Life Bioscience had to reduce its shares to get under 10%...

Life Bioscience had to reduce its shares to get under 10% because 10% is a threshold to become a principal shareholder. A principal shareholder is a person or entity that owns 10% or more of a company's voting shares. As a result, they can influence a company's direction by voting on who becomes CEO or sits on the board of directors. Not all principal shareholders are active in a company's management process.

As you remember Sinclair et al resigned because of "competing priorities" and 10% is a good threshold not to have so much competing interest.