title: High-affinity near-infrared fluorescent small-molecule contrast agents for in vivo imaging of prostate-specific membrane antigen.
abstract: Surgical resection remains a definitive treatment for prostate cancer. Yet, prostate cancer surgery is performed without image guidance for tumor margin, extension beyond the capsule and lymph node positivity, and without verification of other occult metastases in the surgical field. Recently, several imaging systems have been described that exploit near-infrared (NIR) fluorescent light for sensitive, real-time detection of disease pathology intraoperatively. In this study, we describe a high-affinity (9 nM), single nucleophile-containing, small molecule specific for the active site of the enzyme PSMA. We demonstrate production of a tetra-sulfonated heptamethine indocyanine NIR fluorescent derivative of this molecule using a high-yield LC/MS purification strategy. Interestingly, NIR fluorophore conjugation improves affinity over 20-fold, and we provide mechanistic insight into this observation. We describe the preparative production of enzymatically active PSMA using a baculovirus expression system and an adenovirus that co-expresses PSMA and GFP. We demonstrate sensitive and specific in vitro imaging of endogenous and ectopically expressed PSMA in human cells and in vivo imaging of xenograft tumors. We also discuss chemical strategies for improving performance even further. Taken together, this study describes nearly complete preclinical development of an optically based small-molecule contrast agent for image-guided surgery.
authors.affiliation: Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
authors.forename: Valerie
authors.initials: V
authors.lastname: Humblet
authors.forename: Rena
authors.initials: R
authors.lastname: Lapidus
authors.forename: Larry R
authors.initials: LR
authors.lastname: Williams
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsukamoto
authors.forename: Camilo
authors.initials: C
authors.lastname: Rojas
authors.forename: Pavel
authors.initials: P
authors.lastname: Majer
authors.forename: Bunda
authors.initials: B
authors.lastname: Hin
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Ohnishi
authors.forename: Alec M
authors.initials: AM
authors.lastname: De Grand
authors.forename: Atif
authors.initials: A
authors.lastname: Zaheer
authors.forename: Jürgen T
authors.initials: JT
authors.lastname: Renze
authors.forename: Akira
authors.initials: A
authors.lastname: Nakayama
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Slusher
authors.forename: John V
authors.initials: JV
authors.lastname: Frangioni
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000737:chemistry; D001665:Binding Sites; D045744:Cell Line, Tumor; D003287:Contrast Media; D043425:Glutamate Carboxypeptidase II / Q000737:chemistry; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D017430:Prostate-Specific Antigen / Q000737:chemistry; D011470:Prostatic Hyperplasia / Q000175:diagnosis; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging*; D011859:Radiography; D019265:Spectroscopy, Near-Infrared
chemical_list: D000954:Antigens, Surface; D003287:Contrast Media; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II; C485064:Glutamate carboxypeptidase III, mouse; D017430:Prostate-Specific Antigen