A summary of the current drug interaction guidance from the European Medicines Agency and considerations of future updates.

The current EMA drug interaction guideline was published in 2012. This guideline gives important recommendations on the information required to elucidate the interaction potential of an investigational drug, both as effects of the investigational drug on the PK of other drugs and effects of other medicinal products on the PK of the investigational drug. Additional information on the use of PBPK modelling to inform drug interaction information, is also available in the guideline on the reporting of physiologically based modelling and simulation (2018). Some points of clarification on the drug interaction guideline, particularly in the area of enzyme induction screening, have been published as the EMA questions and answers (2014) and these points and further additional points, were proposed to be incorporated into a new update of the guideline, for which a concept paper was published in 2017. This update, which is still in progress, was to include new recommendations in line with relevant emerging scientific data (e.g. in the area of drug transporters). It is also intended to harmonise requirements on drug interactions with other Regulatory Agencies and this will be facilitated by the recently announced ICH initiative.

The Importance of the Human Mass Balance Study in Regulatory Submissions.

The human mass balance study is a key study in the Clinical Pharmacology package of new drug applications. This study, along with the mass balance studies in toxicology species, provides essential information on the exposure of the parent compound and metabolites. Despite current regulatory guidance and previous publications, a lack of this study, or deficiencies in the study, are still seen in regulatory submissions today. This restricts the assessment of the benefit/risk in all populations and on the potential for drug-drug interactions leading to unnecessary precautions in the label. A review of new drug applications identifies a number of examples of inadequate characterization of circulating drug-related components or of elimination pathways, with questions raised during the regulatory review. In light of this, new insight is given on what is required from the mass balance study and on how to ensure sufficient information is captured.

Assessment of interaction potential of AZD2066 using in vitro metabolism tools, physiologically based pharmacokinetic modelling and in vivo cocktail data.

PURPOSE: Static and dynamic (PBPK) prediction models were applied to estimate the drug-drug interaction (DDI) risk of AZD2066. The predictions were compared to the results of an in vivo cocktail study. Various in vivo measures for tolbutamide as a probe agent for cytochrome P450 2C9 (CYP2C9) were also compared. METHODS: In vitro inhibition data for AZD2066 were obtained using human liver microsomes and CYP-specific probe substrates. DDI prediction was performed using PBPK modelling with the SimCYP simulator™ or static model. The cocktail study was an open label, baseline, controlled interaction study with 15 healthy volunteers receiving multiple doses of AD2066 for 12 days. A cocktail of single doses of 100 mg caffeine (CYP1A2 probe), 500 mg tolbutamide (CYP2C9 probe), 20 mg omeprazole (CYP2C19 probe) and 7.5 mg midazolam (CYP3A probe) was simultaneously applied at baseline and during the administration of AZD2066. Bupropion as a CYP2B6 probe (150 mg) and 100 mg metoprolol (CYP2D6 probe) were administered on separate days. The pharmacokinetic parameters for the probe drugs and their metabolites in plasma and urinary recovery were determined. RESULTS: In vitro AZD2066 inhibited CYP1A2, CYP2B6, CYP2C9, CYP2C19 and CYP2D6. The static model predicted in vivo interaction with predicted AUC ratio values of >1.1 for all CYP (except CYP3A4). The PBPK simulations predicted no risk for clinical relevant interactions. The cocktail study showed no interaction for the CYP2B6 and CYP2C19 enzymes, a possible weak inhibition of CYP1A2, CYP2C9 and CYP3A4 activities and a slight inhibition (29 %) of CYP2D6 activity. The tolbutamide phenotyping metrics indicated that there were significant correlations between CLform and AUCTOL, CL, Aemet and LnTOL24h. The MRAe in urine showed no correlation to CLform. CONCLUSIONS: DDI prediction using the static approach based on total concentration indicated that AZD20066 has a potential risk for inhibition. However, no DDI risk could be predicted when a more in vivo-like dynamic prediction method with the PBPK with SimCYP™ software based on early human PK data was used and more parameters (i.e. free fraction in plasma, no DDI risk) were taken into account. The clinical cocktail study showed no or low risks for clinical relevant DDI interactions. Our findings are in line with the hypothesis that the dynamic prediction method predicts DDI in vivo in humans better than the static model based on total plasma concentrations.

AZD1080, a novel GSK3 inhibitor, rescues synaptic plasticity deficits in rodent brain and exhibits peripheral target engagement in humans.

Abnormal tau phosphorylation resulting in detachment of tau from microtubules and aggregation are critical events in neuronal dysfunction, degeneration, and neurofibrillary pathology seen in Alzheimer's disease. Glycogen synthase kinase-3ß (GSK3ß) is a key target for drug discovery in the treatment of Alzheimer's disease and related tauopathies because of its potential to abnormally phosphorylate proteins and contribute to synaptic degeneration. We report the discovery of AZD1080, a potent and selective GSK3 inhibitor that demonstrates peripheral target engagement in Phase 1 clinical studies. AZD1080 inhibits tau phosphorylation in cells expressing human tau and in intact rat brain. Interestingly, subchronic but not acute administration with AZD1080 reverses MK-801-induced deficits, measured by long-term potentiation in hippocampal slices and in a cognitive test in mice, suggesting that reversal of synaptic plasticity deficits in dysfunctional systems requires longer term modifications of proteins downstream of GSK3ß signaling. The inhibitory pattern on tau phosphorylation reveals a prolonged pharmacodynamic effect predicting less frequent dosing in humans. Consistent with the preclinical data, in multiple ascending dose studies in healthy volunteers, a prolonged suppression of glycogen synthase activity was observed in blood mononuclear cells providing evidence of peripheral target engagement with a selective GSK3 inhibitor in humans.

Evaluation of a novel chemokine receptor 2 (CCR2)-antagonist in painful diabetic polyneuropathy.

Background and aims Preclinical data suggest that the chemokine receptor 2 (CCR2) is involved in the pathophysiology of neuropathic pain through modulation of neuronal excitability, synaptic transmission and activation of spinal cord microglia. CCR2-antagonists have shown to be effective in preclinical models of neuropathic pain. The aim of this study was to evaluate the analgesic efficacy, safety and tolerability of a novel CCR2-antagonist, AZD2423, in patients with painful diabetic neuropathy (PDN). Methods This was a double-blind, randomized, parallel-group, multi-center study in patients with symmetric distal sensory polyneuropathy due to type 1 or 2 diabetes and duration of neuropathic pain between 3 months and 5 years. Concomitant treatment with neuropathic pain medications (e.g. anticonvulsants, tricyclic antidepressants, serotonin-noradrenaline uptake inhibitors, opioids, topical lidocaine or capsaicin) was not allowed. 134 patients with PDN were equally randomized to 28 days oral administration of 20 mg AZD2423,150 mg AZD2423, or placebo. The primary efficacy variable was the change of average pain score from 5-days baseline to the last 5 days of treatment, measured with numerical rating scale (NRS, 0-10). The secondary efficacy measures included NRS worst pain scores, patient global impression of change, pain interference on sleep and activity, and neuropathic pain symptom inventory (NPSI). Results The change of NRS average pain score was not significantly different between treatment groups (AZD2423 20mg: -1.50; AZD2423 150 mg: -1.35; placebo: -1.61). The NPSI total score and three out of five subscores (evoked pain, pressing/deep pain and paresthesia/dysesthesia) tended to be reduced more by AZD2423 150 mg than by placebo. No other secondary efficacy variables differed between treatment groups. The frequency and type of adverse events for AZD2423 were similar to placebo. The achieved plasma levels of AZD2423 in the two dose groups were in line with predictions from pharmacokinetic data previously obtained in healthy volunteers. Dose-dependent increase of plasma levels of the ligand of CCR2 (CCL2; chemokine ligand 2) and decrease of the mean levels of monocytes (-27% by AZD2423 150 mg) suggested that the administrated doses of AZD2423 interacted with the CCR2 target. Conclusion The CCR2-antagonist AZD2423 showed no analgesic efficacy in PDN based on NRS average pain scores and global and functional pain outcome measures. The NPSI data suggested possible effects on certain sensory components of pain. There were no major safety or tolerability concerns. Implications Treatment with a CCR2-antagonist does not have a clinically important analgesic effect in an overall PDN population.

MEPS as a rapid sample preparation method to handle unstable compounds in a complex matrix: determination of AZD3409 in plasma samples utilizing MEPS-LC-MS-MS.

The aim of the present investigation is to develop a simple, fast, and sensitive method for the determination of a new candidate drug, AZD3409, in rat, dog, and human plasma samples. AZD3409 is stable in aqueous solutions at low pH (< 4) but not in whole blood or in plasma. In rat plasma at 25 degrees C, more than 90% of the compound is degraded within 40 min. When 20 mg of NaF and 50 microL of protease inhibitor cocktail are added to 1.0 mL of rat blood, AZD3409 is stable for up to about 90 min. Due to the instability of AZD3409, microextraction in packed syringe (MEPS) is used as an online and fast sample-preparation method, followed by liquid chromatography-tandem mass spectrometry (LC-MS-MS) for the quantitation of this compound in plasma samples. In MEPS, the sampling sorbent is 1 mg of polystyrene polymer packed in a 250-microL syringe. When the plasma sample (50-250 microL) is withdrawn through the syringe by an autosampler, the analyte is adsorbed to the solid phase. The analyte is then eluted with an organic solvent such as methanol or the LC mobile phase (20-50 microL) directly into the instrument's injector. MEPS is rapid and easy to use. The lower limit of quantitation for AZD3409 is established to be 0.024 microM. The accuracy of the quality-control samples ranged from 89% to 102%, and the precision (C.V.%) had a value of 11-16% for the plasma samples. The calibration curve in plasma is obtained in the concentration range 0.022-9.0 microM. The coefficients of determination (R2) for plasma samples were > or = 0.998 for all runs. The present method is used for the analysis of rat and dog plasma samples.

Effect of a dental cream containing amorphous cream phosphate complexes on white spot lesion regression assessed by laser fluorescence.

PURPOSE: To investigate and compare the effects of a dental cream containing complexes of casein phosphoprotein-amorphous calcium phosphate (CPP-ACP) and fluoride mouthwashes on the regression of white spot lesions (WSL). MATERIALS AND METHODS: The study group consisted of 26 healthy adolescents (mean age 14.6 years) exhibiting 60 teeth with 152 visible WSL sites on incisors and canines immediately after debonding of fixed orthodontic appliances. After bracket removal, professional tooth cleaning and drying, a visual scoring (0-4) and laser fluorescence (LF) readings were carried out. The patients were randomly assigned to two different treatment protocols with the aim of remineralising the lesions: A) daily topical applications of a dental cream containing CPP-ACP (Topacal) for 3 months followed by a 3-month period of daily toothbrushing with fluoridated dentifrice, or B) daily 0.05% sodium fluoride mouthwash combined with fluoridated dentifrice for 6 months. The registrations were repeated after 1, 3, 6 and 12 months and follow-up data were compared with baseline with aid of chi-square and paired t-tests. RESULTS: A significant improvement of the clinical WSL-scores was found over time in both groups, but there was a statistically significant difference (p < 0.01) concerning the number of sites that totally disappeared after 12 months in favour of the CPP-ACP regime, 63% compared with 25% respectively. The clinical registrations were mirrored by a statistically significant decrease (p < 0.05) in the LF readings at the 6- and 12-month follow-ups compared with baseline. No significant differences were displayed between the groups. CONCLUSIONS: Clinical scoring and LF assessment suggested that both regimens could promote regression of WSL after debonding of fixed orthodontic appliances. The visual evaluation suggested an aesthetically more favourable outcome of the amorphous calcium phosphate treatments.