ASCO presentation: Phase IIb study of CDX-011 in refractory breast cancer.What we already know: Not much. ASCO (or the release of ASCO abstracts) will be the first dissemination of results from this study. Celldex enrolled 120 patients with advanced breast cancer that over-expresses a protein known as GPNMB (confirmed by an independent test). The patients, all of whom no longer respond to currently approved treatments, are then randomized to receive either CDX-011 or physician's choice of treatment. The primary endpoint of the study is overall response rate. Other notes: CDX-011 is a monoclonal antibody drug conjugate. The antibody portion targets cancer cells that express the GPNMB protein, which has been shown to correlate with poorer outcomes in breast cancer patients. When the CDX-011 antibody attaches to GPNMB-expressing tumor cells, it releases a toxic chemotherapy payload. This "drug conjugate" was licensed from Seattle Genetics (SGEN) and is the same one used in the newly approved lymphoma drug Adcetris. Celldex CEO Anthony Marucci has said previously that a meaningful and positive response rate in the study would be 12% to 15% with a progression-free survival of greater than 12 weeks.