What happened

Shares of Agenus (AGEN 5.16%) were jumping 8.2% as of 11:24 a.m. EDT on Tuesday. The only news related to the company was VBI Vaccines' (VBIV 1.56%) announcement that the U.S. Food and Drug Administration (FDA) granted Fast Track designation for cancer vaccine candidate VBI-1901 in treating recurrent glioblastoma, an aggressive type of brain cancer. VBI's experimental vaccine uses GlaxoSmithKline's AS01 adjuvant system, which contains Agenus' QS-21 Stimulon adjuvant.

So what

VBI stock rose a little with the FDA's decision to give Fast Track designation to VBI-1901. The designation could lead to a shorter path to potential approval of the experimental drug. 

Person wearing a coat and tie holding yellow blocks with red letters spelling FDA.

Image source: Getty Images.

Why would Agenus deliver an even bigger gain than VBI? After all, Agenus stands to benefit less than VBI might from the FDA's move. The most likely answer is that the surge in Agenus' share price really didn't stem primarily from the good news for VBI-1901.

Instead, today's jump for Agenus probably just reflects run-of-the-mill volatility. Agenus didn't have any other news that would serve as a catalyst. It's not unusual for clinical-stage biotech stocks to experience big price swings for no apparent reason.

Now what

The main thing to watch with Agenus now is the FDA's decision on accelerated approval of balstilimab in treating cervical cancer. VBI Vaccines also expects an FDA approval decision on its hepatitis B vaccine candidate later this year.