What happened

Shares of Celldex Therapeutics, Inc. (NASDAQ:CLDX) a clinical-stage biotech developing new cancer therapies, fell 12.5% during Tuesday's session. Good, but not great data from mid-stage clinical trials drove the already beaten-down stock to a new 52-week low.

So what 

Yesterday, Celldex presented data from two clinical trials at the American Society of Clinical Oncologists (ASCO) annual meeting. Investors were shaken by early stage data from a trial combining varlilumab and Bristol-Myers Squibb's Opdivo as a treatment for advanced-stage colorectal and ovarian cancer. In the first part of this two-stage trial with a total of 21 patients, just three patients showed partial tumor shrinkage.

Investor looking worried about a falling stock chart.

Image source: Getty Images.

A separate presentation from a study of the company's lead candidate, glemba, in heavily pretreated melanoma patients was fairly positive, which likely helped temper today's market beatdown. In this study, the percentage of patients with tumor shrinkage rose from the 11% reported last October to 16% of the 62 patients treated with glemba.

Now what

A 16% response rate might not seem impressive on the surface, but it's important to point out these patients had relapsed following a median of three different treatments, including Bristol-Meyer's Squibb's Yervoy and a drug from the anti-PD(L)1 class, such as Opdivo or Keytruda. Investors will want to keep their eyes open for results from a second cohort added to this trial last summer that will add varlilumab to treatment with glemba. The company expects to present the combination data this fall.

I wouldn't close the book on a varlilumab and Opdivo combination just yet. Investigators did notice a varlilumab dose-dependent increase in the disease control rate. Just one of five patients given the lowest varlilumab dose had stable disease for at least three months, while six of 15 treated with the highest dose showed this benefit. Investors will want to keep their eyes open for 12-month overall survival data from the second part of the study to be presented at a conference down the road.

Cory Renauer has no position in any stocks mentioned. The Motley Fool recommends Celldex Therapeutics. The Motley Fool has a disclosure policy.