Tetrac (Tetraiodothyroacetic acid), a derivative of L-thyroxine (T4), is a thyrointegrin receptor antagonist. Tetrac blocks the actions of T4 and 3,5,3-triiodo-L-thyronine (T3) at the cell surface receptor for thyroid hormone on integrin alphavbeta3. Tetra has anti-angiogenic and anti-tumor activities[1][2].