Oscar Health has named former AIG executive Sid Sankaran as its new chief financial officer starting March 1, to succeed CFO Brian West who departed the company in November, as the health insurer looks to expand into the growing Medicare market next year.

"Sid embodies an unmatched breadth and depth of experience in subjects critical to any company, such as capital and strategy, as well as those particularly important at Oscar, such as actuarial and risk" knowledge, said Oscar CEO Mario Schlosser in the company's announcement of the appointment.

Sankaran served as CFO of American International Group from 2016 until late last year, during a period in which it fought off activist investor Carl Icahn's push to break up the company. In the six years prior, Sankaran served as AIG's chief risk officer. Oscar's announcement credits him with being a "key member" of the executive team which helped the insurer through its restructuring and relisting in an IPO, after the financial crisis.

Sankaran's appointment comes three years after West was named president and CFO of Oscar. West departed in November to assume the CFO role at Thomson Reuters Refinitiv's financial and risk unit.

Oscar's former chief operating officer, Kevin Campbell, who had been appointed along with West in 2016, left shortly after and has not been replaced; he is now CEO of global consulting at BackOffice Associates.

The management changes come as Oscar prepares to launch new Medicare Advantage plans in 2020. The company received a $375 million investment from Google parent Alphabet last August to help fund its expansion into the market for senior health plans, boosting the 7-year-old start-up a valuation to roughly $3 billion.

Oscar is hoping to leverage its tech-enabled service, which includes access to health coaching and telemedicine consults through its phone app, to enroll baby boomer seniors who want more help managing chronic conditions.

This year, Oscar offered Obamacare exchange plans in nine states, up from six states last year.

Correction: Oscar's former COO left the company in 2016. An earlier version misstated the year he departed the company.