Purpose

Cluster of differentiation 38 (CD38) is a promising therapeutic target in multiple myeloma (MM) patients and has resulted in the development of several CD38 immunotherapies. Current methods to evaluate CD38 expression in the preclinical setting include ex vivo flow cytometry and immunohistochemistry, which can be cumbersome and do not give whole-body information. In vivo imaging technologies such as positron emission tomography rely on decay of radioisotopes, limiting the number of molecular interactions observed at any given time point. Here, we demonstrate the use of near-infrared (NIR) fluorescence imaging for spatiotemporal monitoring of CD38 expression in preclinical MM using the anti-CD38 daratumumab (DARA) conjugated to the NIR fluorophore IRDye800CW (DARA-IRDye800).

Procedures

Stability studies with human serum and binding assays with human myeloma cells were performed with DARA-IRDye800. Immunocompromised mice with intra- and extramedullary tumors (n = 5/group) were administered with DARA-IRDye800 for in vivo imaging up to 7 days after injection. Ex vivo biodistribution and flow cytometry studies were performed to validate in vivo imaging results. A separate therapy study was performed in mice with intramedullary tumors that were treated and not treated with DARA at a therapeutic dose (n = 7/group). DARA-IRDye800 was administered for subsequent in vivo and ex vivo imaging in both cohorts of mice.

Results

DARA-IRDye800 maintained stability and had high affinity for CD38 (K_D = 3.5 ± 0.05 nM). DARA-IRDye800 demonstrated a 5- and 18-fold increase in contrast in tumor-bearing regions of mice with extra- and intramedullary MM. Finally, mice treated with therapeutic doses of DARA and imaged with DARA-IRDye800 showed an 11-fold decrease in fluorescence intensities in vivo compared with untreated controls.

Conclusions

Our studies establish DARA-IRDye800 as a promising contrast agent for preclinical evaluation of CD38 expression and for further investigating myeloma engraftment and kinetics in relation to anti-CD38 therapies.

中文翻译：

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近红外标记 CD38 靶向 Daratumumab 用于多发性骨髓瘤 CD38 光学成像的临床前开发

目的

分化簇 38 (CD38) 是多发性骨髓瘤 (MM) 患者的一个有前景的治疗靶点，并导致了多种 CD38 免疫疗法的发展。目前在临床前环境中评估 CD38 表达的方法包括离体流式细胞术和免疫组织化学，这可能很麻烦并且不提供全身信息。正电子发射断层扫描等体内成像技术依赖于放射性同位素的衰变，限制了在任何给定时间点观察到的分子相互作用的数量。在这里，我们展示了使用近红外 (NIR) 荧光成像使用与 NIR 荧光团 IRDye800CW (DARA-IRDye800) 结合的抗 CD38 daratumumab (DARA) 进行临床前 MM 中 CD38 表达的时空监测。

程序

使用 DARA-IRDye800 进行人血清稳定性研究和人骨髓瘤细胞结合测定。免疫功能低下的具有髓内和髓外肿瘤的小鼠（n = 5/组）在注射后 7 天内使用 DARA-IRDye800 进行体内成像。进行了体外生物分布和流式细胞术研究以验证体内成像结果。在治疗剂量的 DARA 治疗和未治疗的髓内肿瘤小鼠中进行了单独的治疗研究（n = 7/组）。DARA-IRDye800 用于随后在两组小鼠中进行体内和体外成像。

结果

DARA-IRDye800 保持稳定性并且对 CD38 具有高亲和力（K _D = 3.5 ± 0.05 nM）。DARA-IRDye800 在具有髓外和髓内 MM 的小鼠的荷瘤区域中表现出 5 倍和 18 倍的对比度增加。最后，与未治疗的对照相比，用治疗剂量的 DARA 治疗并用 DARA-IRDye800 成像的小鼠体内荧光强度降低了 11 倍。

结论

我们的研究将 DARA-IRDye800 确立为一种有前途的造影剂，可用于 CD38 表达的临床前评估以及进一步研究与抗 CD38 疗法相关的骨髓瘤植入和动力学。