Discovery of an Oral, Beyond-Rule-of-Five Mcl-1 Protein-Protein Interaction Modulator with the Potential of Treating Hematological Malignancies.

Avoidance of apoptosis is critical for the development and sustained growth of tumors. The pro-survival protein myeloid cell leukemia 1 (Mcl-1) is an anti-apoptotic member of the Bcl-2 family of proteins which is overexpressed in many cancers. Upregulation of Mcl-1 in human cancers is associated with high tumor grade, poor survival, and resistance to chemotherapy. Therefore, pharmacological inhibition of Mcl-1 is regarded as an attractive approach to treating relapsed or refractory malignancies. Herein, we disclose the design, synthesis, optimization, and early preclinical evaluation of a potent and selective small-molecule inhibitor of Mcl-1. Our exploratory design tactics focused on structural modifications which improve the potency and physicochemical properties of the inhibitor while minimizing the risk of functional cardiotoxicity. Despite being in the "non-Lipinski" beyond-Rule-of-Five property space, the developed compound benefits from exquisite oral bioavailability in vivo and induces potent pharmacodynamic inhibition of Mcl-1 in a mouse xenograft model.

Intramolecular N-H⋠⋠⋠F Hydrogen Bonding Interaction in a Series of 4-Anilino-5-Fluoroquinazolines: Experimental and Theoretical Characterization of Electronic and Conformational Effects.

The 4-anilino-6,7-ethylenedioxy-5-fluoroquinazoline scaffold is presented as a novel model system for the characterization of the weak NH⋅⋅⋅F hydrogen bonding (HB) interaction. In this scaffold, the aniline NH proton is forced into close proximity with the nearby fluorine (dH,F ∼2.0 Å, ∠∼138°), and a through-space interaction is observed by NMR spectroscopy with couplings (1h JNH,F ) of 19±1 Hz. A combination of experimental (NMR spectroscopy and X-ray crystallography) and theoretical methods (DFT calculations) were used for the characterization of this weak interaction. In particular, the effects of conformational rigidity and steric compression on coupling were investigated. This scaffold was used for the direct comparison of fluoride with methoxy as HB acceptors, and the susceptibility of the NH⋅⋅⋅F interaction to changes in electron distribution and resonance was probed by preparing a series of molecules with different electron-donating or -withdrawing groups in the positions para to the NH and F. The results support the idea that fluorine can act as a weak HB acceptor, and the HB strength can be modulated through additive and linear electronic substituent effects.

Nocturnal cerebral tissue oxygenation in lowlanders with chronic obstructive pulmonary disease travelling to an altitude of 2,590 m: Data from a randomised trial.

Altitude exposure induces hypoxaemia in patients with chronic obstructive pulmonary disease (COPD), particularly during sleep. The present study tested the hypothesis in patients with COPD staying overnight at high altitude that nocturnal arterial hypoxaemia is associated with impaired cerebral tissue oxygenation (CTO). A total of 35 patients with moderate-to-severe COPD, living at <800 m (mean [SD] age 62.4 [12.3] years, forced expiratory volume in 1 s [FEV1 ] 61 [16]% predicted, awake pulse oximetry ≥92%) underwent continuous overnight monitoring of pulse oximetry (oxygen saturation [SpO2 ]) and near-infrared spectroscopy of prefrontal CTO, respectively, at 490 m and 2,590 m. Regression analysis was used to evaluate whether nocturnal arterial desaturation (COPDDesat , SpO2 <90% for >30% of night-time) at 490 m predicted CTO at 2,590 m when controlling for baseline variables. At 2,590 m, mean nocturnal SpO2 and CTO were decreased versus 490 m, mean change -8.8% (95% confidence interval [CI] -10.0 to -7.6) and -3.6% (95% CI -5.7 to -1.6), difference in change ΔCTO-ΔSpO2 5.2% (95% CI 3.0 to 7.3; p < .001). Moreover, frequent cyclic desaturations (≥4% dips/hr) occurred in SpO2 and CTO, mean change from 490 m 35.3/hr (95% CI 24.9 to 45.7) and 3.4/hr (95% CI 1.4 to 5.3), difference in change ΔCTO-ΔSpO2 -32.8/hr (95% CI -43.8 to -21.8; p < .001). Regression analysis confirmed an association of COPDDesat with lower CTO at 2,590 m (coefficient -7.6%, 95% CI -13.2 to -2.0; p = .007) when controlling for several confounders. We conclude that lowlanders with COPD staying overnight at 2,590 m experience altitude-induced hypoxaemia and periodic breathing in association with sustained and intermittent cerebral deoxygenation. Although less pronounced than the arterial deoxygenation, the altitude-induced cerebral tissue deoxygenation may represent a risk of brain dysfunction, especially in patients with COPD with nocturnal hypoxaemia at low altitude.

Development of a Potent Brain-Penetrant EGFR Tyrosine Kinase Inhibitor against Malignant Brain Tumors.

The epidermal growth factor receptor (EGFR) is genetically altered in nearly 60% of glioblastoma tumors; however, tyrosine kinase inhibitors (TKIs) against EGFR have failed to show efficacy for patients with these lethal brain tumors. This failure is attributed to the inability of clinically tested EGFR TKIs to cross the blood-brain barrier (BBB) and achieve adequate pharmacological levels to inhibit various oncogenic forms of EGFR that drive glioblastoma. Through SAR analysis, we developed compound 5 (JCN037) from an anilinoquinazoline scaffold by ring fusion of the 6,7-dialkoxy groups to reduce the number of rotatable bonds and polar surface area and by introduction of an ortho-fluorine and meta-bromine on the aniline ring for improved potency and BBB penetration. Relative to the conventional EGFR TKIs erlotinib and lapatinib, JCN037 displayed potent activity against EGFR amplified/mutant patient-derived cell cultures, significant BBB penetration (2:1 brain-to-plasma ratio), and superior efficacy in an EGFR-driven orthotopic glioblastoma xenograft model.

Automatic Processing of Nasal Pressure Recordings to Derive Continuous Side-Selective Nasal Airflow and Conductance.

Monitoring of nasal airflow and conductance provides crucial insights into the variable nature of the nasal resistance, nasal cycle, and ventilation. We have previously shown that tracking of pressure swings at the entrance of each nasal passage by a dedicated catheter system allows bilateral monitoring of nasal airflow over several hours but requires complex linearization and calibration procedures. Side-selective nasal conductance is derived from linearized and calibrated bilateral nasal pressure swings and corresponding driving pressure, i.e., the transnasal pressure difference derived from an epipharyngeal catheter. Manual analysis of such recordings and computation of instantaneous conductance as the ratio of flow to driving pressure over several hours is extremely tedious, time consuming, and therefore not suitable for routine practice. To address this point, we developed and validated a software for automatic processing of nasal and epipharyngeal pressure recordings as a convenient tool for studying the nasal ventilation. The software applies an eight-parameter logistic model to transform nasal pressure swings into side-selective estimates of airflow that are calibrated and further processed along with epipharyngeal pressure to compute bilateral nasal conductance over consecutive, user-selectable time-segments. Essential processing steps include (1) offset correction, (2) low-pass filtering, (3) cross-correlation, (4) cutting of signals into individual breaths, (5) normalization, (6) ensemble averaging to obtain a mean pressure signal for each nasal side, (7) derivation of airflow, conductance, and further variables. Among four evaluated algorithms for calculation of nasal conductance, the derivative of the airflow-pressure curve according to the mean value theorem agreed closest with the gold standard, i.e., the conductance derived from airflow measured by a pneumotachograph attached to an oral-nasal mask and transnasal pressure. In combination with the nasal catheter system, our novel software represents a valuable tool for use in clinical practice and research to conveniently investigate nasal ventilation and its changes occurring spontaneously or in response to various exposures and therapeutic interventions.

Porphyrin Donor and Tunable Push-Pull Acceptor Conjugates-Experimental Investigation of Marcus Theory.

We report on a series of electron donor-acceptor conjugates incorporating a ZnII -porphyrin-based electron donor and a variety of non-conjugated rigid linkers connecting to push-pull chromophores as electron acceptors. The electron acceptors comprize multicyanobutadienes or extended tetracyanoquinodimethane analogues with first reduction potentials ranging from -1.67 to -0.23 V vs. Fc+ /Fc in CH2 Cl2 , which are accessible through a final-step cycloaddition-retroelectrocyclization (CA-RE) reaction. Characterization of the conjugates includes electrochemistry, spectroelectrochemistry, DFT calculations, and photophysical measurements in a range of solvents. The collected data allows for the construction of multiple Marcus curves that consider electron-acceptor strength, linker length, and solvent, with data points extending well into the inverted region. The enhancement of electron-vibration couplings, resulting from the rigid spacers and, in particular, multicyano-groups in the conformationally highly fixed push-pull acceptor chromophores affects the charge-recombination kinetics in the inverted region drastically.

Cyanobuta-1,3-dienes as novel electron acceptors for photoactive multicomponent systems.

The synthesis, electrochemical, and photophysical properties of five multicomponent systems featuring a Zn(II) porphyrin (ZnP) linked to one or two anilino donor-substituted pentacyano- (PCBD) or tetracyanobuta-1,3-dienes (TCBD), with and without an interchromophoric bridging spacer (S), are reported: ZnP-S-PCBD (1), ZnP-S-TCBD (2), ZnP-TCBD (3), ZnP-(S-PCBD)2 (4), and ZnP-(S-TCBD)2 (5). By means of steady-state and time-resolved absorption and luminescence spectroscopy (RT and 77 K), photoinduced intramolecular energy and electron transfer processes are evidenced, upon excitation of the porphyrin unit. In systems equipped with the strongest acceptor PCBD and the spacer (1, 4), no evidence of electron transfer is found in toluene, suggesting ZnP→PCBD energy transfer, followed by ultrafast (<10 ps) intrinsic deactivation of the PCBD moiety. In the analogous systems with the weaker acceptor TCBD (2, 5), photoinduced electron transfer occurs in benzonitrile, generating a charge-separated (CS) state lasting 2.3 µs. Such a long lifetime, in light of the high Gibbs free energy for charge recombination (ΔG(CR)=-1.39 eV), suggests a back-electron transfer process occurring in the so-called Marcus inverted region. Notably, in system 3 lacking the interchromophoric spacer, photoinduced charge separation followed by charge recombination occur within 20 ps. This is a consequence of the close vicinity of the donor-acceptor partners and of a virtually activationless electron transfer process. These results indicate that the strongly electron-accepting cyanobuta-1,3-dienes might become promising alternatives to quinone-, perylenediimide-, and fullerene-derived acceptors in multicomponent modules featuring photoinduced electron transfer.

Ligand-switchable substrates for a ubiquitin-proteasome system.

Cellular maintenance of protein homeostasis is essential for normal cellular function. The ubiquitin-proteasome system (UPS) plays a central role in processing cellular proteins destined for degradation, but little is currently known about how misfolded cytosolic proteins are recognized by protein quality control machinery and targeted to the UPS for degradation in mammalian cells. Destabilizing domains (DDs) are small protein domains that are unstable and degraded in the absence of ligand, but whose stability is rescued by binding to a high affinity cell-permeable ligand. In the work presented here, we investigate the biophysical properties and cellular fates of a panel of FKBP12 mutants displaying a range of stabilities when expressed in mammalian cells. Our findings correlate observed cellular instability to both the propensity of the protein domain to unfold in vitro and the extent of ubiquitination of the protein in the non-permissive (ligand-free) state. We propose a model in which removal of stabilizing ligand causes the DD to unfold and be rapidly ubiquitinated by the UPS for degradation at the proteasome. The conditional nature of DD stability allows a rapid and non-perturbing switch from stable protein to unstable UPS substrate unlike other methods currently used to interrogate protein quality control, providing tunable control of degradation rates.