In this task, you are given a sentence. You are expected to recognize the name of any form of chemical substances. Although there might be several correct answers, you need to write one of them.

Input: Consider Input: Synthesis of novel estrogen receptor antagonists using metal-catalyzed coupling reactions and characterization of their biological activity.

Output: estrogen

Input: Consider Input: Selective inhibition of cyclooxygenase 2 spares renal function and prostaglandin synthesis in cirrhotic rats with ascites.

Output: prostaglandin

Input: Consider Input: Synergistic enhancement of cancer therapy using a combination of heat shock protein targeted HPMA copolymer-drug conjugates and gold nanorod induced hyperthermia.
Output: HPMA