Targeting agents that are capable of permitting or facilitating transport of an active agent through a human or animal gastro-intestinal tissue. These targeting agents are peptides or their derivatives (e.g., fragments) and peptidomimetics thereof, and the nucleotide sequences coding for the peptides and derivatives. The targeting agents have use in facilitating transport of active agents from the lumenal side of the GIT into the systemic blood system, and/or in targeting active agents to the GIT. Therapeutic methods of administration, pharmaceutical compositions and formulations based on the targeting agent peptides are also provided. Preferably, the active agent is a drug or drug-containing nano- or microparticle.