This study will investigate whether a new experimental treatment, ORM-5029, will be a safe and possibly effective treatment option for patients with solid tumors that have higher levels of a protein called HER2. The study is designed to find a safe and effective dose of ORM-5029.

ORM-5029 is considered investigational, which means it has not been approved by the U.S. Food and Drug Administration (FDA). ORM-5029 has not been tested in humans before.
   
There are two parts to the study, the Dose Escalation (Part 1) and the Dose Expansion (Part 2). In Part 1, the safety and tolerability of ORM-5029 will be explored. During the Dose Escalation part, increasing dose levels of ORM-5029 will be tested in patients with advanced breast cancer. The dose level which is found to be safe and tolerable during this part of testing will then be used in the second part of the study (the Dose Expansion part). In Part 2, we will continue to explore the safety and tolerability of the selected dose of ORM 5029, as well as look at the effectiveness of this dose in patients with different tumor types.

Depending on when the participants join the study, they may participate in either the dose escalation or dose expansion part of the study. The study team will discuss the part of the study with each participant.

Participation will continue until the disease gets worse, there are unacceptable side effects, or participants no longer receive benefits from the study drug.