Inhibitors of the Hedgehog signaling pathway have generated a great deal of interest in the oncology area due to the mounting evidence of their potential to provide promising therapeutic options for ...patients. Herein, we describe the discovery strategy to overcome the issues inherent in lead structure 1 that resulted in the identification of Smoothened inhibitor 1-((2R,4R)-2-(1H-benzodimidazol-2-yl)-1-methylpiperidin-4-yl)-3-(4-cyanophenyl)urea (PF-04449913, 26), which has been advanced to human clinical studies.
The enzyme phosphodiesterase 2A (PF-05270430) is a potential target for development of novel therapeutic agents for the treatment of cognitive impairments. The goal of the present study was to ...evaluate the PDE2A ligand (18)F-PF-05270430, 4-(3-fluoroazetidin-1-yl)-7-methyl-5-(1-methyl-5-(4-(trifluoromethyl)phenyl)-1H-pyrazol-4-yl)imidazo1,5-f1,2,4triazine, in nonhuman primates.
(18)F-PF-05270430 was radiolabeled by 2 methods via nucleophilic substitution of its tosylate precursor. Tissue metabolite analysis in rodents and PET imaging in nonhuman primates under baseline and blocking conditions were performed to determine the pharmacokinetic and binding characteristics of the new radioligand. Various kinetic modeling approaches were assessed to select the optimal method for analysis of imaging data.
(18)F-PF-05270430 was synthesized in greater than 98% radiochemical purity and high specific activity. In the nonhuman primate brain, uptake of (18)F-PF-05270430 was fast, with peak concentration (SUVs of 1.5-1.8 in rhesus monkeys) achieved within 7 min after injection. The rank order of uptake was striatum > neocortical regions > cerebellum. Regional time-activity curves were well fitted by the 2-tissue-compartment model and the multilinear analysis-1 (MA1) method to arrive at reliable estimates of regional distribution volume (VT) and binding potential (BPND) with 120 min of scan data. Regional VT values (MA1) ranged from 1.28 mL/cm(3) in the cerebellum to 3.71 mL/cm(3) in the putamen, with a BPND of 0.25 in the temporal cortex and 1.92 in the putamen. Regional BPND values estimated by the simplified reference tissue model (SRTM) were similar to those from MA1. Test-retest variability in high-binding regions (striatum) was 4% ± 6% for MA1 VT, 13% ± 6% for MA1 BPND, and 13% ± 7% SRTM BPND, respectively. Pretreatment of animals with the PDE2A inhibitor PF-05180999 resulted in a dose-dependent reduction of (18)F-PF-05270430 specific binding, with a half maximal effective concentration of 69.4 ng/mL in plasma PF-05180999 concentration.
(18)F-PF-05270430 displayed fast and reversible kinetics in nonhuman primates, as well as specific binding blockable by a PDE2A inhibitor. This is the first PET tracer with desirable imaging properties and demonstrated ability to image and quantify PDE2A in vivo.
Phosphodiesterase 2A (PDE2A) inhibitors have been reported to demonstrate in vivo activity in preclinical models of cognition. To more fully explore the biology of PDE2A inhibition, we sought to ...identify potent PDE2A inhibitors with improved brain penetration as compared to current literature compounds. Applying estimated human dose calculations while simultaneously leveraging synthetically enabled chemistry and structure-based drug design has resulted in a highly potent, selective, brain penetrant compound 71 (PF-05085727) that effects in vivo biochemical changes commensurate with PDE2A inhibition along with behavioral and electrophysiological reversal of the effects of NMDA antagonists in rodents. This data supports the ability of PDE2A inhibitors to potentiate NMDA signaling and their further development for clinical cognition indications.
Significant efforts through genomic approaches have been dedicated toward the identification of novel protein-protein interactions as promising therapeutic targets for indications such as Alzheimer's ...disease, Parkinson's disease and neuropsychiatric disorders. Additionally, the number of biotherapeutic agents entering the Pharmaceutical sector continues to increase and according to EvaluatePharma's "World Preview 2014" report, "the compounded annual growth rate of biologics is expected to be 8.5 percent from 2008-2014, eight to 10 times greater than the growth rate of small molecules". However, there are limited examples of success in developing biotherapeutic modalities for central nervous system (CNS) diseases in the drug development pipeline. A primary reason for the lack of application of biotherapeutics to neuroscience targets, is that the blood-brain barrier (BBB) isolates and protects CNS structures creating a unique biochemically and immunologically privileged environment, therefore passage of macromolecules across this barrier has additional challenges. An understanding of the anatomical and physiological properties of this barrier with respect to penetration of biotherapeutics is presented in this review document. In this summary, recent advances in biotherapeutic delivery mechanisms across the BBB including transcranial brain drug delivery, focused ultrasound technology, nasal delivery, absorptive endocytosis, and receptor mediated endocytosis are evaluated using an industrial perspective. With acknowledgement that each approach has advantages and disadvantages, this review discusses the opportunities and challenges that are encountered during application of these methods across a variety of therapeutic areas such as, pain, obesity, neuroscience, and oncology. Utilizing an industrial perspective, including consideration of cost of goods and commercial feasibility for these approaches, this review highlights technology features which would enable industry investments toward novel BBB delivery technologies for biologics. Through continued development and improvement of such technology, new therapeutic options to treat and potentially cure central nervous system diseases could eventually evolve.
The metabolism and disposition of 4-4-(4-fluorophenoxy)-benzenesulfonylaminotetrahydropyran-4-carboxylic acid hydroxyamide (CP-544439), a selective inhibitor of matrix metalloproteinase-13, was ...investigated in rats and dogs following oral administration of (14)CCP-544439. Both species showed quantitative recovery of the radiolabel, and feces was the major route of excretion. Whole-body autoradioluminography study in rats suggested distribution of CP-544439 in all tissues except central nervous system. The radiolabel was rapidly eliminated from most tissues except the periodontal ligament. Metabolism of CP-544439 was extensive in both species. Only 8.4 and 1.5% of the total dose constituted unchanged CP-544439 in the rat and dog, respectively. Similarly, pharmacokinetic analysis of (14)CCP-544439 and unchanged CP-544439 indicated that the exposure of the parent drug was 16 and 6.5% of the total radioequivalents in rat and dog, respectively. Metabolic profiling revealed that CP-544439 was primarily metabolized via glucuronidation, reduction, and hydrolysis. Glucuronidation was the primary route of metabolism in dogs, whereas reduction of the hydroxamate moiety was the major pathway in rats. Human plasma and urine obtained from a dose escalation study in healthy human volunteers were also analyzed in this study to assess the metabolism of CP-544439 in humans and ensure that selected animal species were exposed to all major metabolites formed in humans. Analysis suggested that CP-544439 was metabolized via all three pathways in humans consistent with rat and dog; however, the glucuronide conjugate M1 was the major circulating and excretory metabolite in humans. Preliminary in vitro phenotyping studies indicated that glucuronide formation is primarily catalyzed by UGT1A1, 1A3, and 1A9.
Delivery of drug therapeutics across the blood-brain barrier is a challenging task for pharmaceutical scientists. Nasal-to-CNS drug delivery has shown promising results in preclinical efficacy models ...and investigatory human clinical trials. The further development of this technology with respect to the establishment of valid, predictable preclinical species models, translatable pharmacokinetic-pharmacodynamic relationships and definition of toxicology impact will help attract additional pharmaceutical investment in this drug-delivery approach. Further discoveries in nasal nanotechnology, targeted delivery devices and diagnostic olfactory imaging will serve to fuel the advancements in this area of drug delivery.
PF‐05212377 (SAM760) is a potent and selective 5‐HT6 antagonist, previously under development for the treatment of Alzheimer’s disease. In vitro, PF‐05212377 was determined to be a P‐gp/non‐BCRP ...human transporter substrate. Species differences were observed in the in vivo brain penetration of PF‐05212377 with a ratio of the unbound concentration in brain/unbound concentration in plasma (Cbu/Cpu) of 0.05 in rat and 0.64 in non‐human primates (NHP). Based on pre‐clinical evidence, brain penetration and target engagement of PF‐05212377 was confirmed in NHP using positron emission tomography (PET) measured 5‐HT6 receptor occupancy (%RO). The NHP Cpu EC50 of PF‐05212377 was 0.31 nM (consistent with the in vitro human 5HT6 Ki: 0.32 nM). P‐gp has been reported to be expressed in higher abundance at the rat BBB and in similar abundance at the BBB of non‐human primates and human; brain penetration of PF‐05212377 in humans was postulated to be similar to that in non‐human primates. In humans, PF‐05212377 demonstrated dose and concentration dependent increases in 5‐HT6 RO; maximal 5‐HT6 RO of ∼80% was measured in humans at doses of ≥15 mg with an estimated unbound plasma EC50 of 0.37 nM (which was similar to the in vitro human 5HT6 binding Ki 0.32 nM). In conclusion, cumulative evidence from NHP and human PET RO assessments confirmed that NHP is more appropriate than the rat for the prediction of human brain penetration of PF‐05212377, a P‐gp/non‐BCRP substrate.
Clinical trial number: NCT01258751.
PF‐05212377 (5HT6 Ki: 0.32 nM) was determined to be a P‐gp/non‐BCRP substrate. As P‐gp is expressed in similar abundance at the BBB of non‐human primates (NHP) and human, brain penetration of PF‐05212377 in humans was postulated to be similar to NHP. Target engagement was investigated in NHP, using PET RO. In humans, PF‐05212377 demonstrated concentration dependent increases in 5‐HT6 RO confirming that NHP was more appropriate than rat for the evaluating the CNS distribution of PF‐05212377.
PF-05212377 (SAM760) is a potent and selective 5-HT
antagonist, previously under development for the treatment of Alzheimer's disease. In vitro, PF-05212377 was determined to be a P-gp/non-BCRP human ...transporter substrate. Species differences were observed in the in vivo brain penetration of PF-05212377 with a ratio of the unbound concentration in brain/unbound concentration in plasma (C
/C
) of 0.05 in rat and 0.64 in non-human primates (NHP). Based on pre-clinical evidence, brain penetration and target engagement of PF-05212377 was confirmed in NHP using positron emission tomography (PET) measured 5-HT
receptor occupancy (%RO). The NHP C
EC
of PF-05212377 was 0.31 nM (consistent with the in vitro human 5HT6 K
: 0.32 nM). P-gp has been reported to be expressed in higher abundance at the rat BBB and in similar abundance at the BBB of non-human primates and human; brain penetration of PF-05212377 in humans was postulated to be similar to that in non-human primates. In humans, PF-05212377 demonstrated dose and concentration dependent increases in 5-HT
RO; maximal 5-HT6 RO of ∼80% was measured in humans at doses of ≥15 mg with an estimated unbound plasma EC
of 0.37 nM (which was similar to the in vitro human 5HT6 binding K
0.32 nM). In conclusion, cumulative evidence from NHP and human PET RO assessments confirmed that NHP is more appropriate than the rat for the prediction of human brain penetration of PF-05212377, a P-gp/non-BCRP substrate. Clinical trial number: NCT01258751.
Computational modeling was used to direct the synthesis of analogs of previously reported phosphodiesterase 2A (PDE2A) inhibitor 1 with an imidazotriazine core to yield compounds of significantly ...enhanced potency. The analog PF-05180999 (30) was subsequently identified as a preclinical candidate targeting cognitive impairment associated with schizophrenia. Compound 30 demonstrated potent binding to PDE2A in brain tissue, dose responsive mouse brain cGMP increases, and reversal of N-methyl-d-aspartate (NMDA) antagonist-induced (MK-801, ketamine) effects in electrophysiology and working memory models in rats. Preclinical pharmacokinetics revealed unbound brain/unbound plasma levels approaching unity and good oral bioavailability resulting in an average concentration at steady state (C av,ss) predicted human dose of 30 mg once daily (q.d.). Modeling of a modified release formulation suggested that 25 mg twice daily (b.i.d.) could maintain plasma levels of 30 at or above targeted efficacious plasma levels for 24 h, which became part of the human clinical plan.
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