Provided herein are conditionally activated polypeptide constructs comprising a protease-activated domain binding to CD3, at least one half-life extension domain, and two or more domains binding to one or more target antigens. Also provided are pharmaceutical compositions thereof, as well as nucleic acids, recombinant expression vectors and host cells for making such polypeptide constructs. Also disclosed are methods of using the disclosed polypeptide constructs in the prevention, and/or treatment diseases, conditions and disorders.