Preclinical Evaluation of ⁶⁸ Ga-Labeled GSK3326595 for PRMT5 Expression with microPET-CT in Pan-Cancer

PRMT5, a member of the arginine methyltransferase family, is mainly distributed in the nucleus and cytoplasm and is closely involved in tumorigenesis, development, and metastasis. Based on GSK3326595, we first designed and synthesized a PRMT5-targeted precursor (DOTA-FZ-P5R). MOE simulation results indicated a strong binding affinity (KD ≈ 10^-11) of DOTA-FZ-P5R toward PRMT5 (PDB: 4 × 61). The ⁶⁸Ga-labeled tracer exhibited high RCP (>98%) and excellent stability. Western blot and cell uptake studies confirmed that PRMT5 was highly expressed in MDA-MB-231 and AsPC1 cells, while expression in A549 cells was comparatively low. Correspondingly, microPET-CT imaging demonstrated a significantly higher uptake of [⁶⁸Ga]Ga-DOTA-FZ-P5R in MDA-MB-231 and AsPC1 tumor-bearing mice compared to A549. At 30 min postinjection, uptake values were 3.47 ± 1.53%ID/g for MDA-MB-231, 3.63 ± 0.81%ID/g for AsPC1, and 1.53 ± 0.25%ID/g for A549. These results were consistent with PRMT5 expression levels confirmed by IHC, further validating the tracer's specificity and potential for imaging PRMT5 expression <i>in vivo</i>. [⁶⁸Ga]Ga-DOTA-FZ-P5R can dynamically visualize and quantify PRMT5 expression levels in real time across pan-cancer. This research demonstrates that [⁶⁸Ga]Ga-DOTA-FZ-P5R enables rapid imaging of PRMT5-positive tumors. The probe has significant potential to enable individualized and precise diagnosis in patients with PRMT5-positive tumors, define an optimal treatment window, assess therapeutic efficacy, and serve as a predictive imaging modality for tumor resistance.