166 Ho-HA Evaluation as therapeutic agent for rheumatoid arthritis treatment

Aim: Rheumatoid arthritis is a limiting disease having, among its pathological features, the inflammation of synovial tissue with progressive and later destruction of the articulation. This lead to joint deformation and loss of its function, generating pain and reducing the mobility of the affected articulation. The aim was to evaluate 166Ho-Hydroxyapatite (166 Ho-HA) as potential radiopharmaceutical for the syntomatic treatment of chronic and acute arthritis Materials and Methods: 166Holmiun was produced by irradiation of Ho2O3 at La Reina Research Reactor, Nuclear Chilean Energy Commission. Hydroxyapatite was in-house synthetized. Its labelling and quality controls follows the internationally accepted procedures. An antigen arthritis was induced to eight New Zealand rabbits with the 166Ho-HA radiochemical being administred thereafter in two dosage modalities (single and double). The compound therapeutic efficiency was evaluated based upon clinical improvement and images from the inflamated articulation using 67Ga citrate before and after 166 Ho-HA injection. Results: The radiochemical purity of the innoculated compound was greater than 98% as measured under sterility conditions. Clinically, an inflamation reduction (2 cm), appetite improvement and general well being was observed. The 166 Ho-HA distribution and localization was monitored using gamma camera images taken at 4 and 24 h. There was no evidence of extraarticular leakage. From the 67Ga citrate imaging, the acute group shows an overall improvement of well being corresponding to a lesser uptake at the inflamated articulation, regarding to the chronic group. The 166Ho-HA double dosis, compared to the single dosis, suggest a reduced uptake of 67Ga citrate at the inflamated tissue, meaning an increased therapeutic effect. Conclusions: 166 Ho-HA is usefull as therapeutic agent for the syntomatic treatment of rheumatoideal arthritis as shown by imaging and clinical examination (author)