[{"from": "human", "value": "Could you give me a brief overview of this molecule? [C][C][=C][C@@H1][C@H1][Branch2][Ring1][#Branch1][C][C][C@][Branch1][P][C@H1][Ring1][=Branch1][C][C][C@@][Ring1][Branch1][Branch1][=Branch1][C][=Branch1][C][=O][C][O][C][C@@][Branch1][=C][C][Ring2][Ring1][C][=C][C][=Branch1][C][=O][C][C][Ring1][#Branch1][C]"}, {"from": "gpt", "value": "The molecule is a synthetic derivative of progesterone with antiestrogenic activity. Megestrol binds to and activates nuclear receptors which subsequently bind to and activate target genes for transcription. As an antiestrogen, this agent may inhibit the growth-stimulating effects of estrogen on estrogen-sensitive tumor cells. In addition, megestrol stimulates appetite in cachectic subjects."}]