Higher Peak Plasma Concentration Research Articles

Novel biaryloxazolidinone derivatives with broad-spectrum antibacterial activity, favorable drug-like profiles and in vivo efficacy against linezolid-resistant Staphylococcusaureus

The emergence of multidrug-resistant bacteria along with a declining pipeline of clinically useful antibiotics has led to the urgent need for the development of more effective antibacterial agents to treat drug-resistant bacteria. We previously discovered compound OB-158 with potent antibacterial activity but exhibited poor oral bioavailability. Herein, a systematic structural optimization of OB-158 to improve pharmacokinetic profiles yielded 26 novel biaryloxazolidinone analogues, and their activities against Gram-positive S. aureus, multidrug resistant S. aureus and Enterococcus faecalis were evaluated. Remarkably, compound 8b was identified with potent antibacterial activity against S. aureus (MIC=0.06μg/mL), MSSA (MIC=0.125μg/mL), MRSA (MIC=0.06μg/mL), LRSA (MIC=0.125μg/mL) and LREFa (MIC=0.5μg/mL). Compound 8b was demonstrated as a promising candidate through druglikeness evaluation including metabolism in microsomes and plasma, Caco-2cell permeability, plasma protein binding, cytotoxicity, and inhibition of CYP450 and human monoamine oxidase. Notably, compound 8b displayed excellent PK profile with appropriate T1/2 of 1.49h, high peak plasma concentration (Cmax=2320ng/mL), high plasma exposure (AUC0-t=8310hng/mL), and superior oral bioavailability (F=68.1%) in Sprague-Dawley rats. Ultimately, in vivo efficacy of compound 8b in a mouse model of LRSA systemic infection was also demonstrated. Taken together, compound 8b represents a promising drug candidate for the treatment of linezolid-resistant Gram-positive bacterial strains infection.

Novel protocol for multiple-dose oral administration of the L-type Ca2+ channel blocker isradipine in mice: A dose-finding pharmacokinetic study

ABSTRACT Studies in genetically modified animals and human genetics have recently provided new insight into the role of voltage-gated L-type Ca2+ channels in human disease. Therefore, the inhibition of L-type Ca2+ channels in vivo in wildtype and mutant mice by potent dihydropyridine (DHP) Ca2+ channel blockers serves as an important pharmacological tool. These drugs have a short plasma half-life in humans and especially in rodents and show high first-pass metabolism upon oral application. In the vast majority of in vivo studies, they have therefore been delivered through parenteral routes, mostly subcutaneously or intraperitoneally. High peak plasma concentrations of DHPs cause side effects, evident as DHP-induced aversive behaviors confounding the interpretation of behavioral readouts. Nevertheless, pharmacokinetic data measuring the exposure achieved with these applications are sparse. Moreover, parenteral injections require animal handling and can be associated with pain, discomfort and stress which could influence a variety of physiological processes, behavioral and other functional readouts. Here, we describe a noninvasive oral application of the DHP isradipine by training mice to quickly consume small volumes of flavored yogurt that can serve as drug vehicle. This procedure does not require animal handling, allows repeated drug application over several days and reproducibly achieves peak plasma concentrations over a wide range previously shown to be well-tolerated in humans. This protocol should facilitate ongoing nonclinical studies in mice exploring new indications for DHP Ca2+ channel blockers.

Quality by design (QbD) approach to develop fast-dissolving tablets using melt-dispersion paired with surface-adsorption method: formulation and pharmacokinetics of flurbiprofen melt-dispersion granules.

Developing amorphous solid dispersions with good flow properties is always challenging for formulation scientists to convert into tablets. Hence, the present study investigates the impact of the combination of melt-dispersion and surface-adsorption methods to prepare melt-dispersion granules with enhanced dissolution rate and flow properties. This study covers the formulation and pharmacokinetic study of fast-dissolving flurbiprofen tablets using PEG 6000 (hydrophilic carrier) and lactose (adsorbent). Response surface methodology (RSM) using the central composite design (CCD) was used to optimize independent variables like carrier concentrations and adsorbent concentrations, and their interactions with the dependent variables (responses), including solubility, angle of repose, Carr's index, and cumulative % drug release, were investigated. The optimized formulation was selected based on the numerical optimization method and further investigated for FTIR spectroscopy, differential scanning calorimetry, and X-ray diffractometry. Then, the optimized formulation was compressed into tablets and evaluated for both in vitro dissolution and in vivo pharmacokinetics parameters. In vitro dissolution studies revealed that the prepared fast-dissolving tablets released the drug entirely within 15min (Q15 of F4 tablets: 99.34 ± 1.24%), whereas conventional tablets took around 60min for complete dissolution. Pharmacokinetic studies in rats revealed that fast-dissolving tablets showed 1.38-fold higher peak-plasma concentration (Cmax) and 1.39-fold higher bioavailability than conventional tablets. Overall, this study revealed the successful fabrication of fast-dissolving tablets via melt-dispersion paired with the surface-adsorption method to enhance the flow properties and the dissolution rate.

High rifampicin peak plasma concentrations accelerate the slow phase of bacterial decline in tuberculosis patients: Evidence for heteroresistance.

Antibiotic treatments are often associated with a late slowdown in bacterial killing. This separates the killing of bacteria into at least two distinct phases: a quick phase followed by a slower phase, the latter of which is linked to treatment success. Current mechanistic explanations for the in vitro slowdown are either antibiotic persistence or heteroresistance. Persistence is defined as the switching back and forth between susceptible and non-susceptible states, while heteroresistance is defined as the coexistence of bacteria with heterogeneous susceptibilities. Both are also thought to cause a slowdown in the decline of bacterial populations in patients and therefore complicate and prolong antibiotic treatments. Reduced bacterial death rates over time are also observed within tuberculosis patients, yet the mechanistic reasons for this are unknown and therefore the strategies to mitigate them are also unknown. We analyse a dose ranging trial for rifampicin in tuberculosis patients and show that there is a slowdown in the decline of bacteria. We show that the late phase of bacterial killing depends more on the peak drug concentrations than the total drug exposure. We compare these to pharmacokinetic-pharmacodynamic models of rifampicin heteroresistance and persistence. We find that the observation on the slow phase's dependence on pharmacokinetic measures, specifically peak concentrations are only compatible with models of heteroresistance and incompatible with models of persistence. The quantitative agreement between heteroresistance models and observations is very good ([Formula: see text]). To corroborate the importance of the slowdown, we validate our results by estimating the time to sputum culture conversion and compare the results to a different dose ranging trial. Our findings indicate that higher doses, specifically higher peak concentrations may be used to optimize rifampicin treatments by accelerating bacterial killing in the slow phase. It adds to the growing body of literature supporting higher rifampicin doses for shortening tuberculosis treatments.

Design, Formulation, and Characterization of Valsartan Nanoethosomes for Improving Their Bioavailability.

The objective of this study was to formulate and evaluate valsartan (VLT) ethosomes to prepare an optimized formula of VLT-entrapped ethosomes that could be incorporated into a sustained release transdermal gel dosage form. The formulation of the prepared ethosomal gel was investigated and subjected to in vitro drug release studies, ex vivo test, and in vivo studies to assess the effectiveness of ethosomal formulation in enhancing the bioavailability of VLT as a poorly soluble drug and in controlling its release from the transdermal gel dosage form. The acquired results are as follows: Dependent responses were particle size, polydispersity index, zeta potential, and entrapment efficiency. The optimized VLT-ETHs had a nanometric diameter (45.8 ± 0.5 nm), a negative surface charge (-51.4 ± 6.3 mV), and a high drug encapsulation (94.24 ± 0.2). The prepared VLT ethosomal gel (VLT-ethogel) showed a high peak plasma concentration and enhanced bioavailability in rats compared with the oral solution of valsartan presented in the higher AUC (0-∞). The AUC (0-∞) with oral treatment was 7.0 ± 2.94 (μg.h/mL), but the AUC (0-∞) with topical application of the VAL nanoethosomal gel was 137.2 ± 49.88 (μg.h/mL), providing the sustained release pattern of VLT from the tested ethosomal gel.

Abiraterone decanoate (PRL-02): Pharmacology of a single intramuscular (IM) depot injection compared to oral abiraterone acetate (AA) in intact male rats.

160 Background: Oral AA is a standard of care for metastatic prostate cancer. The recommended daily AA 1000 mg dose produces high peak and low trough plasma concentrations that are associated with safety issues (e.g., hepatotoxicity) and inadequate efficacy, respectively. PRL-02 is a novel abiraterone prodrug undergoing evaluation in patients with advanced prostate cancer (NCT04729114). In chemically-castrate monkeys, single doses of PRL-02 suppressed androgens for 14 weeks at much lower plasma exposures than AA (Moore et al, ASCO GU 2021). The present study in intact male rats evaluated the systemic exposures and activity of PRL-02 compared to daily oral AA at 7 and/or 14 days post-treatment start. Methods: Sexually mature male rats (n=4 per timepoint) were administered a single IM dose of PRL-02 (90 mg/kg), daily AA (90 mg/kg) or IM/oral vehicle (VEH). Biological samples were collected on Day 7 (PRL-02/VEH; 0h) or Day 14 (PRL-02/AA/VEH; 2, 6 and 24h) post-dosing. Drug and androgen concentrations were determined by LC-MS/MS. Testicular CYP17 hydroxylase activity was measured ex vivo on Day 14. Results: The Day 14 plasma exposure from abiraterone was greater from AA (5.6 - 210 ng/mL) than from PRL-02 (1.15 – 1.37 ng/mL). However, for Day 14 tissue exposures (AUC0-24) from ‘total abiraterone equivalents’ (TAE; concentration of free abiraterone plus abiraterone from prodrug) were greater from PRL-02 in adrenal, testes, lymph node and bone target tissues than from oral AA; exposures from AA were only greater in non-target tissues such as liver and brain (Table). There was no measurable Day 14 CYP17 hydroxylase activity in testes following PRL-02 or AA dosing; inhibition appeared irreversible from PRL-02 and AA. Compared to VEH, a single IM dose of PRL-02 resulted in 81% and 75% reductions in plasma testosterone (T) on Days 7 and 14 post-dose, and an 80% reduction in testicular T on Day 14. Daily AA resulted in a 98% reduction in plasma T after 14 days. Conclusions: Single-dose IM PRL-02 blocked testicular CYP17 enzyme activity as effectively as daily AA in intact male rats and produced a durable large reduction in plasma T. The pharmacological activity, tissue and plasma distribution of TAE from IM PRL-02 in the rat model, along with results from prior monkey model studies, suggest the potential for a greater therapeutic index than from daily oral AA and support the ongoing evaluation of IM PRL-02 in patients with advanced prostate cancer.[Table: see text]

Final Results of a Phase 1b Study of BET Inhibitor PLX2853 in Patients with Relapsed or Refractory Acute Myeloid Leukemia or High Risk Myelodysplastic Syndrome

Final Results of a Phase 1b Study of BET Inhibitor PLX2853 in Patients with Relapsed or Refractory Acute Myeloid Leukemia or High Risk Myelodysplastic Syndrome

Central nervous system infections and antimicrobial resistance: an evolving challenge.

Antimicrobial resistance is an increasing threat to patients also in nosocomial central nervous system (CNS) infections. The present review focusses on optimizing intravenous treatment in order to achieve sufficient concentrations of antibiotics in the different compartments of the CNS when the causative pathogens have reduced sensitivity to antibiotics or/and the impairment of the blood-cerebrospinal fluid (CSF) and blood-brain barrier is mild. Experience has been gathered with treatment protocols for several established antibiotics using increased doses or continuous instead of intermittent intravenous therapy. Continuous infusion in general does not increase the average CSF concentrations (or the area under the concentration-time curve in CSF) compared to equal daily doses administered by short-term infusion. In some cases, it is postulated that it can reduce toxicity caused by high peak plasma concentrations. In case reports, new β-lactam/β-lactamase inhibitor combinations were shown to be effective treatments of CNS infections. Several antibiotics with a low to moderate toxicity (in particular, β-lactam antibiotics, fosfomycin, trimethoprim-sulfamethoxazole, rifampicin, vancomycin) can be administered at increased doses compared to traditional dosing with low or tolerable adverse effects. Intrathecal administration of antibiotics is only indicated, when multiresistant pathogens cannot be eliminated by systemic therapy. Intravenous should always accompany intrathecal treatment.

Identification of Novel Tricyclic Benzo[1,3]oxazinyloxazolidinones as Potent Antibacterial Agents with Excellent Pharmacokinetic Profiles against Drug-Resistant Pathogens.

A series of conformationally constrained novel benzo[1,3]oxazinyloxazolidinones were designed, synthesized, and evaluated on their activities against Mycobacterium tuberculosis, Gram-positive bacteria, and Gram-negative bacteria. The studies identified a new compound 20aa that displayed good to excellent antibacterial and antitubercular profiles against drug-resistant TB strains (MIC = 0.48-0.82 μg/mL), MRSA (MIC = 0.25-0.5 μg/mL), MRSE (MIC = 1 μg/mL), VISA (MIC = 0.25 μg/mL), and VRE (MIC = 0.25 μg/mL) and some linezolid-resistant strains (MIC 1-2 μg/mL). Compound 20aa was demonstrated as a promising candidate through ADME/T evaluation including microsomal stability, cytotoxicity, and inhibition of hERG and monoamine oxidase. Notably, 20aa showed excellent mouse PK profile with high plasma exposure (AUC0-∞ = 78 669 h·ng/mL), high peak plasma concentration (Cmax = 10 253 ng/mL), appropriate half-life of 3.76 h, and superior oral bioavailability (128%). The present study not only successfully provides a novel benzo[1,3]oxazinyloxazolidinone scaffold with superior druggability but also lays a good foundation for new antibacterial drug development.

Abiraterone decanoate (AD): Potent and long-acting activity of a novel intramuscular (IM) abiraterone prodrug depot in a castrate monkey model.

78 Background: Oral abiraterone acetate (AA) is a standard of care for castration-resistant (CRPC) and castration-sensitive prostate cancer (CSPC). Due to poor oral bioavailability, the recommended AA dose is 1,000 mg (4 x 250mg) once-daily on an empty stomach. The daily oral regimen produces high peak plasma concentrations that may be associated with safety issues (e.g., hepatotoxicity) and low trough concentrations that may be associated with inadequate CYP17 inhibition. AD is one of a series of novel abiraterone prodrugs that were designed to provide a controlled release of abiraterone and long-acting CYP17 inhibition with IM delivery. Following successful preclinical pilot studies, AD was further developed into a clinically acceptable formulation (PRL-02) and its PK/PD characteristics were evaluated and compared to oral AA in a castrate monkey pharmacology model in support of future clinical development. Methods: Sexually mature male cynomolgus monkeys underwent chemical castration using Lupron depot. Plasma samples were analyzed for prodrug, abiraterone and steroid concentrations following a single oral AA dose (5, 15 or 45 mg/kg) and a single IM AD injection (10, 30 or 100 mg/kg) (n=3/dose group). The combined activity of IM AD plus glucocorticoid replacement (single 0.5 mg/kg IM dexamethasone (DEX) dose or weekly doses of 1.29 mg/kg IM methylprednisolone acetate (MPA)) was also evaluated. AD, abiraterone and adrenal steroid levels were evaluated by LC-MS/MS. Results: Chemical castration resulted in a plasma testosterone (T) decrease of 72% from intact. T was further reduced to sub-castrate levels by both AA and AD (98.6% and 99.7% maximum decrease from castrate baseline, respectively). All dose levels of AD were highly effective in reducing plasma T yet led to abiraterone plasma concentrations (Cmax, AUC, Cmin) that were much less than those associated with steady-state clinical levels from oral AA. Sustained T suppression was observed following all single AD IM doses for 14 weeks, the last timepoint tested.The addition of a glucocorticoid replacement (DEX or MPA) starting at week 9 further reduced T in all AD groups. Conclusions: Single-dose IM AD suppressed T to the same or greater extent than single-dose oral AA in castrate monkeys, while providing much lower abiraterone exposures than the oral acetate prodrug. As such, IM AD may offer an improved risk-benefit profile due to the consistently lower abiraterone levels. The durable, profound T reductions provided by all AD doses are consistent with a 3-month clinical regimen that can be given in conjunction with Lupron. IM AD may thus offer patients with CSPC and CRPC a more convenient, safe and effective alternative than daily oral AA.

Phase 1b Study of BET Inhibitor PLX2853 in Patients with Relapsed or Refractory Acute Myeloid Leukemia or High Risk Myelodysplastic Syndrome

Phase 1b Study of BET Inhibitor PLX2853 in Patients with Relapsed or Refractory Acute Myeloid Leukemia or High Risk Myelodysplastic Syndrome

Mifepristone polymorph with enhanced solubility, dissolution and oral bioavailability

Mifepristone is one of potent anti-progesterone agents, which binds to progesterone receptors and glucocorticoid receptors. Until now, there are a lot of research focusing on enhancing the solubility and oral bioavailability of Mifepristone. However, poor solubility and oral bioavailability has some undesirable consequences. In this work, Mifepristone in form D was discovered for the first time and characterized by PXRD, TGA, DSC, FT-IR, SEM and SS NMR. Form D was a metastable crystal type which manifested favorable stability under ambient conditions. Form D had better dissolution characteristic compared with commercial Mifepristone in 0.5% SDS solution. In addition, Mifepristone in form D exhibited a 1.43-fold higher peak plasma concentration (Cmax) and 1.46-fold higher area under the curve (AUC) in rats. The work in this paper is a complement to the present understanding of drug polymorphism on the in vitro and in vivo behavior, and establishes the ground work for future development of Mifepristone in form D as a promising drug for the market.

Abstract C079: Effect of food on the pharmacokinetics of high dose intermittent sunitinib in patients with advanced solid tumors

Abstract Background: Optimization of the clinical use of multi-targeting tyrosine kinase inhibitors (TKIs), as sunitinib, is needed to fully exploit their potential antitumor activity. Sunitinib was developed to inhibit angiogenesis-related kinases, but at conventional daily dosing it also directly inhibits tumor cell growth. The inhibitory activity of sunitinib is dependent on its discriminative affinity for specific kinases, its intracellular concentrations reached at the tumor level and the presence and activity of kinases in tumor cells. Administration of sunitinib in a higher dose, similar to convential chemotherapy, might further utilize this direct antitumor effect and the strong broad kinase inhibitory potency of sunitinib. In a recent phase I trial of high dose intermittent sunitinib the maximum tolerated dose of 700 mg once every two weeks (Q2W) resulted in high peak plasma concentrations (Cmax) of >500 µg/l, without drug accumulation. 63% of 69 heavily pretreated patients with advanced cancer had clinical benefit, with similar toxicity compared to standard daily dosing. Pharmacokinetic (PK) evaluation showed significant interpatient variability of this alternative regimen. In the current study, we evaluated the effect of food on the interpatient variation in bioavailability and studied whether food would further increase Cmax. Methods: 700 mg sunitinib Q2W was administered to patients with refractory solid tumors. Patients were randomized to either start sunitinib after a 10-hour fasted regimen or within 30 minutes after a high fat meal followed by the alternative at the second cycle. PK and safety assessments were obtained. Treatment continued until progression or unacceptable toxicity. Drug plasma concentrations were measured by LC-MS/MS. Geometric mean ratios (GMR) and 90% confidence intervals (CI) of the sum concentration of sunitinib and SU12662 were estimated. Results:Twelve patients were included. Both intake regimens were not bioequivalent. The GMR (fed/fasted) of the AUC0-µ and Cmax were 1.33 (90% CI 1.03-1.70) and 1.30 (90% CI 1.02-1.65), respectively. Compared with the fasted state, a high-fat meal delayed time to maximum plasma concentration by 1.6 hours. The observed non bioequivalence and increase in drug exposure appeared to be mainly caused by 2 patients who suffered from early vomiting (~3hrs) after drug ingestion in the fasted state. After excluding them from the analysis, the GMR of the AUC0-µ and Cmax change to 1.09 (90% CI 0.98-1.22) and 1.09 (90% CI 0.96-1.23), respectively, indicating that both regimens were bioequivalent. The interpatient variability for AUC0-µ was reduced by the intake of food; 32.5% (fasted) to 29% (fed), while for Cmax the interpatient variability was similar 34.4% and 33.3%. Adverse events were similar to our prior phase I study with mainly grade I-II toxicities including fatigue (58%), nausea (50%) and anorexia (42%). Conclusions: Our study demonstrates that high dose sunitinib can be taken with or without food. For the patients without GI toxicity early after intake, the exposure to sunitinib was bioequivalent. Interpatient variability appeared to be modestly reduced by taken sunitinib with food. The results support the recommendation for administration of high dose sunitinib in a fed state to achieve more consistent therapeutic exposure and increased tolerance. Results from ongoing phase II trials with high dose intermittent sunitinib for patients with colorectal cancer and glioblastoma are eagerly awaited. Citation Format: Sophie L. Gerritse, Mariette Labots, Maria Rovithi, Angela Colbers, Olaf J.L. Loosveld, Mikkjal Skardhamar, Nielka P. van Erp, Henk M.W. Verheul. Effect of food on the pharmacokinetics of high dose intermittent sunitinib in patients with advanced solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C079. doi:10.1158/1535-7163.TARG-19-C079

Dose Escalation Study of BET Inhibitor PLX2853 in Patients with Relapsed or Refractory Acute Myeloid Leukemia or High Risk Myelodysplastic Syndrome

Background: PLX2853 is an orally available, non-benzodiazepine BET (bromodomain and extraterminal domain) inhibitor that exhibits low nanomolar potency and a modest preference for binding to the second bromodomain (BD2) of the BET proteins. By regulating genes (e.g. MYC and BCL2) critical to leukemic cell growth and survival, PLX2853 demonstrated broad anti-leukemic activity both as a single agent and in combination with other therapeutic agents in preclinical models. The pharmacokinetic (PK) profile in solid tumor patients revealed a short half-life (< 3 hour) enabling high peak plasma concentrations and nearly complete elimination from the plasma 9 hour post dose. Since strong and prolonged suppression of BET proteins have often untoward effects in normal tissues, the PLX2853 PK profile is hypothesized to be associated with improved tolerability by allowing transient target engagement followed by time for recovery after daily dosing. Methods: We are conducting an open-label, Phase 1b (Ph1b) study of PLX2853 as a single oral agent administered daily in adult patients with relapsed or refractory acute myeloid leukemia (AML) or high risk myelodysplastic syndrome (MDS) using a modified continuous reassessment model (mCRM) with escalation with overdose control (EWOC) to determine the recommended phase 2 dose (RP2D). Up to 36 patients are expected to enroll. The dosing cycle and dose limiting toxicity window (DLT) is 21 days. Primary objectives include safety and PK. Secondary objectives include measures of preliminary efficacy, and exploratory objectives include pharmacodynamics (PD) biomarker assessments in various tissues. Enrollment through Cohort 2 (40 mg QD) is ongoing as of July 2019. Results: Five subjects with relapsed or refractory AML (median age 65 years) have received PLX2853 in escalating doses from 20 to 40 mg QD. Among these first 5 patients treated, the most common treatment emergent adverse events (AEs) regardless of causality in > 1 patient: decreased appetite (n=3), nausea (n=2), diarrhea (n=2), peripheral edema (n=2), cough (n=2), oropharyngeal pain (n=2), blood bilirubin increase (n=2), anemia (n=2), febrile neutropenia (n=2), fatigue (n=2), bacteremia (n=2), headache (n=2), dyspnea (n=2), and hypertension (n=2). Most were grade (G) 1-2. Treatment emergent AEs > G2 in > 1 patient included: anemia (n=2), febrile neutropenia (n=2) and hypertension (n=2). No treatment-related serious AEs or DLTs have been observed. Following a 20 mg daily dose of PLX2853, median time to reach maximal plasma concentrations (Tmax) is 1 hour and the absorption half-life (T1/2) is < 3 hours. Conclusions: In an ongoing Ph1b study, PLX2853 has now completed its first dosing cohort for patients with relapsed or refractory AML or high risk MDS, and no DLT has been observed yet. As dose escalation continues, PK, PD, preliminary safety and efficacy data will be assessed further to determine the clinical significance of target engagement. This clinical trial is registered at clinicaltrials.gov: NCT03787498. Disclosures Pemmaraju: mustangbio: Consultancy, Research Funding; abbvie: Consultancy, Honoraria, Research Funding; samus: Research Funding; celgene: Consultancy, Honoraria; cellectis: Research Funding; Stemline Therapeutics: Consultancy, Honoraria, Research Funding; novartis: Consultancy, Research Funding; plexxikon: Research Funding; Daiichi-Sankyo: Research Funding; sagerstrong: Research Funding; affymetrix: Research Funding; incyte: Consultancy, Research Funding. Borate:Novartis: Consultancy; Takeda: Consultancy; Pfizer: Consultancy; Daiichi Sankyo: Consultancy; AbbVie: Consultancy. Solh:ADC Therapeutics: Research Funding; Amgen: Speakers Bureau; Celgene: Speakers Bureau. Borthakur:Polaris: Research Funding; Arvinas: Research Funding; Agensys: Research Funding; Tetralogic Pharmaceuticals: Research Funding; Cantargia AB: Research Funding; Argenx: Membership on an entity's Board of Directors or advisory committees; BioLine Rx: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Oncoceutics, Inc.: Research Funding; Eli Lilly and Co.: Research Funding; BMS: Research Funding; AstraZeneca: Research Funding; Bayer Healthcare AG: Research Funding; Novartis: Research Funding; FTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; AbbVie: Research Funding; Strategia Therapeutics: Research Funding; Cyclacel: Research Funding; Xbiotech USA: Research Funding; Eisai: Research Funding; Merck: Research Funding; BioTheryX: Membership on an entity's Board of Directors or advisory committees; Oncoceutics: Research Funding; NKarta: Consultancy; Incyte: Research Funding; Janssen: Research Funding; GSK: Research Funding; PTC Therapeutics: Consultancy. DeZern:Astex Pharmaceuticals, Inc.: Consultancy; Celgene: Consultancy. Zhang:Plexxikon Inc.: Employment. Powell:Plexxikon Inc.: Employment. Severson:Plexxikon Inc.: Employment. Inokuchi:Plexxikon Inc.: Employment. Matusow:Plexxikon Inc.: Employment. Halladay:Plexxikon Inc.: Employment. Hsu:Daiichi Sankyo, Inc.: Employment. Watkins:Plexxikon Inc.: Employment. Walling:Myovant Sciences: Consultancy; Nurix: Consultancy; Aduro Biotech: Consultancy; Plexxikon: Consultancy; CytomyX: Consultancy; Flag Therapeutics: Consultancy; Aminex: Consultancy; Immunext: Consultancy; SensenBio: Consultancy; Harpoon Therapeutics: Consultancy. Tsiatis:Plexxikon Inc.: Employment. Mims:PTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; Astellas Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Preclinical toxicity and pharmacokinetics of a new orally bioavailable flubendazole formulation and the impact for clinical trials and risk/benefit to patients.

BackgroundFlubendazole, originally developed to treat infections with intestinal nematodes, has been shown to be efficacious in animal models of filarial infections. For treatment of filarial nematodes, systemic exposure is needed. For this purpose, an orally bioavailable amorphous solid dispersion (ASD) formulation of flubendazole was developed. As this formulation results in improved systemic absorption, the pharmacokinetic and toxicological profile of the flubendazole ASD formulation have been assessed to ensure human safety before clinical trials could be initiated.Methods & findingsSafety pharmacology, toxicity and genotoxicity studies have been conducted with the flubendazole ASD formulation.In animals, flubendazole has good oral bioavailability from an ASD formulation ranging from 15% in dogs, 27% in rats to more than 100% in jirds. In in vivo toxicity studies with the ASD formulation, high systemic exposure to flubendazole and its main metabolites was reached. Flubendazole, up to high peak plasma concentrations, does not induce Cmax related effects in CNS or cardiovascular system. In repeated dose toxicity studies in rats and dogs, flubendazole-induced changes were observed in haematological, lymphoid and gastrointestinal systems and in testes. In dogs, the liver was an additional target organ. Upon treatment cessation, at least partial recovery was observed for these changes in dogs. In rats, the No Observed Adverse Effect Level (NOAEL) was 5 mg (as base)/kg body weight/day (mg eq./kg/day) in males and 2.5 mg eq./kg/day in females. In dogs, the NOAEL was lower than 20 mg eq./kg/day. Regarding genotoxicity, flubendazole was negative in the Ames test, but positive in the in vivo micronucleus test.ConclusionsBased on these results, in combination with previously described genotoxicity and reproductive toxicity data and the outcome of the preclinical efficacy studies, it was concluded that no flubendazole treatment regimen can be selected that would provide efficacy in humans at safe exposure.

Daptomycin Plasma and CSF Levels in Patients with Healthcare-Associated Meningitis.

There are currently few data concerning the cerebrospinal fluid (CSF) penetration of daptomycin in patients with healthcare-associated meningitis. This study aims (1) to better characterize the pharmacokinetics of daptomycin in humans during a 7-day intravenous (IV) therapy course, and (2) to study the penetration of daptomycin in the CSF after IV infusion at the dose of 10mg/kg. In this prospective observational study, we enrolled nine patients with an implanted external ventricular drainage and a diagnosis of a healthcare-associated meningitis. Daptomycin was administered at 10mg/kg for a maximum of 7days. The pharmacokinetic of daptomycin was studied using a two-compartment population/pharmacokinetic (POP/PK) model and by means of a nonlinear mixed effects modeling approach. A large inter-individual variability in plasma area under the curve (Range: 574.7-1366.3hmg/L), paralleled by high-peak plasma concentration (Cmax) (all values > 60mg/L), was noted. The inter-individual variability of CSF-AUC although significant (range: 1.17-6.81hmg/L) was narrower than previously reported and with a late occurrence of CSF-Cmax (range: 6.04-9.54h). The terminal half-life between plasma and CSF was similar. tmax values in CSF did not show a high inter-individual variability, and the fluctuations of predicted CSF concentrations were minimal. The mean value for daptomycin penetration obtained from our model was 0.45%. Our POP/PK model was able to describe the pharmacokinetics of daptomycin in both plasma and CSF, showing that daptomycin (up to 7days at 10mg/kg) has minimal penetration into central nervous system. Furthermore, the observed variability of AUC, tmax and predicted concentration in CSF was lower than what previously reported in the literature. Based on the present findings, it is unlikely that daptomycin could reach CSF concentrations high enough to have clinical efficacy; this should be tested in future studies.

P2.13-20 The Comparative Effectiveness of Gefitinib Versus Erlotinib on the Intracranial Progression-Free Survival in Patients with Brain Metastasis

The high peak plasma concentrations and better blood-brain barrier permeability of erlotinib compared with gefitinib was reported. However, there were few researches comparing their treatment effect for brain metastasis. This study aimed to investigate the comparative effectiveness of gefitinib versus erlotinib on the survival in patients with brain metastasis from lung adenocarcinoma. Incident lung adenocarcinoma patients at National Taiwan University Hospital between Jan 2013 and May 2015 were reviewed and analyzed. The inclusion criteria were: (1) tumor harboring either EGFR exon 19 deletion or L858R mutation (2) patient taking gefitinib or erlotinib as their first-line treatment (3) patients with brain metastasis. Kaplan-Meier analyses with long-rank testing were used to estimate the intracranial progression-free survival (PFS) and overall survival between the gefitinib and erlotinib group. A Cox proportional hazard model was used to calculate the hazard ratio (HR) and 95% confidence intervals (CI) for age, gender, gefitinib vs. erlotinib, Eastern Cooperative Oncology Group performance status(ECOG), and pre-treatment for brain metastasis. Cumulative incidence of intracranial progression using competing risks regression model was also conducted. A total of 84 patients were included; 61 patients were female. 37 patients harbored EGFR exon 19 deletion. 39 patients received erlotinib as their first-line treatment.73 patients had Eastern Cooperative Oncology Group performance status scores of 0-1. 48 patients had multiple brain metastases (number >5) and 14 patients had brain metastasis ≥ 3 cm in size. 25 patients received whole brain radiation therapy and 7 patients received stereotactic radiosurgery before taking the tyrosine kinase inhibitors. The median overall survival for the gefitinib group and the erlotinib group was 874 vs. 750 days (p=0.86, Fig 1), and the median intracranial PFS 652 vs. 833 days (p=0.38, Fig 2). Multivariable analysis indicated that erlotinib was associated with a better intracranial PFS. (HR: 0.34, 95% CI: 0.12-0.97). The competing risks regression model showed erlotinib was associated with a trend toward lower probability of intracranial progression, with adjusted subdistribution hazard ratio of 0.40 (95% CI, 0.16-1.03; p=0.06, Fig 3). In patients with brain metastasis from lung adenocarcinoma, this study showed the beneficial effectiveness of erlotinib on the intracranial progression-free survival compared with gefitinib.

Melatonin Pharmacokinetics Following Oral Administration in Preterm Neonates.

Melatonin possesses potential efficacy in perinatal brain injuries, and has been proposed as adjunctive pharmacological therapy in combination with hypothermia in the clinical setting. However, the pharmacokinetics of melatonin in preterm and term newborns is still unknown. The aim of this study was to analyze the pharmacokinetics of melatonin after intragastric administration in preterm infants. Preterm newborns were enrolled 24–72 h after birth, and randomly assigned to three groups receiving a single bolus of 0.5 mg·kg−1 melatonin, or 3 boluses of 1 or 5 mg·kg−1 of melatonin at 24-h intervals. Blood samples were collected before and at selective times after melatonin administration. The half-life of melatonin in plasma ranged from 7.98 to 10.94 h, and the area under the curve (AUC) from 10.48 to 118.17 µg·mL−1·h−1. Our results indicate a different pharmacokinetic profile in premature newborns, compared to adults and experimental animals. The high peak plasma concentrations and the long half-life indicate that in the neonatal clinical setting, it is possible to obtain and maintain high serum concentrations using a single administration of melatonin repeated every 12/24 h.

Thermosensitive In Situ Gel Based on Solid Dispersion for Rectal Delivery of Ibuprofen.

The objective of this study was to develop a thermosensitive in situ gel based on solid dispersions (SDs) for rectal delivery of ibuprofen (IBU). Thermosensitive (poloxamer 407) and mucoadhesive (hydroxypropylmethyl cellulose E5 and sodium alginate) polymers were used to prepare the in situ gel and the sol-gel transition temperature (T sol-gel) and gel strength were optimized. The in vitro release performance and in vivo pharmacokinetic properties of the in situ gel after their rectal administration to rabbits were investigated. Compared with the solid suppository, the cumulative release of the IBU SDs loaded in situ gel was significantly increased. The in vivo pharmacokinetics indicated that in situ gel had a higher peak plasma concentration (C max) and area under the curve (AUC(0-∞)) in plasma than the solid suppositories. Histopathology results showed that the IBU in situ gel given at a dose of 15mg/kg did not produce any irritation. In conclusion, this study suggested that the in situ gel could be an effective rectal formulation for IBU.

Application of Soluplus to Improve the Flowability and Dissolution of Baicalein Phospholipid Complex

In this study, a novel ternary complex system (TCS) composed of baicalein, phospholipids, and Soluplus was prepared to improve the flowability and dissolution for baicalein phospholipid complex (BPC). TCS was characterized using differential scanning calorimetry (DSC), infrared spectroscopy (IR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The flowability, solubility, oil–water partition coefficient, in vitro dissolution, and in vivo pharmacokinetics of the system were also evaluated. DSC, IR, PXRD, and SEM data confirmed that the crystal form of baicalein disappeared in BPC and TCS. Furthermore, the angle of repose of TCS of 35° indicated an improvement in flowability, and solubility increased by approximately eight-fold in distilled water when TCS was compared with BPC (41.00 ± 4.89 μg/mL vs. 5.00 ± 0.16 μg/mL). Approximately 91.24% of TCS was released at the end of 60 min in 0.5% SDS (pH = 6.8), which suggested that TCS could improve the dissolution velocity and extent. Moreover, TCS exhibited a considerable enhancement in bioavailability with higher peak plasma concentration (25.55 μg/mL vs. 6.05 μg/mL) and increased AUC0–∞ (62.47 μg·h/mL vs. 50.48 μg·h/mL) with 123.75% relative bioavailability compared with BPC. Thus, Soluplus achieved the purpose of improving the flowability and solubility of baicalein phospholipid complexes. The application of Soluplus to phospholipid complexes has great potential.