CYP inhibitors for the development of new drugs for the treatment of prostate cancer and metabolic syndrome

An der menschlichen Steroid-Biosynthese sind sechs CYP Enzyme beteiligt. Vier davon stellen sehr interessante Targets zur Entwicklung neuer Medikamente für die Therapie einer Reihe von hormonabhängigen Krankheiten dar. In dieser Arbeit wurden zwei Targets ausgewählt, zum einen das Schlüsselenzym der Androgenbiosynthese, CYP17, und zum anderen CYP11B1, welches den entscheidenden Schritt in der Cortisolbiosynthese darstellt. Design und Synthese der vorgestellten CYP17 Inhibitoren, die zur Therapie des hormonabhängigen Prostatakarzinoms dienen können, wurden ausgehend von bekannten biphenylischen Grundstrukturen entwickelt. Die dabei entstandenen Inhibitoren konnten, mit IC50 Werten bis zu 52 nM, sowohl bezüglich ihrer Aktivität zum Target CYP17 als auch hinsichtlich ihrer Selektivität gegenüber einer Reihe von weiteren CYP Enzymen stark optimiert werden. Die vorgestellten CYP11B1 Inhibitoren wurden ausgehend von einem Etomidat-basierten Design Konzept entwickelt. Die so gefundenen CYP11B1 Inhibitoren stellen die ersten selektiven Hemmstoffe dieses Enzyms dar. Eine besondere Herausforderung bei der Optimierung dieser Verbindungen war die Selektivität zum mit 93 % hochhomologen CYP11B2. Mit bis zu 49facher Selektivität gegenüber CYP11B2 und gleichzeitig hoher Hemmaktivität gegenüber CYP11B1 mit IC50 Werten im bis zu einstelligen nanomolaren Bereich war der durchgeführte Ansatz erfolgreich. Nach erweiterten pharmakologischen Untersuchungen und gegebenenfalls erforderlichen strukturellen Optimierungen sollen aus den vorgestellten Substanzklassen Entwicklungskandidaten hervorgehen.Six CYP enzymes are involved in human steroid biosynthesis. Four of them constitute very interesting targets for the development of new drugs in order to treat a variety of hormone-dependent diseases. Herein, two targets were selected: on the one hand, CYP17, the key-enzyme in androgen biosynthesis and on the other hand CYP11B1, catalyzing the main step in cortisol biosynthesis. Design and synthesis of the investigated CYP17 inhibitors, which should be promising drugs in the treatment of hormone dependent prostate cancer were developed outgoing from known biphenylic core-structures. Optimization of these compounds yielded inhibitors with IC50 values as low as 52 nM, which showed strong activity toward the target CYP17 as well as high selectivity toward a broad range of further CYPs. The herein presented CYP11B1 inhibitors were developed outgoing from an etomidate-based design concept and are the first selective inhibitors of this enzyme. Particularly challenging was the optimization of these compounds regarding their selectivity toward the 93 % homologuos CYP11B2. With up to 49fold selectivity toward CYP11B2 and at the same time high inhibitory activity toward CYP11B1 in the low nanomolar range, the development was successful. In conclusion, after extended pharmacological testing, and, if required, further structural optimisation, the presented class of substances should give rise to new developmental candidates

A molecular switch driving inactivation in the cardiac k(+) channel HERG

Contains fulltext : 103432.pdf (publisher's version ) (Open Access)K(+) channels control transmembrane action potentials by gating open or closed in response to external stimuli. Inactivation gating, involving a conformational change at the K(+) selectivity filter, has recently been recognized as a major K(+) channel regulatory mechanism. In the K(+) channel hERG, inactivation controls the length of the human cardiac action potential. Mutations impairing hERG inactivation cause life-threatening cardiac arrhythmia, which also occur as undesired side effects of drugs. In this paper, we report atomistic molecular dynamics simulations, complemented by mutational and electrophysiological studies, which suggest that the selectivity filter adopts a collapsed conformation in the inactivated state of hERG. The selectivity filter is gated by an intricate hydrogen bond network around residues S620 and N629. Mutations of this hydrogen bond network are shown to cause inactivation deficiency in electrophysiological measurements. In addition, drug-related conformational changes around the central cavity and pore helix provide a functional mechanism for newly discovered hERG activators

Local anaesthetics block hyperpolarization-activated inward current in rat small dorsal root ganglion neurones

1. Hyperpolarizing voltage steps evoke slowly activating inward currents in a variety of neurones and in cardiac cells. This hyperpolarization-activated inward current (I(h)) is thought to play a significant role in cell excitability, firing frequency, or in setting of the resting membrane potential in these cells. We studied the effects of lidocaine, mepivacaine, QX-314 and bupivacaine as well as its enantiomers on I(h) in the membrane of dorsal root ganglion neurones (DRG). 2. The patch-clamp technique was applied to small dorsal root ganglion neurones identified in 200 μM thin slices of young rat DRGs. Under voltage-clamp conditions, the whole-cell I(h) current was recorded in the presence of different concentrations of the local anaesthetics. In current-clamp mode the resting membrane potential and the voltage response of DRG neurones to injected current pulses were investigated. 3. I(h) was reversibly blocked by bupivacaine, lidocaine and mepivacaine applied externally in clinically relevant concentrations. Concentration–response curves gave half-maximum inhibiting concentrations of 55, 99 and 190 μM, respectively. Bupivacaine block of the I(h) current was not stereoselective. No significant effect was observed when QX-314 was applied to the external surface of the membrane. 4. In current-clamp experiments 60 μM bupivacaine slightly hyperpolarized the membrane. The membrane stimulation by low-amplitude current pulses in the presence of bupivacaine showed an increase of the hyperpolarizing responses. 5. Our findings suggest an important role of the I(h)-block by local anaesthetics in the complex mechanism of drug action during epidural and spinal anaesthesia