Properties:
Erbium-169 (169Er) is a gamma and beta emitter with a half-life of 9.4 d. It emits gamma rays at 8 keV (0.16%) and beta rays at 351 (55%) and 343 keV (45%).
Manufacturing:
169Er is produced by irradiation of 168Er with thermal neutrons [168Er(n,γ)169Er] and therefore, cannot be obtained carrier free.
Source and availability:
There is only one site in the world (Russia) that irradiates targets of 168Er and the demand is very low. There is not much competition for this radionuclide either. However, the production of 169Er will face a major issue as the starting material 168Er is becoming extremely scarce and its price has soared.
Derivatives:
There are limited applications. The major application is for use in radiosynovectomy (finger joints) in Europe and some Asian countries (e.g., the Philippines) with 169Er-Erbium citrate. The average dose used for this modality remains below 1 mCi per joint.
Price:
Bulk 169Er is available at around EUR 10/mCi (US$ 13/mCi), but this price may increase drastically within the next years.
Issues:
Radionuclide only available as carrier-added bulk product and used for local injection.
Comments:
The long half-life, the low energy and the very low specific activity does not make 169Er an interesting candidate for therapy with labeled molecules. There are no identified development programs for 169Er-labeled molecules.
The upcoming unavailability of the precursor 168Er and the high price have pushed the companies Clear Vascular and R-NAV, now Serene, to suggest 117mSn as an alternative to 169Er for applications in radiosynovectomy.