Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, United States.
Department of Radiology, Stony Brook University, Stony Brook, New York 11794, United States.
Mol Pharm. 2022 Sep 5;19(9):3217-3227. doi: 10.1021/acs.molpharmaceut.2c00361. Epub 2022 Jul 27.
An immunosuppressive tumor microenvironment and tumor heterogeneity have led to the resilience of metastatic castrate resistant prostate cancer (mCRPC) to current treatments. To address these challenges, we developed and evaluated a new drug paradigm, Radio-IMmunostimulant (RIMS), in a syngeneic model of murine prostate cancer. RIMS-1 was generated using a convergent synthesis employing solid phase peptide and solution chemistries. The prostate-specific membrane antigen (PSMA) inhibitory constant for Lu-RIMS-1 was determined, and radiolabeling with Lu generated Lu-RIMS-1. The TLR 7/8 agonist payload release from Lu-RIMS-1 was determined using a cathepsin B assay. The biodistribution of Lu-RIMS-1 was evaluated in a bilateral xenograft model in NCru nude mice bearing PSMA(+) (PC3-PiP) and PSMA(-) (PC3-Flu) tumors at 2, 24, and 72 h. The therapeutic effect of Lu-RIMS-1 was evaluated in C57BL/6J mice bearing RM1-PGLS (PSMA-positive, green fluorescent protein-positive, and luciferase-positive) tumors and compared to that of Lu-PSMA-617 at the same total administered radioactivity of 57 MBq and molar activity of 5.18 MBq/nmol. Lu-RIMS-1 and vehicle were evaluated as the controls. Immuno-positron emission tomography (PET) using Zr-DFO-anti-CD3 was used to visualize T-cell distribution during treatment. Lu-RIMS-1 was quantitatively radiolabeled at >99% radiochemical purity and maintained a high affinity toward PSMA ( = 3.77 ± 0.5 nM). Cathepsin B efficiently released the entire immunostimulant payload in 17.6 h. Lu-RIMS-1 displayed a sustained uptake in PSMA(+) tumor tissue up to 72 h (2.65 ± 1.03% ID/g) and was not statistically different ( = 0.1936) compared to Lu-PSMA-617 (3.65 ± 0.59% ID/g). All animals treated with Lu-RIMS-1 displayed tumor growth suppression and provided a median survival of 30 days ( = 0.0007) while Lu-PSMA-617 provided a median survival of 15 days, which was not statistically significant ( = 0.3548) compared to the vehicle group (14 days). ImmunoPET analysis revealed 2-fold more tumor infiltrating T-cells in Lu-RIMS-1-treated animals compared to Lu-PSMA-617-treated animals; Lu-RIMS-1 improves therapeutic outcomes in a syngeneic model of mouse prostate cancer and elicits greater T-cell infiltration to the tumor compared to Lu-PSMA-617. These results support further investigation of the RIMS paradigm as the first example of a single molecular entity combining radiotherapy and immunostimulation.
免疫抑制性肿瘤微环境和肿瘤异质性导致转移性去势抵抗性前列腺癌（mCRPC）对现有治疗方法产生耐药性。为了解决这些挑战，我们在前列腺癌的同种异体模型中开发并评估了一种新的药物范式，即放射免疫刺激剂（RIMS）。RIMS-1 是使用固相肽和溶液化学的收敛合成方法生成的。测定了 Lu-RIMS-1 对前列腺特异性膜抗原（PSMA）的抑制常数，并通过 Lu 进行放射性标记生成 Lu-RIMS-1。使用组织蛋白酶 B 测定法测定 Lu-RIMS-1 中 TLR 7/8 激动剂有效载荷的释放。在双侧异种移植模型中，在携带 PSMA(+)（PC3-PiP）和 PSMA(-)（PC3-Flu）肿瘤的 NCru 裸鼠中，在 2、24 和 72 小时评估 Lu-RIMS-1 的生物分布。在携带 RM1-PGLS（PSMA 阳性、绿色荧光蛋白阳性和荧光素酶阳性）肿瘤的 C57BL/6J 小鼠中评估 Lu-RIMS-1 的治疗效果，并与相同的总放射性活度为 57 MBq 和摩尔活性为 5.18 MBq/nmol 的 Lu-PSMA-617 进行比较。将 Lu-RIMS-1 和载体作为对照进行评估。使用 Zr-DFO-抗 CD3 进行免疫正电子发射断层扫描（PET），以在治疗过程中可视化 T 细胞分布。Lu-RIMS-1 以>99%的放射化学纯度定量放射性标记，并保持对 PSMA 的高亲和力（=3.77±0.5 nM）。组织蛋白酶 B 在 17.6 小时内有效地释放了整个免疫刺激剂有效载荷。Lu-RIMS-1 在 PSMA(+)肿瘤组织中的摄取可持续至 72 小时（2.65±1.03%ID/g），与 Lu-PSMA-617（3.65±0.59%ID/g）相比无统计学差异（=0.1936）。所有接受 Lu-RIMS-1 治疗的动物均显示肿瘤生长抑制，并提供 30 天的中位生存时间（=0.0007），而 Lu-PSMA-617 提供 15 天的中位生存时间，与载体组（14 天）相比无统计学意义（=0.3548）。免疫 PET 分析显示，与 Lu-PSMA-617 治疗的动物相比，接受 Lu-RIMS-1 治疗的动物肿瘤浸润性 T 细胞增加了 2 倍；与 Lu-PSMA-617 相比，RIMS-1 可改善同种异体小鼠前列腺癌模型中的治疗效果，并引起更多的 T 细胞浸润肿瘤。这些结果支持进一步研究 RIMS 范式作为第一个将放射治疗和免疫刺激结合在一起的单一分子实体的范例。
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