• 29 patients on the Phase II study with progression on trastuzumab (H) received pertuzumab (P), and 1 had an objective response.
• In 17 of these patients, H was added back and 3 objective responses were observed, further supporting the synergy between H and P.

This is another small trial, but the take-away message from it appears to be quite large, most notably that pertuzumab is not highly effective as monotherapy yet when it is combined with trastuzumab much more activity can be observed. As such, dual anti-HER2 targeting continues to emerge rapidly as a management concept with plenty of supportive data for trastuzumab/lapatinib and now trastuzumab/pertuzumab. Although the explanatory science behind these observations is evolving, with pertuzumab’s recent FDA indication as first-line therapy for metastatic disease with trastuzumab and docetaxel (or paclitaxel according to the NCCN guidelines) a 2-pronged approach to HER2 blockade is now part of standard practice.