Abstract: Engineered peptides that bind with high affinity (low equilibrium dissociation constant (Kd)) to the cell surface receptors of fibronectin (?5?1) or vitronectin (?v?3 and ?v?5 integrins) are disclosed as useful as imaging tissue. These peptides are based on a molecular scaffold into which a subsequence containing the RGD integrin-binding motif has been inserted. The subsequence (RGD mimic) comprises about 9-13 amino acids, and the RGD contained within the subsequence can be flanked by a variety of amino acids, the sequence of which was determined by sequential rounds of selection (in vitro evolution). The molecular scaffold is preferably based on a knottin, e.g., EETI (Trypsin inhibitor 2 (Trypsin inhibitor II) (EETI-II) [Ecballium elaterium (Jumping cucumber)], AgRP (Agouti-related protein), and Agatoxin IVB, which peptides have a rigidly defined three-dimensional conformation. It is demonstrated that EETI tolerates mutations in other loops and that the present peptides may be used as imaging agents.

Abstract: Engineered peptides that bind with high affinity (low equilibrium dissociation constant (Kd)) to the cell surface receptors of fibronectin (?5?1) or vitronectin (?v?3 and ?v?5 integrins) are disclosed as useful as imaging tissue. These peptides are based on a molecular scaffold into which a subsequence containing the RGD integrin-binding motif has been inserted. The subsequence (RGD mimic) comprises about 9-13 amino acids, and the RGD contained within the subsequence can be flanked by a variety of amino acids, the sequence of which was determined by sequential rounds of selection (in vitro evolution). The molecular scaffold is preferably based on a knottin, e.g., EETI (Trypsin inhibitor 2 (Trypsin inhibitor II) (EETI-II) [Ecballium elaterium (Jumping cucumber)], AgRP (Agouti-related protein), and Agatoxin IVB, which peptides have a rigidly defined three-dimensional conformation. It is demonstrated that EETI tolerates mutations in other loops and that the present peptides may be used as imaging agents.

Abstract: Engineered peptides that bind with high affinity (low equilibrium dissociation constant (Kd)) to the cell surface receptors of fibronectin (?5?1) or vitronectin (?v?3 and ?v?5 integrins) are disclosed as useful as imaging tissue. These peptides are based on a molecular scaffold into which a subsequence containing the RGD integrin-binding motif has been inserted. The subsequence (RGD mimic) comprises about 9-13 amino acids, and the RGD contained within the subsequence can be flanked by a variety of amino acids, the sequence of which was determined by sequential rounds of selection (in vitro evolution). The molecular scaffold is preferably based on a knottin, e.g., EETI (Trypsin inhibitor 2 (Trypsin inhibitor II) (EETI-II) [Ecballium elaterium (Jumping cucumber)], AgRP (Agouti-related protein), and Agatoxin IVB, which peptides have a rigidly defined three-dimensional conformation. It is demonstrated that EETI tolerates mutations in other loops and that the present peptides may be used as imaging agents.

Abstract: Engineered peptides that bind with high affinity (low equilibrium dissociation constant (Kd)) to the cell surface receptors of fibronectin (?5?1) or vitronectin (?v?3 and ?v?5 integrins) are disclosed as useful as imaging tissue. These peptides are based on a molecular scaffold into which a subsequence containing the RGD integrin-binding motif has been inserted. The subsequence (RGD mimic) comprises about 9-13 amino acids, and the RGD contained within the subsequence can be flanked by a variety of amino acids, the sequence of which was determined by sequential rounds of selection (in vitro evolution). The molecular scaffold is preferably based on a knottin, e.g., EETI (Trypsin inhibitor 2 (Trypsin inhibitor II) (EETI-II) [Ecballium elaterium (Jumping cucumber)], AgRP (Agouti-related protein), and Agatoxin IVB, which peptides have a rigidly defined three-dimensional conformation. It is demonstrated that EETI tolerates mutations in other loops and that the present peptides may be used as imaging agents.

Abstract: Engineered peptides that bind with high affinity (low equilibrium dissociation constant (Kd)) to the cell surface receptors of fibronectin (?5?1) or vitronectin (?v?3 and ?v?5 integrins) are disclosed as useful as imaging tissue. These peptides are based on a molecular scaffold into which a subsequence containing the RGD integrin-binding motif has been inserted. The subsequence (RGD mimic) comprises about 9-13 amino acids, and the RGD contained within the subsequence can be flanked by a variety of amino acids, the sequence of which was determined by sequential rounds of selection (in vitro evolution). The molecular scaffold is preferably based on a knottin, e.g., EETI (Trypsin inhibitor 2 (Trypsin inhibitor II) (EETI-II) [Ecballium elaterium (Jumping cucumber)], AgRP (Agouti-related protein), and Agatoxin IVB, which peptides have a rigidly defined three-dimensional conformation. It is demonstrated that EETI tolerates mutations in other loops and that the present peptides may be used as imaging agents.

Abstract: Disclosed are peptides comprising a molecular scaffold portion and a loop portion that binds to integrin ?v?6. This integrin is expressed on pancreatic tumors, making the peptides useful as imaging agents, among other uses. The peptides showed single-digit nanomolar dissociation constants similar to antibodies used clinically for imaging and therapy. The peptides rapidly accumulated in ?v?6-positive tumors, which led to excellent tumor-to-normal contrast. The peptides are specific for the targeted integrin ?v?6 receptors expressed on orthotopic pancreatic tumors and various xenografts used. Additionally, pharmacokinetic-stabilization strategies endowed knots with rapid renal clearance, which significantly reduced off-target dosing.

Abstract: Disclosed are peptides comprising a molecular scaffold portion and a loop portion that binds to integrin ?v?6. This integrin is expressed on pancreatic tumors, making the peptides useful as imaging agents, among other uses. The peptides showed single-digit nanomolar dissociation constants similar to antibodies used clinically for imaging and therapy. The peptides rapidly accumulated in ?v?6-positive tumors, which led to excellent tumor-to-normal contrast. The peptides are specific for the targeted integrin ?v?6 receptors expressed on orthotopic pancreatic tumors and various xenografts used. Additionally, pharmacokinetic-stabilization strategies endowed knots with rapid renal clearance, which significantly reduced off-target dosing.