Intrathecal viral vector delivery of trastuzumab prevents or inhibits tumor growth of human HER2-positive xenografts in mice

Breast cancer brain metastases are a deadly sequela of primary breast tumors that overexpress human epidermal growth factor receptor 2 (HER2); median survival for patients with these tumors is 10-13 months from the time of diagnosis. Current treatments for HER2-positive breast cancer brain metastases are invasive, toxic, and largely ineffective. Here we have developed an adeno-associated virus serotype 9 (AAV9) vector to express the anti-HER2 monoclonal antibody trastuzumab (Herceptin®) in vivo. A single prophylactic intrathecal administration of AAV9.trastuzumab vector in a novel orthotopic Rag1-/- murine xenograft model of HER2-positive breast cancer brain metastases significantly increased median survival, attenuated brain tumor growth, and preserved both the HER2 antigen specificity and the natural killer cell-associated mechanism of action of trastuzumab. When administered as a tumor treatment, AAV9.trastuzumab increased median survival. Dose-escalation studies revealed that higher doses of AAV9.trastuzumab resulted in smaller tumor volumes. Our results indicate that intrathecal AAV9.trastuzumab may provide significant anti-tumor activity in patients with HER2-positive breast cancer brain metastases.

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