Evaluation of an 131I-labeled HER2-specific single domain antibody fragment for the radiopharmaceutical therapy of HER2-expressing cancers

Yutian Feng,Robert E Reiman,Robin Marjoram,Rebecca Meshaw,Darryl Mcdougald,Jeffrey L Schaal,Zhengyuan Zhou,Stephen A Jannetti,Xiao-Guang Zhao,Erica Pippen,Michael R Zalutsky,Ganesan Vaidyanathan

doi:10.1038/s41598-022-07006-9

Yutian Feng, Robert E Reiman + Show 10 more

Open Access

https://doi.org/10.1038/s41598-022-07006-9

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Abstract

Radiopharmaceutical therapy (RPT) is an attractive strategy for treatment of disseminated cancers including those overexpressing the HER2 receptor including breast, ovarian and gastroesophageal carcinomas. Single-domain antibody fragments (sdAbs) exemplified by the HER2-targeted VHH_1028 evaluated herein are attractive for RPT because they rapidly accumulate in tumor and clear faster from normal tissues than intact antibodies. In this study, VHH_1028 was labeled using the residualizing prosthetic agent N-succinimidyl 3-guanidinomethyl 5-[131I]iodobenzoate (iso-[131I]SGMIB) and its tissue distribution evaluated in the HER2-expressing SKOV-3 ovarian and BT474 breast carcinoma xenograft models. In head-to-head comparisons to [131I]SGMIB-2Rs15d, a HER2-targeted radiopharmaceutical currently under clinical investigation, iso-[131I]SGMIB-VHH_1028 exhibited significantly higher tumor uptake and significantly lower kidney accumulation. The results demonstrated 2.9 and 6.3 times more favorable tumor-to-kidney radiation dose ratios in the SKOV-3 and BT474 xenograft models, respectively. Iso-[131I]SGMIB-VHH_1028 was prepared using a solid-phase extraction method for purification of the prosthetic agent intermediate Boc2-iso-[131I]SGMIB that reproducibly scaled to therapeutic-level doses and obviated the need for its HPLC purification. Single-dose (SKOV-3) and multiple-dose (BT474) treatment regimens demonstrated that iso-[131I]SGMIB-VHH_1028 was well tolerated and provided significant tumor growth delay and survival prolongation. This study suggests that iso-[131I]SGMIB-VHH_1028 is a promising candidate for RPT of HER2-expressing cancers and further development is warranted.

Highlights

Radiopharmaceutical therapy (RPT) is an attractive strategy for treatment of disseminated cancers including those overexpressing the human epidermal growth factor receptor type 2 (HER2) receptor including breast, ovarian and gastroesophageal carcinomas
Reaction of VHH_1028 with iso-SGMIB provided a mono-substituted conjugate, isolated in 25% yield by HIC HPLC, which showed a single peak with a molecular weight of 13,147.6 Da on size-exclusion HPLC–MS
Encouraged by the advancement of the HER2-targeted [131I]SGMIB-2Rs15d to clinical trial[18], we have developed iso-[131I]SGMIB-VHH_1028, which has incorporated several distinguishing design features: a prosthetic agent imparting more favorable in vivo characteristics and an anti-HER2 Single-domain antibody fragments (sdAbs) with higher HER2 binding affinity and better internalization

Summary

Introduction

Radiopharmaceutical therapy (RPT) is an attractive strategy for treatment of disseminated cancers including those overexpressing the HER2 receptor including breast, ovarian and gastroesophageal carcinomas. Single-domain antibody fragments (sdAbs) exemplified by the HER2-targeted VHH_1028 evaluated are attractive for RPT because they rapidly accumulate in tumor and clear faster from normal tissues than intact antibodies. VHH_1028 was labeled using the residualizing prosthetic agent N-succinimidyl 3-guanidinomethyl 5-[131I]iodobenzoate (iso-[131I] SGMIB) and its tissue distribution evaluated in the HER2-expressing SKOV-3 ovarian and BT474 breast carcinoma xenograft models. Much more favorable results were obtained when sdAbs were labeled using N-succinimidyl 4-guanidinomethyl 3-[131I] iodobenzoate ([131I]SGMIB)—an agent combining the properties of good tumor residualization with radiolabeled catabolites that undergo rapid renal e xcretion[10,11]. The human epidermal growth factor receptor type 2 (HER2) has been the most widely investigated molecule for targeting radiolabeled sdAbs to tumors[12] This transmembrane receptor is frequently expressed on breast, gastric and ovarian c arcinomas[13]. For metastases to the brain, a common and frequently lethal manifestation in patients with HER2-positive breast cancer[15], the smaller size of sdAbs compared with existing HER2-targeted intact antibodies and their drug conjugates could be a dvantageous[16,17]

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