Prostate cancer (PCa) is the most common cancer in men worldwide. In general, PCa responds poorly to chemotherapy. Therefore, antibody–drug conjugates (ADCs) have been developed to specifically deliver highly cytotoxic drugs to the tumor. Because the prostate-specific membrane antigen (PSMA) is overexpressed in PCa, it represents a promising target for ADC-based therapies. The aim of this study was to evaluate the therapeutic efficacy of site-specifically conjugated duocarmycin- and monomethyl auristatin E (MMAE)–based anti-PSMA ADCs with drug-to-antibody ratios (DARs) of 2 and 4. Methods: The glycan group of the anti-PSMA antibody D2B was chemoenzymatically conjugated with duocarmycin or MMAE. Preservation of the immunoreactivity of the antibody on site-specific conjugation was investigated in vitro. Biodistribution and small-animal SPECT/CT imaging (18.5 ± 2.6 MBq) with 25 μg of ¹¹¹In-labeled ADCs were performed on BALB/c nude mice with subcutaneous PSMA-positive LS174T-PSMA xenografts. Finally, the therapeutic efficacy of the 4 different ADCs was assessed in mice with LS174T-PSMA tumors. Results: The immunoreactivity of the anti-PSMA antibody was preserved on site-specific conjugation. Biodistribution revealed high tumor uptake of all agents. The highest tumor uptake was observed in mice administered with ¹¹¹In-D2B-DAR2-MMAE, reaching 119.7 ± 37.4 percentage injected dose per gram at 3 d after injection. Tumors of mice injected with ¹¹¹In-D2B, ¹¹¹In-D2B-DAR2-duocarmycin, ¹¹¹In-D2B-DAR4-duocarmycin, ¹¹¹In-D2B-DAR2-MMAE, and ¹¹¹In-D2B-DAR4-MMAE could clearly be visualized with small-animal SPECT/CT. In contrast to unconjugated D2B or vehicle, treatment with either of the MMAE-based ADCs, but not with a duocarmycin-based ADC, significantly impaired tumor growth and prolonged median survival from 13 d (phosphate-buffered saline) to 20 and 29 d for DAR2 and DAR4 ADC, respectively. Tumor-doubling time increased from 3.5 ± 0.5 d to 5.2 ± 1.8 and 9.2 ± 2.1 d after treatment with D2B-DAR2-MMAE and D2B-DAR4-MMAE, respectively. Conclusion: The site-specifically conjugated anti-PSMA ADCs D2B-DAR2-MMAE and D2B-DAR4-MMAE efficiently targeted PSMA-expressing xenografts, effectively inhibited tumor growth of PSMA-expressing tumors, and significantly prolonged survival of mice.

前列腺癌（PCa）是全世界男性中最常见的癌症。通常，PCa对化学疗法的反应较差。因此，已经开发出抗体-药物结合物（ADC），以将高细胞毒性药物特异性地递送至肿瘤。由于前列腺特异性膜抗原（PSMA）在PCa中过表达，因此它代表了基于ADC的疗法的有希望的靶标。这项研究的目的是评估基于位点特异性偶联的以杜卡霉素和单甲基澳瑞他汀E（MMAE）为基础的抗PSMA ADC的药效比（DARs）为2和4的治疗效果。方法：将抗PSMA抗体D2B的聚糖基与杜卡霉素或MMAE化学酶联。在体外研究了抗体对位点特异性缀合的免疫反应性的保存。生物分布和小动物SPECT / CT成像（18.5±2.6活度）用25微克的¹¹¹ In标记的ADC中对BALB执行/ c。与皮下PSMA阳性LS174T-PSMA异种移植物的裸鼠。最后，在患有LS174T-PSMA肿瘤的小鼠中评估了4种不同ADC的治疗效果。结果：抗PSMA抗体的免疫反应性在位点特异性结合中得以保留。生物分布显示所有药物对肿瘤的高吸收。在给予^111的小鼠中观察到最高的肿瘤吸收In-D2B-DAR2-MMAE，在注射后3 d达到每克注射剂量的119.7±37.4％。注射¹¹¹ In-D2B，¹¹¹ In-D2B-DAR2-杜卡霉素，¹¹¹ In-D2B-DAR4-杜卡霉素，¹¹¹ In-D2B-DAR2-MMAE和¹¹¹的小鼠的肿瘤In-D2B-DAR4-MMAE可以通过小动物SPECT / CT清晰地看到。与未结合的D2B或媒介相比，使用任何基于MMAE的ADC进行治疗，但不使用基于双卡霉素的ADC进行治疗，则显着削弱了肿瘤的生长，并将中位生存期从13 d（磷酸盐缓冲液）延长至20 d和29 d DAR2和DAR4 ADC分别。用D2B-DAR2-MMAE和D2B-DAR4-MMAE治疗后，肿瘤加倍时间分别从3.5±0.5 d和5.2±1.8 d延长至5.2±1.8 d和9.2±2.1 d。结论：位点特异性结合的抗PSMA ADC D2B-DAR2-MMAE和D2B-DAR4-MMAE有效地靶向了表达PSMA的异种移植物，有效抑制了表达PSMA的肿瘤的生长，并显着延长了小鼠的存活时间。