SAN FRANCISCO – Dynamic as ever in the wake of this summer's mixed news on Biogen Inc. and Eisai Co. Ltd.'s anti-beta-amyloid approach, drug developers in the Alzheimer's field are increasingly looking to genetics and biomarkers as they seek new paths of attack for the global scourge. Now, with the success of precision approaches in cancer, scientists are also beginning to think about combination approaches to the complex neurodegenerative disease, representatives of Denali Therapeutics Inc., E-Scape Bio Inc., Alkahest Inc. and Neurotrope Inc. said Thursday at the BIO Investor Forum.