[^99mTc]Tc-NTP 15 - 5, a new proteoglycan tracer for functional imaging of joint cartilage: phase I (CARSPECT)

[^99mTc]Tc-NTP 15 - 5 showed affinity for joint cartilage proteoglycans on preclinical studies but has not been tested in humans. This phase I trial (CARPECT: NCT04481230) aims to define the optimal of [^99mTc]Tc-NTP 15 - 5 injected activity to obtain the best visual contrast of cartilage, without toxicity. Quantitative analyses of cartilage, periarticular uptakes, biodistribution, pharmacokinetic and dosimetry of this new tracer were also studied.

Between November 2020 and June 2022, five patients with unilateral knee osteoarthritis or breast cancer treated with hormonal therapy inducing cartilage disease were injected with [^99mTc]Tc-NTP 15 - 5, at increasing activity levels: 5, 10 and 15 MBq/kg. No major toxicity was reported, according to NCICTC 4.0 scale. With an activity of 15 MBq/Kg, the median rate of joint uptakes higher than diaphysis' one on whole body planar scintigraphy was 80.6% (80.60-85.45) at 2 h p.i. and increased with time. S/N ratio with muscular background measured on SPECT-CT was superior to 3 from 2h30 p.i for cartilage. Uptake evolution depending on time from 1h00 to 6h30 p.i. permitted to discriminate cartilage and pooled proteoglycan structures from background and cartilage from ligaments + tendons for all examination times (p < 0.001), and cartilage from bursa at 1 h p.i. (p < 0.05). Pharmacokinetic, biodistribution and dosimetry were in line with preclinical studies.

This study confirms the usability and accuracy of [^99mTc]Tc-NTP 15 - 5 for cartilage human functional imaging 2 h after injection, at 15 MBq/kg.

Clinicaltrials.gov: NCT04481230. https://clinicaltrials.gov/ct2/show/NCT04481230 . Registration date: November, 12th, 2020.