An imaging study to evaluate the D2 receptor activities and safety of I-123-IBZM SPECT in the differential diagnosis of Parkinsonian syndromes

Objectives 123I-Iodobenzamide (123I-IBZM) functions as a dopamine D2/D3 receptor imaging agent for single photon emission computerized tomography (SPECT). The objective of this study is to evaluate the D2 receptor activities and safety of 123I-IBZM SPECT in the differential diagnosis of Parkinsonian syndromes.

Methods An open-label, multi-center, non-comparative, single-arm study was designed to enroll 100 evaluable subjects aged 50 to 70 years old. Each subject underwent two sets of SPECT imaging: 99mTc-TRODAT-1 to collect the striatum uptake ratio of dopamine transporter (DAT); 123I-IBZM to evaluate the D2 receptor activities in the differential diagnosis of Parkinsonian syndromes and safety of 123I-IBZM SPECT imaging.

Results A total of 100 evaluable subjects were completed for this study, including 40 IPD patients, 40 non-IPD patients (including 25 MSA patients and 15 PSP patients), and 20 normal healthy volunteers. The result of DAT imaging showed a difference in the mean striatal uptake between normal healthy volunteers and PD (IPD+non-IPD) groups. The result of D2 receptor imaging with 123I-IBZM showed increased striatal uptake in the IPD group than that in the non-IPD group. No treatment-emergent AE was observed, and no death, SAE, and other significant adverse event were reported in this study.

Conclusions 123I-IBZM is generally well-tolerated and the study results demonstrated different alterations of dopamine transporter and D2 receptor function between the IPD and non-IPD group. 123I-IBZM might be a promising imaging agent to distinguish IPD and non-IPD group