It's a tough act to follow.Few biotech companies have made more noise than Viking Therapeutics (VKTX 4.41%) this year, and that's saying something. The drugmaker had been a relatively small and unknown player in the industry. However, Viking's prominence and stock price soared thanks to excellent clinical progress. The biotech's shares are up by 154% since early January.Can Viking Therapeutics perform nearly as well during the second half of the year? Is it already too late to buy the stock? Let's find out. ...