an>Leu <span  title="" class="an ">&ensp;</span><span  title="CAP" class="an CAP">SP</span><span  title="" class="an ">&ensp;</span>an <span  title="" class="an ">&ensp;</span><span  title="CAP" class="an CAP">SP</span><span  title="" class="an ">&ensp;</span>analog <span  title="" class="an ">&ensp;</span>claimed <span  title="" class="an ">&ensp;</span>to <span  title="" class="an ">&ensp;</span>be <span  title="" class="an ">&ensp;</span>an <span  title="" class="an ">&ensp;</span>antagonist <span  title