U.S. digital marketing investment company The Stagwell Group has infused $100 million in advertising and marketing holding company MDC Partners.

The Stagwell made the investment through the acquisition of $50 million in MDC Partners common shares and $50 million non-voting convertible preference shares.

The company bought 14.2 million Class A shares of MDC for $3.50 per share, which represents an 18 percent premium to the 30-day average closing price of $2.96 per share.

MDC Partners plans to use the net proceeds to pay down existing debt under its credit facility and for general corporate purposes.