High-affinity near-infrared fluorescent small-molecule contrast agents for in vivo imaging of prostate-specific membrane antigen.
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.
Humblet
Valerie
V
Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
Lapidus
Rena
R
Williams
Larry R
LR
Tsukamoto
Takashi
T
Rojas
Camilo
C
Majer
Pavel
P
Hin
Bunda
B
Ohnishi
Shunsuke
S
De Grand
Alec M
AM
Zaheer
Atif
A
Renze
Jürgen T
JT
Nakayama
Akira
A
Slusher
Barbara S
BS
Frangioni
John V
JV
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
D000954:Antigens, Surface; D003287:Contrast Media; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II; C485064:Glutamate carboxypeptidase III, mouse; D017430:Prostate-Specific Antigen