The possible explanation is GPNMB typically expressed in tumor epithelium for TNBC, while non-TNBC might be expressed in stroma. The question is whether CDX011 works one way better than the other.
I think they said on the call that it in general it didn't appear to make much difference whether the expression was in tumor or in stroma. There is perhaps some bystander effect, so for small tumors it might not make that much difference.