Advances in precision molecular imaging promise to transform our ability
to detect, diagnose and treat disease. Here, we describe the
engineering and validation of a new cystine knot peptide (knottin) that
selectively recognizes human integrin αvβ6 with single-digit
nanomolar affinity. We solve its 3D structure by NMR and x-ray
crystallography and validate leads with 3 different radiolabels in
pre-clinical models of cancer. We evaluate the lead tracer’s safety,
biodistribution and pharmacokinetics in healthy human volunteers, and
show its ability to detect multiple cancers (pancreatic, cervical and
lung) in patients at two study locations. Additionally, we demonstrate
that the knottin PET tracers can also detect fibrotic lung disease in
idiopathic pulmonary fibrosis patients. Our results indicate that these
cystine knot PET tracers may have potential utility in multiple disease
states that are associated with upregulation of integrin αvβ6.