Money manager Security Benefit today signed a definitive purchase agreement to acquire the fund company Rydex Investments for an undisclosed amount. The combined entity is expected to have roughly $35 billion in assets under management and $52 billion of assets under administration at closing.

Through its subsidiaries, Topeka, Kan.-based Security Benefit has about $20 billion in assets under management and provides individual and employer-based retirement programs. For institutional investors it offers an array of investment options such as specialty fixed income, domestic and global equity strategies in separate accounts, mutual funds, commingled funds, insurance trusts, and packaged variable or fixed annuities. Roughly $11 billion is managed within Security Global Investors, its asset management arm.

Rydex manages nearly $15 billion in assets through more than 80 mutual funds, exchange traded products and institutional products, and is a leader in developing innovative investment vehicles.

Rydex will retain its current management team and facilities in Rockville, Md., and will be a separate line of business under Security Benefit's holding company. Other Security Benefit business lines include Security Global Investors, Employer, Advisor and se2/business processing.

The deal is expected to close in the fourth quarter.