Why has model-informed precision dosing not yet become common clinical reality? lessons from the past and a roadmap for the future.

Patient groups prone to polypharmacy and special subpopulations are susceptible to suboptimal treatment. Refined dosing in special populations is imperative to improve therapeutic response and/or lowering the risk of toxicity. Model-informed precision dosing (MIPD) may improve treatment outcomes by achieving the optimal dose for an individual patient. There is, however, relatively little published evidence of large-scale utility and impact of MIPD, where it is often implemented as local collaborative efforts between academia and healthcare. This article highlights some successful applications of bringing MIPD to clinical care and proposes strategies for wider integration in healthcare. Considerations are brought up herein that will need addressing to see MIPD become "widespread clinical practice," among those, wider interdisciplinary collaborations and the necessity for further evidence-based efficacy and cost-benefit analysis of MIPD in healthcare. The implications of MIPD on regulatory policies and pharmaceutical development are also discussed as part of the roadmap.

A quantitative systems pharmacology model of blood coagulation network describes in vivo biomarker changes in non-bleeding subjects.

Essentials Baseline coagulation activity can be detected in non-bleeding state by in vivo biomarker levels. A detailed mathematical model of coagulation was developed to describe the non-bleeding state. Optimized model described in vivo biomarkers with recombinant activated factor VII treatment. Sensitivity analysis predicted prothrombin fragment 1 + 2 and D-dimer are regulated differently. SUMMARY: Background Prothrombin fragment 1 + 2 (F1 + 2 ), thrombin-antithrombin III complex (TAT) and D-dimer can be detected in plasma from non-bleeding hemostatically normal subjects or hemophilic patients. They are often used as safety or pharmacodynamic biomarkers for hemostatis-modulating therapies in the clinic, and provide insights into in vivo coagulation activity. Objectives To develop a quantitative systems pharmacology (QSP) model of the blood coagulation network to describe in vivo biomarkers, including F1 + 2 , TAT, and D-dimer, under non-bleeding conditions. Methods The QSP model included intrinsic and extrinsic coagulation pathways, platelet activation state-dependent kinetics, and a two-compartment pharmacokinetics model for recombinant activated factor VII (rFVIIa). Literature data on F1 + 2 and D-dimer at baseline and changes with rFVIIa treatment were used for parameter optimization. Multiparametric sensitivity analysis (MPSA) was used to understand key proteins that regulate F1 + 2 , TAT and D-dimer levels. Results The model was able to describe tissue factor (TF)-dependent baseline levels of F1 + 2 , TAT and D-dimer in a non-bleeding state, and their increases in hemostatically normal subjects and hemophilic patients treated with different doses of rFVIIa. The amount of TF required is predicted to be very low in a non-bleeding state. The model also predicts that these biomarker levels will be similar in hemostatically normal subjects and hemophilic patients. MPSA revealed that F1 + 2 and TAT levels are highly correlated, and that D-dimer is more sensitive to the perturbation of coagulation protein concentrations. Conclusions A QSP model for non-bleeding baseline coagulation activity was established with data from clinically relevant in vivo biomarkers at baseline and changes in response to rFVIIa treatment. This model will provide future mechanistic insights into this system.

Geometrical modified nesbit corporoplasty to correct different types of penile curvature: description of the surgical procedure based on geometrical principles and long-term results.

We present the use of a modified corporoplasty, based on geometrical principles, to determine the exact site for the incision in the tunica or plaque and the exact amount of albuginea for overlaying to correct with extreme precision the different types of congenital or acquired penile curvature due to Peyronie's disease. To describe our experience with a new surgical procedure for the enhancement of penile curvature avoiding any overcorrection or undercorrection. Between March 2004 and April 2013, a total of 74 patients underwent the geometrical modified corporoplasty. All patients had congenital curvature until 90° or acquired stable penile curvature 'less' than 60°, that made sexual intercourse very difficult or impossible, normal erectile function, absence of hourglass or hinge effect. Preoperative testing included a physical examination, 3 photographs (frontal, dorsal and lateral) of penis during erection, a 10 mcg PGE1-induced erection and Doppler ultrasound, administration of the International Index of Erectile Function (IIEF-15) questionnaire. A follow-up with postoperative evaluation at 12 weeks, 12 and 24 months, included the same preoperative testing. Satisfaction rates were better assessed with the use of validated questionnaire such as the International Erectile Dysfunction Inventory of the Treatment Satisfaction (EDITS). Statistical analysis with Student's t-test was performed using commercially available, personal computer software. A total of 25 patients had congenital penile curvature with a mean deviation of 46.8° (range 40-90), another 49 patients had Peyronie's disease with a mean deviation of 58.4 (range 45-60). No major complications were reported. Postoperative correction of the curvature was achieved in all patients (100%). Neither undercorrection nor overcorrection were recorded. No significant relapse (curvature>15°) occurred in our patients. Shortening of the penis was reported by 74% but did not influence the high overall satisfaction of 92% (patients completely satisfied with their sexual life). The erectile function was analyzed in both groups, Student's t-test showed a significant improvement in erectile function, preoperative average IIEF-15 scores were 17.43±4.67, whereas postoperatively it was 22.57±4.83 (P=0.001). This geometrical modified Nesbit corporoplasty is a valid therapy which allows penile straightening. The geometric principles make the technique reproducible in multicentre studies.

Ignorance is not bliss: Statistical power is not probability of trial success.

The purpose of this commentary is to place probability of trial success, or assurance, in the context of decision making in drug development, and to illustrate its properties in an intuitive manner for the readers of Clinical Pharmacology and Therapeutics. The hope is that this will stimulate a dialog on how assurance should be incorporated into a quantitative decision approach for clinical development and trial design that uses all available information.

Minimally invasive infrapubic inflatable penile prosthesis implant for erectile dysfunction: evaluation of efficacy, satisfaction profile and complications.

Erectile dysfunction (ED), the second most common male sexual disorder, has an important impact on man sexuality and quality of life affecting also female partner's sexual life. ED is usually related to cardiovascular disease or is an iatrogenic cause of pelvic surgery. Many non-surgical treatments have been developed with results that are controversial, while surgical treatment has reached high levels of satisfaction. The aim is to evaluate outcomes and complications related to prosthesis implant in patients suffering from ED not responding to conventional medical therapy or reporting side effects with such a therapy. One hundred eighty Caucasian male suffering from ED were selected. The patient population were divided into two groups: 84 patients with diabetes and metabolic syndrome (group A) and 96 patients with dysfunction following laparoscopic radical prostatectomy for prostate cancer (group B). All subjects underwent primary inflatable penile prosthesis implant with an infrapubic minimally invasive approach. During 12 months of follow-up, we reported 3 (1.67%) explants for infection, 1 (0.56%) urethral erosion, 1 (0.56%) prosthesis extrusion while no intraoperative complications were reported. Mean International Index of Erectile Function-5 (IIEF-5) was 8.2 ± 4.0 and after the surgery (12 months later) was 20.6 ± 2.7. The improvement after the implant is significant in both groups without a statistically significant difference between the two groups (P-value 0.65). Mean Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) score 1 year after the implant is 72.2 ± 20.7, and there was no statistically significant difference between groups A and B (P-value 0.55). Implantation of an inflatable prosthesis, for treatment of ED, is a safe and efficacious approach; and the patient and partner satisfaction is very high. Surgical technique should be minimally invasive and latest technology equipment should be implanted in order to decrease after surgery common complications (infection and mechanical failure).

Precision medicine in the age of big data: The present and future role of large-scale unbiased sequencing in drug discovery and development.

High throughput molecular and functional profiling of patients is a key driver of precision medicine. DNA and RNA characterization has been enabled at unprecedented cost and scale through rapid, disruptive progress in sequencing technology, but challenges persist in data management and interpretation. We analyze the state-of-the-art of large-scale unbiased sequencing in drug discovery and development, including technology, application, ethical, regulatory, policy and commercial considerations, and discuss issues of LUS implementation in clinical and regulatory practice.

Using a Systems Pharmacology Model of the Blood Coagulation Network to Predict the Effects of Various Therapies on Biomarkers.

A number of therapeutics have been developed or are under development aiming to modulate the coagulation network to treat various diseases. We used a systems model to better understand the effect of modulating various components on blood coagulation. A computational model of the coagulation network was built to match in-house in vitro thrombin generation and activated Partial Thromboplastin Time (aPTT) data with various concentrations of recombinant factor VIIa (FVIIa) or factor Xa added to normal human plasma or factor VIII-deficient plasma. Sensitivity analysis applied to the model revealed that lag time, peak thrombin concentration, area under the curve (AUC) of the thrombin generation profile, and aPTT show different sensitivity to changes in coagulation factors' concentrations and type of plasma used (normal or factor VIII-deficient). We also used the model to explore how variability in concentrations of the proteins in coagulation network can impact the response to FVIIa treatment.

A mechanistic, multiscale mathematical model of immunogenicity for therapeutic proteins: part 1-theoretical model.

A mechanistic, multiscale mathematical model of immunogenicity for therapeutic proteins was formulated by recapitulating key biological mechanisms, including antigen presentation, activation, proliferation, and differentiation of immune cells, secretion of antidrug antibodies (ADA), as well as in vivo disposition of ADA and therapeutic proteins. This system-level model contains three scales: a subcellular level representing antigen presentation processes by dendritic cells; a cellular level accounting for cell kinetics during humoral immune response; and a whole-body level accounting for therapeutic protein in vivo disposition. The model simulations for in vivo responses against antigenic protein challenge are consistent with many known immunological observations. By simulating immune responses under various initial parameter conditions, the model suggests hypotheses for future experimental investigation and contributes to the mechanistic understanding of immunogenicity. With future experimental validation, this model may potentially provide a platform to generate and test hypotheses about immunogenicity risk assessment and ultimately aid in immunogenicity prediction.

A mechanistic, multiscale mathematical model of immunogenicity for therapeutic proteins: part 2-model applications.

A mechanistic, multiscale mathematical model of immunogenicity for therapeutic proteins was built by recapitulating key underlying known biological processes for immunogenicity. The model is able to simulate immune responses based on protein-specific antigenic properties (e.g., number of T-epitopes and their major histocompatibility complex (MHC)-II binding affinities) and host-specific immunological/physiological characteristics (e.g., MHC-II allele genotype, drug clearance rate). Preliminary validation was performed using mouse studies with antigens such as ovalbumin (OVA) or OVA-derived peptide. Further, using adalimumab as an example therapeutic protein, the model is able to simulate immune responses against adalimumab in individual subjects and in a population, and also provides estimations of immunogenicity incidence and drug exposure reduction that can be validated experimentally. This is a first attempt at modeling immunogenicity of biologics, so the model simulations should be used to help understand the immunogenicity mechanisms and impacting factors, rather than making direct predictions. This prototype model needs to be subjected to extensive experimental validation and refinement before fulfilling its ultimate mission of predicting immunogenicity. Nevertheless, the current model could potentially set up the starting framework to integrate various in silico, in vitro, in vivo, and clinical immunogenicity assessment results to help meet the challenge of immunogenicity prediction.

Translation of anticancer efficacy from nonclinical models to the clinic.

Mouse cancer models have provided critical insights into tumor biology; however, clinical translation of these findings has been challenging. This perspective posits that factors impacting on successful translation start with limitations in capturing human cancer pathophysiology and end with challenges in generating robust translatable preclinical end points. A comprehensive approach that considers clinically relevant mouse models with both an integrated biomarker strategy and a complementary modeling and simulation effort will strengthen the current oncology drug development paradigm.

Whither pharmacometrics?: present state and future choices.

The theme of this month's issue of Clinical Pharmacology & Therapeutics is pharmacometrics. When looking back at the early days of pharmacometrics, current contributions to the drug development process look impressive. The questions are whether the original promise is being kept and how the impact can become even greater.

UniPR129 is a competitive small molecule Eph-ephrin antagonist blocking in vitro angiogenesis at low micromolar concentrations.

BACKGROUND AND PURPOSE: The Eph receptor tyrosine kinases and their ephrin ligands are key players in tumorigenesis and many reports have correlated changes in their expression with a poor clinical prognosis in many solid tumours. Agents targeting the Eph-ephrin system might emerge as new tools useful for the inhibition of different components of cancer progression. Even if different classes of small molecules targeting Eph-ephrin interactions have been reported, their use is hampered by poor chemical stability and low potency. Stable and potent ligands are crucial to achieve robust pharmacological performance. EXPERIMENTAL APPROACH: UniPR129 (the L-homo-Trp conjugate of lithocholic acid) was designed by means of computational methods, synthetized and tested for its ability to inhibit the interaction between the EphA2 receptor and the ephrin-A1 ligand in an elisa binding study. The ability of UniPR129 to disrupt EphA2-ephrin-A1 interaction was functionally evaluated in a prostate adenocarcinoma cell line and its anti-angiogenic effect was tested in vitro using cultures of HUVECs. KEY RESULTS: UniPR129 disrupted EphA2-ephrin-A1 interaction with Ki = 370 nM in an elisa binding assay and with low micromolar potency in cellular functional assays, including inhibition of EphA2 activation, inhibition of PC3 cell rounding and disruption of in vitro angiogenesis, without cytotoxic effects. CONCLUSIONS AND IMPLICATIONS: The discovery of UniPR129 represents not only a major advance in potency compared with the existing Eph-ephrin antagonists but also an improvement in terms of cytotoxicity, making this molecule a useful pharmacological tool and a promising lead compound.

Pharmacometrics and Systems Pharmacology Software Tutorials and Use: Comments and Guidelines for PSP Contributions.

In addition to methodological Tutorials,(1) CPT:PSP has recently started to publish software Tutorials.(2,3) Our readership and authors may be wondering what kind of format or product is expected, and the review of submissions we have already received prompted several discussions within the PSP Editorial Team. This editorial reflects on these discussions and summarizes their salient points. It aims at providing some details about the current vision of CPT:PSP for software tutorial articles. In addition, it brings some clarity on the topic of what role commercial software tutorials can have in CPT:PSP and how CPT:PSP tutorials differ from publications which describe the software itself, as those which can be found in other computer science journals. Finally, the discussion includes reproducibility considerations and the general use of commercial and noncommercial software in CPT:PSP publications. We hope our thoughts, and especially a stated requirement to publish user input to the software to aid in reproducibility, will help in guiding our authors and will stimulate healthy debate among our readers about the evolving nature of our science, how it can be facilitated using software and associated databases as a conduit, and what role this journal can play in fostering both the best modeling and simulation practices and the best scientific approaches to computational modeling, to bring the advantages of modeling and simulation to all regular practitioners, and not to just a (self) selected few.

Systems pharmacology for drug discovery and development: paradigm shift or flash in the pan?

Systems pharmacology is an emerging approach that sets out to use quantitative concepts rooted in the synergy between modeling and simulation on one hand and large-scale data collection and analysis on the other to investigate biological systems and design therapeutic interventions. Interest in this field has recently increased substantially, but so have perceived challenges and misunderstandings, especially related to implementation. This Commentary explores the opportunities and challenges in the rapidly evolving area of systems pharmacology from a drug discovery and development perspective.

Magnesium sulphate for prevention of eclampsia: are intramuscular and intravenous regimens equivalent? A population pharmacokinetic study.

OBJECTIVE: To compare magnesium sulphate concentrations achieved by intramuscular and intravenous regimens used for the prevention of eclampsia. SETTING: Low-resource obstetric hospitals in Nagpur and Vellore, India. POPULATION: Pregnant women at risk for eclampsia due to hypertensive disease. METHODS: A pharmacokinetic study was performed as part of a randomised trial that enrolled 300 women comparing intramuscular and intravenous maintenance regimens of magnesium dosing. Data from 258 enrolled women were analysed in the pharmacokinetic study. A single sample was drawn per woman with the expectation of using samples in a pooled data analysis. MAIN OUTCOME MEASURES: Pharmacokinetic parameters of magnesium distribution and clearance. RESULTS: Magnesium clearance was estimated to be 48.1 dl/hour, volume of distribution to be 156 dl and intramuscular bioavailability to be 86.2%. The intramuscular regimen produced higher initial serum concentrations, consistent with a substantially larger loading dose. At steady state, magnesium concentrations in the intramuscular and intravenous groups were comparable. With either regimen, a substantial number of women would be expected to have serum concentrations lower than those generally held to be therapeutic. CONCLUSIONS: Clinical implications were that a larger loading dose for the intravenous regimen should be considered; where feasible, individualised dosing of magnesium sulphate would reduce the variability in serum concentrations and might result in more women with clinically effective magnesium concentrations; and lower dose magnesium sulphate regimens should be considered with caution.

OS034. Magnesium sulfate for prevention of eclampsia: Are intramuscularand intravenous regimens equivalent?

INTRODUCTION: Magnesium sulfate is the agent of choice for the treatment and prevention of eclampsia. Optimal loading and maintenance dosing has not been determined. OBJECTIVES: To compare the pharmacokinetic parameters if IM vs. IV magnesium sulfate. METHODS: A pharmacokinetic study was performed as part of a randomized trial that enrolled 300 women comparing IM and IV regimens of magnesium dosing in two low resource sites in India. Data from 258 enrolled women were analyzed in the pharmacokinetic study. Due to infrastructure available at the sites, a single sample was drawn per subject with the expectation of utilizing samples in a pooled data analysis. RESULTS: Magnesium clearance was estimated via pharmacokinetic modeling to be 48.1dL/h, volume of distribution 156dL and IM bioavailability 86.2%. The IM regimen produced higher initial serum concentrations, consistent with a substantially larger loading dose. At steady state, Mg concentrations in the IM and IV Groups were comparable. With either regimen, a substantial number of subjects would be expected to have serum concentrations lower than those generally expected to be therapeutic. CONCLUSION: A larger loading dose for the IV regimen should be considered. Where feasible, individualized higher doses of magnesium sulfate would yield a greater number of treated women with clinically effective magnesium concentrations.

Multiscale modeling in drug discovery and development: future opportunities and present challenges.

Modeling and simulation (M&S) is a diverse discipline that uses tools from mathematics, statistics, and computer science to arrive at quantitative predictions. Its application to biological systems has a checkered history with respect to success and failure. The instances of failure may reflect the heterogeneity of M&S approaches. In order to ensure a successful outcome, M&S must be fit for purpose and responsive; connecting with biological concepts is critical; sharing of results has to be done properly; buy-in is achieved in stages. These concepts are being applied in drug discovery and development and are yielding success. However, bottlenecks remain.

A model-based meta-analysis of the effect of latanoprost chronotherapy on the circadian intraocular pressure of patients with glaucoma or ocular hypertension.

Several reports have demonstrated that the efficacy of latanoprost is influenced by the time of dosing. This model-based meta-analysis validates previous findings that evening dosing is superior to morning dosing and predicts the optimal time for dosing, based on the quantitative assessment of baseline and latanoprost-treated 24-h circadian intraocular pressure (IOP) curves. The results confirm the importance of the time of dosing as a factor that influences the extent of reduction in IOP and underline the need to take this factor into consideration in the design of glaucoma trials and therapy.

Are we optimizing gestational diabetes treatment with glyburide? The pharmacologic basis for better clinical practice.

Glyburide's pharmacokinetics (PK) and pharmacodynamics have not been studied in women with gestational diabetes mellitus (GDM). The objective of this study was to assess steady-state PK of glyburide, as well as insulin sensitivity, beta-cell responsivity, and overall disposition indices after a mixed-meal tolerance test (MMTT) in women with GDM (n = 40), nonpregnant women with type 2 diabetes mellitus (T2DM) (n = 26), and healthy pregnant women (n = 40, MMTT only). At equivalent doses, glyburide plasma concentrations were approximately 50% lower in pregnant women than in nonpregnant subjects. The average umbilical cord/maternal plasma glyburide concentration ratio at the time of delivery was 0.7 +/- 0.4. Insulin sensitivity was approximately fivefold lower in women with GDM as compared with healthy pregnant women. Despite comparable beta-cell responsivity indices, the average beta-cell function corrected for insulin resistance was more than 3.5-fold lower in women with glyburide-treated GDM than in healthy pregnant women. Women with GDM in whom glyburide treatment has failed may benefit from alternative medication or dosage escalation; however, fetal safety should be kept in mind.