonised by a panel of experts across different software packages prior to conduct of any simulation. Overall prediction performance and software packages comparison were evaluated based on performance indicators (Fold error (FE), Average fold error (AFE) and absolute average fold error (AAFE)) of pharmacokinetic (PK) parameters. On average, PK parameters (Area Under the Concentration-time curve (AUC(0-tlast)), Maximal concentration (C-max), half-life (t(1/2))) were predicted with AFE values between 1.11 and 1.97. Variability in FEs of these PK parameters was relatively high with AAFE values ranging from 2.08 to 2.74. Around half of the simulations were within the 2-fold error for AUC(0-tlast) and around 90% of the simulations were within 10-fold error for AUC(0-tlast). Oral bioavailability (F-oral) predictions, which were limited to 19 APIs having intravenous (i.v.) human data, showed AFE and AAFE of values 1.37 and 1.75 respectively. Across different APIs, AFE of AUC(0-tlast) predictions were between 0.22 and 22.76 with 70% of the APIs showing an AFE > 1. When compared across different formulations and routes of administration, AUC(0-tlast) for oral controlled release and i.v. administration were better predicted than that for oral immediate release formulations. Average predictive performance did not clearly differ between software packages but some APIs showed a high level of variability in predictive performance across different software packages. This variability could be related to several factors such as compound specific properties, the quality and availability of information, and errors in scaling from in vitro and preclinical in vivo data to human in vivo behaviour which will be explored further. Results were compared with previous similar exercise when the input data selection was carried by the modeller rather than a panel of experts on each in vitro test. Overall, average predictive performance was increased as reflected in smaller AAFE value of 2.8 as compared to AAFE value of 3.8 in case of previous exercise.

Our HCV research program investigated novel 2'-dihalogenated nucleoside HCV polymerase inhibitors and identified compound 1, a 5'-phosphoramidate prodrug of 2'-deoxy-2'-alpha-bromo-beta-chloro uridine. Although 1 had a favorable in vitro activity profile in HCV replicons, oral dosing in dog resulted in low levels of the active 5'-triphosphate (TP) in liver. Metabolism studies using human hepatocytes provided a simple assay for screening alternative phosphoramidate prodrug analogs. Compounds that produced high TP concentrations in hepatocytes were tested in dog liver biopsy studies. This method identified 2-aminoisobutyric acid ethyl ester (AIBEE) phosphoramidate prodrug 14, which provided 100-fold higher TP concentrations in dog liver in comparison to 1 (4 and 24 h after 5 mg/kg oral dose).

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.

There is an urgent global need for a safe macrofilaricide drug to accelerate elimination of the neglected tropical diseases onchocerciasis and lymphatic filariasis. From an anti-infective compound library, the macrolide veterinary antibiotic, tylosin A, was identified as a hit against Wolbachia. This bacterial endosymbiont is required for filarial worm viability and fertility and is a validated target for macrofilaricidal drugs. Medicinal chemistry was undertaken to develop tylosin A analogs with improved oral bioavailability. Two analogs, A-1535469 and A-1574083, were selected. Their efficacy was tested against the gold-standard second-generation tetracycline antibiotics, doxycycline and minocycline, in mouse and gerbil infection models of lymphatic filariasis (Brugia malayi and Litomosoides sigmodontis) and onchocerciasis (Onchocerca ochengi). A 1- or 2-week course of oral A-1535469 or A-1574083 provided >90% Wolbachia depletion from nematodes in infected animals, resulting in a block in embryogenesis and depletion of microfilarial worm loads. The two analogs delivered comparative or superior efficacy compared to a 3- to 4-week course of doxycycline or minocycline. A-1574083 (now called ABBV-4083) was selected for further preclinical testing. Cardiovascular studies in dogs and toxicology studies in rats and dogs revealed no adverse effects at doses (50 mg/kg) that achieved plasma concentrations >10-fold above the efficacious concentration. A-1574083 (ABBV-4083) shows potential as an anti-Wolbachia macrolide with an efficacy, pharmacology, and safety profile that is compatible with a short-term oral drug course for treating lymphatic filariasis and onchocerciasis.

Hepatitis C virus (HCV) nucleoside inhibitors have been a key focus of nearly 2 decades of HCV drug research due to a high barrier to drug resistance and pan-genotypic activity profile provided by molecules in this drug class. Our investigations focused on several potent 2'-halogenated uridine-based HCV polymerase inhibitors, resulting in the discovery of novel 2'-deoxy-2'-dihalo-uridine analogs that are potent inhibitors in replicon assays for all genotypes. Further studies to improve in vivo performance of these nucleoside inhibitors identified aminoisobutyric acid ethyl ester (AIBEE) phosphoramidate prodrugs 18a and 18c, which provide high levels of the active triphosphate in dog liver. AIBEE prodrug 18c was compared with sofosbuvir (1) by co-dosing both compounds by oral administration in dog (5 mg/kg each) and measuring liver concentrations of the active triphosphate metabolite at both 4 and 24 h post dosing. In this study, 18c provided liver triphosphate concentrations that were 6-fold higher than sofosbuvir (1) at both biopsy time points, suggesting that 18c could be a highly effective agent for treating HCV infected patients in the clinic.

Venetoclax, a selective B-cell lymphoma-2 inhibitor, is a biopharmaceutics classification system class IV compound. The aim of this study was to develop a physiologically based pharmacokinetic (PBPK) model to mechanistically describe absorption and disposition of an amorphous solid dispersion formulation of venetoclax in humans. A mechanistic PBPK model was developed incorporating measured amorphous solubility, dissolution, metabolism, and plasma protein binding. A middle-out approach was used to define permeability. Model predictions of oral venetoclax pharmacokinetics were verified against clinical studies of fed and fasted healthy volunteers, and clinical drug interaction studies with strong CYP3A inhibitor (ketoconazole) and inducer (rifampicin). Model verification demonstrated accurate prediction of the observed food effect following a low-fat diet. Ratios of predicted versus observed Cmax and area under the curve of venetoclax were within 0.8- to 1.25-fold of observed ratios for strong CYP3A inhibitor and inducer interactions, indicating that the venetoclax elimination pathway was correctly specified. The verified venetoclax PBPK model is one of the first examples mechanistically capturing absorption, food effect, and exposure of an amorphous solid dispersion formulated compound. This model allows evaluation of untested drug-drug interactions, especially those primarily occurring in the intestine, and paves the way for future modeling of biopharmaceutics classification system IV compounds.

The purpose of this study was to conduct a head-to-head comparison of different solubility-enabling formulations, and their consequent solubility-permeability interplay. The low-solubility anticancer drug etoposide was formulated in several strengths of four solubility-enabling formulations: hydroxypropyl-β-cyclodextrin, the cosolvent polyethylene glycol 400 (PEG-400), the surfactant sodium lauryl sulfate, and an amorphous solid dispersion formulation. The ability of these formulations to increase the solubility of etoposide was investigated, followed by permeability studies using the parallel artificial membrane permeability assay (PAMPA) and examination of the consequent solubility-permeability interplay. All formulations significantly increased etoposide's apparent solubility. The cyclodextrin-, surfactant-, and cosolvent-based formulations resulted in a concomitant decreased permeability that could be modeled directly from the proportional increase in the apparent solubility. On the contrary, etoposide permeability remained constant when using the ASD formulation, irrespective of the increased apparent solubility provided by the formulation. In conclusion, supersaturation resulting from the amorphous form overcomes the solubility-permeability tradeoff associated with other formulation techniques. Accounting for the solubility-permeability interplay may allow to develop better solubility-enabling formulations, thereby maximizing the overall absorption of lipophilic orally administered drugs.

ObjectiveABT-751, a novel orally available antitubulin agent, is mainly eliminated as inactive glucuronide (ABT-751G) and sulfate (ABT-751S) conjugates. We performed a pharmacogenetic investigation of ABT-751 pharmacokinetics using in-vitro data to guide the selection of genes for genotyping in a phase I trial of ABT-751.MethodsUDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) enzymes were screened for ABT-751 metabolite formation in vitro. Forty-seven cancer patients treated with ABT-751 were genotyped for 21 variants in these genes.ResultsUGT1A1, UGT1A4, UGT1A8, UGT2B7, and SULT1A1 were found to be involved in the formation of inactive ABT-751 glucuronide (ABT-751G) and sulfate (ABT-751S). SULT1A1 copy number (>2) was associated with an average 34% increase in ABT-751 clearance (P=0.044), an 18% reduction in ABT-751 AUC (P=0.045), and a 50% increase in sulfation metabolic ratios (P=0.025). UGT1A8 rs6431558 was associated with a 28% increase in glucuronidation metabolic ratios (P=0.022), and UGT1A4*2 was associated with a 65% decrease in ABT-751 C-trough (P=0.009).ConclusionThese results might represent the first example of a clinical pharmacokinetic effect of the SULT1A1 copy number variant on the clearance of a SULT1A1 substrate. A-priori selection of candidate genes guided by in-vitro metabolic screening enhanced our ability to identify genetic determinants of interpatient pharmacokinetic variability.

Veliparib (ABT-888) is largely eliminated as parent drug in human urine (70% of the dose). Renal unbound clearance exceeds glomerular filtration rate, suggesting the involvement of transporter-mediated active secretion. Clinically relevant pharmacokinetic interactions in the kidney have been associated with OAT1, OAT3, OCT2, MATE1, and MATE2K. In the present study, interactions of veliparib with these transporters were investigated. Veliparib inhibited OAT1, OAT3, OCT2, MATE1, and MATE2K with IC50 values of 1371, 505, 3913, 69.9, and 69.5μM, respectively. The clinical unbound maximum plasma concentration of veliparib after single oral dose of 50mg (0.45μM) is manyfold lower than IC50 values for OAT1, OAT3, OCT2, MATE1, or MATE2K. These results indicate a low potential for drug–drug interaction (DDI) with OAT1/3, OCT2, or MATE1/2K. Additional studies demonstrated that veliparib is a substrate of OCT2. In Oct1/Oct2 double-knockout mice, the plasma exposure of veliparib was increased by 1.5-fold, and the renal clearance was decreased by 1.8-fold as compared with wild-type mice, demonstrating that organic cation transporters contribute to the renal elimination in vivo. In summary, the in vitro transporter data for veliparib predicts minimal potential for an OAT1/3-, OCT2-, and MATE1/2K-mediated DDI given the clinical exposure after single oral dose of 50mg.

Recently, we have revealed a trade-off between solubility increase and permeability decrease when solubility-enabling oral formulations are employed. We have shown this trade-off phenomenon to be ubiquitous, and to exist whenever the aqueous solubility is increased via solubilizing excipients, regardless if the mechanism involves decreased free fraction (cyclodextrins complexation, surfactant micellization) or simple cosolvent solubilization. Discovering a way to increase drug solubility without concomitant decreased permeability represents a major advancement in oral delivery of lipophilic drugs and is the goal of this work. For this purpose, we sought to elucidate the solubility-permeability interplay when increased apparent solubility is obtained via supersaturation from an amorphous solid dispersion (ASD) formulation. A spray-dried ASD of the lipophilic drug progesterone was prepared in the hydrophilic polymer hydroxypropyl methylcellulose acetate succinate (HPMC-AS), which enabled supersaturation up to 4× the crystalline drug's aqueous solubility (8 μg/mL). The apparent permeability of progesterone from the ASD in HPMC-AS was then measured as a function of increasing apparent solubility (supersaturation) in the PAMPA and rat intestinal perfusion models. In contrast to previous cases in which apparent solubility increases via cyclodextrins, surfactants, and cosolvents resulted in decreased apparent permeability, supersaturation via ASD resulted in no decrease in apparent permeability with increasing apparent solubility. As a result, overall flux increased markedly with increasing apparent solubility via ASD as compared to the other formulation approaches. This work demonstrates that supersaturation via ASDs has a subtle yet powerful advantage over other solubility-enabling formulation approaches. That is, increased apparent solubility may be achieved without the expense of apparent intestinal membrane permeability. Thus, supersaturation via ASDs presents a markedly increased opportunity to maximize overall oral drug absorption.

We have recently reported the interplay between apparent aqueous solubility and intestinal membrane permeability, showing the trade-off between the two when using cyclodextrin- and surfactant-based systems as solubility-enabling formulations. In these cases, the decreased permeability could be attributed directly to decreased free fraction of drug due to the complexation/micellization inherent in these solubilization methods. The purpose of this study was to investigate the direct solubility-permeability interplay, using formulations in which complexation is not the mechanism for increased solubilization. The apparent aqueous solubility (S(aq)) and rat intestinal permeability (P(eff)) of the lipophilic drug progesterone were measured in systems containing various levels of the cosolvents propylene glycol and PEG-400, since this solubilization method does not involve decreased free fraction. Thermodynamic activity was maintained equivalent in all permeability studies (75% equilibrium solubility). Both cosolvents increased progesterone S(aq) in nonlinear fashion. Decreased P(eff) with increased S(aq) was observed, despite the constant thermodynamic activity, and the nonrelevance of free fraction. A mass-transport analysis was developed to describe this interplay. The model considers the effects of solubilization on the membrane permeability (P(m)) and the unstirred water layer (UWL) permeability (P(aq)), to predict the overall P(eff) dependence on S(aq). The analysis revealed that (1) the effective UWL thickness quickly decreases with ↑S(aq), such that P(aq) markedly increases with ↑S(aq); (2) the apparent membrane/aqueous partitioning decreases with ↑S(aq), thereby reducing the thermodynamic driving force for permeability such that ↓P(m) with ↑S(aq); (3) since ↑P(aq) and ↓P(m) with ↑S(aq), the UWL is shorted out and P(eff) becomes membrane control with ↑S(aq). The model enabled excellent quantitative prediction of P(eff) as a function of S(aq). This work demonstrates that a direct trade-off exists between the apparent solubility and permeability, which must be taken into account when developing solubility-enabling formulations to strike the optimal solubility-permeability balance, in order to maximize the overall oral absorption.

Neuronal acetylcholine nicotinic receptors (nAChRs) are targets for the development of novel treatments of brain diseases. However, adverse effects (for example, emesis or nausea) associated with high drug maximal exposures or Cmax at nAChRs often hinder the advancement of experimental compounds in clinical trials. Therefore, it is essential to explore the feasibility of maintaining exposures below a predetermined Cmax while sustaining targeted CNS effects. By use of a [123I]5-IA [5-[123I]iodo-3-[2(S)-azetidinylmethoxy]pyridine] displacement SPECT imaging paradigm in nonhuman primates, we compared brain nAChR binding activity elicited by either a bolus injection or by slow infusion of an identical dose of a novel neuronal nicotinic agonist, ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine dihydrochloride], where the slow infusion scheme was derived from a two-compartment pharmacokinetic modeling designed to limit the Cmax. We determined [123I]5-IA displacement using doses of ABT-089 (0.04, 0.4, and 1.0 mg/kg i.v.) that encompassed efficacious drug exposures in nonhuman primates and examined the relationship between ABT-089 displacement ratios and plasma exposures. Our results indicated that calculated displacement ratios were quite similar between the two different dosing regimens despite substantial differences in Cmax. In addition, displacement ratios correlated well with drug exposures calculated as the area-under-curve (AUC) of plasma concentration and varied in a dose-dependent manner, suggesting that displacement ratios are driven by the AUC of drug plasma exposure but not Cmax. Our data demonstrate the feasibility of predicting plasma exposures using a two-compartment pharmacokinetic model and its potential for optimizing dosing regimens.