Dierick Herlinde, Navarro Laurent, Van den Block Sonja, Saliën Jelena, Lahoutte Tony, Caveliers Vicky, Bridoux Jessica
Molecular Imaging and Therapy Research Group (MITH), Vrije Universiteit Brussel (VUB), Brussels, Belgium.
Nuclear Medicine Department, Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis Brussel (UZ Brussel), Brussels, Belgium.
EJNMMI Radiopharm Chem. 2024 Nov 14;9(1):77. doi: 10.1186/s41181-024-00306-7.
With the next generation of Human Epidermal Growth Factor Receptor 2 (HER2) -targeting therapies, such as antibody-drug conjugates, showing benefit in "HER2 low" and even "HER2 ultralow" patients, the need for novel methods to quantify HER2 expression accurately becomes even more important for clinical decision making. A HER2 PET/CT imaging assessment could evaluate HER2 positive disease locations while improving patient care, reducing the need for invasive biopsies. A single-domain antibody (sdAb)-based PET tracer could combine the high specificity of sdAbs with short-lived radionuclides such as fluorine-18 (F) and gallium-68 (Ga). SdAb-based PET tracers have clinically been used via a Ga-chelator approach. However, the distribution of Ga-labelled pharmaceuticals to peripheral PET centres is more challenging to organize due to the short half-life of Ga, most certainly when the available activity is limited by a generator. Cyclotron produced Ga has removed this limitation. Distribution of F-labelled pharmaceuticals remains less challenging due to its slightly longer half-life, and radiofluorination of sdAbs via N-succinimidyl-4-[F]fluorobenzoate ([F]SFB) has shown to be a promising strategy for developing sdAb-based PET tracers. Although [F]SFB automation has been reported, automating protein conjugation proves challenging. Herein we report the fully automated, cartridge-based production of [F]FB-HER2 sdAb on a single synthesis module.
[F]FB-HER2 sdAb (> 6 GBq) was obtained after a fully automated production (95 min), with a RCP > 95%, apparent molar activity > 20 GBq/µmol and decay-corrected radiochemical yield (RCY d.c.) of 14 ± 2% (n = 4). Further upscaling amounted to production batches of 16 GBq with an apparent molar activity > 40 GBq/µmol and RCY d.c. of 8 ± 1% (n = 4). Ex vivo biodistribution and PET imaging showed specific HER2-positive tumour targeting and low kidney retention.
The [F]FB-HER2 sdAb tracer was produced with clinically relevant activities using a fully automated production method. The automated production method was designed to ease the translation to the clinic and has the potential to be used not only in mono-centre but also multi-centre clinical trials with one central production site. [F]FB-HER2 sdAb showed a favourable biodistribution pattern and could be a valuable alternative to Ga-labelled sdAb-based PET tracers in the clinic.
随着下一代靶向人表皮生长因子受体2（HER2）的疗法，如抗体药物偶联物，在“HER2低表达”甚至“HER2超低表达”患者中显示出疗效，对于临床决策而言，准确量化HER2表达的新方法变得更加重要。HER2正电子发射断层扫描/计算机断层扫描（PET/CT）成像评估可以在改善患者护理的同时评估HER2阳性疾病部位，减少侵入性活检的需求。基于单域抗体（sdAb）的PET示踪剂可以将sdAb的高特异性与短寿命放射性核素如氟-18（F）和镓-68（Ga）相结合。基于sdAb的PET示踪剂在临床上已通过镓螯合剂方法使用。然而，由于Ga的半衰期短，将镓标记的药物分发给外周PET中心更具挑战性，尤其是当可用活度受到发生器限制时。回旋加速器生产的Ga消除了这一限制。由于F的半衰期稍长，F标记药物的分发难度较小，并且通过N-琥珀酰亚胺基-4-[F]氟苯甲酸酯（[F]SFB）对sdAb进行放射性氟化已被证明是开发基于sdAb的PET示踪剂的一种有前景的策略。尽管已有[F]SFB自动化的报道，但蛋白质偶联的自动化被证明具有挑战性。在此，我们报告了在单个合成模块上基于盒式系统的[F]FB-HER2 sdAb的全自动化生产。
经过全自动化生产（95分钟）后获得了[F]FB-HER2 sdAb（>6 GBq），放射化学纯度（RCP）>95%，表观摩尔活度>20 GBq/µmol，衰变校正放射化学产率（RCY d.c.）为14±2%（n = 4）。进一步扩大规模可生产16 GBq的批次，表观摩尔活度>40 GBq/µmol，RCY d.c.为8±1%（n = 4）。体外生物分布和PET成像显示出对HER2阳性肿瘤的特异性靶向以及低肾脏摄取。
使用全自动化生产方法生产出了具有临床相关活度的[F]FB-HER2 sdAb示踪剂。该自动化生产方法旨在便于向临床转化，不仅有可能用于单中心临床试验，也有可能用于有一个中央生产站点的多中心临床试验。[F]FB-HER2 sdAb显示出良好的生物分布模式，在临床上可能是基于Ga标记的sdAb的PET示踪剂的有价值替代物。
