23andMe Inc., the personal genetics company, has sold enough DNA spit kits to accumulate genetic information on 850,000 customers. Now it plans to mine that database for drug targets, and it has picked a star drug developer to lead the effort.

The closely held Mountain View, Calif., company on Thursday said Richard Scheller, who retired in December as head of research and early development at Roche Holding AG, will become chief science officer next month and will lead a new therapeutics group that will seek to discover new...