In Vitro ADME and Preclinical Pharmacokinetics of Ulotaront, a TAAR1/5-HT1A Receptor Agonist for the Treatment of Schizophrenia.

PURPOSE: Ulotaront (SEP-363856) is a TAAR1 agonist with 5-HT1A agonist activity currently in clinical development for the treatment of schizophrenia. The objectives of the current study were to characterize the in vitro ADME properties, preclinical PK, and to evaluate the DDI potential of ulotaront and its major metabolite SEP-383103. METHODS: Solubility, permeability, plasma protein binding, CYP inhibition and induction, transporter inhibition and uptake studies were conducted in vitro. Phenotyping studies were conducted using recombinant human CYPs and FMOs, human liver microsomes and human liver homogenates. Preclinical plasma and brain pharmacokinetics were determined after a single intraperitoneal, intravenous, and oral administration of ulotaront. RESULTS: Ulotaront is a compound of high solubility, high permeability, and low binding to plasma proteins. Ulotaront metabolism is mediated via both NADPH-dependent and NADPH-independent pathways, with CYP2D6 as the major metabolizing enzyme. Ulotaront is an inducer of CYP2B6, and an inhibitor of CYP2D6, OCT1 and OCT2, while SEP-383103 is neither a CYP inducer nor a potent inhibitor of CYPs and human transporters. Ulotaront exhibits rapid absorption, greater than 70% bioavailability, approximately 3.5 L/kg volume of distribution, 1.5-4 h half-life, 12-43 ml/min/kg clearance, and good penetration across the blood-brain barrier in preclinical species. CONCLUSIONS: Ulotaront has been designated as a BCS1 compound by US FDA. The ability of ulotaront to penetrate the blood-brain barrier for CNS targeting has been demonstrated in mice and rats. The potential for ulotaront and SEP-383103 to act as perpetrators of CYP and transporter-mediated DDIs is predicted to be remote.

Population pharmacokinetic and pharmacodynamic analysis of BIIB023, an anti-TNF-like weak inducer of apoptosis (anti-TWEAK) monoclonal antibody.

AIMS: Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) is implicated in the pathogenesis of lupus nephritis. This study evaluated the pharmacokinetics, using the population approach, and pharmacodynamics of BIIB023, an anti-TWEAK monoclonal antibody, in healthy Chinese, Japanese and Caucasian volunteers. METHODS: In this single-dose, randomized, double-blind, phase 1 study of BIIB023 in healthy volunteers, BIIB023 was administered by intravenous infusion (3 or 20 mg kg(-1) ) on Day 1; follow-up occurred through Day 71. BIIB023 serum concentration was measured using a validated enzyme-linked immunosorbent assay; BIIB023 concentration-time data were subjected to noncompartmental analysis. Population pharmacokinetic analysis was performed using data from this study and a prior phase 1 study of BIIB023 in subjects with rheumatoid arthritis. Soluble TWEAK and TWEAK: BIIB023 complex were evaluated. RESULTS: There were no differences in BIIB023 pharmacokinetics requiring dose adjustment among the three ethnic groups or between healthy volunteers and arthritis patients. BIIB023 central compartment volume (3050 ml) and clearance (7.42 ml h(-1) ) were comparable to those observed for other monoclonal antibody drugs. BIIB023 serum exposure increased in a dose-dependent manner in all groups, but not in direct proportion to dose level; at concentrations below ~10 µg ml(-1) , nonlinear clearance was observed. Soluble TWEAK levels decreased to below the level of quantitation after BIIB023 treatment, with concomitant changes in TWEAK: BIIB023 complex levels. CONCLUSIONS: No clinically meaningful differences were observed in BIIB023 pharmacokinetic and pharmacodynamic properties in healthy Chinese, Japanese and Caucasian volunteers; pharmacodynamic measures suggested target engagement. TWEAK may be an attractive therapeutic target for lupus nephritis treatment.

A phase 1, open-label, dose-escalation study of BIIB022 (anti-IGF-1R monoclonal antibody) in subjects with relapsed or refractory solid tumors.

PURPOSE: The IGF-1R signaling pathway has been implicated in multiple cancers as important for cell survival, proliferation, invasion and metastasis. BIIB022 is a non-glycosylated human IgG4 monoclonal antibody (mAb) with specificity for IGF-1R. Unlike other anti-IGF1R antibodies, BIIB022 has no effector functions. Additionally, inhibition is via an allosteric rather than competitive mechanism, which further differentiates this antibody from others. We sought to determine the safety and tolerability of BIIB022 and determine the pharmacokinetic (PK) and pharmacodynamic (PD) profile of this antibody. METHODS: A multi-institutional phase I study evaluated the safety of escalating doses of BIIB022 given IV q3wk until progression or unacceptable toxicity in patients with advanced solid tumors. Five sequential BIIB022 dose cohorts were evaluated using a standard 3 + 3 dose-escalation design (1.5, 5. 10, 20, 30 mg/kg); 10 additional patients were treated at the recommended phase 2 dose. RESULTS: 34 patients were treated. Toxicities were manageable and mostly low grade; grade 3-4 hyperglycemia was not observed. No RECIST responses were observed, although three patients had metabolic responses associated with prolonged stable disease. The PK of BIIB022 was nearly linear in the dose range from 10 to 30 mg/kg, with some nonlinearity at lower doses (1.5-5.0 mg/kg), likely due to target-mediated drug disposition of BIIB022 at low serum concentrations. PD analyses showed decrease in IGF-1R levels on leucocytes, with stable serum values of IGF-1 and IGF-2. CONCLUSIONS: BIIB022 can be safely given at 30 mg/kg IV every 3 weeks with preliminary evidence of biological activity in selected patients.

Evaluation of OCT2-mediated drug-drug interactions between ulotaront and metformin in subjects with schizophrenia.

Ulotaront (SEP-363856) is a TAAR1 agonist, with 5-HT1A agonist activity, currently in clinical development for the treatment of schizophrenia. In vitro studies indicate ulotaront is an OCT2-specific inhibitor with IC50 of 1.27 µM. The primary objective of this study is to determine if a single dose of ulotaront affects the PK of metformin, an index substrate of OCT2, in subjects with schizophrenia. In a randomized, single-blind, 2-period crossover study, 25 adults with schizophrenia received a single dose of metformin-HCl 850 mg (approximately 663 mg metformin) with and without coadministration of 100 mg ulotaront. The plasma samples were analyzed by fully validated LC-MS/MS methods. The primary PK endpoints for metformin were AUCinf, AUClast, Cmax, and tmax. The highest-anticipated clinical dose of ulotaront (100 mg) had no statistically significant effect on the PK of a single dose of metformin based on Cmax and AUCinf. Geometric least squares mean ratios were 89.98% and 110.63%, respectively, with the 90% confidential interval (CI) for each parameter contained within 80%-125%. Median tmax was comparable across the treatments. Ulotaront does not act as a perpetrator of OCT2-mediated DDI against metformin. Co-administration of ulotaront is not expected to require dose adjustment of metformin or other drugs cleared by OCT2.

Considerations for Industry-Preparing for the FDA Model-Informed Drug Development (MIDD) Paired Meeting Program.

A recent industry perspective published in this journal describes the benefits received by drug companies from participation in the MIDD Pilot Program. Along with the primary objectives of supporting good decision-making in drug development, there were substantial savings in time and development costs. Furthermore, many sponsors reported qualitative benefits such as new learnings and clarity on MIDD strategies and methodology that could be applied to other development programs. Based on the success of the Pilot Program, the FDA recently announced the continuation of the MIDD Paired Meeting Program as part of the Prescription Drug User Fee Act (PDUFA VII). In this report, we describe the collective experiences of industry participants in the MIDD Program to date, including all aspects of the process from meeting request submission to follow-up actions. The purpose is to provide future participants with information to optimize the value of the MIDD Program.

Discovery and Model-Informed Drug Development of a Controlled-Release Formulation of Nonracemic Amisulpride that Reduces Plasma Exposure but Achieves Pharmacodynamic Bioequivalence in the Brain.

Nonracemic amisulpride (SEP-4199) is an investigational 85:15 ratio of aramisulpride to esamisulpride and currently in clinical trials for the treatment of bipolar depression. During testing of SEP-4199, a pharmacokinetic/pharmacodynamic (PK/PD) disconnect was discovered that prompted the development of a controlled-release (CR) formulation with improved therapeutic index for QT prolongation. Observations that supported the development of a CR formulation included (i) plasma concentrations of amisulpride enantiomers were cleared within 24-hours, but brain dopamine D2 receptor (D2R) occupancies, although achieving stable levels during this time, required 5 days to return to baseline; (ii) nonracemic amisulpride administered to non-human primates produced significantly greater D2R occupancies during a gradual 6-hour administration compared with a single bolus; (iii) concentration-occupancy curves were left-shifted in humans when nonracemic amisulpride was gradually administered over 3 and 6 hours compared with immediate delivery; (iv) CR solid oral dose formulations of nonracemic amisulpride were able to slow drug dissolution in vitro and reduce peak plasma exposures in vivo in human subjects. By mathematically solving for a drug distribution step into an effect compartment, and for binding to target receptors, the discovery of a novel PK/PD model (termed here as Distribution Model) accounted for hysteresis between plasma and brain, a lack of receptor saturation, and an absence of accumulation of drug occupancy with daily doses. The PK/PD disconnect solved by the Distribution Model provided model-informed drug development to continue in Phase III using the non-bioequivalent CR formulation with diminished QT prolongation as dose-equivalent to the immediate release (IR) formulation utilized in Phase II.

A randomized, single-dose, crossover study of the effects of ulotaront on electrocardiogram intervals in subjects with schizophrenia.

This study (NCT04369391) evaluated the effects of ulotaront (SEP-363856), a novel trace amine-associated receptor 1 (TAAR1) agonist in development for schizophrenia, on electrocardiogram parameters. Study design was a randomized, single-dose, three-period crossover (ulotaront 150 mg, placebo, moxifloxacin 400 mg). Sixty subjects with schizophrenia completed all periods. Ulotaront had no clinically relevant effect on heart rate, PR interval, or QRS duration. In by-time-point analysis (secondary analysis), the upper bound of the two-sided 90% confidence interval for ΔΔQTcF (QT interval corrected for heart rate using Fridericia's formula) was below 10 ms at all time points for ulotaront. In concentration-QTc analysis (primary analysis), a linear mixed-effects model with ulotaront and its major metabolite SEP-383103 was selected as the primary model based on prespecified criteria. Effect on ∆∆QTcF exceeding 10 ms can be excluded within observed ranges of ulotaront and SEP-383103 plasma concentrations up to ~574 and ~272 ng/mL, respectively. The upper bound of 90% CI for ΔΔQTcF can be predicted to be below 10 ms at the highest anticipated clinical exposure, currently defined as steady-state mean Cmax at ulotaront 100 mg/day in CYP2D6 poor metabolizers, ~416 and ~211 ng/mL for ulotaront and SEP-383103, respectively. Assay sensitivity was demonstrated by the QTc effect caused by moxifloxacin. In conclusion, ulotaront is unlikely to cause clinically relevant QTc prolongation in patients with schizophrenia at the anticipated maximum therapeutic dose.

Comparative Bioequivalence of Tablet and Capsule Formulations of Ulotaront and the Effect of Food on the Pharmacokinetics of the Tablet Form in Humans.

INTRODUCTION: Ulotaront (SEP-363856), a dual trace animeassociated receptor 1 (TAAR1) and 5-HT1A receptor agonist, is in phase 3 clinical development for the treatment of schizophrenia. This study evaluated the comparative bioequivalence (BE) between tablet and capsule formulations of ulotaront and the food effect (FE) on pharmacokinetics (PK) of tablet form in healthy adult human subjects. METHODS: The BE study applied an open-label two-period crossover design in 24 healthy volunteers. Subjects were randomly assigned (1:1) to dosing sequence AB or BA (A, 25 mg ulotaront tablet; B, 25 mg ulotaront capsule). The FE study also used an open-label randomized two-period crossover design in 20 healthy volunteers. Subjects were fasted overnight then randomly assigned (1:1) to dosing sequence AB or BA (A, fasted condition; B, fed condition). Dosing periods were separated by 1 week for both studies. Serial plasma samples from each period were collected and analyzed by LC-MS/MS. PK parameters were calculated using Phoenix WinNonlin® software. RESULTS: For the BE study, geometric mean ulotaront Cmax values were 93.28 and 86.98 ng/mL for tablet and capsule, respectively. Cmax ratio was 107.25% (90% CI 101.84-112.94%). Geometric mean ulotaront area under the plasma concentration-time curve from time 0 to infinity (AUC0-∞) values were 868.8 and 829.3 ng·h/mL for tablet and capsule, respectively. AUC0-∞ ratio was 104.76% (90% CI 100.68109.01%). For the FE study, geometric mean ulotaront Cmax was 157.89 and 157.95 ng/mL under fed and fasted conditions, respectively. Geometric mean ratio of Cmax was 99.96% (90% CI 94.48-105.77%). Geometric mean ulotaront AUC0-∞ was 1584.2 ng·h/mL fed and 1589.2 ng·h/mL fasted. Geometric mean ratio for AUC0-∞ was 99.69% (90% CI 95.02-104.58%). There was a delay in tmax (median difference 1.47 h) in the fed condition. CONCLUSIONS: The results showed geometric mean ratios and 90% CIs for both Cmax and AUC0-∞ for ulotaront were well within typical bioequivalence criteria of 80-125% for both the BE and FE studies, thereby confirming the bioequivalence of the two dosage forms and no significant food effect.

A Phase I, Open-Label, Fixed Sequence Study to Investigate the Effect of Cytochrome P450 2D6 Inhibition on the Pharmacokinetics of Ulotaront in Healthy Subjects.

BACKGROUND: Ulotaront is a novel psychotropic agent with agonist activity at trace amine-associated receptor 1 (TAAR1) and 5-hydroxytryptamine type 1A (5-HT1A) receptors in phase III clinical development for the treatment of schizophrenia. OBJECTIVE: This study aimed to investigate the effect of paroxetine, a strong cytochrome P450 (CYP) 2D6 inhibitor, on ulotaront pharmacokinetics (PK) in healthy volunteers. METHODS: Subjects received a single oral dose of 25 mg ulotaront on Day 1 and an oral dose of 20 mg paroxetine once daily from Days 5 to 10 to achieve steady-state plasma paroxetine levels. On Day 11, subjects received another single oral dose of 25 mg ulotaront, with continued daily oral dosing of 20 mg paroxetine from Days 11 to 14. All 24 subjects were CYP2D6 normal metabolizers. RESULTS: Coadministration of paroxetine increased ulotaront maximum observed plasma concentration (Cmax) and area under the plasma concentration-time curve from time zero to infinity (AUC∞) by 31% and 72%, respectively, and decreased ulotaront apparent clearance (CL/F) by approximately 42%. While coadministration of paroxetine increased AUC∞ of active but minor metabolite SEP-363854 by 32%, it had no effect on SEP-363854 Cmax, or on SEP-363854 to the ulotaront AUC from time zero to the last quantifiable concentration (AUClast) ratio. Based on the acceptable adverse event profile of ulotaront across previous phase II studies, the increase in ulotaront exposure is unlikely to be clinically meaningful. CONCLUSIONS: Weak drug-drug interactions were observed between ulotaront and the strong CYP2D6 inhibitor paroxetine; however, dose adjustment as a precondition when ulotaront is coadministered with strong CYP2D6 inhibitors or administered to CYP2D6 poor metabolizers should not be necessary.

A sensitive LC-MS/MS method for simultaneous quantification of ulotaront and its N-desmethyl metabolite in human plasma and application to a clinical study.

Ulotaront (SEP-363856) is a novel non-D2-receptor-binding agent under development for the treatment of patients with schizophrenia. A highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with lower limit of quantitation of 0.0200 ng/mL (i.e. 20.0 pg/mL) was successfully developed and validated for the simultaneous quantitation of ulotaront and its N-desmethyl metabolite (M11A) in human plasma. Plasma samples were extracted by solid phase extraction with Oasis MCX 96-well plate, followed by a reversed phase LC separation coupled with MS/MS detection in positive mode (m/z 184.1 → 135.0 for ulotaront and 170.1 → 135.0 for M11A). Stable isotope-labeled compounds SEP-363856-d3 and M11A-d4 were used as internal standards (IS) for corresponding analytes. The validated calibration curve range was 0.0200-20.0 ng/mL for both analytes using a 0.200 mL plasma. Extraction recoveries were found to be 75.7% and 75.1% for ulotaront and IS1, and 82.7% and 83.9% for M11A and IS2, respectively. Frozen plasma samples were confirmed to be stable for up to 730 days at both -20 °C and -70 °C. The validated method has been successfully used to evaluate the pharmacokinetics (PK) of ulotaront and M11A in clinical studies. The application to the first-in-human PK study (single ascending dose) presented in this work demonstrated that ulotaront exhibited near dose proportionality for both Cmax (maximum concentration) and AUC (area under the curve) over the dose range from 5 to 125 mg. M11A was found as a minor metabolite with an exposure of about 2-3% of the parent compound.

ECG Evaluation as Part of the Clinical Pharmacology Strategy in the Development of New Drugs: A Review of Current Practices and Opportunities Based on Five Case Studies.

The International Conference on Harmonization (ICH) E14 document was revised in 2015 to allow concentration-corrected QT interval (C-QTc) analysis to be applied to data from early clinical pharmacology studies to exclude a small drug-induced effect on QTc. Provided sufficiently high concentrations of the drug are obtained in the first-in-human (FIH) study, this approach can be used to obviate the need for a designated thorough QT (TQT) study. The E14 revision has resulted in a steady reduction in the number of TQT studies and an increased use of FIH studies to evaluate electrocardiogram (ECG) effects of drugs in development. In this review, five examples from different sponsors are shared in which C-QTc analysis was performed on data from FIH studies. Case 1 illustrates a clearly negative C-QTc evaluation, despite observations of QTc prolongation at high concentrations in nonclinical studies. In case 2 C-QTc analysis of FIH data was performed prior to full pharmacokinetic characterization in patients, and the role of nonclinical assays in an integrated risk assessment is discussed. Case 3 illustrates a positive clinical C-QTc relationship, despite negative nonclinical assays. Case 4 demonstrates a strategy for characterizing the C-QTc relationship for a nonracemic therapy and formulation optimization, and case 5 highlights an approach to perform a preliminary C-QTc analysis early in development and postpone the definitive analysis until proof of efficacy is demonstrated. The strategy of collecting and storing ECG data from FIH studies to enable an informed decision on whether and when to apply C-QTc analysis to obviate the need for a TQT study is described.

Population pharmacokinetic analysis of ulotaront in subjects with schizophrenia.

Ulotaront (SEP-363856) is a trace amine-associated receptor 1 agonist with 5-HT1A agonist activity in phase III development for the treatment of schizophrenia. The efficacy of ulotaront is not mediated by blockade of D2 or 5-HT2A receptors. The aim of this study was to evaluate the population pharmacokinetics (PopPKs) of ulotaront in adult subjects using pooled data from seven phase I studies, one phase II acute study, and one 6-month extension study. Single and multiple (up to 7 days) oral doses (5-150 mg/day) were studied in both healthy adult subjects (with intensive serial plasma sampling) and adult patients with schizophrenia (some with intensive and some with sparse plasma sampling). Ulotaront was well-absorbed and exhibited dose-proportionality in doses ranging from 10 to 100 mg, in mean maximum concentration, area under the concentration-time curve, and minimum concentration. Moderate interindividual variability was observed in concentration-time profiles. The estimated median time to maximal concentration was 2.8 h and the median effective half-life was 7 h, corresponding to an exposure accumulation ratio of 1.10 at steady-state with daily dosing. There was no indication of time-dependent changes in PKs after up to 12 weeks of daily dose administration. No clinically meaningful effects on ulotaront PK parameters were observed based on race, age, sex, formulation (capsule or tablet), or clinical status (healthy volunteer vs. patient with schizophrenia); body weight was the only meaningful covariate.

Acute lymphoid and gastrointestinal toxicity induced by selective p38alpha map kinase and map kinase-activated protein kinase-2 (MK2) inhibitors in the dog.

Exposure to moderately selective p38alpha mitogen-activated protein kinase (MAPK) inhibitors in the Beagle dog results in an acute toxicity consisting of mild clinical signs (decreased activity, diarrhea, and fever), lymphoid necrosis and depletion in the gut-associated lymphoid tissue (GALT), mesenteric lymph nodes and spleen, and linear colonic and cecal mucosal hemorrhages. Lymphocyte apoptosis and necrosis in the GALT is the earliest and most prominent histopathologic change observed, followed temporally by neutrophilic infiltration and acute inflammation of the lymph nodes and spleen and multifocal mucosal epithelial necrosis and linear hemorrhages in the colon and cecum. These effects are not observed in the mouse, rat, or cynomolgus monkey. To further characterize the acute toxicity in the dog, a series of in vivo, in vitro, and immunohistochemical studies were conducted to determine the relationship between the lymphoid and gastrointestinal (GI) toxicity and p38 MAPK inhibition. Results of these studies demonstrate a direct correlation between p38alpha MAPK inhibition and the acute lymphoid and gastrointestinal toxicity in the dog. Similar effects were observed following exposure to inhibitors of MAPK-activated protein kinase-2 (MK2), further implicating the role of p38alpha MAPK signaling pathway inhibition in these effects. Based on these findings, the authors conclude that p38alpha MAPK inhibition results in acute lymphoid and GI toxicity in the dog and is unique among the species evaluated in these studies.

Modulation of the sustained delivery of myelopoietin (Leridistim) encapsulated in multivesicular liposomes (DepoFoam).

Myelopoietins (MPO) are novel chimeric growth factors containing IL-3 and G-CSF receptor agonists that enhance the biological properties of both cytokines. These cytokines, like many therapeutic proteins, clear rapidly from circulation and must be administered daily to provide efficacy. Therefore, a controlled and sustained delivery system comprised of a biocompatible and biodegradable matrix, would offer important therapeutic advantages in the clinic, such as significantly reducing dose frequency and providing efficacy without toxicity. We report here the encapsulation of Leridistim (a protein from the MPO family) in multivesicular liposomes (DepoFoam) for sustained delivery, and demonstrate that a single injection of DepoFoam-encapsulated Leridistim results in elevated neutrophil counts for 10 days, in contrast to only 2 days for un-encapsulated Leridistim. Moreover, varying the lipid content of the DepoFoam matrix modulated the duration of elevated neutrophils from 2-3 to 9-10 days. The encapsulated Leridistim was released in vivo from the multivesicular liposomes in a uniform manner, consistent with its pharmacodynamic duration. Finally, a reproducible pharmacodynamic effect was observed with several batches of a DepoLeridistim formulation, indicating consistency of the manufacturing process of the DepoFoam delivery system. The capability of altering the release rates by varying the lipid composition provides maximum flexibility for controlled delivery of cytokine therapeutics.

Interferon beta assessment in non-Chinese and Chinese subjects: pharmacokinetics and pharmacodynamic activity of an endogenous cytokine are not race dependent.

Interferon beta-1a (IFNß-1a) is a first-line therapy for relapsing multiple sclerosis when administered as 30 mcg intramuscularly (IM) once weekly. This endogenous cytokine displays pharmacokinetic (PK) attributes consistent with a glycoprotein of 20-kDa molecular weight that is administered IM. In this study, 24 healthy Chinese subjects (11 male, 13 female) each received 4 once-weekly 60-mcg IM doses of IFNß-1a. Serial blood samples were drawn for PK and pharmacodynamic (PD) assessments following the first and last dose of drug. Results were compared with historical data from a recent PK/PD assessment conducted in non-Chinese subjects. Noncompartmental analysis revealed that no meaningful differences in either IFNß-1a exposure or response were apparent between the Chinese and non-Chinese populations. Thus, it was concluded that no adjustment in dose regimen is warranted for future assessments of safety and efficacy in multiple sclerosis patients of Chinese origin.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of anti-TWEAK monoclonal antibody in patients with rheumatoid arthritis.

BACKGROUND: Persistent upregulation of signaling by cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK) through its receptor fibroblast growth factor-inducible molecule-14 (Fn14) promotes chronic inflammation and tissue destruction. OBJECTIVE: The aim of this study was to explore the safety and tolerability of the TWEAK-blocking monoclonal antibody BIIB023 and determine its pharmacokinetics and effects on TWEAK pathway pharmacodynamic markers in rheumatoid arthritis (RA). METHODS: Phase I, first-in-human, 2-part, multicenter, double-blind, dose-escalation study. Patients were randomized to a single dose of BIIB023 (0.03-20 mg/kg) (n = 38) or placebo (n = 15) as an add-on to methotrexate. Three open-label cohorts of RA patients taking background disease-modifying antirheumatic drugs and stable tumor necrosis factor (TNF) inhibitor therapy (n = 12) received a single-dose of BIIB023 of 2, 10, or 20 mg/kg and were assessed over 70 days. RESULTS: The incidence of treatment-emergent adverse events for the BIIB023 monotherapy cohorts and open-label cohorts of BIIB023 as add-on therapy to TNF inhibitors compared with placebo were 47% and 50% versus 33%, respectively. Serum exposure to BIIB023 increased in a dose-dependent manner from 0.03 to 20 mg/kg, but not in direct proportion to dose level. After administration, the time course of BIIB023 serum concentration was multiphasic and showed expedited elimination when levels decreased to < 10 µg/mL. Serum-soluble TWEAK levels were suppressed at all dose levels by 6 hours post-dose and recovered to baseline between days 7 and 28. A trend toward downward modulation of serum biomarkers of inflammatory response was suggested in monocyte chemoattractant protein 1, inducible protein 10, macrophage inflammatory protein 1ß, and tissue inhibitor of metalloproteinase 1 in the BIIB023 group versus placebo. CONCLUSIONS: Single-dose BIIB023 showed a favorable safety and tolerability profile in RA. Suppression of serum-soluble TWEAK for ≤ 28 days was observed and downward trends in serum biomarkers suggested.

Plasma protein binding in drug discovery and development.

This review describes methods for quantifying the binding of small molecule drug candidates to plasma proteins and the application of these methods in drug discovery and development. Particular attention is devoted to methods amenable to medium-to-high throughput analysis and those well suited for measurement of compounds that are highly protein bound. The methods reviewed herein include the conventional techniques of equilibrium dialysis, ultrafiltration and ultracentrifugation, as well as some more novel approaches utilizing micropartitioning and biosensor-based analysis. Additional concepts that are discussed include plasma protein structure, enantioselective protein binding, drug displacement, the effect of patient demographics and disease states on free (unbound) drug levels, and the influence of protein binding on drug candidate pharmacokinetics and pharmacodynamics. Practical considerations pertaining to the evaluation of highly protein bound drug candidates are also highlighted.