Population pharmacokinetic and exposure-efficacy analysis of ixekizumab in paediatric patients with moderate-to-severe plaque psoriasis (IXORA-PEDS)

AIMS

Ixekizumab is a high-affinity monoclonal antibody that selectively targets interleukin-17A used in the treatment of adult and paediatric patients with moderate-to-severe psoriasis. This analysis evaluated the pharmacokinetics (PK) of ixekizumab and the exposure-efficacy relationship in paediatric patients aged 6 to <18 years with psoriasis.

METHODS

Population PK and exposure-efficacy models were developed. The models used data from paediatric patients with psoriasis participating in the Phase 3 IXORA-PEDS trial in which patients were dosed according to weight categories. The exposure-efficacy model is a Psoriasis Area and Severity Index (PASI) time course model using data up to Week 12, a co-primary efficacy endpoint.

RESULTS

A 2-compartment population PK model describes the PK of ixekizumab in paediatric patients with the effect of body weight incorporated on clearance and volume terms using an allometric relationship. The weight category-based dosing ensured that ixekizumab mean trough serum concentrations in paediatric patients with psoriasis (3.20-3.33 μg/mL) were within the range of concentrations observed in adult patients with psoriasis (mean [standard deviation]: 3.48 [2.16] μg/mL) administered an efficacious dosing regimen. The observed PASI response rates at Week 12 in paediatric patients (91.9/81.8/52.5% for PASI75/90/100) are well predicted by the final exposure-efficacy model and response rates are similar or higher than those achieved in adults (86.2/66.6/35.0% for PASI75/90/100).

CONCLUSION

This analysis is the first to describe the PK and exposure-efficacy relationship of ixekizumab in paediatric patients with psoriasis. The analyses support the selection of the weight category-based ixekizumab dosing regimens approved for use in paediatric patients with psoriasis.

Population Pharmacokinetics of Tadalafil in Pediatric Patients with Pulmonary Arterial Hypertension: A Combined Adult/Pediatric Model

BACKGROUND

Tadalafil 40 mg once daily is approved for adult patients with pulmonary arterial hypertension (PAH). To investigate and potentially fulfill an unmet need in pediatric patients with PAH, pharmacokinetic (PK) data were explored in a pediatric phase Ib/II study and pooled with prior phase III (pulmonary arterial hypertension and response to tadalafil [PHIRST-1]) adult data to develop the first population PK model for tadalafil in pediatric patients with PAH.

METHODS

H6D-MC-LVIG (NCT01484431) was an open-label, multicenter, multiple ascending dose study in pediatric patients with PAH, while PHIRST-1 was a phase III, multicenter, randomized, double-blind, placebo-controlled, parallel design study in adults with PAH who received one of five treatments (tadalafil 2.5, 10, 20, or 40 mg, or placebo orally, once daily). PK data from the studies were pooled to develop a pediatric population PK model for tadalafil that characterized relationships among dose, exposure, and the effects of covariates with an aim to develop a population PK model that could simulate concentration-time profiles and assess exposure-matched dosing strategies in a pediatric PAH population.

RESULTS

In line with the observed data, modeling and simulation demonstrated that the doses studied in the pediatric population produced area under the concentration-time curves (AUCs) within the range of those associated with improved exercise ability in adults with PAH. The analyses included 1430 observations from 305 adult patients (PHIRST-1: 69 males and 236 females, 1102 observations) and 19 pediatric patients (LVIG: 6 males and 13 females, 328 observations) who received tadalafil once daily at different dose levels. The best-fit base model retained an effect of weight on apparent volume of distribution (V/F), fixed to the allometric scaling value of 1, and did not include an effect of weight on apparent clearance (CL/F). Other covariate effects were that bosentan increased CL/F, V/F decreased with decreasing body weight, and bioavailability (F) decreased with increasing dose and decreasing age. The PK model reliably predicted the observed concentrations and overall variability evident from the overlap of the individual observed concentrations with the distributions of simulated concentrations.

CONCLUSIONS

A one-compartment model parameterized in terms of F, absorption rate constant, CL/F, and V/F described the data well. The model demonstrated that plasma tadalafil concentrations in pediatric patients aged 2 to < 18 years were similar to those in adults at similar doses, and confirmed that dosing of 40 mg once daily in pediatric patients with a bodyweight ≥ 40 kg, and a dose of 20 mg once daily in patients with a body weight < 40 kg and aged ≥ 2 years are suitable for phase III evaluation.

TRIAL REGISTRATION NUMBER (DATE OF REGISTRATION)

LVIG: ClinicalTrials.gov identifier: NCT01484431 (2 December 2011). PHIRST-1: ClinicalTrials.gov identifier: NCT00125918 (2 August 2005).

Blocking TIM-3 in Treatment-refractory Advanced Solid Tumors: A Phase Ia/b Study of LY3321367 with or without an Anti-PD-L1 Antibody

PURPOSE

T-cell immunoglobulin and mucin-domain-containing molecule-3 (TIM-3) blunts anticancer immunity and mediates resistance to programmed death 1 (PD-1) and PD ligand 1 (PD-L1) inhibitors. We assessed a novel, first-in-class, TIM-3 mAb, LY3321367, alone or in combination with the anti-PD-L1 antibody, LY300054 in patients with advanced solid tumor.

PATIENTS AND METHODS

This open-label, multicenter, phase Ia/b study aimed to define the safety/tolerability and recommended phase II dose (RP2D) of LY3321367 with or without LY300054. Secondary objectives included pharmacokinetics/pharmacodynamics, immunogenicity, and efficacy. Biomarkers were assessed in exploratory analysis.

RESULTS

No dose-limiting toxicities were observed in the monotherapy (N = 30) or combination (N = 28) dose escalation. LY3321367 treatment-related adverse events (≥2 patients) included pruritus, rash, fatigue, anorexia, and infusion-related reactions. Dose-proportional increase in LY3321367 concentrations was not affected by either LY300054 or antidrug antibodies (observed in 50%-70% of patients). Pharmacokinetic/pharmacodynamic modeling indicated 100% target engagement at doses ≥600 mg. LY3321367 RP2D was 1,200 mg biweekly for four doses followed by 600 mg every 2 weeks thereafter. In the non-small cell lung cancer monotherapy expansion cohort, outcomes varied by prior anti-PD-1 therapy response status: anti-PD-1/L1 refractory patients [N = 23, objective response rate (ORR) 0%, disease control rate (DCR) 35%, progression-free survival (PFS) 1.9 months] versus anti-PD-1/L1 responders (N = 14, ORR 7%, DCR 50%, PFS 7.3 months). In combination expansion cohorts (N = 91), ORR and DCR were 4% and 42%; CD8 infiltration in paired biopsies increased in approximately half these patients.

CONCLUSIONS

LY3321367 exhibited acceptable safety profile with favorable pharmacokinetics/pharmacodynamics but only modest antitumor activity. The therapeutic relevance of TIM-3 blockade requires further investigation.

A phase Ia/b study of TIM-3/PD-L1 bispecific antibody in patients with advanced solid tumors

TPS2654

Background: Programmed cell death 1 immune checkpoint inhibitors (anti-PD-1, anti-PD-L1) have demonstrated clinical benefit in a subset of patients with manageable safety across a variety of tumor types. T-cell immunoglobulin and mucin-domain-containing molecule-3 (TIM-3) can be co-expressed with PD-1 on exhausted T-cells and may be upregulated in tumors refractory to anti-PD-1 therapy (Koyama et al. 2016). Pre-clinical studies demonstrated that blockade of both PD-1 and TIM-3 improved survival of tumor-bearing mice compared to blocking anti-PD-1 only (Koyama et al. 2016). LY3415244 is a TIM-3/PD-L1 bispecific antibody that has the ability to target and inhibit both TIM-3 and PD-L1 and the potential to overcome primary and acquired anti-PD-(L)1 resistance by a novel mechanism to bridge TIM-3- and PD-L1-expressing cells. Methods: Study JZDA is a multicenter, nonrandomized, open-label, Phase 1a/1b study of LY3415244 in patients with advanced solid tumors. In Phase 1a, subjects with any tumor type who are either PD-(L)1 inhibitor-naïve or exposed are eligible. In Phase 1b, expansion cohorts are planned in subjects with PD-(L)1-experienced NSCLC, urothelial carcinoma, and melanoma. Patients with malignant mesothelioma are not required to have received prior anti-PD-(L)1 therapy. The primary objective is to assess safety and tolerability of LY3415244 and identify the recommended Phase 2 dose (RP2D) in Phase 1a (dose escalation). Safety and tolerability of the RP2D will be assessed in Phase 1b (dose expansion). The secondary objectives are to assess the pharmacokinetics of LY3415244 in Phase 1a/1b and assess early antitumor activity of LY3415244 in Phase 1b cohorts. Pre- and on-treatment biopsies will be obtained to explore potential biomarkers of response. During Phase 1a, dose escalation cohorts will proceed via a modified toxicity probability interval-2 (mTPI-2) design with a 1-cycle (28-day) dose-limiting toxicity (DLT) observation period. LY3415244 will be dosed intravenously every 2 weeks. Data from Phase 1a will determine the RP2D, which will be used for all cohorts in Phase 1b. The study is currently open to enrollment. Clinical trial information: NCT03752177.

A phase Ia/Ib study of an anti-TIM-3 antibody (LY3321367) monotherapy or in combination with an anti-PD-L1 antibody (LY3300054): Interim safety, efficacy, and pharmacokinetic findings in advanced cancers

12

Background: Combined targeting of both the TIM-3 and PD-L1 immune checkpoint pathways may improve efficacy. LY3321367 mAb targets TIM-3 on immune cells and LY3300054 mAb targets PD-L1 on tumor cells and tumor-infiltrating immune cells. This analysis presents safety, efficacy, pharmacokinetic (PK) and pharmacodynamics/soluble target engagement (TE) results from LY3321367 (anti-TIM-3) monotherapy and in combination with LY3300054 (anti-PD-L1) in patients (pts) with advanced cancer. Methods: This ongoing, open-label phase 1a/1b, dose escalation and expansion study enrolled pts with histologically confirmed advanced relapsed/refractory solid tumors. Pts received IV infusions of 3mg-1200mg LY3321367 Q2W monotherapy (Arm A) or 70mg-1200mg LY3321367 + 200mg-700mg LY3300054 Q2W combination therapy (Arm B). Primary objectives assessed safety and tolerability and determined the RP2D. PK, soluble target TE, anti-drug antibodies (ADAs), and clinical efficacy (RECIST v1.1) were also evaluated. Results: At data cutoff (3 August 2018), LY3321367 monotherapy was administered to 23 pts (Arm A); 18 pts received LY3321367 combination therapy (Arm B) as phase 1a dose escalation (3 mths median follow-up). Treatment-related AEs observed in Arms A and B were mild (Gr ≤2), except for 1 pt with Gr 3 anemia in Arm B (200 mg LY3321367 + 700 mg LY3300054). No dose limiting toxicities, dose limiting-equivalent toxicities, treatment-related SAEs, or deaths were observed in Arm A or B. For LY3321367, 68.2% (Arm A) and 88.2% (Arm B) of pts were positive for treatment-emergent ADAs. Despite ADAs, no effect on PK was noted; ADA titers were low, except for 1 pt with an infusion-related reaction. LY3321367 t1/2 was ~22 days. Full TE was maintained 2 wks after 1200 mg dose; 600 mg Q2W maintained TE at steady-state. In Arm A, 2 pts had > 20% tumor regression, 1 of which was later confirmed as a PR in a post-PD-1 SCLC pt. Conclusions: LY3321367 is well tolerated as a monotherapy and in combination with LY3300054. The RP2D for LY3321367 combination therapy is 1200 mg IV infusions Q2W for cycles 1-2; 600 mg infusions Q2W starting at cycle 3 onward. Clinical trial information: NCT03099109.

Biomarkers for Diagnosis and Prognosis of Sinusoidal Obstruction Syndrome after Hematopoietic Cell Transplantation

Reliable, noninvasive methods for diagnosing and prognosing sinusoidal obstruction syndrome (SOS) early after hematopoietic cell transplantation (HCT) are needed. We used a quantitative mass spectrometry-based proteomics approach to identify candidate biomarkers of SOS by comparing plasma pooled from 20 patients with and 20 patients without SOS. Of 494 proteins quantified, we selected 6 proteins (L-Ficolin, vascular cell adhesion molecule-1 [VCAM1], tissue inhibitor of metalloproteinase-1, von Willebrand factor, intercellular adhesion molecule-1, and CD97) based on a differential heavy/light isotope ratio of at least 2 fold, information from the literature, and immunoassay availability. Next, we evaluated the diagnostic potential of these 6 proteins and 5 selected from the literature (suppression of tumorigenicity-2 [ST2], angiopoietin-2 (ANG2), hyaluronic acid [HA], thrombomodulin, and plasminogen activator inhibitor-1) in samples from 80 patients. The results demonstrate that together ST2, ANG2, L-Ficolin, HA, and VCAM1 compose a biomarker panel for diagnosis of SOS. L-Ficolin, HA, and VCAM1 also stratified patients at risk for SOS as early as the day of HCT. Prognostic Bayesian modeling for SOS onset based on L-Ficolin, HA, and VCAM1 levels on the day of HCT and clinical characteristics showed >80% correct prognosis of SOS onset. These biomarkers may provide opportunities for preemptive intervention to minimize SOS incidence and/or severity.

A population PK model for citalopram and its major metabolite, N-desmethyl citalopram, in rats

A population PK model was developed in order to simultaneously describe citalopram and its major metabolite, n-desmethyl citalopram, plasma concentrations in two different strain of rats after intravenous (IV) and oral (PO) administration of citalopram. Citalopram was administered to Sprague-Dawley (SD) rats at doses: 0.3, 1, 3, and 10 mg/kg IV and 10 mg/kg PO. The compound was dosed orally to Wistar rats at doses: 0.3, 1, 3, 10, 30 and 60 mg/kg. Plasma samples were collected for citalopram and metabolite. Pharmacokinetic analyses were conducted using NONMEM 7.2. Values below the quantification limit (BLQ < 0.1 ng/mL) were included in the analyses and treated as censored information. The disposition of citalopram was best described by a 3-compartment model and its desmethyl metabolite by a 2-compartment model. Several models for the absorption rate were explored (e.g. first, zero order and combined first and zero order absorption, Michaelis-Menten, lag time) in combination with dose and/or time dependent covariate effects. Dose dependent oral bioavailability properties were also identified in this analysis. Citalopram IV clearance and metabolite formation rate were adequately described as linear processes. Metabolite clearance was adequately described using a Michaelis-Menten clearance with different parameters depending on the strain. This analysis demonstrates a very complex absorption/metabolism process explaining the highly non-linear pharmacokinetics observed across all the doses. This is the first combined parent/metabolite population PK analysis in both SD and Wistar rats over a wide range of IV and PO dosages for citalopram, a compound that exhibits highly nonlinear oral pharmacokinetics in rats.

Prediction of brain clozapine and norclozapine concentrations in humans from a scaled pharmacokinetic model for rat brain and plasma pharmacokinetics

BACKGROUND

Clozapine is highly effective in treatment-resistant schizophrenia, although, there remains significant variability in the response to this drug. To better understand this variability, the objective of this study was to predict brain extracellular fluid (ECF) concentrations and receptor occupancy of clozapine and norclozapine in human central nervous system by translating plasma and brain ECF pharmacokinetic (PK) relationships in the rat and coupling these with known human disposition of clozapine in the plasma.

METHODS

Unbound concentrations of clozapine and norclozapine were measured in rat brain ECF using quantitative microdialysis after subcutaneous administration of a 10 mg/kg single dose of clozapine or norclozapine. These data were linked with plasma concentrations obtained in the same rats to develop a plasma-brain ECF compartmental model. Parameters describing brain ECF disposition were then allometrically scaled and linked with published human plasma PK to predict human ECF concentrations. Subsequently, prediction of human receptor occupancy at several CNS receptors was based on an effect model that related the predicted ECF concentrations to published concentration-driven receptor occupancy parameters.

RESULTS

A one compartment model with first order absorption and elimination best described clozapine and norclozapine plasma concentrations in rats. A delay in the transfer of clozapine and norclozapine from plasma to the brain ECF compartment was captured using a transit compartment model approach. Human clozapine and norclozapine concentrations in brain ECF were simulated, and from these the median percentage of receptor occupancy of dopamine-2, serotonin-2A, muscarinic-1, alpha-1 adrenergic, alpha-2 adrenergic and histamine-1 for clozapine, and dopamine-2 for norclozapine were consistent with values reported in the literature.

CONCLUSIONS

A PK model that relates clozapine and norclozapine disposition in rat plasma and brain, including blood-brain barrier transport, was developed. Using allometry and published human plasma PK, the model was successfully translated to predict clozapine and norclozapine concentrations and accordant receptor occupancy of both agents in human brain. These predicted exposure and occupancy measures at several receptors that bind clozapine may be employed to extend our understanding of clozapine's complex behavioral effects in humans.

Therapeutic hypothermia decreases phenytoin elimination in children with traumatic brain injury

OBJECTIVE

Preclinical and clinical studies have suggested that therapeutic hypothermia, while decreasing neurologic injury, may also lead to drug toxicity that may limit its benefit. Cooling decreases cytochrome P450 (CYP)-mediated drug metabolism, and limited clinical data suggest that drug levels are elevated. Fosphenytoin is metabolized by cytochrome P450 2C, has a narrow therapeutic range, and is a commonly used antiepileptic medication. The objective of this study was to evaluate the impact of therapeutic hypothermia on phenytoin levels and pharmacokinetics in children with severe traumatic brain injury.

DESIGN

Pharmacokinetic analysis of subjects participating in a multicenter randomized phase III study of therapeutic hypothermia for severe traumatic brain injury.

SETTING

ICU at the Children's Hospital of Pittsburgh.

PATIENTS

Nineteen children with severe traumatic brain injury.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A sum of 121 total and 114 free phenytoin levels were evaluated retrospectively in 10 hypothermia-treated and nine normothermia-treated children who were randomized to 48 hours of cooling to 32-33°C followed by slow rewarming or controlled normothermia. Drug dosing, body temperatures, and demographics were collected during cooling, rewarming, and posttreatment periods (8 d). A trend toward elevated free phenytoin levels in the hypothermia group (p=0.051) to a median of 2.2 mg/L during rewarming was observed and was not explained by dosing differences. Nonlinear mixed-effects modeling incorporating both free and total levels demonstrated that therapeutic hypothermia specifically decreased the time-variant component of the maximum velocity of phenytoin metabolism (Vmax) 4.6-fold (11.6-2.53 mg/hr) and reduced the overall Vmax by ~50%. Simulations showed that the increased risk for drug toxicity extends many days beyond the end of the cooling period.

CONCLUSIONS

Therapeutic hypothermia significantly reduces phenytoin elimination in children with severe traumatic brain injury leading to increased drug levels for an extended period of time after cooling. Pharmacokinetic interactions between hypothermia and medications should be considered when caring for children receiving this therapy.

Dynamic cross-regulation of antigen-specific effector and regulatory T cell subpopulations and microglia in brain autoimmunity

Background

Multiple Sclerosis (MS) is considered a T-cell-mediated autoimmune disease with a prototypical oscillatory behavior, as evidenced by the presence of clinical relapses. Understanding the dynamics of immune cells governing the course of MS, therefore, has many implications for immunotherapy. Here, we used flow cytometry to analyze the time-dependent behavior of antigen-specific effector (T_eff) and regulatory (T_reg) T cells and microglia in mice model of MS, Experimental Autoimmune Encephalomyelitis (EAE), and compared the observations with a mathematical cross-regulation model of T-cell dynamics in autoimmune disease.

Results

We found that T_eff and T_reg cells specific to myelin olygodendrocyte glycoprotein (MOG) developed coupled oscillatory dynamics with a 4- to 5-day period and decreasing amplitude that was always higher for the T_eff populations, in agreement with the mathematical model. Microglia activation followed the oscillations of MOG-specific T_eff cells in the secondary lymphoid organs, but they were activated before MOG-specific T-cell peaks in the CNS. Finally, we assessed the role of B-cell depletion induced by anti-CD20 therapy in the dynamics of T cells in an EAE model with more severe disease after therapy. We observed that B-cell depletion decreases T_eff expansion, although its oscillatory behavior persists. However, the effect of B cell depletion was more significant in the T_reg population within the CNS, which matched with activation of microglia and worsening of the disease. Mathematical modeling of T-cell cross-regulation after anti-CD20 therapy suggests that B-cell depletion may influence the dynamics of T cells by fine-tuning their activation.

Conclusions

The oscillatory dynamics of T-cells have an intrinsic origin in the physiological regulation of the adaptive immune response, which influences both disease phenotype and response to immunotherapy.

Exploring the morphospace of communication efficiency in complex networks

Graph theoretical analysis has played a key role in characterizing global features of the topology of complex networks, describing diverse systems such as protein interactions, food webs, social relations and brain connectivity. How system elements communicate with each other depends not only on the structure of the network, but also on the nature of the system's dynamics which are constrained by the amount of knowledge and resources available for communication processes. Complementing widely used measures that capture efficiency under the assumption that communication preferentially follows shortest paths across the network (“routing”), we define analytic measures directed at characterizing network communication when signals flow in a random walk process (“diffusion”). The two dimensions of routing and diffusion efficiency define a morphospace for complex networks, with different network topologies characterized by different combinations of efficiency measures and thus occupying different regions of this space. We explore the relation of network topologies and efficiency measures by examining canonical network models, by evolving networks using a multi-objective optimization strategy, and by investigating real-world network data sets. Within the efficiency morphospace, specific aspects of network topology that differentially favor efficient communication for routing and diffusion processes are identified. Charting regions of the morphospace that are occupied by canonical, evolved or real networks allows inferences about the limits of communication efficiency imposed by connectivity and dynamics, as well as the underlying selection pressures that have shaped network topology.

Lexical access changes in patients with multiple sclerosis: a two-year follow-up study

The aim of the study was to analyze lexical access strategies in patients with multiple sclerosis (MS) and their changes over time. We studied lexical access strategies during semantic and phonemic verbal fluency tests and also confrontation naming in a 2-year prospective cohort of 45 MS patients and 20 healthy controls. At baseline, switching lexical access strategy (both in semantic and in phonemic verbal fluency tests) and confrontation naming were significantly impaired in MS patients compared with controls. After 2 years follow-up, switching score decreased, and cluster size increased over time in semantic verbal fluency tasks, suggesting a failure in the retrieval of lexical information rather than an impairment of the lexical pool. In conclusion, these findings underline the significant presence of lexical access problems in patients with MS and could point out their key role in the alterations of high-level communications abilities in MS.