Michael Haerter

NO- and haem-independent activation of soluble guanylyl cyclase: molecular basis and cardiovascular implications of a new pharmacological principle

Soluble guanylyl cyclase (sGC) is the only proven receptor for the ubiquitous biological messenger nitric oxide (NO) and is intimately involved in many signal transduction pathways, most notably in regulating vascular tone and platelet function. sGC is a heterodimeric (α/ß) protein that converts GTP to cyclic GMP; NO binds to its prosthetic haem group. Here, we report the discovery of a novel sGC activating compound, its interaction with a previously unrecognized regulatory site and its therapeutic implications. Through a high‐throughput screen we identified BAY 58‐2667, an amino dicarboxylic acid which potently activates sGC in an NO‐independent manner. In contrast to NO, YC‐1 and BAY 41‐2272, the sGC stimulators described recently, BAY 58‐2667 activates the enzyme even after it has been oxidized by the sGC inhibitor ODQ or rendered haem deficient. Binding studies with radiolabelled BAY 58‐2667 show a high affinity site on the enzyme. Using photoaffinity labelling studies we identified the amino acids 371 (α‐subunit) and 231 – 310 (ß‐subunit) as target regions for BAY 58‐2667. sGC activation by BAY 58‐2667 results in an antiplatelet activity both in vitro and in vivo and a potent vasorelaxation which is not influenced by nitrate tolerance. BAY 58‐2667 shows a potent antihypertensive effect in conscious spontaneously hypertensive rats. In anaesthetized dogs the hemodynamic effects of BAY 58‐2667 and GTN are very similar on the arterial and venous system. This novel type of sGC activator is a valuable research tool and may offer a new approach for treating cardiovascular diseases.

Inhibition of murine cytomegalovirus and human cytomegalovirus by a novel non-nucleosidic compound in vivo

Novel non-nucleosidic compounds have recently been identified as potent inhibitors of the human cytomegalovirus (HCMV) and murine cytomegalovirus (MCMV) in vitro. We have now investigated the antiviral activity of these compounds in MCMV-infected NOD/LtSz-scid/j mice that lack functional T, B and, in contrast to C.B-17/Icr scid/scid mice, natural killer cells, and represent a novel model for cytomegalovirus infection in immunocompromised hosts. BAY 38-4766 (3-hydroxy-2,2-dimethyl-N-[4(([5-(dimethylamino)-1-naphthyl]sulfonyl)amino)- phenyl]propanamide) was identified as the most potent representative of this class of antiviral compounds. Per os administration of BAY 38-4766 at dosages > or = 10 mg/kg body weight led to antiviral effects that were comparable to ganciclovir 9-(1,3-dihydroxy-2-propoxymethyl)-guanine (Cymevene) as measured by survival and levels of viral DNA in organs of infected mice. In order to assess the anti-HCMV activity of BAY 38-4766 in vivo, we used a model, in which HCMV-infected human cells were entrapped in hollow fibers and subsequently transplanted into immunodeficient mice. Using this model, we demonstrated antiviral activity of BAY 38-4766 similar to that of ganciclovir. We conclude that BAY 38-4766 shows potential as an anti-HCMV drug.