June 11 (Reuters) - ATAI Life Sciences B.V., backed by billionaire investor Peter Thiel, said on Friday it is looking to raise as much as $214.3 million through a U.S. initial public offering, targeting a valuation of about $2.3 billion. The Berlin-based biotech startup, which is exploring the use of psychedelic treatments for mental health disorders, said it plans to sell around 14.29 million shares priced between $13 and $15 per share. (bit.ly/3iA5ste) (Reporting by Sohini Podder in Bengaluru; Editing by Amy Caren Daniel) Our Standards: The Thomson Reuters Trust Principles.