Why did Liz Barrett turn her back on a top job at Novartis in exchange for the helm of a biotech you never heard of?

Why did Liz Barrett turn her back on a top job at Novartis in exchange for the helm of a biotech you never heard of?

Source: 
Endpoints
snippet: 

Liz Barrett wasn’t looking for a job in biotech when she got the call from a corporate headhunter she knew well. The timing was terrible — just into a new job as head of Novartis’ global, $14 billion oncology group under a new CEO looking to push a longterm change in culture.