Tc-99m-NTP 15-5 is a companion radiotracer for assessing joint functional response to sprifermin (rhFGF-18) in a murine osteoarthritis model

With the emergence of disease modifying osteoarthritis drugs (DMOAD), imaging methods to quantitatively demonstrate their efficacy and to monitor osteoarthritis progression at the functional level are urgently needed. Our group showed that articular cartilage can be quantitatively assessed in nuclear medicine imaging by our radiotracer Tc-99m-NTP 15-5 targeting cartilage proteoglycans. In this work, surgically induced DMM mice were treated with sprifermin or saline. We investigated cartilage remodelling in the mice knees by Tc-99m-NTP 15-5 SPECT-CT imaging over 24 weeks after surgery, as wells as proteoglycan biochemical assays. OA alterations were scored by histology according to OARSI guidelines. A specific accumulation of Tc-99m-NTP 15-5 in cartilage joints was evidenced in vivo by SPECT-CT imaging as early as 30 min post-iv injection. In DMM, Tc-99m-NTP 15-5 accumulation in cartilage within the operated joints, relative to contralateral ones, was observed to initially increase then decrease as pathology progressed. Under sprifermin, Tc-99m-NTP 15-5 uptake in pathological knees was significantly increased compared to controls, at 7-, 12- and 24-weeks, and consistent with proteoglycan increase measured 5 weeks post-surgery, as a sign of cartilage matrix remodelling. Our work highlights the potential of Tc-99m-NTP 15-5 as an imaging-based companion to monitor cartilage remodelling in OA and DMOAD response.