How to select the initial dose for a pediatric study?

In typical clinical development programs, a new drug is first developed for the adult use. Drugs are often approved for adult use or in the process of obtaining approval in adults in the target indication before pediatric development is initiated. In designing the first pediatric clinical trial, one of the challenges is to select the initial dose to be tested. The ICH E11 R1 guidance advises that chronologic age alone may not always be the most appropriate categorical determinant to define developmental subgroups in pediatric studies. In this manuscript, the approaches to utilize available data in adults related to those factors beyond age to inform the starting dose selection in pediatric drug development are discussed. Practical considerations and approaches are provided for informing pediatric starting dose. Additional considerations to use pre-clinical information are provided in the case when adult information is limited or not available.

The potent and selective RIPK2 inhibitor BI 706039 improves intestinal inflammation in the TRUC mouse model of inflammatory bowel disease.

Mouse and human data implicate the NOD1 and NOD2 sensors of the intestinal microbiome and the associated signal transduction via the receptor interacting protein kinase 2 (RIPK2) as a potential key signaling node for the development of inflammatory bowel disease (IBD) and an attractive target for pharmacological intervention. The TRUC mouse model of IBD was strongly indicated for evaluating RIPK2 antagonism for its effect on intestinal inflammation based on previous knockout studies with NOD1, NOD2, and RIPK2. We identified and profiled the BI 706039 molecule as a potent and specific functional inhibitor of both human and mouse RIPK2 and with favorable pharmacokinetic properties. We dosed BI 706039 in the spontaneous TRUC mouse model from age 28 to 56 days. Oral, daily administration of BI 706039 caused dose-responsive and significant improvement in colonic histopathological inflammation, colon weight, and terminal levels of protein-normalized fecal lipocalin (all P values <0.001). These observations correlated with dose responsively increasing systemic levels of the BI 706039 compound, splenic molecular target engagement of RIPK2, and modulation of inflammatory genes in the colon. This demonstrates that a relatively low oral dose of a potent and selective RIPK2 inhibitor can modulate signaling in the intestinal immune system and significantly improve disease associated intestinal inflammation.NEW & NOTEWORTHY The RIPK2 kinase at the apex of microbiome immunosensing is an attractive target for pharmacological intervention. A low oral dose of a RIPK2 inhibitor leads to significantly improved intestinal inflammation in the murine TRUC model of colitis. A selective and potent inhibitor of the RIPK2 kinase may represent a new class of therapeutics that target microbiome-driven signaling for the treatment of IBD.

Dynamic development paths for expanding a proof-of-concept study to explore dose range.

In Phase II clinical development of a new drug, the two most important deliverables are proof of concept (PoC) and dose ranging. Traditionally, a PoC study is designed as the first Phase II clinical trial. In this PoC, there are two treatment groups-a high dose of the study medication, against the placebo control. After the concept is proven, the next Phase II study is a dose-ranging design with many test doses. This paper proposes a two-stage design with the first stage attempting to generate an early signal of efficacy. If successful, the second stage will adopt a "Go Fast" plan to expand the current study and add lower study doses of the test drug to explore the efficacy dose range. Otherwise, a "Go Slow" strategy is triggered, and the study will stop at a reduced sample size with high dose and placebo only.

Bayesian sample size determination for a Phase III clinical trial with diluted treatment effect.

When Phase III treatment effect is diluted from what was observed from Phase II results, we propose to determine the Bayesian sample size for a Phase III clinical trial based on the normal, uniform, and truncated normal prior distributions of the treatment effects on an interval, which starts from an acceptable treatment effect to the observed treatment effect from Phase II. After incorporating the prior information of the treatment effects, the Bayesian sample size is the number of patients of the Phase III trial for a given Bayesian Predictive Power (BPP) or Bayesian Historical Predictive Power (BHPP). After that, the numerical simulations are carried out to determine the Bayesian sample size for the Phase III clinical trial. In particular, there exists a hook phenomenon for the BHPP when the number of patients of the Phase II trial equals 70 assuming the normal, uniform, or truncated normal treatment effect. Moreover, we add some sensitivity analysis of the Bayesian sample size about the parameters in the simulations. Finally, we determine the Bayesian sample size (number of events or deaths) of the Phase III trial for a fixed power, Bayesian Historical Power (BHP), and BHPP in the axitinib example.

Contribution of Major Metabolites toward Complex Drug-Drug Interactions of Deleobuvir: In Vitro Predictions and In Vivo Outcomes.

The drug-drug interaction (DDI) potential of deleobuvir, an hepatitis C virus (HCV) polymerase inhibitor, and its two major metabolites, CD 6168 (formed via reduction by gut bacteria) and deleobuvir-acyl glucuronide (AG), was assessed in vitro. Area-under-the-curve (AUC) ratios (AUCi/AUC) were predicted using a static model and compared with actual AUC ratios for probe substrates in a P450 cocktail of caffeine (CYP1A2), tolbutamide (CYP2C9), and midazolam (CYP3A4), administered before and after 8 days of deleobuvir administration to HCV-infected patients. In vitro studies assessed inhibition, inactivation and induction of P450s. Induction was assessed in a short-incubation (10 hours) hepatocyte assay, validated using positive controls, to circumvent cytotoxicity seen with deleobuvir and its metabolites. Overall, P450 isoforms were differentially affected by deleobuvir and its two metabolites. Of note was more potent CYP2C8 inactivation by deleobuvir-AG than deleobuvir and P450 induction by CD 6168 but not by deleobuvir. The predicted net AUC ratios for probe substrates were 2.92 (CYP1A2), 0.45 (CYP2C9), and 0.97 (CYP3A4) compared with clinically observed ratios of 1.64 (CYP1A2), 0.86 (CYP2C9), and 1.23 (CYP3A4). Predictions of DDI using deleobuvir alone would have significantly over-predicted the DDI potential for CYP3A4 inhibition (AUC ratio of 6.15). Including metabolite data brought the predicted net effect close to the observed DDI. However, the static model over-predicted the induction of CYP2C9 and inhibition/inactivation of CYP1A2. This multiple-perpetrator DDI scenario highlights the application of the static model for predicting complex DDI for CYP3A4 and exemplifies the importance of including key metabolites in an overall DDI assessment.

Sample size determination with familywise control of both type I and type II errors in clinical trials.

The concept of controlling familywise type I and type II errors at the same time is essentially an integrated process to deal with multiplicity issues in clinical trials. The process will select a multiple testing procedure (MTP) which controls the familywise type I error and calculate the per hypothesis sample size such that the "studywise power" is maintained at desired level. The power of a study can be defined in several ways and it depends on the objective. In this article, we provide general guidance on how to make the selection of MTPs and calculate sample size simultaneously. We introduce the concept of strong and weak control of the familywise type II error and generalized familywise type II error. We also proposed the novel Bonferroni+ and optimal Bonferroni+ procedures to allocate per hypothesis type II error. We demonstrated the value of the proposed work as it cannot be replaced by simple simulations. A real clinical trial is discussed throughout the article as an example.

Graphical assessment of consistency in treatment effect among countries in multi-regional clinical trials.

BACKGROUND: One key objective of a multi-regional clinical trial (MRCT) is to use the trial results to 'bridge' from the global level to local region in support of local registrations. However, data from each individual country are typically limited and the large number of countries will increase the chance of false positive findings. PURPOSE: Graphical tools to facilitate identification of potential outlying countries could be useful for country-level assessment. Existing methods such as funnel plot and expected range of treatment effect can substantially increase the false positive rate. The expected range approach can also have a very low power when there are a large number of small countries, which is typical in a MRCT. METHODS: In this article, we apply normal probability plots, commonly used as a diagnostic tool in linear regression analysis, to assess the differences among countries. Evidence of possible inconsistency, which incorporates both the estimated treatment effect and sample size, is plotted against its expected order statistic. RESULTS: A simulation study is conducted to assess the impact of the negative correlation among residuals due to unequal sample sizes among countries and the performance of the proposed methods compared to existing approaches. The proposed methods tend to have a balanced consideration with substantially smaller false positive rate and reasonable probability to identify outlying countries in realistic scenarios. LIMITATIONS: While much lower than that of commonly used methods, the false positive rates of the proposed methods are not strictly controlled. This may be acceptable for these graphical tools with intention to flag potential outliers for investigation. CONCLUSIONS: We recommend routine use of normal probability plots in MRCTs as a tool to identify potential outliers. If the normal probability plot is approximately linear but has heavy tails with a few outlying countries, these potential outliers should be examined carefully to understand the possible reasons.

A proof-of-concept clinical trial design combined with dose-ranging exploration.

In recent years, the pharmaceutical industry has experienced many challenges in discovering and developing new drugs, including long clinical development timelines with significant investment risks. In response, many sponsors are working to speed up the clinical development process. One strategy is to combine the proof-of-concept (PoC) and the dose-ranging clinical studies into a single trial. This manuscript proposes approaches to help address both PoC and dose-ranging objectives in such a combined design. One proposal is to use a linear trend test for PoC, together with a serial gatekeeping method (TGK) to identify individual doses; the other is to use the dose-response curve estimated from a three-parameter Emax model to establish PoC and explore activities of various doses. Simulations were performed to evaluate the performance of both proposals with recommendations based on the simulation results.

Maraviroc versus efavirenz, both in combination with zidovudine-lamivudine, for the treatment of antiretroviral-naive subjects with CCR5-tropic HIV-1 infection.

BACKGROUND: The MERIT (Maraviroc versus Efavirenz in Treatment-Naive Patients) study compared maraviroc and efavirenz, both with zidovudine-lamivudine, in antiretroviral-naive patients with R5 human immunodeficiency virus type 1 (HIV-1) infection. METHODS: Patients screened for R5 HIV-1 were randomized to receive efavirenz (600 mg once daily) or maraviroc (300 mg once or twice daily) with zidovudine-lamivudine. Coprimary end points were proportions of patients with a viral load <400 and <50 copies/mL at week 48; the noninferiority of maraviroc was assessed. RESULTS: The once-daily maraviroc arm was discontinued for not meeting prespecified noninferiority criteria. In the primary 48-week analysis (n = 721), maraviroc was noninferior for <400 copies/mL (70.6% for maraviroc vs 73.1% for efavirenz) but not for <50 copies/mL (65.3% vs 69.3%) at a threshold of -10%. More maraviroc patients discontinued for lack of efficacy (11.9% vs 4.2%), but fewer discontinued for adverse events (4.2% vs 13.6%). In a post hoc reanalysis excluding 107 patients (15%) with non-R5 screening virus by the current, more sensitive tropism assay, the lower bound of the 1-sided 97.5% confidence interval for the difference between treatment groups was above -10% for each end point. CONCLUSIONS: Twice-daily maraviroc was not noninferior to efavirenz at <50 copies/mL in the primary analysis. However, 15% of patients would have been ineligible for inclusion by a more sensitive screening assay. Their retrospective exclusion resulted in similar response rates in both arms Trial registration. ClinicalTrials.gov identifier: (NCT00098293) .

Proof of Concept: Drug Selection? Or Dose Selection? Thoughts on Multiplicity Issues.

In new drug development process, one of the most important milestones for a drug candidate is to establish Proof of Concept (PoC) at early Phase II stage. Among many challenges in PoC clinical trial design and analysis, the application of multiplicity comparison procedures (MCP) is frequently discussed when multiple doses or drugs are included in one PoC study. In such discussion, one fundamental question of applying multiplicity adjustment is which error one should consider to control and at what level. Should it be the experiment-wise error or the compound-wise error? In this paper, the multiplicity issues in two cases of PoC studies are used as examples to discuss the concept of different types of error and the level of the error rate control. With a clear understanding of the type of error and error rate control, the debate of applications of the multiplicity adjustment procedures in the PoC studies can be reconciled.

Two confidence interval approaches on the dependability coefficient in a two-factor crossed design.

For decisions based on the absolute level of performance among individuals, the dependability coefficient-a ratio of variance components-is used as a measure of reliability. Two methods developed for a two-factor random effects crossed (or one-facet) design-the Arteaga, Jeyaratnam, and Graybill (AJG) approach and the Cappelleri and Ting (CT) approach-are applied to construct confidence intervals on the dependability coefficient. A simulation study is conducted to investigate and compare the confidence interval coverage on the dependability coefficient based on AJG and CT. Both methods generally meet at least the nominal coverage. Both methods are illustrated with examples.

Evaluation of the effect of the specific CCR1 antagonist CP-481715 on the clinical and cellular responses observed following epicutaneous nickel challenge in human subjects.

BACKGROUND: The CC-chemokine receptor-1 (CCR1) is thought to be involved in recruitment of inflammatory cells in allergic contact dermatitis (ACD). CP-481715 is a specific antagonist of CCR1. OBJECTIVES: To determine the inhibitory effects of CP-418 715 in ACD by evaluating the clinical signs and cellular infiltration in skin biopsies following epicutaneous nickel challenge in allergic subjects. SUBJECTS/METHODS: In this phase 1/2 study, 40 subjects were randomized to 5 days of treatment in four parallel groups (placebo three times daily (TID), placebo once daily (QD), 1000 mg CP-418 715 TID, and 3000 mg CP-418 715 QD). Twenty-four hours after the first drug administration, nickel sulfate patches were applied on subjects' backs and removed 48 hours later. RESULTS: Pretreatment with 1000 mg CP-481715 TID resulted in significant reductions in visual scores of the nickel reactions (P = 0.01). Instrumentally measured erythema tended to decrease in the CP-481715 mg TID group (P = 0.06). No differences were noted between the 3000 mg CP-481715 mg QD group and pooled placebo. No significant differences were found for immunohistological cell counts. CP-418 715 was generally safe and well tolerated. CONCLUSIONS: Blocking of CCR1 only partly inhibited clinical manifestations of ACD. Several chemokine receptors are likely relevant for the cellular influx observed in ACD lesions.

Statistical Interactions in a Clinical Trial.

New statisticians entering industry tend to "test statistical interactions" whenever there is a need. However, in many real-world applications, especially in clinical development of new drugs, most interactions need to be estimated, instead of tested. In this manuscript, the distinction between hypothesis testing and estimation will be articulated, and the use of statistical interactions in clinical development programs will be discussed. According to ICH E-9, the treatment by subgroup interaction should not be included in the prespecified primary statistical analysis model. The reasons behind this ICH E-9 recommendation are also clarified in this manuscript.

Exacerbation recovery patterns in newly diagnosed or maintenance treatment-naïve patients with COPD: secondary analyses of TICARI 1 trial data.

Background: Little is known about the recovery patterns from acute exacerbations of chronic obstructive pulmonary disease (AECOPD) in newly diagnosed or maintenance treatment-naïve patients with COPD. This study describes the course of AECOPD in these patients at the time of treatment for the symptoms of acute respiratory tract infection (RTI). Methods: This study was a secondary analysis of data from a 12-week, randomized clinical trial (TICARI 1) testing the efficacy and safety of once-daily tiotropium 18 µg maintenance therapy versus placebo in newly diagnosed or maintenance treatment-naïve COPD patients with acute RTI symptoms for ≤7 days. Patients received standard care for AECOPD and RTI. Due to under-recruitment, the trial ended early and hence was underpowered to detect treatment differences. Data were pooled and exacerbation recovery patterns examined by using the EXAcerbation of Chronic Pulmonary Disease Tool (EXACT), forced expiratory volume in 1 second, rescue medication use, COPD Assessment Test™, Functional Assessment of Chronic Illness Therapy-Short Form, and Work Productivity and Activity Impairment Questionnaire: Respiratory Symptoms. Results: Of 140 patients, 73.6% had a prior COPD diagnosis without maintenance therapy; 80.0% had moderate-to-severe airflow obstruction. In addition to study drug, 40.0% were prescribed pharmacologic therapy (corticosteroids [34.3%], antibiotics [16.4%], and short-acting ß2-adrenergic agonists [5.0%]) within ±7 days of randomization. Over 12 weeks, 78.6% exhibited symptomatic recovery (EXACT score) in a median of 5.0 days. Across all patients, 49.3% recovered without relapse, 29.3% recovered and then relapsed, and 21.4% had persistent symptoms (recovery criteria unmet). Conclusion: A substantial portion of newly diagnosed or maintenance treatment-naïve patients with COPD experience relapse or persistent symptoms following a clinic visit for AECOPD with symptoms of RTI. Whether initiating maintenance therapy could improve outcomes and reduce exacerbation risk requires further study.

A Prospective, Randomized, Open-Label Study to Evaluate Two Management Strategies for Gastrointestinal Symptoms in Patients Newly on Treatment with Dabigatran.

INTRODUCTION: In the pivotal RE-LY trial, dabigatran etexilate (DE) at the dose of 150-mg twice daily (BID), significantly reduced total stroke and ischemic stroke compared with warfarin in patients with non-valvular atrial fibrillation (NVAF), while the 110-mg BID dose had efficacy equivalent to warfarin, and major bleeds were significantly reduced. Both DE regimens were generally well tolerated; however, approximately 4% of the patients discontinued treatment with DE due to gastrointestinal (GI) discomfort. METHODS: Clinical trial NCT01493557 was a multicenter, randomized, active control, open-label study to assess the efficacy of two simple GI symptom (GIS) management strategies in DE-treated patients who developed GIS: (1) concurrent treatment with the proton pump inhibitor pantoprazole (DE-P), or (2) ingestion of DE after a meal (DE-M). Patients were initially randomized to either GIS management strategy. If the first did not resolve their GIS, patients had the option to "add on" the alternative strategy. RESULTS: A total of 1067 patients with NVAF received DE therapy BID for 3 months (United States, 150-mg or 75-mg; Canada, 150-mg or 110-mg). Of these, 117 (11%) patients reported GIS and were randomized to one of two GIS management strategies. At 4 weeks, a significantly higher rate of complete or partial effectiveness was observed in patients on DE-P than in those receiving DE-M, [50/58 (86.2%) versus 40/59 (67.8%), respectively; p = 0.0273]. Patients with ongoing GIS were asked to "add on" the alternate strategy for an additional 4 weeks. Overall, 92/117 (78.6%) of randomized patients experienced complete or partial effectiveness using either the initial strategy or a combination of the two strategies: DE-P, 47 (81.0%); and DE-M, 45 (76.3%, no significant difference) (by initial strategy). CONCLUSION: The majority of patients enrolled either did not experience GIS at all, or their GIS resolved using either one individually, or a combination of the two strategies described. TRIAL REGISTRATION: http://www.ClinicalTrials.gov identifier: NCT01493557.

Interactions of the hepatitis C virus protease inhibitor faldaprevir with cytochrome P450 enzymes: in vitro and in vivo correlation.

The potential inhibition of the major human cytochrome P450 (CYP) enzymes by faldaprevir was evaluated both in vitro and in clinical studies (healthy volunteers and hepatitis C virus [HCV] genotype 1-infected patients). In vitro studies indicated that faldaprevir inhibited CYP2B6, CYP2C9, and CYP3A, and was a weak-to-moderate inactivator of CYP3A4. Faldaprevir 240 mg twice daily in healthy volunteers demonstrated moderate inhibition of hepatic and intestinal CYP3A (oral midazolam: 2.96-fold increase in AUC(0-24 h)), weak inhibition of hepatic CYP3A (intravenous midazolam: 1.56-fold increase in AUC(0-24 h)), weak inhibition of CYP2C9 ([S]-warfarin: 1.29-fold increase in AUC(0-120 h)), and had no relevant effects on CYP1A2, CYP2B6, or CYP2D6. Faldaprevir 120 mg once daily in HCV-infected patients demonstrated weak inhibition of hepatic and intestinal CYP3A (oral midazolam: 1.52-fold increase in AUC(0-∞)), and had no relevant effects on CYP2C9 or CYP1A2. In vitro drug-drug interaction predictions based on inhibitor concentration ([I])/inhibition constant (Ki) ratios tended to overestimate clinical effects and a net-effect model provided a more accurate approach. These studies suggest that faldaprevir shows a dose-dependent inhibition of CYP3A and CYP2C9, and does not induce CYP isoforms.

An Application of Graphical Approach to Construct Multiple Testing Procedures in a Hypothetical Phase III Design.

Many multiple testing procedures (MTP) have been developed in recent years. Among these new procedures, the graphical approach is flexible and easy to communicate with non-statisticians. A hypothetical Phase III clinical trial design is introduced in this manuscript to demonstrate how graphical approach can be applied in clinical product development. In this design, an active comparator is used. It is thought that this test drug under development could potentially be superior to this comparator. For comparison of efficacy, the primary endpoint is well established and widely accepted by regulatory agencies. However, an important secondary endpoint based on Phase II findings looks very promising. The target dose may have a good opportunity to deliver superiority to the comparator. Furthermore, a lower dose is included in case the target dose may demonstrate potential safety concerns. This Phase III study is designed as a non-inferiority trial with two doses, and two endpoints. This manuscript will illustrate how graphical approach is applied to this design in handling multiple testing issues.

Efficacy and safety of combining olodaterol Respimat(®) and tiotropium HandiHaler(®) in patients with COPD: results of two randomized, double-blind, active-controlled studies.

BACKGROUND: Combining bronchodilators with different mechanisms of action may improve efficacy and reduce risk of side effects compared to increasing the dose of a single agent in chronic obstructive pulmonary disease (COPD). We investigated this by combining two long-acting bronchodilators: once-daily muscarinic antagonist tiotropium and once-daily ß2-agonist olodaterol. METHODS: Two replicate, double-blind, randomized, 12-week studies (ANHELTO 1 [NCT01694771] and ANHELTO 2 [NCT01696058]) evaluated the efficacy and safety of olodaterol 5 µg once daily (via Respimat(®)) combined with tiotropium 18 µg once daily (via HandiHaler(®)) versus tiotropium 18 µg once daily (via HandiHaler(®)) combined with placebo (via Respimat(®)) in patients with moderate to severe COPD. Primary efficacy end points were area under the curve from 0-3 hours of forced expiratory volume in 1 second (FEV1 AUC0-3) and trough FEV1 after 12 weeks (for the individual trials). A key secondary end point was health status by St George's Respiratory Questionnaire (SGRQ) total score (combined data set). RESULTS: Olodaterol + tiotropium resulted in significant improvements over tiotropium + placebo in FEV1 AUC0-3 (treatment differences: 0.117 L [P<0.001], ANHELTO 1; 0.106 L [P<0.001], ANHELTO 2) and trough FEV1 (treatment differences: 0.062 L [P<0.001], ANHELTO 1; 0.040 L [P=0.0029], ANHELTO 2); these were supported by secondary end points. These effects translated to improvements in SGRQ total scores (treatment difference -1.85; P<0.0001). The tolerability profile of olodaterol + tiotropium was similar to tiotropium monotherapy. CONCLUSION: These studies demonstrated that olodaterol (Respimat(®)) and tiotropium (HandiHaler(®)) provided bronchodilatory effects above tiotropium alone in patients with COPD. In general, both treatments were well tolerated.