Boehringer Ingelheim (BI) GmbH's clinical hold on the oral beta secretase (BACE) inhibitor BI 1181181 for Alzheimer's disease (AD) because of skin reactions in some patients put a dent in shares of partner Vitae Pharmaceuticals Inc., but if worse comes to worse, the pair can move on to a different, structurally distinct candidate in the same class that's ready for testing.