The Wellcome Trust, the world’s second-biggest medical charity and an early backer of Alibaba Group Holding Ltd, is nearing a sale of about $300 million in venture-capital fund stakes to Lexington Partners Inc, according to a person with knowledge of the matter.

Lexington Partners, one of the largest firms dedicated to buying private-equity holdings, is purchasing part of the portfolio that the London-based trust started showing to buyers earlier this year, said the person, who asked not be named because the information is private. Wellcome Trust hired Cogent Partners to manage the sale of $750 million in venture-capital fund stakes, people with knowledge of the matter said.

Wellcome Trust is seeking to sell venture-capital stakes as it places bigger bets with fewer managers and benefit from a resurgence of interest in the asset class. Venture capitalists are seeing their best returns since the late 1990s dot-com bubble after several venture-backed companies went public in the United States last year with market capitalizations above $1 billion at the time of offering. Alibaba, the Chinese e-commerce giant, last Friday launched the biggest initial public offering in history at about $25 billion.

Mark Henderson, a Wellcome Trust spokesman, declined to comment, as did Rebecca John, a partner at Lexington Partners.

Wellcome Trust’s venture-capital funds returned 18 percent for the year ending Sept 30, according to the firm’s 2013 annual report, the same as the trust’s overall return in the previous fiscal year. Venture capital accounted for about 8 percent, or 1.4 billion pounds ($2.3 billion), of the 17.3 billion pounds in trust assets as of Sept 30.