Preclinical efficacy and brain uptake of an insulin-mediated nanoparticle co-delivering trastuzumab and pertuzumab (AxS007) in HER2+ breast cancer brain metastasis models.

2027 Background: Anti-HER2 antibodies are standard therapies for metastatic HER2+ breast cancer but demonstrate limited intracranial activity due to restricted penetration across the blood–brain barrier (BBB). AxS007 is an insulin-mediated nanoparticle conjugated to trastuzumab and pertuzumab designed to enhance BBB transport and increase brain exposure. Methods: Brain uptake and distribution were assessed in C57BL mice using biodistribution analysis (5 min–90 days, n=25) and two-photon microscopy, comparing AxS007, a non-insulin-conjugated nanoparticle control, and free trastuzumab. Brain uptake was also evaluated in non-human primates (NHPs). Based on confirmed BBB penetration and brain exposure, AxS007 antitumor activity was evaluated in vitro in HER2+ cell lines (BT474, SKBR3, N87) and in vivo in BT474 subcutaneous (SC; n=20) and intracranial xenografts. Tumor growth inhibition (TGI) was assessed by MRI, and survival was compared between vehicle, AxS007 (IV, 10 mg/kg), and free trastuzumab + pertuzumab (IV, 10 mg/kg each). Safety was further investigated through single ascending dose (SAD) and multiple ascending dose (MAD) toxicological studies. Results: In mice, AxS007 demonstrated measurable brain uptake within 30 min and widespread parenchymal distribution at 24 h, with markedly higher brain exposure than free trastuzumab; in contrast, the non-insulin control and free antibodies showed minimal BBB crossing. In NHPs, AxS007 increased brain antibody exposure ~50-fold versus free antibodies at 48 h. In vitro, AxS007 showed antitumor activity comparable to or greater than free antibodies (SKBR3: 90% vs 50%; BT474: 50% vs 64%). In vivo, AxS007 achieved near-complete tumor elimination in SC tumors and demonstrated 82% TGI versus vehicle (p<0.01) and 60% TGI versus free trastuzumab +pertuzumab (p<0.05) in intracranial tumors, as assessed at day 60 post-inoculation. In an overall survival study, AxS007 extended survival approximately 3-fold compared with free trastusumab + pertuzumab. AxS007 exhibited a good safety profile with no drug related side effects. Conclusions: AxS007 showed enhanced BBB penetration and increased brain antibody exposure, with improved preclinical efficacy versus free antibodies in HER2+ breast cancer brain metastasis models. These findings support further translational advancement of AxS007 toward first-in-human clinical testing.