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Antibody-drug conjugate shrinks some breast cancer tumors-study

(Reuters) – Interim results from a mid-stage trial of Celldex Therapeutics Inc’s experimental drug showed trends toward reducing tumors in patients with advanced breast cancer, with rates improving for those patients with high levels of a key surface protein.

The drug, CDX-011, “also demonstrated strong response rates in patients with triple negative breast cancer…where treatment options are extremely limited,” the researchers said in a statement.

CDX-011 or glembatumumab vedotin, was tested in 122 patients whose breast cancer had progressed despite several previous rounds of standard therapy.

The National Cancer Institute’s drug dictionary defines the agent as “consisting of the fully human monoclonal antibody CR011 directed against glycoprotein NMB (GPNMB) and conjugated via a cathepsin B-sensitive valine-citrulline linkage to the cytotoxic agent monomethyl auristatin E.”

In the study, released by the company on Wednesday, 19% of patients taking the antibody-drug conjugate saw their tumors shrink, compared with 14% of those treated with standard chemotherapy.

In trial patients with GPNMB on the surfaces of at least 25% of tumor cells, 32% responded, compared with 13% of chemotherapy patients.

“GPNMB helps the tumor cell to move around,” said Dr. Linda Vahdat, director of the breast cancer research program at Weill Cornell Medical College and the study’s lead investigator. “It almost seems like this drug puts the brakes on that process by taking away its legs.”

For patients with high levels of GPNMB as well as triple negative breast cancer, the response rate was 36%, compared with no responses in the control group. In this group, a statistically significant progression-free survival benefit is currently observed (p=0.0032), the researchers say.

Side effects included rash and peripheral neuropathy.

The company said it expects to announce updated results from the Phase II trial in the fourth quarter of this year.

“This patient population has a very real need,” said Tom Davis, chief medical officer at Celldex. “It is reasonable to consider a single-arm study … a randomized study is also a possibility.”

About 15% of breast cancer patients are triple negative, while high expression of GPNMB occurs in about 27%, according to Celldex. Because there is some overlap, both groups account for an estimated 35% of the total breast cancer population.