In November 2017, MemberSuite accepted a $5.5M round of funding. Check out the SEC filing.
To the best of my knowledge, MemberSuite is the only venture capital-backed AMS in the market, and has raised $13M in funding since September 2016. They appointed a new CEO in November 2017. This round of funding may have been used to acquire the shares owned by the founder and former CEO, transferring ownership of the company to new shareholders.