What happened

Celldex Therapeutics (NASDAQ:CLDX) closed on Monday up 12.8%, with no apparent news to justify the double-digit gain by the biotech company.

So what

The move follows an 8.1% jump on Friday. Sometimes, moves like these are associated with leaks of upcoming data or acquisition talks, but they're also associated with investors thinking there might be those unannounced news events even though they don't actually exist.

In other words, there could be some stock-driving event coming, but it's just as likely -- probably more so -- that day traders are playing with the stock price for their own amusement and benefit. That's easier to do with a biotech, with which the likelihood of clinical trial news or an acquisition is substantially higher than in other related industries.

Cancer patient holding hands with a friend

Image source: Getty Images.

Now what

The most important stock-moving data will come from Celldex's lead candidate, glembatumumab vedotin, which is in a phase 2b trial in women with triple negative breast cancer, but data from that trial isn't expected until the second quarter of 2018. 

It's also possible that this move is just a matter of investors' realization that the decline around the time of the American Society of Clinical Oncology meeting last summer wasn't really justified. With today's move, shares of Celldex are basically where they were back in May, before the decline started.

One of Celldex's investors, Meditor Group, seems to have come to the conclusion that the biotech is a value; the healthcare investing fund reportedly upped its holding of Celldex stock to 5.8 million shares, from 4.15 million shares last quarter.

If there is actual news to announce, investors will find out about it when President and CEO Anthony Marucci speaks at the Cantor Fitzgerald Global Healthcare Conference on Tuesday.

Long-term investors shouldn't hold their breath.