The purpose of this study is to determine the safety, tolerability, and pharmacokinetics (PK) of 2B3-101 both as single agent and in combination with trastuzumab. Furthermore, the study will explore the preliminary antitumor activity of 2B3-101 as single agent in patients with with solid tumors and brain metastases or recurrent malignant glioma as well as in patients with various forms of breast cancer with and in combination with trastuzumab in HER2+ breast cancer patients with brain metastases.