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What happened

Celldex Therapeutics (CLDX 0.65%) closed up 11% Tuesday without any obvious news to support the double-digit gain.

So what

As often happens, investors may be piling into Celldex on Tuesday ahead of expected data from a phase 2 clinical trial testing the biotech's lead drug, glembatumumab vedotin, in melanoma patients. The data will be presented at the European Society for Medical Oncology (ESMO), which starts on Oct. 7.

Some of the ESMO abstracts are scheduled to be released Wednesday at 6:00 a.m. EDT, so Tuesday's bounce could be from last-minute investors hoping that the data in the abstract will cause an even bigger bounce on Wednesday.

Keep in mind that abstracts for the meeting were due in May, so Celldex's abstract won't have the most up-to-date data -- the study only completed enrollment in April -- and investors will have to wait for the meeting to get a complete picture of how glembatumumab vedotin performed. And if Celldex Therapeutics was given an oral presentation spot, the abstract won't be released until Oct. 5.

What we do know is that the clinical trial was deemed successful -- defined as at least six responses in the first 52 treated patients -- which Thomas Davis, Celldex's chief medical officer, said was "met and exceeded."

Now what

Exceeded by how much is really the key question. These are melanoma patients that have failed other treatments, so a substantially high response rate could be enough to get the drug an accelerated approval or, at the very least, give investors confidence that the drug is working. Celldex is also testing glembatumumab vedotin in combination with one of its other drugs, varlilumab, in melanoma patients and in a separate study in patients with metastatic triple negative breast cancer.