It's Fools' favorite time of the year: earnings season.

In the video below, senior biotech specialist Brian Orelli and health-care bureau chief Max Macaluso discuss a few biotechs that will release first quarter earnings shortly.

Gilead Sciences (NASDAQ:GILD) is scheduled to release earnings on Tuesday after the market closes. We know sales of its new hepatitis C drug Sovaldi will be good, but just how good remains to be seen. Investors should also listen for what management says about sustainability of sales ahead of the approval of a combination product under review with the FDA.

Sales of Arena Pharmaceuticals' (NASDAQ:ARNA) obesity drug Belviq won't be Sovaldi-good. Not even close. But sales of Belviq might pass sales of VIVUS' (NASDAQ:VVUS) Qsymia, which would be a good start to reaching its full potential. Neither VIVUS nor Arena have announced the date they plan to report first quarter earnings, but investors should get the Belviq sales figure when its partner Eisai reports on May 13 if Arena hasn't reported yet.

For Biogen Idec (NASDAQ:BIIB), which will report on Wednesday, the key drug to watch is its oral multiple sclerosis drug Tecfidera. Investors should not only be concerned with how the launch is going, but whether sales of Tecfidera is cutting into sales of Biogen's other multiple sclerosis drugs, Avonex and Tysabri.

Watch the video below for more thoughts on the three companies.