ERBB2 and breast carcinoma: While it is not yet known whether the higher affinity of 10D7 is advantageous for its anti-cancer actions, we note that Herceptin, a therapeutic mAb clinically approved for breast cancer, has an affinity of 5 nM for its target HER2 44, and that optimal tumor targeting is in the 1-10 nM KD range because higher affinity mAbs may be more rapidly degraded thereby limiting tumor penetration 45, 46.