A 19% overall response rate for Celldex Therapeutics'
The biotech figured it out.
CLDX-011 is a targeted therapy that uses an antibody that attacks glycoprotein NMB, or GPNMB, attached to a cell killing chemotherapy. Celldex licensed the antibody drug conjugate technology from Seattle Genetics
In tumors where more than 25% of tumor cells expressed GPNMB -- as opposed to greater than 5% in the full data set -- CDX-011 produced an overall response rate of 32% versus 13% for patients who got chemotherapy. That's exactly what you'd expect to see, targeted therapies like Seattle Genetics' Adcetris and even antibody drugs without toxic payloads like Bristol-Myers Squibb
In patients who have very aggressive tumors, called triple-negative because they don't require estrogen, progesterone, or a protein called Her2 to grow, the data looked even better. These patients don't typically respond to later rounds of chemotherapy, as evidenced by the 0% overall response rate in the chemotherapy arm. Triple-negative patients taking CDX-011, on the other hand, produced a 21% overall response rate, which jumped to 36% for triple-negative patients who also expressed a high level of GPNMB.
The only downside to this data is that when you pull out patients, you get fairly small numbers. Celldex enrolled 122 patients and 81 got CDX-011. Of those, only 25 were high GPNMB expressers. There were 24 triple-negative patients who got the drug. And only 11 patients who got CDX-011 were both high expressers and triple-negative.
Obviously that's not enough to get the drug approved -- that wasn't the point of the trial -- but the data give Celldex a testable hypothesis and should give investors a little more confidence that the next trial will be positive.