PT  - JOURNAL ARTICLE
AU  - Sally J. DeNardo
AU  - Ruiwu Liu
AU  - Huguette Albrecht
AU  - Arutselvan Natarajan
AU  - Julie L. Sutcliffe
AU  - Carolyn Anderson
AU  - Li Peng
AU  - Riccardo Ferdani
AU  - Simon R. Cherry
AU  - Kit S. Lam
TI  - <sup>111</sup>In-LLP2A-DOTA Polyethylene Glycol–Targeting α4β1 Integrin: Comparative Pharmacokinetics for Imaging and Therapy of Lymphoid Malignancies
AID  - 10.2967/jnumed.108.056903
DP  - 2009 Apr 01
TA  - Journal of Nuclear Medicine
PG  - 625--634
VI  - 50
IP  - 4
4099  - http://jnm.snmjournals.org/content/50/4/625.short
4100  - http://jnm.snmjournals.org/content/50/4/625.full
SO  - J Nucl Med2009 Apr 01; 50
AB  - N-[[4-[[[(2-ethylphenyl)amino]carbonyl]amino]phenyl]acetyl]-Nε-6-[(2E)-1-oxo-3-(3-pyridinyl-2-propenyl)]-l-lysyl-l-2-aminohexanedioyl-(1-amino-1-cyclohexane)carboxamide (LLP2A) is a high-affinity, high-specificity peptidomimetic ligand (inhibitory concentration of 50% = 2 pM) that binds the activated α4β1 integrin found on a variety of malignant lymphoid cell lines. To better determine whether this ligand holds promise for imaging and therapy in lymphoid malignancies, 6 LLP2A derivatives, as LLP2A-1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (LLP2A-DOTA) and LLP2A-DOTA-polyethylene glycol (LLP2A-DOTA-PEG), were designed, synthesized, and radiolabeled with 111In. Comparative pharmacokinetic studies in mice with Raji B-cell lymphoma xenografts were then complemented by small-animal PET of the lead molecular LLP2A format using 64Cu-LLP2A-11-bis(carboxymethyl)-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (64Cu-LLP2A-CB-TE2A). Methods: LLP2A-DOTA and LLP2A-CB-TE2A were prepared using solid-phase synthesis; LLP2A-DOTA-PEG2,000, LLP2A-DOTA-PEG5,000, LLP2A-DOTA-PEG10,000, (LLP2A-DOTA)2PEG10,000, and (LLP2A-DOTA)4PEG10,000 were prepared by PEGylation. 111In radiolabeling of DOTA and 64Cu radiolabeling of CB-TE2A conjugates yielded 370–1,850 and 3,700–7,400 kBq/μg (10–50 and 100–200 μCi/μg), respectively. The pharmacokinetics of the six 111In radioconjugates were studied in vivo using biodistribution data (4 and 24 h) and whole-body autoradiography (24 h) in mice with Raji tumor xenografts. 64Cu-LLP2A-CB-TE2A was imaged (4 and 24 h) on a small-animal PET scanner in the same mouse model. Results: The highest tumor uptake in pharmacokinetic studies was obtained with LLP2A-DOTA and (LLP2A-DOTA)4-PEG10,000. For 111In-LLP2A-DOTA (1 nM) at 4 and 24 h after injection, ratios of tumor to blood and tumor to nontumor (normal) organ (T/NT) were 8 to 35:1 for all organs or tissue except the spleen, marrow, and kidney, which were between 2:1 and 1:1. Tetravalent (LLP2A-DOTA)4-PEG10,000 (1.1 nM) had tumor uptake similar to the univalent LLP2A-DOTA but higher liver, marrow, and kidney uptake. The excellent T/NT of LLP2A was also demonstrated by small-animal PET with 64Cu-LLP2A-CB-TE2A at both 4 and 24 h after injection; obvious spleen targeting was apparent, but little kidney or liver activity was observed. Conclusion: Of the conjugates investigated, the univalent, non-PEGylated ligand 111In-LLP2A-DOTA exhibited the best T/NT ratios and showed the greatest potential for imaging of α4β1 in human lymphoma. Furthermore, this univalent non-PEGylated LLP2A format, as 64Cu-LLP2A-CB-TE2A, demonstrated excellent tumor targeting by small-animal PET and warrants further investigation as an agent for the study of α4β1 expression in human lymphoid malignancies.