Discovery of novel hepatoselective HMG-CoA reductase inhibitors for treating hypercholesterolemia: a bench-to-bedside case study on tissue selective drug distribution.

The design of drugs with selective tissue distribution can be an effective strategy for enhancing efficacy and safety, but understanding the translation of preclinical tissue distribution data to the clinic remains an important challenge. As part of a discovery program to identify next generation liver selective HMG-CoA reductase inhibitors we report the identification of (3R,5R)-7-(4-((3-fluorobenzyl)carbamoyl)-5-cyclopropyl-2-(4-fluorophenyl)-1H-imidazol-1-yl)-3,5-dihydroxyheptanoic acid (26) as a candidate for treating hypercholesterlemia. Clinical evaluation of 26 (PF-03491165), as well as the previously reported 2 (PF-03052334), provided an opportunity for a case study comparison of the preclinical and clinical pharmacokinetics as well as pharmacodynamics of tissue targeted HMG-CoA reductase inhibitors.

Short-Term Efficacy Reliably Predicts Long-Term Clinical Benefit in Rheumatoid Arthritis Clinical Trials as Demonstrated by Model-Based Meta-Analysis.

The objective of this study was to assess the relationship between short-term and long-term treatment effects measured by the American College of Rheumatology (ACR) 50 responses and to assess the feasibility of predicting 6-month efficacy from short-term data. A rheumatoid arthritis (RA) database was constructed from 68 reported trials. We focused on the relationship between 3- and 6-month ACR50 treatment effects and developed a generalized nonlinear model to quantify the relationship and test the impact of covariates. The ΔACR50 at 6 months strongly correlated with that at 3 months, moderately correlated with that at 2 months, and only weakly correlated with results obtained at <2 months. A scaling factor that reflected the ratio of 6- to 3-month treatment effects was estimated to be 0.997, suggesting that the treatment effects at 3 months are approaching a "plateau." Drug classes, baseline Disease Activity Score in 28 Joints, and the magnitude of control arm response did not show significant impacts on the scaling factor. This work quantitatively supports the empirical clinical development paradigm of using 3-month efficacy data to predict long-term efficacy and to inform the probability of clinical success based on early efficacy readout.

A model-based dose-response meta-analysis of ocular hypotensive agents as a drug development tool to evaluate new therapies in glaucoma.

PURPOSE: To characterize dose and response for intraocular pressure (IOP) reduction and incidence of hyperemia using a model-based meta-analysis of IOP-lowering monotherapy studies to evaluate new ocular antihypertensive therapies for glaucoma. METHODS: Published randomized controlled trials, regulatory documents, and sponsor reports of IOP-lowering monotherapies were used to develop dose-response models to characterize efficacy (IOP change from baseline) and safety (incidence of hyperemia) profiles. RESULTS: The meta-analysis for efficacy included 31 trials with 6,516 patients receiving bimatoprost, latanoprost, travoprost, timolol, or placebo. Estimated IOP reduction with placebo was -2.01 mmHg. Maximal IOP reduction was similar among the prostaglandin analogs (estimate, -6.27 mmHg; baseline, 25 mmHg). Estimated median effective IOP-lowering dose (ED50) was 0.002%, 0.00098%, and 0.00063% daily with bimatoprost, latanoprost, and travoprost, respectively. The hyperemia (safety) analysis included 25 trials with 6,244 patients. Typical maximal estimated difference between drug and placebo was 43%, and estimated ED50 of 0.011%, 0.014%, and 0.0015% daily for bimatoprost, latanoprost, and travoprost, respectively. Latanoprost treatment was predicted to incur the lowest rate of hyperemia of the prostaglandins, for equivalent IOP reduction. CONCLUSIONS: Model-based meta-analyses for IOP reduction and incidence of hyperemia among prostaglandin analogs are well described by maximal efficacy models and can provide a useful methodology for evaluating glaucoma therapies.

Pharmacokinetics of melagatran and the effect on ex vivo coagulation time in orthopaedic surgery patients receiving subcutaneous melagatran and oral ximelagatran: a population model analysis.

OBJECTIVE: Ximelagatran, an oral direct thrombin inhibitor, is rapidly bioconverted to melagatran, its active form. The objective of this population analysis was to characterise the pharmacokinetics of melagatran and its effect on activated partial thromboplastin time (APTT), an ex vivo measure of coagulation time, in orthopaedic surgery patients sequentially receiving subcutaneous melagatran and oral ximelagatran as prophylaxis for venous thromboembolism. To support the design of a pivotal dose-finding study, the impact of individualised dosage based on bodyweight and calculated creatinine clearance was examined. DESIGN AND METHODS: Pooled data obtained in three small dose-guiding studies were analysed. The patients received twice-daily administration, with either subcutaneous melagatran alone or a sequential regimen of subcutaneous melagatran followed by oral ximelagatran, for 8-11 days starting just before initiation of surgery. Nonlinear mixed-effects modelling was used to evaluate rich data of melagatran pharmacokinetics (3326 observations) and the pharmacodynamic effect on APTT (2319 observations) in samples from 216 patients collected in the three dose-guiding trials. The pharmacokinetic and pharmacodynamic models were validated using sparse data collected in a subgroup of 319 patients enrolled in the pivotal dose-finding trial. The impact of individualised dosage on pharmacokinetic and pharmacodynamic variability was evaluated by simulations of the pharmacokinetic-pharmacodynamic model. RESULTS: The pharmacokinetics of melagatran were well described by a one-compartment model with first-order absorption after both subcutaneous melagatran and oral ximelagatran. Melagatran clearance was correlated with renal function, assessed as calculated creatinine clearance. The median population clearance (creatinine clearance 70 mL/min) was 5.3 and 22.9 L/h for the subcutaneous and oral formulations, respectively. The bioavailability of melagatran after oral ximelagatran relative to subcutaneous melagatran was 23%. The volume of distribution was influenced by bodyweight. For a patient with a bodyweight of 75kg, the median population estimates were 15.5 and 159L for the subcutaneous and oral formulations, respectively. The relationship between APTT and melagatran plasma concentration was well described by a power function, with a steeper slope during and early after surgery but no influence by any covariates. Simulations demonstrated that individualised dosage based on creatinine clearance or bodyweight had no clinically relevant impact on the variability in melagatran pharmacokinetics or on the effect on APTT. CONCLUSIONS: The relatively low impact of individualised dosage on the pharmacokinetic and pharmacodynamic variability of melagatran supported the use of a fixed-dose regimen in the studied population of orthopaedic surgery patients, including those with mild to moderate renal impairment.

Similar relationship between the time course of bone mineral density improvement and vertebral fracture risk reduction with denosumab treatment in postmenopausal osteoporosis and prostate cancer patients on androgen deprivation therapy.

Denosumab has received approval in many countries and indications include treating women with postmenopausal osteoporosis (PMO) at increased or high risk for fracture and men at high risk for fracture receiving androgen deprivation therapy (ADT) for non-metastatic prostate cancer. Increases in total hip bone mineral density (BMD) with denosumab explained a large percentage of new vertebral fracture risk reduction in women with PMO; however, this effect has not been studied in men with prostate cancer receiving ADT. We compared the relationship between the time course of BMD changes and new vertebral fracture risk reduction with denosumab in women with PMO and men with prostate cancer. After adjusting for different baseline hazards, a significant and similar relationship between time course of total hip and lumbar spine BMD changes and new vertebral fracture risk was observed in both patient populations. Time course of total hip BMD changes with denosumab was the best predictor for changes in fracture risk and explained 88% of the new vertebral fracture risk reduction in women with PMO and 91% in men with prostate cancer. Therefore, total hip BMD is a useful surrogate to measure the clinical impact of denosumab on fracture risk reduction in both patient populations.

Time course of bone mineral density changes with denosumab compared with other drugs in postmenopausal osteoporosis: a dose-response-based meta-analysis.

OBJECTIVE: Our objective was to compare the time course of bone mineral density (BMD) changes at the lumbar spine (LS) and total hip (TH) in postmenopausal women during treatment with denosumab, bisphosphonates, selective estrogen receptor modulators, PTH, or calcitonin. DATA SOURCES AND STUDY SELECTION: Data were extracted from 142 randomized controlled trials for prevention or treatment of postmenopausal osteoporosis representing over 113,000 women. DATA EXTRACTION AND DATA SYNTHESIS: The percent change from baseline in BMD was analyzed using a nonlinear least-squares random-effects meta-regression analysis. The dose-response relationship of BMD changes was well characterized by a maximal effect (EMax) model with a different EMax for LS and TH for each drug class. The ratio of LS and TH BMD changes was significantly different across the different drug classes. The time course of BMD changes was well characterized by an exponential onset with a different rate for LS and TH for each drug class. The dose-response relationship for denosumab showed that the approved dosing regimen of 60 mg every 6 months resulted in maximal BMD changes. CONCLUSION: This exploratory analysis shows that 3 years of treatment with denosumab resulted in bigger changes in LS and TH BMD compared with 3 years of treatment with 10 mg/d oral alendronate, 5 mg/y i.v. zoledronic acid, 5 mg/d oral risedronate, 150 mg/mo oral ibandronate, 3 mg i.v. ibandronate every 3 months, 60 mg/d oral raloxifene, and 200 IU/d calcitonin. Treatment with PTH resulted in larger changes in LS BMD compared with denosumab; however, denosumab treatment provided larger changes in TH BMD.

Model-based development of gemcabene, a new lipid-altering agent.

The purpose of this study was to evaluate the value of model-based, quantitative decision making during the development of gemcabene, a novel lipid-altering agent. The decisions were driven by a model of the likely clinical profile of gemcabene in comparison with its competitors, such as 3-hydroxymethylglutaryl coenzyme A reductase inhibitors (statins), the cholesterol absorption inhibitor ezetimibe, and their combination. Dose-response models were developed for the lipid effects (low-density lipoprotein cholesterol [LDL-C] and high-density lipoprotein cholesterol); adverse effects, such as persistent alanine aminotransferase elevation and myalgia; tolerability issues, such as headache; and risk reduction for coronary artery disease-related events for 5 statins, ezetimibe, gemcabene, and their combinations. The integrated model was based on the joint analysis of publicly available summary-level data and proprietary patient-level data and included information from almost 10,000 patients. The model was made available and accessible to the development team by using the Pharsight Drug Model Explorer model visualization technology. The modeling greatly enhanced the understanding of the clinical profile of gemcabene when given alone or in combination with a statin. The interaction between statins and gemcabene for the LDL-C lowering effect was found to be significantly different from the interaction between statins and ezetimibe. Ezetimibe was found to have a pharmacological-independent interaction resulting in additional LDL-C lowering over the entire statin dose range. The gemcabene interaction was found to be less than independent, resulting in almost no additional LDL-C lowering at high-statin doses, although the drug has a significant LDL-C effect when administered alone or in combination with a low dose of a statin. The quick availability of the model after completion of the first phase II trial in the target patient population and the ability of the team to explore the potential clinical efficacy and safety of gemcabene in comparison with alternative treatment options facilitated a quick decision to stop development.

The use of clinical trial simulation to support dose selection: application to development of a new treatment for chronic neuropathic pain.

PURPOSE: Pregabalin is being evaluated for the treatment of neuropathic pain. Two phase 2 studies were simulated to determine how precisely the dose that caused a one-point reduction in the pain score could be estimated. The likelihood of demonstrating at least a one-point change for each available dose strength was also calculated. METHODS: A pharmacokinetic-pharmacodynamic (PK/PD) model relating pain relief to gabapentin plasma concentrations was derived from a phase 3 study. The PK component of the model was modified to reflect pregabalin PK. The PD component was modified by scaling the gabapentin concentration-effect relationship to reflect pregabalin potency, which was based on preclincal data. Uncertainty about the potency difference and the steepness of the concentration-response slope necessitated simulating a distribution of outcomes for a series of PK/PD models. RESULTS: Analysis of the simulated data suggested that after accounting for the uncertainty, there was an 80% chance that the dose defining the clinical feature was within 45% of the true value. The likelihood of estimating a dose that was within an acceptable predefined precision range relative to a known value approximated 60%. The minimum dose that should be studied to have a reasonable chance of estimating the dose that caused a one-point change was 300 mg. CONCLUSIONS: Doses that identify predefined response may be imprecisely estimated, suggesting that replication of a similar outcome may be elusive in a confirmatory study. Quantification of this precision provides a rationale for phase 2 trial design and dose selection for confirmatory studies.