Discovery of Clinical Candidate PF-06648671: A Potent γ-Secretase Modulator for the Treatment of Alzheimer's Disease.

Herein, we describe the design and synthesis of γ-secretase modulator (GSM) clinical candidate PF-06648671 (22) for the treatment of Alzheimer's disease. A key component of the design involved a 2,5-cis-tetrahydrofuran (THF) linker to impart conformational rigidity and lock the compound into a putative bioactive conformation. This effort was guided using a pharmacophore model since crystallographic information was not available for the membrane-bound γ-secretase protein complex at the time of this work. PF-06648671 achieved excellent alignment of whole cell in vitro potency (Aß42 IC50 = 9.8 nM) and absorption, distribution, metabolism, and excretion (ADME) parameters. This resulted in favorable in vivo pharmacokinetic (PK) profile in preclinical species, and PF-06648671 achieved a human PK profile suitable for once-a-day dosing. Furthermore, PF-06648671 was found to have favorable brain availability in rodent, which translated into excellent central exposure in human and robust reduction of amyloid ß (Aß) 42 in cerebrospinal fluid (CSF).

Sulfur(VI) fluorides as tools in biomolecular and medicinal chemistry.

Recent advances in the synthesis of sulfur(VI)-fluorides has enabled incredible growth in their application in biomolecular chemistry. This review aims to serve as a primer highlighting synthetic strategies toward a diversity of S(VI) fluorides and their application in chemical biology, bioconjugation, and medicinal chemistry.

Fluorophosphonates on-Demand: A General and Simplified Approach toward Fluorophosphonate Synthesis.

Herein, we report a general and simplified synthesis of fluorophosphonates directly from p-nitrophenylphosphonates. This FP on-demand reaction is mediated by a commercially available polymer-supported fluoride reagent that produces a variety (25 examples) of fluorophosphonates in high yields while only requiring reagent filtration for pure fluorophosphonate isolation. This reaction protocol facilitates the rapid profiling of serine hydrolases with diverse and novel sets of activated phosphonates with differential proteome reactivity. Moreover, slight modification of the procedure into a reaction-to-assay format has enabled additional screening efficiency.

Photoaffinity Labeling and Quantitative Chemical Proteomics Identify LXRß as the Functional Target of Enhancers of Astrocytic apoE.

Utilizing a phenotypic screen, we identified chemical matter that increased astrocytic apoE secretion in vitro. We designed a clickable photoaffinity probe based on a pyrrolidine lead compound and carried out probe-based quantitative chemical proteomics in human astrocytoma CCF-STTG1 cells to identify liver x receptor ß (LXRß) as the target. Binding of the small molecule ligand stabilized LXRß, as shown by cellular thermal shift assay (CETSA). In addition, we identified a probe-modified peptide by mass spectrometry and proposed a model where the photoaffinity probe is bound in the ligand-binding pocket of LXRß. Taken together, our findings demonstrated that the lead chemical matter bound directly to LXRß, and our results highlight the power of chemical proteomic approaches to identify the target of a phenotypic screening hit. Additionally, the LXR photoaffinity probe and lead compound described herein may serve as valuable tools to further evaluate the LXR pathway.

SuFEx Activation with Ca(NTf2)2: A Unified Strategy to Access Sulfamides, Sulfamates, and Sulfonamides from S(VI) Fluorides.

A method to activate sulfamoyl fluorides, fluorosulfates, and sulfonyl fluorides with calcium triflimide and DABCO for SuFEx with amines is described. The reaction was applied to a diverse set of sulfamides, sulfamates, and sulfonamides at room temperature under mild conditions. Additionally, we highlight this transformation to parallel medicinal chemistry to generate a broad array of nitrogen-based S(VI) compounds.

Safety, Pharmacokinetics, and Pharmacodynamics of ME-401, an Oral, Potent, and Selective Inhibitor of Phosphatidylinositol 3-Kinase P110δ, Following Single Ascending Dose Administration to Healthy Volunteers.

PURPOSE: ME-401 is a novel selective inhibitor of phosphatidylinositol 3 kinase p110δ, an enzyme often found overexpressed and overactive in B-cell malignancies. The current study was performed to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of single ascending oral doses of ME-401 in healthy volunteers. METHODS: This analysis was an open-label, nonrandomized study in healthy male volunteers. Three sequential groups were dosed. Each group received single doses of ME-401 on two occasions; the doses tested ranged from 10 to 150 mg. Blood was drawn at various time points to analyze plasma concentrations of ME-401 and inhibition of basophil activation, a marker of phosphatidylinositol 3 kinase p110δ inhibition. FINDINGS: Fifteen subjects received a single dose of ME-401 on two occasions. Three adverse events that were considered possibly related to the study drug were reported: one event of pain, one event of headache, and one event of upper abdominal pain. ME-401 exhibited dose proportionality up to 60 mg, and supra-proportional increases in exposure were observed above doses of 60 mg. In addition, there was a dose-proportional increase in the inhibition of basophil activation up to 60 mg. Mean t1/2 ranged from 9.36 to 29.23 hours across the dose range. A 60 mg dose of ME-401 approached 90% inhibition of basophil activation, and thereafter no further increase to the percent inhibition of basophil activation was observed for higher doses. Once-daily dosing of 60 mg ME-401 was forecasted to result in trough plasma levels exceeding the concentration needed for 90% inhibition of basophil activation. IMPLICATIONS: This first-in-human study showed that ME-401 was well tolerated after single doses up to 150 mg. Pharmacologic activity was confirmed after administration of single ascending oral doses of 10 to 150 mg. ME-401 60 mg, administered once daily, was selected as the starting dose for patient studies. ClinicalTrials.gov identifier: NCT02521389.

Introduction of a Crystalline, Shelf-Stable Reagent for the Synthesis of Sulfur(VI) Fluorides.

The design, synthesis, and application of [4-(acetylamino)phenyl]imidodisulfuryl difluoride (AISF), a shelf-stable, crystalline reagent for the synthesis of sulfur(VI) fluorides, is described. The utility of AISF is demonstrated in the synthesis of a diverse array of aryl fluorosulfates and sulfamoyl fluorides under mild conditions. Additionally, a single-step preparation of AISF was developed that installed the bis(fluorosulfonyl)imide group on acetanilide utilizing an oxidative C-H functionalization protocol.

Identification and Profiling of a Selective and Brain Penetrant Radioligand for in Vivo Target Occupancy Measurement of Casein Kinase 1 (CK1) Inhibitors.

To enable the clinical development of our CNS casein kinase 1 delta/epsilon (CK1δ/ε) inhibitor project, we investigated the possibility of developing a CNS positron emission tomography (PET) radioligand. For this effort, we focused our design and synthesis efforts on the initial CK1δ/ε inhibitor HTS hits with the goal of identifying a compound that would fulfill a set of recommended PET ligand criteria. We identified [3H]PF-5236216 (9) as a tool ligand that meets most of the key CNS PET attributes including high CNS MPO PET desirability score and kinase selectivity, CNS penetration, and low nonspecific binding. We further used [3H]-9 to determine the binding affinity for PF-670462, a literature CK1δ/ε inhibitor tool compound. Lastly, [3H]-9 was used to measure in vivo target occupancy (TO) of PF-670462 in mouse and correlated TO with CK1δ/ε in vivo pharmacology (circadian rhythm modulation).

Discovery of cyclopropyl chromane-derived pyridopyrazine-1,6-dione γ-secretase modulators with robust central efficacy.

Herein we describe the discovery of a novel series of cyclopropyl chromane-derived pyridopyrazine-1,6-dione γ-secretase modulators for the treatment of Alzheimer's disease (AD). Using ligand-based design tactics such as conformational analysis and molecular modeling, a cyclopropyl chromane unit was identified as a suitable heterocyclic replacement for a naphthyl moiety that was present in the preliminary lead 4. The optimized lead molecule 44 achieved good central exposure resulting in robust and sustained reduction of brain amyloid-ß42 (Aß42) when dosed orally at 10 mg kg-1 in a rat time-course study. Application of the unpaced isolated heart Langendorff model enabled efficient differentiation of compounds with respect to cardiovascular safety, highlighting how minor structural changes can greatly impact the safety profile within a series of compounds.

Design of Pyridopyrazine-1,6-dione γ-Secretase Modulators that Align Potency, MDR Efflux Ratio, and Metabolic Stability.

Herein we describe the design and synthesis of a series of pyridopyrazine-1,6-dione γ-secretase modulators (GSMs) for Alzheimer's disease (AD) that achieve good alignment of potency, metabolic stability, and low MDR efflux ratios, while also maintaining favorable physicochemical properties. Specifically, incorporation of fluorine enabled design of metabolically less liable lipophilic alkyl substituents to increase potency without compromising the sp(3)-character. The lead compound 21 (PF-06442609) displayed a favorable rodent pharmacokinetic profile, and robust reductions of brain Aß42 and Aß40 were observed in a guinea pig time-course experiment.

Casein kinase 1δ/ε inhibitor PF-5006739 attenuates opioid drug-seeking behavior.

Casein kinase 1 delta (CK1δ) and casein kinase 1 epsilon (CK1ε) inhibitors are potential therapeutic agents for a range of psychiatric disorders. The feasibility of developing a CNS kinase inhibitor has been limited by an inability to identify safe brain-penetrant compounds with high kinome selectivity. Guided by structure-based drug design, potent and selective CK1δ/ε inhibitors have now been identified that address this gap, through the design and synthesis of novel 4-[4-(4-fluorophenyl)-1-(piperidin-4-yl)-1H-imidazol-5-yl]pyrimidin-2-amine derivatives. PF-5006739 (6) possesses a desirable profile, with low nanomolar in vitro potency for CK1δ/ε (IC50 = 3.9 and 17.0 nM, respectively) and high kinome selectivity. In vivo, 6 demonstrated robust centrally mediated circadian rhythm phase-delaying effects in both nocturnal and diurnal animal models. Further, 6 dose-dependently attenuated opioid drug-seeking behavior in a rodent operant reinstatement model in animals trained to self-administer fentanyl. Collectively, our data supports further development of 6 as a promising candidate to test the hypothesis of CK1δ/ε inhibition in treating multiple indications in the clinic.

Ligand-protein interactions of selective casein kinase 1δ inhibitors.

Casein kinase 1δ (CK1δ) and 1ε (CK1ε) are believed to be necessary enzymes for the regulation of circadian rhythms in all mammals. On the basis of our previously published work demonstrating a CK1ε-preferring compound to be an ineffective circadian clock modulator, we have synthesized a series of pyrazole-substitued pyridine inhibitors, selective for the CK1δ isoform. Additionally, using structure-based drug design, we have been able to exploit differences in the hinge region between CK1δ and p38 to find selective inhibitors that have minimal p38 activity. The SAR, brain exposure, and the effect of these inhibitors on mouse circadian rhythms are described. The in vivo evaluation of these inhibitors demonstrates that selective inhibition of CK1δ at sufficient central exposure levels is capable of modulating circadian rhythms.

Discovery of two clinical histamine H(3) receptor antagonists: trans-N-ethyl-3-fluoro-3-[3-fluoro-4-(pyrrolidinylmethyl)phenyl]cyclobutanecarboxamide (PF-03654746) and trans-3-fluoro-3-[3-fluoro-4-(pyrrolidin-1-ylmethyl)phenyl]-N-(2-methylpropyl)cyclobutanecarboxamide (PF-03654764).

The discovery of two histamine H(3) antagonist clinical candidates is disclosed. The pathway to identification of the two clinical candidates, 6 (PF-03654746) and 7 (PF-03654764) required five hypothesis driven design cycles. The key to success in identifying these clinical candidates was the development of a compound design strategy that leveraged medicinal chemistry knowledge and traditional assays in conjunction with computational and in vitro safety tools. Overall, clinical compounds 6 and 7 exceeded conservative safety margins and possessed optimal pharmacological and pharmacokinetic profiles, thus achieving our initial goal of identifying compounds with fully aligned oral drug attributes, "best-in-class" molecules.

Selective inhibition of casein kinase 1 epsilon minimally alters circadian clock period.

The circadian clock links our daily cycles of sleep and activity to the external environment. Deregulation of the clock is implicated in a number of human disorders, including depression, seasonal affective disorder, and metabolic disorders. Casein kinase 1 epsilon (CK1epsilon) and casein kinase 1 delta (CK1delta) are closely related Ser-Thr protein kinases that serve as key clock regulators as demonstrated by mammalian mutations in each that dramatically alter the circadian period. Therefore, inhibitors of CK1delta/epsilon may have utility in treating circadian disorders. Although we previously demonstrated that a pan-CK1delta/epsilon inhibitor, 4-[3-cyclohexyl-5-(4-fluoro-phenyl)-3H-imidazol-4-yl]-pyrimidin-2-ylamine (PF-670462), causes a significant phase delay in animal models of circadian rhythm, it remains unclear whether one of the kinases has a predominant role in regulating the circadian clock. To test this, we have characterized 3-(3-chloro-phenoxymethyl)-1-(tetrahydro-pyran-4-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-ylamine (PF-4800567), a novel and potent inhibitor of CK1epsilon (IC(50) = 32 nM) with greater than 20-fold selectivity over CK1delta. PF-4800567 completely blocks CK1epsilon-mediated PER3 nuclear localization and PER2 degradation. In cycling Rat1 fibroblasts and a mouse model of circadian rhythm, however, PF-4800567 has only a minimal effect on the circadian clock at concentrations substantially over its CK1epsilon IC(50). This is in contrast to the pan-CK1delta/epsilon inhibitor PF-670462 that robustly alters the circadian clock under similar conditions. These data indicate that CK1epsilon is not the predominant mediator of circadian timing relative to CK1delta. PF-4800567 should prove useful in probing unique roles between these two kinases in multiple signaling pathways.

Metabolism, distribution and excretion of a selective N-methyl-D-aspartate receptor antagonist, traxoprodil, in rats and dogs.

Disposition of traxoprodil ({1-[2-hydroxy-2-(4-hydroxy-phenyl)-1-methyl-ethyl]-4-phenyl-piperidin-4-ol}mesylate; TRX), a selective antagonist of the N-methyl-d-aspartate class of glutamate receptors, was investigated in rats and dogs after administration of a single i.v. bolus dose of [(14)C]TRX. Total mean recoveries of the radiocarbon were 92.5 and 88.2% from rats and dogs, respectively. Excretion of radioactivity was rapid and nearly complete within 48 h after dosing in both species. Whole-body autoradioluminography study suggested that TRX radioactivity was retained more by uveal tissues, kidney, and liver than by other tissues. TRX is extensively metabolized in rats and dogs since only 8 to 15% of the administered radioactivity was excreted as unchanged drug in the urine of these species. The metabolic pathways included aromatic hydroxylation at the phenylpiperidinol moiety, hydroxylation at the hydroxyphenyl ring, and O-glucuronidation. There were notable species-related qualitative and quantitative differences in the metabolism of TRX in rats and dogs. The hydroxylation at the 3-position of the phenol ring followed by methylation of the resulting catechol intermediate and subsequent conjugation were identified as the main metabolic pathways in dogs. In contrast, formation of the major metabolites in rats was due to oxidation at the 4'-position of the phenylpiperidinol moiety followed by further oxidation and phase II conjugation. TRX glucuronide conjugate was identified as the major circulating component in rats, whereas the glucuronide and sulfate conjugates of O-methyl catechol metabolite were the major metabolites in dog plasma. The site of conjugation of regioisomeric glucuronides was established from the differences in the collision-induced dissociation product ion spectra of their methylated products.

Effect of once- or twice-daily MMX mesalamine (SPD476) for the induction of remission of mild to moderately active ulcerative colitis.

BACKGROUND & AIMS: SPD476 (MMX mesalamine), a novel, once-daily mesalamine formulation, uses MMX Multi Matrix System (MMX) technology to delay and extend delivery of active drug throughout the colon. We performed a randomized, double-blind, parallel-group, placebo-controlled, multicenter phase III study in patients with mild to moderately active ulcerative colitis. METHODS: Two hundred eighty patients with mild to moderately active ulcerative colitis received MMX mesalamine 2.4 g/day given twice daily (n = 93), 4.8 g/day given once daily (n = 94), or placebo (n = 93) for 8 weeks. The primary end point was the percentage of patients in clinical and endoscopic remission (modified ulcerative colitis disease activity index score of < or =1, with a score of 0 for rectal bleeding and stool frequency, and at least a 1-point reduction in sigmoidoscopy score) at week 8. Patients with mucosal friability were not considered to have achieved this end point. RESULTS: Clinical and endoscopic remission at week 8 was achieved by 34.1% and 29.2% of patients receiving MMX mesalamine 2.4 g/day given twice daily and MMX mesalamine 4.8 g/day given once daily, respectively, versus 12.9% receiving placebo (P < .01). MMX mesalamine was generally well-tolerated. CONCLUSIONS: MMX mesalamine given once or twice daily is well-tolerated and, compared with placebo, demonstrated efficacy for the induction of clinical and endoscopic remission in mild to moderately active ulcerative colitis.

Once-daily, high-concentration MMX mesalamine in active ulcerative colitis.

BACKGROUND & AIMS: SPD476 (LIALDA in the US; MEZAVANT in the EU; otherwise known as MMX mesalamine; Shire Pharmaceuticals Inc., Wayne, PA, under license from Giuliani SpA, Milan, Italy) is a novel, once-daily, high-strength (1.2 g/tablet) formulation of mesalamine, utilizing MMX Multi Matrix System (MMX) technology designed to deliver the active drug throughout the colon. We performed a double-blind, multicenter study, comparing MMX mesalamine vs placebo for the treatment of active ulcerative colitis. A delayed-release oral mesalamine (ASACOL; Procter & Gamble, Cincinnati, OH) reference arm was included. METHODS: Three hundred forty-three patients with active, mild-to-moderate ulcerative colitis received MMX mesalamine 2.4 g/day or 4.8 g/day given once daily, ASACOL 2.4 g/day given in 3 divided doses, or placebo for 8 weeks. The primary end point was the proportion of patients in clinical and endoscopic remission (modified ulcerative colitis disease activity index of < or =1 with rectal bleeding and stool frequency scores of 0, no mucosal friability, and a > or =1-point reduction in sigmoidoscopy score from baseline). RESULTS: A significantly greater proportion of patients receiving MMX mesalamine 2.4 g/day given once daily (40.5%; P = .01) and 4.8 g/day given once daily (41.2%; P = .007) achieved clinical and endoscopic remission at week 8, vs placebo (22.1%). The clinical and endoscopic remission rate for ASACOL (32.6%; P = .124) was not significantly superior to placebo. All active treatments were well-tolerated. CONCLUSIONS: Once-daily MMX mesalamine was efficacious and well-tolerated for the induction of clinical and endoscopic remission. MMX mesalamine offers effective and convenient mesalamine therapy, potentially improving treatment compliance.

Plasma levels of B-lymphocyte stimulator increase with HIV disease progression.

We measured the plasma levels of B-lymphocyte stimulator (BLyS) in 101 HIV-1-infected patients and 18 controls. BLyS levels were higher among HIV-positive patients [median 5.70 (3.90) versus 4.62 (1.04) ng/ml, P = 0.002], who had significantly higher BLyS and total serum globulin levels with decreasing CD4 cell counts. Moreover, BLyS levels increased exponentially below 100 CD4 cells/microl. BLyS and globulin levels increase as HIV dis ease progresses, suggesting a role for BLyS in the hypergammaglobulinemia of HIV infection.