Frigerio Barbara, Luison Elena, Desideri Alessandro, Iacovelli Federico, Camisaschi Chiara, Seregni Ettore C, Canevari Silvana, Figini Mariangela
Biomarkers Unit, Department of Applied Research and Technical Development, Fondazione IRCCS Istituto Nazionale dei Tumori, 20133 Milan, Italy.
Laboratory of Structural Biology, Department of Biology, University of Rome "Tor Vergata", 00133 Rome, Italy.
Biomedicines. 2021 Dec 10;9(12):1870. doi: 10.3390/biomedicines9121870.
Prostate cancer (PCa) is the second leading cause of cancer among men, and its diagnosis and adequate staging are fundamental. Among the biomarkers identified in recent years for PCa management, prostate-specific-membrane-antigen (PSMA), physiologically expressed at a low level on healthy prostate and in other normal tissues and highly overexpressed in PCa, represents a reliable marker ideal for imaging and therapy. The development of anti-PSMA antibodies, such as D2B, demonstrated slow clearance of intact antibodies compared with fragments resulting in low tumor-to-blood ratios; however, the modular structural and functional nature of antibodies allowed the generation of smaller fragments, such as scFvs. In this review of the anti-PSMA antibody fragment scFvD2B, we combined further characterization of its biomolecular and tissue cross-reactivity characteristics with a comprehensive summary of what has already been performed in preclinical models to evaluate imaging and therapeutic activities. A molecular dynamics study was performed, and ScFvD2B occupied a limited conformational space, characterized by low-energy conformational basins, confirming the high stability of the protein structure. In the cross-reactivity study, the weak/absent immunoreactivity in non-tumor tissues was comparable to the PSMA expression reported in the literature. Biodistribution studies and therapeutic treatments were conducted in different animal models obtained by subcutaneous or locoregional injection of PSMA-positive-versus-negative xenografts. The maximum tumor uptake was observed for I(SPECT), I(PET), and optical imaging, which avoids kidney accumulation (compared with radiometals) and leads to an optimal tumor-to-kidney and tumor-to-background ratios. Regarding its possible use in therapy, experimental data suggested a strong and specific antitumor activity, in vitro and in vivo, obtained using CAR-T or NK-92/CAR cells expressing scFvD2B. Based on presented/reviewed data, we consider that scFvD2B, due to its versatility and robustness, seems to: (i) overcome some problems observed in other studied scFvs, very often relatively unstable and prone to form aggregates; (ii) have sufficient tumor-to-background ratios for targeting and imaging PSMA-expressing cancer; (iii) significantly redirect immune killing cells to PSMA-positive tumors when inserted in second-generation CAR-T or NK-92/CAR cells. These data suggest that our product can be considered the right reagent to fill the gap that still exists in PCa diagnosis and treatment.
前列腺癌（PCa）是男性中第二大致癌原因，其诊断和准确分期至关重要。在近年来确定用于PCa管理的生物标志物中，前列腺特异性膜抗原（PSMA）在健康前列腺和其他正常组织中生理表达水平较低，而在PCa中高度过表达，是一种用于成像和治疗的理想可靠标志物。抗PSMA抗体（如D2B）的研发表明，完整抗体的清除速度比片段慢，导致肿瘤与血液的比率较低；然而，抗体的模块化结构和功能性质使得能够产生更小的片段，如单链抗体片段（scFv）。在这篇关于抗PSMA抗体片段scFvD2B的综述中，我们将其生物分子和组织交叉反应特性的进一步表征与临床前模型中已进行的评估成像和治疗活性的综合总结相结合。进行了一项分子动力学研究，scFvD2B占据有限的构象空间，其特征为低能量构象盆地，证实了蛋白质结构的高稳定性。在交叉反应性研究中，非肿瘤组织中弱/无免疫反应性与文献报道的PSMA表达情况相当。在通过皮下或局部注射PSMA阳性与阴性异种移植获得的不同动物模型中进行了生物分布研究和治疗。对于单光子发射计算机断层扫描（I(SPECT)）、正电子发射断层扫描（I(PET)）和光学成像，观察到最大肿瘤摄取，这避免了肾脏蓄积（与放射性金属相比），并导致最佳的肿瘤与肾脏以及肿瘤与背景比率。关于其在治疗中的可能应用，实验数据表明，使用表达scFvD2B的嵌合抗原受体T细胞（CAR-T）或NK-92/CAR细胞在体外和体内均获得了强大且特异性的抗肿瘤活性。基于所呈现/综述的数据，我们认为scFvD2B由于其多功能性和稳健性，似乎：（i）克服了在其他研究的scFv中观察到的一些问题，这些scFv通常相对不稳定且易于形成聚集体；（ii）具有足够的肿瘤与背景比率以靶向和成像表达PSMA的癌症；（iii）当插入第二代CAR-T或NK-92/CAR细胞时，能显著将免疫杀伤细胞重定向至PSMA阳性肿瘤。这些数据表明，我们的产品可被视为填补PCa诊断和治疗中仍然存在的空白的合适试剂。
