Towards translation of 212Pb as a clinical therapeutic; getting the lead in!

Abstract

Targeted α-particle therapy offers the potential for more specific tumor cell killing with less damage to surrounding normal tissue than β-emitters because of the combination of short path length (50-80 μm) with the high linear energy transfer (100 keV μm(-1)) of this emission. These physical properties offer the real possibility of targeted (pre-targeted) α-therapy suitable for the elimination of minimal residual or micrometastatic disease. Targeted and pre-targeted radioimmunotherapy (RIT) using α-emitters such as (212)Bi (T(1/2) = 1.01 h) and (212)Pb (T(1/2) = 10.6 h) has demonstrated significant utility in both in vitro and in vivo model systems. (212)Pb, a promising α-particle emitting source, is the longer-lived parent nuclide of (212)Bi, and serves as an in vivo generator of (212)Bi. The radionuclide has been successfully used in RIT and pre-targeted RIT and demonstrated an enhanced therapeutic efficacy in combination with chemotherapeutics, such as gemcitabine and paclitaxel. The following perspective addresses the modes of radionuclide production, radiolabelling and chelation chemistry, as well as the application of (212)Pb to targeted and pre-targeted radiation therapy.

Figure 1

Decay Schemes for the Production of ²¹²Pb

Figure 2

Selected Structure of DOTA and its analogues in RIT

Figure 3

Image with ²⁰³Pb-B72.3-DOTA in athymic mice bearing LS-174T tumors.

Figure 4

Structure of ²¹²Pb-DOTA-Re(Arg¹¹)CCMSH and ²⁰³Pb-DOTA-Re(Arg¹¹)CCMSH