Population Pharmacokinetics and Pharmacodynamics of Burosumab in Adult and Pediatric Patients With X-linked Hypophosphatemia.

Burosumab is a fully human monoclonal antibody against fibroblast growth factor 23, which has been approved to treat X-linked hypophosphatemia (XLH) in adult and pediatric patients. The present work describes the pharmacokinetics (PK) of burosumab and the pharmacokinetic-pharmacodynamic (PK-PD) relationship between burosumab and serum phosphorus in adult and pediatric patients with XLH. A total of 2844 measurable serum concentrations of burosumab and 6047 measurable serum concentrations of phosphorus in 277 subjects from 9 clinical studies were included in the population PK and PK-PD modeling. The serum concentration of burosumab following a subcutaneous administration was well described by a population PK model comprising a first-order absorption, 1-compartmental distribution, and a linear elimination. The relationship between serum burosumab and serum phosphorus was adequately described by a sigmoid maximal efficacy model. Body weight was the only covariate associated with PK and PK-PD parameters. No other intrinsic factors affected PK or PK-PD relationship in adult and pediatric patients with XLH. Further simulations helped to guide the dosing regimen of burosumab in adult and pediatric patients with XLH including age groups with no clinical data.

Robustness and the evolution of length control strategies in the T3SS and flagellar hook.

Bacterial cells construct many structures, such as the flagellar hook and the type III secretion system (T3SS) injectisome, that aid in crucial physiological processes such as locomotion and pathogenesis. Both of these structures involve long extracellular channels, and the length of these channels must be highly regulated in order for these structures to perform their intended functions. There are two leading models for how length control is achieved in the flagellar hook and T3SS needle: the substrate switching model, in which the length is controlled by assembly of an inner rod, and the ruler model, in which a molecular ruler controls the length. Although there is qualitative experimental evidence to support both models, comparatively little has been done to quantitatively characterize these mechanisms or make detailed predictions that could be used to unambiguously test these mechanisms experimentally. In this work, we constructed a mathematical model of length control based on the ruler mechanism and found that the predictions of this model are consistent with experimental data-not just for the scaling of the average length with the ruler protein length, but also for the variance. Interestingly, we found that the ruler mechanism allows for the evolution of needles with large average lengths without the concomitant large increase in variance that occurs in the substrate switching mechanism. In addition to making further predictions that can be tested experimentally, these findings shed new light on the trade-offs that may have led to the evolution of different length control mechanisms in different bacterial species.

The Pharmacokinetics of Triheptanoin and Its Metabolites in Healthy Subjects and Patients With Long-Chain Fatty Acid Oxidation Disorders.

Long-chain fatty acid oxidation disorders (LC-FAODs) are a group of life-threatening autosomal recessive disorders caused by defects in nuclear genes encoding mitochondrial enzymes involved in the conversion of dietary long-chain fatty acids into energy. Triheptanoin is an odd-carbon, medium-chain triglyceride consisting of 3 fatty acids with 7 carbons each on a glycerol backbone developed to treat adult and pediatric patients with LC-FAODs. The pharmacokinetics of triheptanoin and circulating metabolites were explored in healthy subjects and patients with LC-FAODs using noncompartmental analyses. Systemic exposure to triheptanoin following an oral administration was negligible, as triheptanoin is extensively hydrolyzed to glycerol and heptanoate in the gastrointestinal tract. Multiple peaks for triheptanoin metabolites were observed in the plasma following oral administration of triheptanoin, generally coinciding with the time that meals were served. Heptanoate, the pharmacologically active metabolite of triheptanoin supplementing energy sources in patients with LC-FAODs, showed the greatest exposure among the metabolites of triheptanoin in human plasma following oral administration of triheptanoin. The exposure of heptanoate was approximately 10-fold greater than that of beta-hydroxypentoate, a downstream metabolite of heptanoate. Exposure to triheptanoin metabolites appeared to increase following multiple doses as compared with the single dose, and with the increase in triheptanoin dose levels.

Pharmacokinetic and Pharmacodynamic Modeling to Optimize the Dose of Vestronidase Alfa, an Enzyme Replacement Therapy for Treatment of Patients with Mucopolysaccharidosis Type VII: Results from Three Trials.

INTRODUCTION: Mucopolysaccharidosis type VII (MPS VII, Sly Syndrome) is a progressive, debilitating, ultra-rare lysosomal storage disorder caused by the deficiency of ß-glucuronidase (GUS), an enzyme required for breakdown of glycosaminoglycans (GAGs). Vestronidase alfa, a recombinant human GUS, is an enzyme replacement therapy approved in the US and EU for the treatment of MPS VII. METHODS: The pharmacokinetics (PK) and pharmacodynamics (PD) of vestronidase alfa were evaluated in 23 adult and pediatric subjects with MPS VII enrolled in phase I-III clinical trials to optimize the clinical dosing regimen of vestronidase alfa. The serum concentration-time profiles were adequately described by a two-compartment population PK model incorporating subjects' body weight as the only significant covariate. RESULTS: Model-based simulations predicted a substantially decreased time duration of serum exposures exceeding the level of Kuptake (the in vitro determined vestronidase alfa concentration corresponding to 50% maximum rate of cellular uptake) for 4 or 8 mg/kg once every 4 weeks dosing, compared with 4 mg/kg once every other week (QOW) dosing by intravenous infusion, suggesting that given the same total monthly dose, the QOW dosing frequency should result in more efficient delivery to the GUS-deficient tissue cells, and therefore superior treatment efficacy. A standard inhibitory maximal effect model reasonably explained the observed pharmacological PD responses of reduction in urinary GAGs from pretreatment baseline, which appeared to have reached the plateau of maximal effect at the 4 mg/kg QOW dose. CONCLUSION: The modeling results, together with the clinical evidence of safety and efficacy, supported the recommended 4 mg/kg QOW dosing regimen of vestronidase alfa for pediatric and adult patients with MPS VII. CLINICAL TRIAL REGISTRATION: NCT01856218, NCT02418455, NCT02230566.

Correction to: Pharmacokinetic and Pharmacodynamic Modeling to Optimize the Dose of Vestronidase Alfa, an Enzyme Replacement Therapy for Treatment of Patients with Mucopolysaccharidosis Type VII: Results from Three Trials.

Introduction section, para 3, lines 2-4 which previously read.

A randomised, open-label, phase 2 study of the IDO1 inhibitor epacadostat (INCB024360) versus tamoxifen as therapy for biochemically recurrent (CA-125 relapse)-only epithelial ovarian cancer, primary peritoneal carcinoma, or fallopian tube cancer.

OBJECTIVE: Indoleamine 2,3-dioxygenase-1 (IDO1) is a key regulator of immune tolerance in ovarian cancer. This study investigated efficacy and safety of the IDO1 enzyme inhibitor epacadostat versus tamoxifen in patients with biochemical-only recurrence (CA-125 elevation) following complete remission after first-line chemotherapy for advanced epithelial ovarian, primary peritoneal, or fallopian tube cancer. METHODS: In this open-label, phase 2 study (NCT01685255), patients were randomised 1:1 to epacadostat 600mg or tamoxifen 20mg twice daily for successive 28-day cycles and stratified by time since completion of first-line chemotherapy to first CA-125 elevation (3 to <12 or ≥12months). The primary endpoint was investigator-assessed progression-free survival (PFS; RECIST v1.1). Secondary endpoints included CA-125 response (Gynecologic Cancer InterGroup criteria), overall survival, safety, and tolerability. RESULTS: The study was terminated primarily due to slow accrual and lack of evidence of superiority. Median PFS was 3.75months for epacadostat (n=22) versus 5.56months for tamoxifen (n=20; HR, 1.34 [95% CI, 0.58-3.14]; P=0.54). Of evaluable patients, 1 (5.0%) epacadostat and 3 (15.8%) tamoxifen patients had confirmed CA-125 responses. The most common treatment-emergent adverse event was fatigue (epacadostat, 36.4%; tamoxifen, 40.0%). Immune-related adverse events, observed with epacadostat only, were primarily rash (18.2%) and pruritus (9.1%). Epacadostat pharmacokinetics/pharmacodynamics were consistent with its known mechanism of action. IDO1 expression was observed in 94% of archival tumour samples. CONCLUSIONS: This first report of immunotherapy evaluation in biochemical-only relapse ovarian cancer and of IDO1 inhibitor monotherapy in ovarian cancer found no significant difference in efficacy between epacadostat and tamoxifen. Epacadostat was generally well tolerated.

In Vitro Interactions of Epacadostat and its Major Metabolites with Human Efflux and Uptake Transporters: Implications for Pharmacokinetics and Drug Interactions.

Epacadostat (EPAC) is a first-in-class, orally active inhibitor of the enzyme indoleamine 2,3-dioxygenase 1 and has demonstrated promising clinical activity. In humans, three major plasma metabolites have been identified: M9 (a glucuronide-conjugate), M11 (a gut microbiota metabolite), and M12 (a secondary metabolite formed from M11). It is proposed, based on the human pharmacokinetics of EPAC, that the biliary excretion of M9, the most abundant metabolite, leads to the enterohepatic circulation of EPAC. Using various in vitro systems, we evaluated in the present study the vitro interactions of EPAC and its major metabolites with major drug transporters involved in drug absorption and disposition. EPAC is a substrate for efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), but it is not a substrate for hepatic uptake transporters [organic anion transporting polypeptides OATP1B1 and OATP1B3]. The low permeability of M9 suggests an essential role for transporters in its disposition. M9 is likely excreted from hepatocytes into bile via multidrug resistance-associated protein 2 (MRP2) and BCRP, excreted into blood via MRP3, and transported from blood back into hepatocytes via OATP1B1 and OATP1B3. M11 and M12 are not substrates for P-gp, OATP1B1 or OATP1B3, and M11, but not M12, is a substrate for BCRP. With respect to inhibition of drug transporters, the potential of EPAC, M9, M11, and M12 to cause clinical drug-drug interactions via inhibition of P-gp, BCRP, OATP1B1, OATP1B3, OAT1, OAT3, or organic cation transporter 2 was estimated to be low. The current investigation underlines the importance of metabolite-transporter interactions in the disposition of clinically relevant metabolites, which may have implications for the pharmacokinetics and drug interactions of parent drugs.

First-in-Human Phase I Study of the Oral Inhibitor of Indoleamine 2,3-Dioxygenase-1 Epacadostat (INCB024360) in Patients with Advanced Solid Malignancies.

Purpose: Indoleamine 2,3-dioxygenase-1 (IDO1) catalyzes the degradation of tryptophan to N-formyl-kynurenine. Overexpressed in many solid malignancies, IDO1 can promote tumor escape from host immunosurveillance. This first-in-human phase I study investigated the maximum tolerated dose, safety, pharmacokinetics, pharmacodynamics, and antitumor activity of epacadostat (INCB024360), a potent and selective inhibitor of IDO1.Experimental Design: Fifty-two patients with advanced solid malignancies were treated with epacadostat [50 mg once daily or 50, 100, 300, 400, 500, 600, or 700 mg twice daily (BID)] in a dose-escalation 3 + 3 design and evaluated in 28-day cycles. Treatment was continued until disease progression or unacceptable toxicity.Results: One dose-limiting toxicity (DLT) occurred at the dose of 300 mg BID (grade 3, radiation pneumonitis); another DLT occurred at 400 mg BID (grade 3, fatigue). The most common adverse events in >20% of patients overall were fatigue, nausea, decreased appetite, vomiting, constipation, abdominal pain, diarrhea, dyspnea, back pain, and cough. Treatment produced significant dose-dependent reductions in plasma kynurenine levels and in the plasma kynurenine/tryptophan ratio at all doses and in all patients. Near maximal changes were observed at doses of ≥100 mg BID with >80% to 90% inhibition of IDO1 achieved throughout the dosing period. Although no objective responses were detected, stable disease lasting ≥16 weeks was observed in 7 of 52 patients.Conclusions: Epacadostat was generally well tolerated, effectively normalized kynurenine levels, and produced maximal inhibition of IDO1 activity at doses of ≥100 mg BID. Studies investigating epacadostat in combination with other immunomodulatory drugs are ongoing. Clin Cancer Res; 23(13); 3269-76. ©2017 AACR.

Population Pharmacokinetic and Pharmacodynamic Modeling of Epacadostat in Patients With Advanced Solid Malignancies.

Epacadostat (EPA, INCB024360) is a selective inhibitor of the enzyme indoleamine 2,3-dioxygenase 1 (IDO1) and is being developed as an orally active immunotherapy to treat advanced malignancies. In the first clinical study investigating the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of EPA in oncology patients, increasing doses of EPA ranging from 50 mg once daily to 700 mg twice daily were administered as a monotherapy to 52 subjects with advanced solid tumors. The EPA plasma concentration-time profiles were adequately described by a population PK model comprised of the first-order kinetics of oral absorption with 2-compartment distribution and constant clearance from the central compartment. Body weight was the only significant covariant to influence EPA PK. Determination of EPA's on-target potency, ie, its half-maximal inhibitory concentration (IC50 ) against IDO1, is important for dose selection but complicated by the bioconversion of tryptophan (TRP) to kynurenine (KYN) catalyzed by both IDO1 and TRP 2,3-dioxygenase (TDO). In vitro and ex vivo, the IC50 was estimated following the selective induction of IDO1, rendering the TDO activity relatively insignificant; however, it was desirable to determine the in vivo IC50 without inducing an IDO1 abundance. A mechanistic population PD model was developed based on time-matched EPA, TRP, and KYN plasma concentrations in 44 oncology patients, and EPA in vivo IC50 was estimated to be ∼70 nM, consistent with the ex vivo value independently determined. The model suggests that ∼60% and 40% of TRP→KYN bioconversion was mediated by IDO1 and TDO, respectively, in the cancer patients at baseline. For this study population of limited numbers of subjects, neither age nor sex was a significant covariate for EPA PK or PD.

Roles of UGT, P450, and Gut Microbiota in the Metabolism of Epacadostat in Humans.

Epacadostat (EPA, INCB024360) is a first-in-class, orally active, investigational drug targeting the enzyme indoleamine 2,3-dioxygenase 1 (IDO1). In Phase I studies, EPA has demonstrated promising clinical activity when used in combination with checkpoint modulators. When the metabolism of EPA was investigated in humans, three major, IDO1-inactive, circulating plasma metabolites were detected and characterized: M9, a direct O-glucuronide of EPA; M11, an amidine; and M12, N-dealkylated M11. Glucuronidation of EPA to form M9 is the dominant metabolic pathway, and in vitro, this metabolite is formed by UGT1A9. However, negligible quantities of M11 and M12 were detected when EPA was incubated with a panel of human microsomes from multiple tissues, hepatocytes, recombinant human cytochrome P450s (P450s), and non-P450 enzymatic systems. Given the reductive nature of M11 formation and the inability to define its source, the role of gut microbiota was investigated. Analysis of plasma from mice dosed with EPA following pretreatment with either antibiotic (ciprofloxacin) to inhibit gut bacteria or 1-aminobenzotriazole (ABT) to systemically inhibit P450s demonstrated that gut microbiota is responsible for the formation of M11. Incubations of EPA in human feces confirmed the role of gut bacteria in the formation of M11. Further, incubations of M11 with recombinant P450s showed that M12 is formed via N-dealkylation of M11 by CYP3A4, CYP2C19, and CYP1A2. Thus, in humans three major plasma metabolites of EPA were characterized: two primary metabolites, M9 and M11, formed directly from EPA via UGT1A9 and gut microbiota, respectively, and M12 formed as a secondary metabolite via P450s from M11.

Mathematical Model for Length Control by the Timing of Substrate Switching in the Type III Secretion System.

Type III Secretion Systems (T3SS) are complex bacterial structures that provide gram-negative pathogens with a unique virulence mechanism whereby they grow a needle-like structure in order to inject bacterial effector proteins into the cytoplasm of a host cell. Numerous experiments have been performed to understand the structural details of this nanomachine during the past decade. Despite the concerted efforts of molecular and structural biologists, several crucial aspects of the assembly of this structure, such as the regulation of the length of the needle itself, remain unclear. In this work, we used a combination of mathematical and computational techniques to better understand length control based on the timing of substrate switching, which is a possible mechanism for how bacteria ensure that the T3SS needles are neither too short nor too long. In particular, we predicted the form of the needle length distribution based on this mechanism, and found excellent agreement with available experimental data from Salmonella typhimurium with only a single free parameter. Although our findings provide preliminary evidence in support of the substrate switching model, they also make a set of quantitative predictions that, if tested experimentally, would assist in efforts to unambiguously characterize the regulatory mechanisms that control the growth of this crucial virulence factor.

Potential Underprediction of Warfarin Drug Interaction From Conventional Interaction Studies and Risk Mitigation: A Case Study With Epacadostat, an IDO1 Inhibitor.

Drug-drug interaction (DDI) studies involving warfarin are typically conducted with subtherapeutic doses of warfarin to ensure the safety of volunteers. However, this approach may potentially have a systemic bias of underestimating pharmacodynamic (PD) DDI effect on warfarin at therapeutic levels of anticoagulation. We demonstrate here the utility of model-based DDI prediction for a clinically relevant warfarin regimen, using the example of epacadostat (INCB024360), the first-in-class indoleamine 2,3-dioxygenase 1 inhibitor in clinical development as a novel orally active immuno-oncological therapy. Observed data from a dedicated clinical DDI study using subtherapeutic warfarin suggested warfarin pharmacokinetics (PK), but not PD (anticoagulation), was significantly affected by concomitant epacadostat. However, subsequent PK/PD modeling and simulations indicated a clinically important DDI effect on warfarin PD at a higher baseline of the international normalization ratio (INR) and enabled recommendation of warfarin dose adjustment that is dependent on epacadostat dosing regimen and target INR.

The pharmacokinetics, pharmacodynamics, and safety of baricitinib, an oral JAK 1/2 inhibitor, in healthy volunteers.

Baricitinib (also known as LY3009104 or INCB028050), a novel and potent small molecule inhibitor of Janus kinase family of enzymes (JAKs) with selectivity for JAK1 and JAK2, is currently in clinical development for the treatment of rheumatoid arthritis (RA) and other inflammatory disorders. Two double-blind, randomized, and placebo-controlled studies were conducted to evaluate single ascending doses of 1-20 mg and multiple ascending doses of 2-20 mg QD and 5 mg BID for 10 or 28 days in healthy volunteers. Following oral administration, baricitinib plasma concentration typically attains its peak value within 1.5 hours postdose and subsequently declines in a bi-exponential fashion. Baricitinib demonstrates dose-linear and time-invariant pharmacokinetics, with low oral-dose clearance (17 L/h) and minimal systemic accumulation observed following repeat dosing. The mean renal clearance of baricitinib was determined to be ∼2 L/h. The effect of a high-fat meal on baricitinib pharmacokinetics was insignificant. The pharmacodynamics of baricitinib, evaluated by the inhibition of STAT3 phosphorylation following cytokine stimulation in the whole blood ex vivo, was well correlated with baricitinib plasma concentrations. Baricitinib was generally safe and well tolerated, with no serious treatment-related adverse events (AEs) reported from either of the studies. An expected rapidly reversible, dose-related decline in absolute neutrophil count was seen with baricitinib.

Pharmacokinetics and pharmacodynamics of orally administered ruxolitinib (INCB018424 phosphate) in renal and hepatic impairment patients.

Hepatic and renal impairment studies were conducted with ruxolitinib, a JAK1&2 inhibitor that is cleared predominantly by metabolism. Both studies were open label, single-dose studies. Ruxolitinib area under the curve (AUC) was increased by 87%, 28%, and 65%, respectively, in subjects with mild, moderate, and severe hepatic impairment compared to healthy subjects with no correlation between exposure of ruxolitinib and the degree of hepatic impairment. The pharmacodynamics (PD) data were consistent with ruxolitinib pharmacokinetics (PK). The renal impairment study showed a surprising finding. While there was no change in ruxolitinib PK with varying degrees of renal impairment, the PD showed increasing pharmacological activity with increased severity of renal impairment. Analysis of the metabolite exposures revealed that active metabolites contributed to the observed incremental increase in PD activity. The recovery of ruxolitinib in dialysate was negligible. The starting dose of ruxolitinib in subjects with any hepatic impairment or moderate or severe renal impairment should be decreased to 10 mg twice daily (BID) if their platelet counts are between 100 × 10(9) /L and 150 × 10(9) /L. Subjects on dialysis should initiate dosing with a single dose of 15 or 20 mg, based on platelet counts, with dosing only on the days of dialysis.

Construction of a two-parameter empirical model of left ventricle wall motion using cardiac tagged magnetic resonance imaging data.

BACKGROUND: A one-parameter model was previously proposed to characterize the short axis motion of the LV wall at the mid-ventricle level. The single parameter of this model was associated with the radial contraction of myocardium, but more comprehensive model was needed to account for the rotation at the apex and base levels. The current study developed such model and demonstrated its merits and limitations with examples. MATERIALS AND METHODS: The hearts of five healthy individuals were visualized using cardiac tagged magnetic resonance imaging (tMRI) covering the contraction and relaxation phases. Based on the characteristics of the overall dynamics of the LV wall, its motion was represented by a combination of two components - radial and rotational. Each component was represented by a transformation matrix with a time-dependent variable α or ß.Image preprocessing step and model fitting algorithm were described and applied to estimate the temporal profiles of α and ß within a cardiac cycle at the apex, mid-ventricle and base levels. During this process, the tagged lines of the acquired images served as landmark reference for comparing against the model prediction of the motion. Qualitative and quantitative analyses were performed for testing the performance of the model and thus its validation. RESULTS: The α and ß estimates exhibited similarities in values and temporal trends once they were scaled by the radius of the epicardium (r(epi))and plotted against the time scaled by the period of the cardiac cycle (T(cardiac)) of each heart measured during the data acquisition. α/repi peaked at about Δt/T(cardiac)=0.4 and with values 0.34, 0.4 and 0.3 for the apex, mid-ventricle and base level, respectively. ß/r(epi) similarly maximized in amplitude at about Δt/T(cardiac)=0.4, but read 0.2 for the apex and - 0.08 for the base level. The difference indicated that the apex twisted more than the base. CONCLUSION: It is feasible to empirically model the spatial and temporal evolution of the LV wall motion using a two-parameter formulation in conjunction with tMRI-based visualization of the LV wall in the transverse planes of the apex, mid-ventricle and base. In healthy hearts, the analytical model will potentially allow deriving biomechanical entities, such as strain, strain rate or torsion, which are typically used as diagnostic, prognostic or predictive markers of cardiovascular diseases including diabetes.

Preliminary clinical activity of a topical JAK1/2 inhibitor in the treatment of psoriasis.

BACKGROUND: Janus-associated kinases (JAKs) are involved in signal transduction from a variety of cytokines implicated in the pathogenesis of psoriasis, including interleukin (IL)-12, IL-23, and interferon-γ. INCB018424, a small molecule inhibitor of JAK1 and JAK2, inhibits cytokine-induced JAK/signal transducers and activators of transcription signaling and the resultant production of inflammatory proteins (eg, IL-17). OBJECTIVE: We sought to demonstrate proof of concept in patients with stable plaque psoriasis. METHODS: Patients were dosed with vehicle, 0.5% or 1.0% INCB018424 phosphate cream once a day or 1.5% twice a day for 28 days. Additional groups included two active comparators (calcipotriene 0.005% cream or betamethasone dipropionate 0.05% cream). RESULTS: Both the 1% and the 1.5% cream improved lesion thickness, erythema, and scaling and reduced lesion area compared with placebo. A composite lesion score decreased by greater than 50% with the efficacious doses of INCB018424 compared with 32% for vehicle controls. Topical application of INCB018424 was well tolerated with few mild adverse events noted. Mean plasma concentrations of INCB018424 after topical application of 0.5% to 1.5% cream were in the low nanomolar range, representing a fraction (<1%) of the half maximal inhibitory concentration (IC(50)) in whole blood for inhibition of cytokine-stimulated signal transducers and activators of transcription-3 phosphorylation. LIMITATIONS: This study was limited by the relatively short study duration and small sample size. CONCLUSION: Topical INCB018424 is safe, is well tolerated, and exhibits clinical activity in the topical treatment of psoriasis.

The effect of CYP3A4 inhibition or induction on the pharmacokinetics and pharmacodynamics of orally administered ruxolitinib (INCB018424 phosphate) in healthy volunteers.

Ruxolitinib, a selective Janus kinase (JAK) 1&2 inhibitor in development for the treatment of myeloproliferative neoplasms, is primarily metabolized by CYP3A4. The effects of inhibition or induction of CYP3A4 on single oral dose ruxolitinib pharmacokinetics (PK) and pharmacodynamics (PD) were evaluated in healthy volunteers. Coadministration of ketoconazole (a potent CYP3A4 inhibitor) and erythromycin (a moderate CYP3A4 inhibitor) increased total ruxolitinib plasma exposure (AUC(0-∞)) by 91% and 27%, respectively, and ruxolitinib PD, as measured by the inhibition of interleukin (IL)-6-stimulated STAT3 phosphorylation in whole blood, was generally consistent with the PK observed. Pretreatment with rifampin, a potent CYP3A4 inducer, decreased ruxolitinib AUC(0-∞) by 71% while resulting in only a 10% decrease in the overall PD activity. This apparent PK/PD discrepancy may be explained, in part, by an increase in the relative abundance of ruxolitinib active metabolites with the rifampin coadministration. The collective PK/PD data suggest that starting doses of ruxolitinib should be reduced by 50% if coadministered with a potent CYP3A4 inhibitor, whereas adjustments in ruxolitinib starting doses may not be needed when coadministered with inducers or mild/moderate inhibitors of CYP3A4. All study doses of ruxolitinib were generally safe and well tolerated when given alone and in combination with ketoconazole, erythromycin, or rifampin.

Preclinical evaluation of local JAK1 and JAK2 inhibition in cutaneous inflammation.

JAKs are required for signaling initiated by several cytokines (e.g., IL-4, IL-12, IL-23, thymic stromal lymphopoietin (TSLP), and IFNγ) implicated in the pathogenesis of inflammatory skin diseases such as psoriasis and atopic dermatitis (AD). Direct antagonism of cytokines, such as IL-12 and IL-23 using ustekinumab, has proven effective in randomized studies in psoriasis patients. We hypothesized that local inhibition of cytokine signaling using topical administration of INCB018424, a small molecule inhibitor of JAK1 and JAK2, would provide benefit similar to systemic cytokine neutralization. In cellular assays, INCB018424 inhibits cytokine-induced JAK/signal transducers and activators of transcription (STAT) signaling and the resultant production of inflammatory proteins (e.g., IL-17, monocyte chemotactic protein-1, and IL-22) in lymphocytes and monocytes, with half-maximal inhibitory concentration values <100 nM. In vivo, topical application of INCB018424 resulted in suppression of STAT3 phosphorylation, edema, lymphocyte infiltration, and keratinocyte proliferation in a murine contact hypersensitivity model and inhibited tissue inflammation induced by either intradermal IL-23 or TSLP. Topical INCB018424 was also well tolerated in a 28-day safety study in Gottingen minipigs. These results suggest that localized JAK1/JAK2 inhibition may be therapeutic in a range of inflammatory skin disorders such as psoriasis and AD. Clinical evaluation of topical INCB018424 is ongoing.

The pharmacokinetics, pharmacodynamics, and safety of orally dosed INCB018424 phosphate in healthy volunteers.

INCB018424 phosphate, a potent inhibitor of JAK enzymes with selectivity for JAK1&2, is in development for the treatment of myelofibrosis (MF). The oral dose pharmacokinetics, pharmacodynamics, safety, and tolerability of INCB018424 were evaluated in healthy volunteers in 2 double-blind, randomized, and placebo-controlled studies. The first study evaluated single ascending doses of 5 to 200 mg INCB018424 and the effect of food, whereas the second study evaluated multiple ascending doses, including both once- and twice-daily dosing for 10 days. As a Biopharma-ceutical Classification System class I drug, INCB018424 exhibited good oral bioavailability and dose-proportional systemic exposures. INCB018424 showed low oral dose clearance and a small volume of distribution, with an approximate 3-hour plasma half-life and insignificant accumulation following repeat dosing. A high-fat meal reduced INCB018424 C(max) by 24% but had little effect on INCB018424 AUC. INCB018424 was cleared primarily by metabolism with negligible renal excretion. The pharmacodynamics of INCB018424, evaluated by the inhibition of phosphorylated STAT3 following cytokine stimulation in whole blood, showed good correlation with INCB018424 plasma concentrations. INCB018424 was generally safe and well tolerated, with 25 mg bid and 100 mg qd established as the maximum tolerated doses in healthy volunteers.