“The witnesses’ candor of the complete events of that evening has come into question as there are striking differences of what was told to police and what was later written in declarations and spoken in the depositions,” the prosecutors said in a memo obtained by The Seattle Times.

Prior to his arrest and resignation from Seagen, Siegall was among biotech’s highest-paid and best-known executives, having built Seagen from a small startup to one of the industry’s most valuable companies. The company, which specializes in a type of medicine known as an antibody-drug conjugate, has successfully developed and won Food and Drug Administration approval of four cancer treatments.

Last week, Pfizer announced a deal to acquire Seagen for $43 billion, the largest biotech buyout of the past few years. Leading deal negotiations for Seagen was David Epstein, a former Novartis executive named as Siegall’s full-time successor last year.

Morphimmune, the company Siegall will now run, is far smaller than Seagen, having been formed just a few years ago around research by its scientific cofounder and serial biotech entrepreneur Philip Low.

“Clay immediately understood the vision for Morphimmune and is the right leader to advance our goal of saving patient lives,” said Low in a statement on Siegall’s appointment.