The invention relates to oligomer compounds (oligomers), which target HER3 mRNA in a cell, leading to reduced expression of HER3 and/or HER2 and/or EGFR. Reduction of HER3 and/or HER2 and/or EGFR expression is beneficial for a range of medical disorders, such hyperproliferative disorders (e.g., cancer). The invention provides therapeutic compositions comprising oligomers and methods for modulating the expression of HER3 and/or HER2 and/or EGFR using said oligomers, including methods of treatment.