Pharmacokinetics, Pharmacodynamics, and Safety of Vadadustat in Healthy Volunteers and Patients with Chronic Kidney Disease.

Vadadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor for treating anemia in chronic kidney disease (CKD). Single ascending dose (SAD) and multiple ascending dose (MAD) studies assessed pharmacokinetics (PK), pharmacodynamics (PD), and safety of vadadustat in healthy volunteers. A single-dose, open-label study was conducted in patients with CKD stages 3 and 4 not on dialysis. In the SAD study, 48 healthy adult men (n = 8/cohort) received single doses of vadadustat (80-1,200 mg) or placebo. In the MAD study, 34 healthy adult men (n = 8-9/cohort) received daily vadadustat (500-900 mg) or placebo for 10 days. In the single-dose CKD study, 22 male and female patients with CKD (stage 3: n = 10; stage 4: n = 12) received single doses of vadadustat (500 mg). PK parameters included plasma vadadustat; PD biomarkers were measured, including erythropoietin (EPO) levels, reticulocytes, and others. Plasma vadadustat peaked 3-4 hours after single or multiple dosing in healthy volunteers, with a mean t1/2 of approximately 4.5 hours. In patients with CKD, plasma vadadustat peaked at 5-6 hours, with a mean t1/2 of 7.2 (stage 3) and 8.5 (stage 4) hours. Vadadustat AUC∞ and Cmax increased dose proportionally in SAD and MAD trials. In all trials, EPO concentrations increased in a dose-related manner and returned approximately to baseline by 24 hours. Adverse events were mild and considered not study drug related. The PK and PD results of these studies were utilized for further clinical development of vadadustat for treatment of anemia in CKD patients.

Parallel purification of microscale libraries via automated solid phase extraction.

High-throughput experimentation (HTE) has become more widely utilized in drug discovery for rapid reaction optimization and generation of large synthetic compound arrays. While this has accelerated medicinal chemistry design, make, test (DMT) iterations, the bottleneck of purification persists, consuming time and resources. Herein we describe a general parallel purification approach based on solid phase extraction (SPE) that provides a more efficient and sustainable workflow producing compound libraries with significantly upgraded purity. This robust, user-friendly workflow is fully automated and integrated with HTE library synthesis, as demonstrated by its application to a diverse parallel library compound array generated via amide-bond coupling in HTE microscale format.

Photoredox-Catalyzed Giese Reactions: Decarboxylative Additions to Cyclic Vinylogous Amides and Esters.

An effective strategy has been developed for the photoredox-catalyzed decarboxylative addition of cyclic amino acids to both vinylogous amides and esters leading to uniquely substituted heterocycles. The additions take place exclusively trans to the substituent present on the dihydropyridone ring affording stereochemical control about the new carbon-carbon bond. These reactions are operationally simplistic and afford the desired products in good to excellent isolated yields.

Exposure-Response Analyses of Letermovir Following Oral and Intravenous Administration in Allogeneic Hematopoietic Cell Transplantation Recipients.

The cytomegalovirus (CMV) viral terminase inhibitor letermovir is approved for prophylaxis of CMV infection and disease in adult CMV-seropositive allogeneic hematopoietic stem cell transplantation recipients. In a phase III trial (NCT02137772), letermovir significantly reduced clinically significant CMV infection (CS-CMVi) rate vs. placebo through Week 24 (primary end point) and Week 14 (secondary end point) post transplantation. Here, exposure-response relationships were investigated using efficacy and selected safety end points from the phase III trial to inform the proposed clinical dose. Post hoc exposure estimates were derived from a population pharmacokinetic model. No significant exposure dependencies were found for CS-CMVi through Week 24 or Week 14 among letermovir-treated participants. Evaluated covariates had no impact on exposure-efficacy relationships and letermovir plasma exposure did not affect time of CS-CMVi onset. There was no dependence between adverse event incidence and letermovir exposure. These results support current dosing recommendations in several countries and regions, including the United States and European Union.

Synthesis of HDAC Inhibitor Libraries via Microscale Workflow.

An integrated workflow has been established that enables the synthesis, purification, and subsequent biological testing of compound libraries on a microgram scale. This approach utilizes mass directed preparative HPLC in conjunction with charged aerosol detection (CAD) to generate solutions of investigational compounds at high purity and standardized concentrations, facilitating high fidelity biological testing. This new workflow successfully delivered libraries of histone deacetylase (HDAC) inhibitors that afforded biological data consistent with that obtained from standard scale parallel medicinal chemistry techniques. The advantages of this new approach to library synthesis include greatly reduced material requirements and amenability to high-throughput experimentation.

Population pharmacokinetics of letermovir following oral and intravenous administration in healthy participants and allogeneic hematopoietic cell transplantation recipients.

Letermovir is indicated for prophylaxis of cytomegalovirus infection and disease in allogeneic hematopoietic stem cell transplant (HSCT) recipients. Two-stage population pharmacokinetic (PK) modeling of letermovir was conducted to support dose rationale and evaluate the impact of intrinsic/extrinsic factors. Data from healthy phase I study participants over a wide dose range were modeled to evaluate the effects of selected intrinsic factors, including pharmacogenomics; next, phase III HSCT-recipient data at steady-state following clinical doses were modeled. The model in HSCT recipients adequately described letermovir PK following both oral or i.v. administration, and was consistent with the healthy participant model at steady-state clinical doses. Intrinsic factor effects were not clinically meaningful. These staged analyses indicate that letermovir PK in HSCT recipients and healthy participants differ only with respect to bioavailability and absorption rate. The HSCT recipient model was suitable for predicting exposure for exposure-response analysis supporting final dose selection.

Development of indazole mineralocorticoid receptor antagonists and investigation into their selective late-stage functionalization.

The derivatization of pharmaceuticals is a core activity in the discovery and development of new medicines. Late-stage functionalization via modern CH functionalization chemistry has emerged as a powerful technique with which to diversify advanced pharmaceutical intermediates. We report herein a case study in late-stage functionalization towards the development of a new class of indazole-based mineralocorticoid receptor antagonists (MRA). An effort to modify the electronics of the core indazole heterocycle inspired the use of modern CH borylation chemistry. New reactivity patterns were revealed and studied computationally. Ultimately, a de novo synthesis delivered a key 6-fluoroindazole compound 26, a potent MRA with excellent metabolic stability.

Benzimidazole-based DGAT1 inhibitors with a [3.1.0] bicyclohexane carboxylic acid moiety.

Previously disclosed benzimidazole-based DGAT1 inhibitors containing a cyclohexane carboxylic acid moiety suffer from isomerization at the alpha position of the carboxylic acid group, generating active metabolites which exhibit DGAT1 inhibition comparable to the corresponding parent compounds. In this report, we describe the design, synthesis and profiling of benzimidazole-based DGAT1 inhibitors with a [3.1.0] bicyclohexane carboxylic acid moiety. Our results show that single isomer 3A maintains in vitro and in vivo inhibition against DGAT1. In contrast to previous lead compounds, 3A does not undergo isomerization during in vitro hepatocyte incubation study or in vivo mouse study.

Model-Informed Drug Discovery and Development: Current Industry Good Practice and Regulatory Expectations and Future Perspectives.

Good practices around model-informed drug discovery and development (MID3) aim to improve the implementation, standardization, and acceptance of these approaches within drug development and regulatory review. A survey targeted to clinical pharmacology and pharmacometric colleagues across industry, the US Food and Drug Administration (FDA), and the European Medicines Agency (EMA) was conducted to understand current and future roles of MID3. The documented standards were generally affirmed as a "good match" to current industry practice and regulatory expectations, with some identified gaps that are discussed. All have seen at least a "modest" step forward in MID3 implementation associated with greater organizational awareness and share the expectation for a future wider use and impact. The priority within organizations was identified as a limitation with respect to the future of MID3. Finally, potential solutions, including a global overarching MID3 regulatory guideline, to facilitate greater acceptance by industry and regulatory decision makers are discussed.

Microscale High-Throughput Experimentation as an Enabling Technology in Drug Discovery: Application in the Discovery of (Piperidinyl)pyridinyl-1H-benzimidazole Diacylglycerol Acyltransferase 1 Inhibitors.

Miniaturization and parallel processing play an important role in the evolution of many technologies. We demonstrate the application of miniaturized high-throughput experimentation methods to resolve synthetic chemistry challenges on the frontlines of a lead optimization effort to develop diacylglycerol acyltransferase (DGAT1) inhibitors. Reactions were performed on ∼1 mg scale using glass microvials providing a miniaturized high-throughput experimentation capability that was used to study a challenging SNAr reaction. The availability of robust synthetic chemistry conditions discovered in these miniaturized investigations enabled the development of structure-activity relationships that ultimately led to the discovery of soluble, selective, and potent inhibitors of DGAT1.

Correction: The medicinal chemist's toolbox for late stage functionalization of drug-like molecules.

Correction for 'The medicinal chemist's toolbox for late stage functionalization of drug-like molecules' by Tim Cernak et al., Chem. Soc. Rev., 2016, 45, 546-576.

Photoredox-Catalyzed Hydroxymethylation of Heteroaromatic Bases.

We report the development of a method for room-temperature C-H hydroxymethylation of heteroarenes. A key enabling advance in this work was achieved by implementing visible light photoredox catalysis that proved to be applicable to many classes of heteroarenes and tolerant of diverse functional groups found in druglike molecules.

The medicinal chemist's toolbox for late stage functionalization of drug-like molecules.

The advent of modern C-H functionalization chemistries has enabled medicinal chemists to consider a synthetic strategy, late stage functionalization (LSF), which utilizes the C-H bonds of drug leads as points of diversification for generating new analogs. LSF approaches offer the promise of rapid exploration of structure activity relationships (SAR), the generation of oxidized metabolites, the blocking of metabolic hot spots and the preparation of biological probes. This review details a toolbox of intermolecular C-H functionalization chemistries with proven applicability to drug-like molecules, classified by regioselectivity patterns, and gives guidance on how to systematically develop LSF strategies using these patterns and other considerations. In addition, a number of examples illustrate how LSF approaches have been used to impact actual drug discovery and chemical biology efforts.

Chemistry informer libraries: a chemoinformatics enabled approach to evaluate and advance synthetic methods.

Major new advances in synthetic chemistry methods are typically reported using simple, non-standardized reaction substrates, and reaction failures are rarely documented. This makes the evaluation and choice of a synthetic method difficult. We report a standardized complex molecule diagnostic approach using collections of relevant drug-like molecules which we call chemistry informer libraries. With this approach, all chemistry results, successes and failures, can be documented to compare and evolve synthetic methods. To aid in the visualization of chemistry results in drug-like physicochemical space we have used an informatics methodology termed principal component analysis. We have validated this method using palladium- and copper-catalyzed reactions, including Suzuki-Miyaura, cyanation and Buchwald-Hartwig amination.

Reporting guidelines for population pharmacokinetic analyses.

The purpose of this work was to develop a consolidated set of guiding principles for the reporting of population pharmacokinetic (PK) analyses based on input from a survey of practitioners as well as discussions between industry, consulting, and regulatory scientists. The survey found that identification of population covariate effects on drug exposure and support for dose selection (in which population PK frequently serves as preparatory analysis for exposure-response modeling) are the main areas of influence for population PK analysis. The proposed guidelines consider 2 main purposes of population PK reports: (1) to present key analysis findings and their impact on drug development decisions, and (2) as documentation of the analysis methods for the dual purpose of enabling review of the analysis and facilitating future use of the models. This work also identified 2 main audiences for the reports: (1) a technically competent group responsible for in-depth review of the data, methodology, and results; and (2) a scientifically literate but not technically adept group, whose main interest is in the implications of the analysis for the broader drug development program. We recommend a generalized question-based approach with 6 questions that need to be addressed throughout the report. We recommend 8 sections (Synopsis, Introduction, Data, Methods, Results, Discussion, Conclusions, Appendix) with suggestions for the target audience and level of detail for each section. A section providing general expectations regarding population PK reporting from a regulatory perspective is also included. We consider this an important step toward industrialization of the field of pharmacometrics such that a nontechnical audience also understands the role of pharmacometric analyses in decision making. Population PK reports were chosen as representative reports to derive these recommendations; however, the guiding principles presented here are applicable for all pharmacometric reports including pharmacokinetics/pharmacodynamics and simulation reports.

Heterocyclic Regioisomer Enumeration (HREMS): A Cheminformatics Design Tool.

We report the development and implementation of a cheminformatics tool which aids in the design of compounds during exploratory chemistry and lead optimization. The Heterocyclic Regioisomer Enumeration and MDDR Search (HREMS) tool allows medicinal chemists to build greater structural diversity into their synthetic planning by enabling a systematic, automated enumeration of heterocyclic regioisomers of target structures. To help chemists overcome biases arising from past experience or synthetic accessibility, the HREMS tool further provides statistics on clinical testing for each enumerated regioisomer substructure using an automated search of a commercial database. Ready access to this type of information can help chemists make informed choices on the targets they will pursue being mindful of past experience with these structures in drug development. This tool and its components can be incorporated into other cheminformatics workflows to leverage their capabilities in triaging and in silico compound enumeration.

Reporting guidelines for population pharmacokinetic analyses.

The purpose of this work was to develop a consolidated set of guiding principles for reporting of population pharmacokinetic (PK) analyses based on input from a survey of practitioners as well as discussions between industry, consulting and regulatory scientists. The survey found that identification of population covariate effects on drug exposure and support for dose selection (where population PK frequently serves as preparatory analysis to exposure-response modeling) are the main areas of influence for population PK analysis. The proposed guidelines consider two main purposes of population PK reports (1) to present key analysis findings and their impact on drug development decisions, and (2) as documentation of the analysis methods for the dual purpose of enabling review of the analysis and facilitating future use of the models. This work also identified two main audiences for the reports: (1) a technically competent group responsible for in-depth review of the data, methodology, and results, and (2) a scientifically literate, but not technically adept group, whose main interest is in the implications of the analysis for the broader drug development program. We recommend a generalized question-based approach with six questions that need to be addressed throughout the report. We recommend eight sections (Synopsis, Introduction, Data, Methods, Results, Discussion, Conclusions, Appendix) with suggestions for the target audience and level of detail for each section. A section providing general expectations regarding population PK reporting from a regulatory perspective is also included. We consider this an important step towards industrialization of the field of pharmacometrics such that non-technical audience also understands the role of pharmacometrics analyses in decision making. Population PK reports were chosen as representative reports to derive these recommendations; however, the guiding principles presented here are applicable for all pharmacometric reports including PKPD and simulation reports.

Discovery of a Potent and Selective DGAT1 Inhibitor with a Piperidinyl-oxy-cyclohexanecarboxylic Acid Moiety.

We report the discovery of a novel series of DGAT1 inhibitors in the benzimidazole class with a piperdinyl-oxy-cyclohexanecarboxylic acid moiety. This novel series possesses significantly improved selectivity against the A2A receptor, no ACAT1 off-target activity at 10 µM, and higher aqueous solubility and free fraction in plasma as compared to the previously reported pyridyl-oxy-cyclohexanecarboxylic acid series. In particular, 5B was shown to possess an excellent selectivity profile by screening it against a panel of more than 100 biological targets. Compound 5B significantly reduces lipid excursion in LTT in mouse and rat, demonstrates DGAT1 mediated reduction of food intake and body weight in mice, is negative in a 3-strain Ames test, and appears to distribute preferentially in the liver and the intestine in mice. We believe this lead series possesses significant potential to identify optimized compounds for clinical development.

Late-stage functionalization of biologically active heterocycles through photoredox catalysis.

The direct CH functionalization of heterocycles has become an increasingly valuable tool in modern drug discovery. However, the introduction of small alkyl groups, such as methyl, by this method has not been realized in the context of complex molecule synthesis since existing methods rely on the use of strong oxidants and elevated temperatures to generate the requisite radical species. Herein, we report the use of stable organic peroxides activated by visible-light photoredox catalysis to achieve the direct methyl-, ethyl-, and cyclopropylation of a variety of biologically active heterocycles. The simple protocol, mild reaction conditions, and unique tolerability of this method make it an important tool for drug discovery.

Model-based development of anacetrapib, a novel cholesteryl ester transfer protein inhibitor.

A model-based strategy was used to inform the early clinical development of anacetrapib, a novel cholesteryl ester transfer protein inhibitor under development for the treatment of hyperlipidemia. The objectives of this model-based approach were to enable bridging variable pharmacokinetic effects, differences among formulations used in development, and to identify an appropriate dose for the phase III confirmatory program. Nonlinear mixed effects PK/PD models were initially developed based on data obtained from multiple phase I studies and later were updated with data from a phase IIb study. The population pharmacokinetic model described differences between the liquid-filled capsule used in phase I and phase IIb and the hot-melt extruded (HME) tablet formulation introduced in phase III, allowing for bridging of the two formulations, and quantified the complex relationship of apparent anacetrapib bioavailability with subject meal intake. Proportional E(max) models quantified the relationships between anacetrapib trough concentration and lipoprotein effects (LDL-C and HDL-C), with covariate effects of study population (normal volunteers vs. patients), and co-administration with HMG-CoA reductase inhibitor ("statin"). The interaction between anacetrapib and atorvastatin suggested pharmacological independence, i.e., that when given together, each agent exerts the same proportional lipid effect observed from monotherapy. Clinical trial simulation was used to examine the robustness of the effects to random dietary indiscretion, and found that the results were robust as long as patients generally adhered to a low-fat diet. These results allowed the selection of the 100 mg dose with the HME formulation for phase III development even though this dose and formulation were not specifically studied in a phase IIb trial.