Identification of Brain-Penetrant ATP-Competitive mTOR Inhibitors for CNS Syndromes

The allosteric inhibitor of the mechanistic target of rapamycin (mTOR) everolimus reduces seizures in tuberous sclerosis complex (TSC) patients through partial inhibition of mTOR functions. Due to its limited brain permeability, we sought to develop a catalytic mTOR inhibitor optimized for central nervous system (CNS) indications. We recently reported an mTOR inhibitor (1) that is able to block mTOR functions in the mouse brain and extend the survival of mice with neuronal-specific ablation of the Tsc1 gene. However, 1 showed the risk of genotoxicity in vitro. Through structure-activity relationship (SAR) optimization, we identified compounds 9 and 11 without genotoxicity risk. In neuronal cell-based models of mTOR hyperactivity, both corrected aberrant mTOR activity and significantly improved the survival rate of mice in the Tsc1 gene knockout model. Unfortunately, 9 and 11 showed limited oral exposures in higher species and dose-limiting toxicities in cynomolgus macaque, respectively. However, they remain optimal tools to explore mTOR hyperactivity in CNS disease models.

Rationally Designed PI3Kα Mutants to Mimic ATR and Their Use to Understand Binding Specificity of ATR Inhibitors

ATR, a protein kinase in the PIKK family, plays a critical role in the cell DNA-damage response and is an attractive anticancer drug target. Several potent and selective inhibitors of ATR have been reported showing significant antitumor efficacy, with most advanced ones entering clinical trials. However, due to the absence of an experimental ATR structure, the determinants contributing to ATR inhibitors' potency and specificity are not well understood. Here we present the mutations in the ATP-binding site of PI3Kα to progressively transform the pocket to mimic that of ATR. The generated PI3Kα mutants exhibit significantly improved affinity for selective ATR inhibitors in multiple chemical classes. Furthermore, we obtained the X-ray structures of the PI3Kα mutants in complex with the ATR inhibitors. The crystal structures together with the analysis on the inhibitor affinity profile elucidate the roles of individual amino acid residues in the binding of ATR inhibitors, offering key insights for the binding mechanism and revealing the structure features important for the specificity of ATR inhibitors. The ability to obtain structural and binding data for these PI3Kα mutants, together with their ATR-like inhibitor binding profiles, makes these chimeric PI3Kα proteins valuable model systems for structure-based inhibitor design.

Discovery of imidazo[1,2-a]-pyridine inhibitors of pan-PI3 kinases that are efficacious in a mouse xenograft model

Alterations in PI3K/AKT signaling are known to be implicated with tumorigenesis. The PI3 kinases family of lipid kinases has been an attractive therapeutic target for cancer treatment. Imidazopyridine compound 1, a potent, selective, and orally available pan-PI3K inhibitor, identified by scaffold morphing of a benzothiazole hit, was further optimized in order to achieve efficacy in a PTEN-deleted A2780 ovarian cancer mouse xenograft model. With a hypothesis that a planar conformation between the core and the 6-heteroaryl ring will allow for the accommodation of larger 5'-substituents in a hydrophobic area under P-loop, SAR efforts focused on 5'-alkoxy heteroaryl rings at the 6-position of imidazopyridine and imidazopyridazine cores that have the same dihedral angle of zero degrees. 6'-Alkoxy 5'-aminopyrazines in the imidazopyridine series were identified as the most potent compounds in the A2780 cell line. Compound 14 with 1,1,1-trifluoroisopropoxy group at 6'-position demonstrated excellent potency and selectivity, good oral exposure in rats and in vivo efficacy in A2780 tumor-bearing mouse. Also, we disclose the X-ray co-crystal structure of one enantiomer of compound 14 in PI3Kα, confirming that the trifluoromethyl group fits nicely in the hydrophobic hot spot under P-loop.

Transcatheter device occlusion of the left ventricular outflow tract as treatment for severe aortic regurgitation in hypoplastic left heart syndrome

Aortic regurgitation is a rare but dangerous condition in patients with hypoplastic left heart syndrome (HLHS). We report the case of a 2-year-old girl with HLHS with aortic/mitral stenosis (AS-MS) subtype after stage II palliation via the bilateral bidirectional Glenn (BBDG) procedure, when aortic regurgitation presented with the clinical manifestation of a paroxysmal coronary steal phenomenon provoked by exertion. Transcatheter closure of the left ventricular outflow tract (LVOT) with an Amplatzer(TM) Vascular Plug 4 minimized and finally abolished aortic reflux without compromising either coronary perfusion or atrioventricular (AV) conduction. Midterm follow-up over 3 years revealed complete disappearance of her symptoms, and follow-up catheterization displayed complete LVOT closure. This case illustrates the promising potential of modern cardiac catherization techniques in certain cases and emphasizes that precise assessment of the native aorta and coronary system is critical in HLHS patients.

Structure-Based Drug Design of Novel, Potent, and Selective Azabenzimidazoles (ABI) as ATR Inhibitors

Compound 13 was discovered through morphing of the ATR biochemical HTS hit 1. The ABI series was potent and selective for ATR. Incorporation of a 6-azaindole afforded a marked increase in cellular potency but was associated with poor PK and hERG ion channel inhibition. DMPK experiments established that CYP P450 and AO metabolism in conjunction with Pgp and BCRP efflux were major causative mechanisms for the observed PK. The series also harbored the CYP3A4 TDI liability driven by the presence of both a morpholine and an indole moiety. Incorporation of an adjacent fluorine or nitrogen into the 6-azaindole addressed many of the various medicinal chemistry issues encountered.

Structure-Based Drug Design of Novel Potent and Selective Tetrahydropyrazolo[1,5-a]pyrazines as ATR Inhibitors

A saturation strategy focused on improving the selectivity and physicochemical properties of ATR inhibitor HTS hit 1 led to a novel series of highly potent and selective tetrahydropyrazolo[1,5-a]pyrazines. Use of PI3Kα mutants as ATR crystal structure surrogates was instrumental in providing cocrystal structures to guide the medicinal chemistry designs. Detailed DMPK studies involving cyanide and GSH as trapping agents during microsomal incubations, in addition to deuterium-labeled compounds as mechanistic probes uncovered the molecular basis for the observed CYP3A4 TDI in the series.

Potent nonimmunosuppressive cyclophilin inhibitors with improved pharmaceutical properties and decreased transporter inhibition

Nonimmunosuppressive cyclophilin inhibitors have demonstrated efficacy for the treatment of hepatitis C infection (HCV). However, alisporivir, cyclosporin A, and most other cyclosporins are potent inhibitors of OATP1B1, MRP2, MDR1, and other important drug transporters. Reduction of the side chain hydrophobicity of the P4 residue preserves cyclophilin binding and antiviral potency while decreasing transporter inhibition. Representative inhibitor 33 (NIM258) is a less potent transporter inhibitor relative to previously described cyclosporins, retains anti-HCV activity in cell culture, and has an acceptable pharmacokinetic profile in rats and dogs. An X-ray structure of 33 bound to rat cyclophilin D is reported.

A new functional assay for the diagnosis of X-linked inhibitor of apoptosis (XIAP) deficiency

X-linked inhibitor of apoptosis (XIAP) deficiency, caused by mutations in BIRC4, is an immunodeficiency associated with immune dysregulation and a highly variable clinical presentation. Current diagnostic screening tests such as flow cytometry for XIAP expression or lymphocyte apoptosis assays have significant limitations. Based on recent evidence that XIAP is essential for nucleotide-binding and oligomerization domains (NOD)1/2 signalling, we evaluated the use of a simple flow cytometric assay assessing tumour necrosis factor (TNF) production of monocytes in response to NOD2 stimulation by muramyl dipeptides (L18-MDP) for the functional diagnosis of XIAP deficiency. We investigated 12 patients with XIAP deficiency, six female carriers and relevant disease controls. Irrespective of the diverse clinical phenotype, the extent of residual protein expression or the nature of the mutation, the TNF response was severely reduced in all patients. On average, L18-MDP induced TNF production in 25% of monocytes from healthy donors or female carriers, while fewer than 6% of monocytes responded in affected patients. Notably, the assay clearly discriminated affected patients from disease controls with other immunodeficiencies accompanied by lymphoproliferation, hypogammaglobulinaemia or inflammatory bowel disease. Functional testing of the NOD2 signalling pathway is an easy, fast and reliable assay in the diagnostic evaluation of patients with suspected XIAP deficiency.

[Hemorrhagic skin lesions associated with infections]

Eine Vielzahl von bakteriellen, viralen oder parasitären Infektionserkrankungen kann mit hämorrhagischen Effloreszenzen einhergehen. Die Symptomkonstellation Fieber und Petechien kann Vorbote einer fulminanten bakteriellen Sepsis sein, die einer sofortigen intensiven Therapie zugeführt werden muss. Viel häufiger liegt der Symptomatik aber ein harmloser selbstlimitierender Virusinfekt zugrund, sodass man in Bezug auf das Ausmaß der notwendigen Diagnostik vor einem Dilemma steht. Der vorliegende Beitrag gibt eine Übersicht über die Differenzialdiagnosen und Pathophysiologie infektionsassoziierter Hautblutungen, und es wird ein differenzialdiagnostischer Algorithmus für die Diagnosefindung bei der Konstellation Fieber plus Petechien vorgeschlagen.

Dispelling myths on ambulance accidents

There appears to be a self-perpetuating trail of misinformation surrounding the issue of ambulance accidents. As with all problems, we must first acknowledge that a problem does exist and clearly distinguish the facts from the myths. The intent of this article was to clarify some of those misconceptions by using an analysis of one state's four-year experience with ambulance accidents. The next step in solving this problem is to create driver education programs that modify the behavior of ambulance drivers, adjust their attitudes about driving an emergency vehicle and make them fully aware of the hazards encountered in driving an ambulance. In addition, consider adjusting the agency standard operating procedure so that all ambulances must come to a complete stop at all stop signs and red lights to minimize the number of accidents that occur in the intersection. Readers who would like to learn more about this subject should contact their state EMS offices to determine if they offer emergency vehicle operator courses or continuing education programs that deal with ambulance driving. New York State has developed a network of 90 instructors who are qualified to teach the Ambulance Accident Prevention Seminar, a nine-hour classroom-based ambulance driver "attitude adjustment" program. Two other organizations that have developed driving courses geared specifically for ambulance driving are: Failsafe Driving Inc. Alvin F. Davenport, president 2529 San Pablo Ave. Pinole, CA 94564 National Academy for Professional Driving Dick Turner, chairman 1001-A South Interstate 45 P.O. Box 649 Hutchins, TX 75141.

An evaluation of emergency medical technicians' ability to use manual ventilation devices

Three hundred twenty emergency medical technicians (EMTs) were tested for their ability to ventilate a precalibrated Recording Resusci-Annie (Laerdal Medical Corporation) using both a bag-valve-mask and a pocket mask. More than 50% of the EMTs were not capable of ventilating to the minimum standard using a bag-valve-mask. The study demonstrates that the pocket mask method is far superior to the bag-valve-mask method. If these experimental results are confirmed by clinical findings, we recommend that future educational courses teach the bag-valve-mask as a four-hand/two-person skill, with one rescuer squeezing the bag with both hands and the second rescuer maintaining hyperextension.