Head to head comparison of two PET/CT imaging agents, [18F]D3FSP ([18F]P16-129) and [18F]AV45, in patients with alzheimer's disease

Background A new beta-amyloid (A beta) targeting radiotracer, [F-18]D3FSP ([F-18]P16-129), for diagnosis of Alzheimer's disease (AD) is reported. This radiotracer is a deuterated N-methyl derivative of Amyvid (AV-45, florbetapir f18) which was FDA-approved in 2013. Deuteration may alter a tracer's PK such that imaging performance is improved. A head-to-head comparison between these two imaging agents was conducted in AD patients. A separate biodistribution study was conducted on six healthy subjects, and radiation dosimetry estimation was obtained. Results Eight patients, clinically diagnosed with Alzheimer's disease, had an average age of 61.1 +/- 10.0 years, and an average MMSE score of 21 +/- 4. Each patient underwent paired 90-minute dynamic PET/CT scans separately within a few weeks (323 +/- 31 MBq of [F-18]D3FSP or [F-18]AV45; florbetapir f18). SUVR (50-70 min) and Distribution Volume Ratio (DVR) of 43 brain regions were evaluated. The average SUVR across cortical gray matter was 1.65 +/- 0.21 for [F-18]AV45 and 1.65 +/- 0.23 for [F-18]D3FSP, while global DVRs were 1.36 +/- 0.14 and 1.37 +/- 0.13 for [F-18]AV45 and [F-18]D3FSP respectively. Strong correlations (R-2 = 0.8-0.9) were observed between tracers for both SUVR and DVR, with slopes of similar to 0.9 (SUVR) and similar to 1 (DVR). No image artifacts or confounds influenced the visual interpretation of [F-18]D3FSP compared to [F-18]AV45. Conclusions Results showed no difference between [F-18]D3FSP and [F-18]AV45 and no benefit of deuteration at the N-methyl site. Even so, [F-18]D3FSP may be a useful alternative for PET/CT imaging of A beta deposits in the brain as its binding characteristics were very similar to its non-deuterated analog, the FDA-approved drug [F-18]AV45.