Abstract
A class of diuretic/aquaretic agents based on mirror-image oligonucleotides (so-called Spiegelmers) has been identified. These molecules directly bind and inhibit the neuropeptide vasopressin (AVP). AVP is the major regulatory component of body fluid homeostasis mediated through binding to the renal V(2) receptor. Elevated plasma levels of AVP are implicated in several pathological conditions, mainly cardiovascular diseases. In congestive heart failure, AVP is part of a neuroendocrine imbalance that is responsible for progressive worsening of the disease. Employing in vitro selection techniques, RNA aptamers that bind to the unnatural d-configuration of AVP were isolated. The best aptamer displayed an affinity to d-AVP of approximately 560 pM at 37 degrees C. The corresponding Spiegelmer, a 38-mer mirror-image oligonucleotide (l-RNA) termed NOX-F37, inhibits vasopressin-dependent activation of V(1a) as well as V(2) receptors with IC(50) values of 6.1 nM and 1 nM, respectively. NOX-F37 administered to healthy rats effectively neutralized AVP and increased diuresis dose-dependently for 24 h. The mode of action was strictly aquaretic, i.e., the increase in urine volume was not accompanied by an increase in electrolytes. These results clearly prove the in vivo efficacy of NOX-F37 and points out its potential as a drug in the treatment of diseases that are associated with body fluid overload.