I took another look at the Transcend/Trastuzumab paper published in Pharm Res in 2016 entitled "Anti-cancer Antibody Trastuzumab-Melanotransferrin Conjugate (BT2111) for the Treatment of Metastatic HER2+ Breast Cancer Tumors in the Brain: an In-Vivo Study." In the discussion, it states: "To our knowledge, trastuzumab has not been conjugated to a delivery peptide or vehicle as a chemotherapeutic." However, it appears Angiochem had presented data on this two years prior for their ANG4043 chemical conjugate of Angiopep-2 (An2) with an anti-HER2 mAb. The posters don't explicitly refer to the anti-HER2 mAb as Trastuzumab, but I'm pretty sure that they are one and the same.

AACR 2014 Angiochem poster

Neuroscience 2014 Angiochem poster