Celldex designed the phase II study to test the theory that CDX-011 would work better in breast cancer patients whose tumors over-express the GPNMB protein. The 122 patients enrolled in the study had breast cancer in which at least 5% of the cells screened positive for GPNMB. All the patients had advanced breast cancer that was no longer responding to a median of five to six prior therapies. Two-thirds of patients were treated with injections of CDX-011, while the remaining third of patients were treated with chemotherapy of the doctor's choice.

Treatment with CDX-011 partially shrank tumors in 19% of all patients enrolled in the phase II study compared to 14% of patients treated with "investigator's choice" chemotherapy.

In patients with breast cancer tumors that contained high levels of the protein GPNMB, the CDX-011 response rate was 32% compared to 13% for patients treated with single-agent chemotherapy.

Back to the bear story for a moment: They raise questions about the legitimacy of GPNMB as an anti-cancer target for CDX-011. To them, the Celldex-GPNMB story is similar to Clovis Oncology's development of pancreatic cancer drug CO-101 in patients who were low expressers of hENT1 protein. Clovis' drug blew up in a phase III study because low hENT1 turned out to have no role at all in pancreatic cancer. Celldex bears believe GPNMB's role in breast cancer may also be a fallacy.

-- Reported by Adam Feuerstein in Boston.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

If you liked this article you might like

What Adam Feuerstein Got Right and Wrong About Biotech Stocks in 2016

2016 Was a Terrible Year for Biotech but the Tweets Were on Point

Corbus Pharma Bear Thesis Is Alive and Well on Sclerosis Drug Data Skewed Positive

Celldex Therapeutics (CLDX) Stock Up on Q2 Results

Celldex Therapeutics (CLDX) Is Strong On High Volume Today