OBJECTIVEProstate-specific membrane antigen (PSMA) is a well-known biomarker of prostate cancer. Previously, our group reported that the succinimidyl-cystatin-urea-glutamate (SCUE) moiety has a high affinity for PSMA. In this study, we developed the novel technetium-99m-labeled PSMA-targeting probe "[^99mTc]Tc-(Ham-SCUE)₂" based on a hydroxamamide chelate with a bivalent SCUE and evaluated its potential as a SPECT imaging probe for the diagnosis of PSMA-expressing prostate cancer.METHODSHam-SCUE was synthesized by a one-step reaction with Ham-Mal and cysteine-urea-glutamine. Then, Ham-SCUE was reacted with [^99mTc]NaTcO₄ for 10 min at room temperature to obtain [^99mTc]Tc-(Ham-SCUE)₂. [^99mTc]Tc-(Ham-SCUE)₂ was added to LNCaP (high PSMA expression) cells or PC3 (low PSMA expression) cells, and their radioactivity was measured 60 min after administration. The blocking study was performed by co-incubation of LNCaP cells with various concentrations of 2-PMPA (a PSMA inhibitor) for 15 min before adding [^99mTc]Tc-(Ham-SCUE)₂. The biodistribution of [^99mTc]Tc-(Ham-SCUE)₂ in LNCaP/PC3 dual xenografted C.B.-17/Icr scid/scid Jcl mice was evaluated for 120 min after intravenous injection. The blocking study was performed by pretreatment of mice with 2-PMPA (10 mg/kg weight).RESULTS[^99mTc]Tc-(Ham-SCUE)₂ was acquired at radiochemical yields of 56% with a radiochemical purity of over 95%. The cellular uptake level of [^99mTc]Tc-(Ham-SCUE)₂ by LNCaP cells was significantly higher than that by PC3 cells (LNCaP: 11.12 ± 0.71 vs. PC3: 1.40 ± 0.13%uptake/mg protein, p < 0.01), and the uptake was significantly suppressed by pretreatment with 2-PMPA (2.56 ± 0.37%uptake/mg protein, p < 0.05). IC₅₀ of 2-PMPA was 245 ± 47 nM. In the in vivo study, the radioactivity of LNCaP tumor tissue was significantly higher than that of PC3 tumor tissue at 120 min after the administration of [^99mTc]Tc-(Ham-SCUE)₂ (LNCaP: 9.97 ± 2.79, PC3: 1.16 ± 0.23%ID/g, p < 0.01), and was suppressed by pretreatment with 2-PMPA (2.50 ± 0.45%ID/g, p < 0.01).CONCLUSION[^99mTc]Tc-(Ham-SCUE)₂ has the potential to be a SPECT imaging agent for diagnosing high PSMA-expressing prostate cancer.

2024-07-01·Nuclear Medicine and Biology

PSMA-reactive NB7 single domain antibody fragment: A potential scaffold for developing prostate cancer theranostics

Article

作者: Feng, Yutian ; Zhao, Xiao-Guang ; Vaidyanathan, Ganesan ; Huynh, Truc T. ; Papo, Niv ; Meshaw, Rebecca ; Zalutsky, Michael R. ; Rosenfeld, Lior

INTRODUCTIONSingle domain antibody fragments (sdAbs) are an appealing scaffold for radiopharmaceutical development due to their small size (~15 kDa), high solubility, high stability, and excellent tumor penetration. Previously, we developed NB7 sdAb, which has very high affinity for an epitope on PSMA that is different from those targeted by small molecule PSMA inhibitors. Herein, we evaluated NB7 after radioiodination using [*I]SGMIB (1,3,4-isomer) and iso-[*I]SGMIB (1,3,5-isomer), as well as their ²¹¹At-labeled analogues.METHODS[*I]SGMIB, iso-[*I]SGMIB, [²¹¹At]SAGMB, and iso-[²¹¹At]SAGMB conjugates of NB7 sdAb were synthesized and their binding affinity, cell uptake and internalization were assessed in PSMA⁺ PC3 PIP and PSMA^- PC3 flu cells. Biodistribution studies were performed in mice bearing PSMA⁺ PC3 PIP xenografts. First, a single-label experiment evaluated the tissue distribution of a NB7 bearing a His₆-tag (NB7H6) and labeled with iso-[¹²⁵I]SGMIB. Three paired-label experiments then were performed to compare: a) NB7 labeled using [*I]SGMIB and iso-[*I]SGMIB, b) ¹³¹I- vs ²¹¹At-labeled NB7 conjugates and c) [¹²⁵I]SGMIB-NB7H6 to the small molecule PSMA inhibitor [¹³¹I]YF2.RESULTSAll NB7 radioconjugates bound specifically to PSMA with dissociation constants, K_d, in the low nM range (1.4-6.4 nM). An initial biodistribution study demonstrated good tumor uptake for iso-[¹²⁵I]SGMIB-NB7H6 (7.2 ± 1.5 % ID/g at 1 h) and no deleterious effect of the His₆-tag on renal activity levels, which declined to 3.1 ± 1.1 % ID/g by 4 h. Paired-label biodistribution found no distinction between the two SGMIB isomer NB7 conjugates with the [¹³¹I]SGMIB-NB7-to-iso-[¹²⁵I]SGMIB-NB7 tumor uptake ratios not significantly different from unity: 1.06 ± 0.08 at 1 h, 1.04 ± 0.12 at 4 h, and 1.07 ± 0.09 at 24 h. Both isomer conjugates cleared rapidly from normal tissues and exhibited very low uptake in thyroid, lacrimal and salivary glands. Paired-label biodistribution of [¹³¹I]SGMIB-NB7H6 and [²¹¹At]SAGMB-NB7H6 demonstrated similar tumor uptake and kidney clearance for the two radioconjugates. However, levels of ²¹¹At in thyroid, stomach, salivary and lacrimal glands were significantly higher (P < 0.05) that those for ¹³¹I suggesting greater dehalogenation for [²¹¹At]SAGMB-NB7H6. Finally, co-administration of [¹²⁵I]SGMIB-NB7H6 and [¹³¹I]YF2 demonstrated good tumor uptake for both with considerably more rapid renal clearance for the NB7 radioconjugate.CONCLUSIONNB7 radioconjugates exhibited good accumulation in PSMA-positive xenografts with rapid clearance from kidney and other normal tissues. We conclude that NB7 is a potentially useful scaffold for developing PSMA-targeted theranostics with different characteristics than current small molecule and antibody-based approaches.

2024-05-10·ACS Pharmacology & Translational Science

Synthesis and Preclinical Evaluation of Urea-Based Prostate-Specific Membrane Antigen-Targeted Conjugates Labeled with ¹⁷⁷Lu

Article

作者: Yusubov, Mekhman S. ; Tretyakova, Maria ; Zyk, Nikolay Yu. ; Bezverkhniaia, Ekaterina ; Bodenko, Vitalina ; Yuldasheva, Feruza ; Tolmachev, Vladimir ; Larkina, Mariia S. ; Zelchan, Roman ; Machulkin, Aleksei E. ; Petrov, Stanislav A. ; Stasyuk, Elena ; Majouga, Alexander G. ; Orlova, Anna ; Plotnikov, Evgenii ; Beloglazkina, Elena K.

¹⁷⁷Lu-labeled small-molecule prostate-specific membrane antigen (PSMA) targeted tracers are therapeutic agents for metastatic castration-resistant prostate cancer. Optimizing molecular design holds the potential to further enhance the pharmacokinetic properties of PSMA-targeted agents while preserving their potent therapeutic effects. In this study, six novel N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-(S)-l-lysine (DCL) urea-based PSMA ligand 2,2',2″,2‴-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid conjugates were synthesized. These conjugates feature polypeptide linkers containing the Phe-Phe peptide sequence and an aromatic fragment at the ε-NH-Lys group of the DCL fragment. The synthesis yielded products with satisfactory yields ranging from 60% to 72%, paving the way for their preclinical evaluation. The labeling of the new variants of urea-based PSMA inhibitors provided a radiochemical yield of over 95%. The ¹⁷⁷Lu-labeled conjugates demonstrated specific and moderate affinity binding to PSMA-expressing human cancer cells PC3-pip in vitro and specific accumulation in PSMA-expressing xenografts in vivo. Based on the results, both the lipophilicity and the type of substituent in the linker significantly influence the binding properties of the PSMA inhibitor and its biodistribution profile. Specifically, the studied variants containing a bromine substituent or a hydroxyl group introduced into the aromatic fragment of the phenylalanyl residue in DCL exhibit higher affinities to PSMA compared to variants with only a chlorine-substituted aromatic fragment or variants without any substituents. The [¹⁷⁷Lu]Lu-13C with the bromine substituent was characterized by the highest activity accumulation in blood, salivary glands, muscle, bone, and gastrointestinal tract and had inasmuch as an unfavorable pharmacokinetic profile. The negative charge of the carboxyl group in the phenyl moiety of the [¹⁷⁷Lu]Lu-13A variant has demonstrated a positive effect on reducing the retention of activity in the liver and the kidneys (the ratio of tumor to kidneys was 1.3-fold). Low accumulation in normal tissues in vivo indicates that this novel PSMA-targeting inhibitor is a promising radioligand.

100 项与 PSMA inhibitors(Alpha-9 Theranostics) 相关的药物交易

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