The Girl in the Rabbit Hole (Girl in a Rabbit Hole) by R.J. Law

Claire Foley, a brilliant scientist, becomes the target of a powerful, shadowy corporation that systematically dismantles her life until she is forced to accept a position with them. She is subsequently abducted and imprisoned in a subterranean jungle labyrinth alongside a kidnapped group of top-tier scientists. Under the control of a mad billionaire, Claire must find a way to escape the high-security facility before she is forced to help engineer a horrific, fatal immortality serum.