GP-681

Main study objectives: By measuring the time of influenza symptom relief in people at high risk of influenza complications, evaluate the effectiveness of GP681 tablets compared with placebo in treating people at high risk of influenza complications. Secondary study objectives: 1) Evaluate the effectiveness of GP681 tablets in treating people at high risk of influenza complications through other secondary endpoints; 2) Evaluate the safety of GP681 tablets in treating people at high risk of influenza complications. 3) Evaluate the pharmacokinetic (PK) characteristics of GP681 tablets after treating people at high risk of influenza complications, and establish the corresponding exposure response model for this characteristic population in combination with previous clinical research data.