Targeting Mek/Erk Signaling in the Treatment of Mitral Valve Prolapse

摘要

ABSTRACT Mitral valve prolapse (MVP) is one of the most common forms of cardiac valve disease, affecting 1 in 40 humans and ~70% of small breed dogs. There are no effective nonsurgical treatments for MVP and therapeutic efforts have been hindered due to an incomplete understanding of its fundamental causes. Recent studies by our group have described the genetic basis for non-syndromic MVP and have provided new insights into molecular processes that underlie the disease. We have used this genetic information to identify druggable targets that can provide a non-surgical option for humans. In particular, we have identified the Mek/Erk pathway as the major disease initiating pathway and prolonged hyperactivation of Mek/Erk drives disease progression and severity. Activation of the Mek/Erk pathway leads to increased proliferation, aberrant differentiation, and production of matrix metallopeptidases (MMPs). Thus, we hypothesize that pharmacological blockade of Mek/Erk activities will sufficiently arrest the disease pathway and maintain the valves in a sub-clinical condition. This hypothesis will be tested by screening novel and FDA- approved mitogen-activated protein kinase kinase (MEK1) inhibitors in vitro (Aim 1) and in vivo (Aim 2). Aim 1 of this proposal involves an in vitro screen of MEK1 inhibitors using canine MVP and human mitral valve interstitial cells, as well as performing enzyme kinetics using non-activated MEK1 protein. MEK1 is an attractive therapeutic target within the Mek/Erk signaling pathway. MEK1 inhibitors are well-tolerated and FDA- approved for melanoma, non-small cell lung cancer (NSCLC), and colorectal cancer (CRC); however, every single MEK1 inhibitor, both FDA-approved and in clinical trials, interacts with major cytochromes and/or suffers from deleterious off-target side-effects. Our group has identified novel, highly selective, MEK1 inhibitors that exhibit exceptional docking scores in silico and do not inhibit major cytochromes. Thus, in Aim 1 we will test the hypothesis that superior MEK1 inhibitors can be developed using computer-aided drug design. In Aim 2, we will assess the efficacy of MEK1 drug treatment in mouse and canine MVP patients. In experiment 1, we will administer both novel and FDA-approved MEK1 inhibitors to Dzip1S24R/+ mice; a disease model that phenocopies human MVP. Readouts will include: functional measurements obtained from mouse echocardiography; quantification of valve volume; histopathology, and RNA-sequencing. In experiment 2, we plan to test our hypothesis with a double-blinded, placebo-controlled clinical trial with 40 dogs with stage B1 MVP in each arm (placebo or trametinib). Readouts will include echocardiography, complete blood count, serum chemistry, NT-proBNP, and high sensitivity cardiac troponin (hs-cTnI). Results from this study may serve as a stepping stone towards developing the first non-surgical treatment for human patients with MVP. In addition to developing a better understand of MVP and potential therapeutic approaches, this fellowship will provide me with training in cutting-edge techniques that will support my development as a physician scientist.