A 4-week intrathecal toxicity and pharmacokinetic study with trastuzumab in cynomolgus monkeys

Trastuzumab is indicated for the treatment of patients with breast cancer overexpressing human epidermal growth factor 2 (HER2). Women with HER2-positive tumors have an increased risk of brain metastases. The blood-brain barrier and blood-cerebrospinal fluid (CSF) barrier may prevent trastuzumab from reaching appropriate concentrations in the brain and CSF following standard intravenous administration. To evaluate the potential of effects on the central nervous system, a 4-week toxicology study with weekly intrathecal administration of trastuzumab was performed in cynomolgus monkeys at doses of 0, 3, or 15 mg. No trastuzumab-related effects on body weight, clinical signs, neurological function, clinical pathology, or anatomic pathology were noted. The applied doses and CSF concentrations achieved in the current study exceeded those reported in patients after intrathecal administration. The results support future studies for further evaluation of intrathecal application of trastuzumab in patients with brain metastases in HER2-positive breast cancer.