Specific details of the sale, which included 8,656,500 shares of MWG, were not disclosed.
GeneScan also has purchased about €2 million in MWG convertible bonds from the shareholders.
MWG Biotech said separately that it has sold convertible bonds totaling €6.5 million. Proceeds of the sale will be used to support MWG's ongoing restructuring, the company noted.
In November, the company said it expected to raise €10 million through the sale of its convertible bonds.