Optimising the radioimmunotherapy of malignant disease: the broadening choice of carrier and effector moieties

Production and characterization of 111Ag radioisotope for medical use in a TRIGA Mark II nuclear research reactor

Radio Pharmaceutical Therapy (RPT) comes forth as a promising technique to treat a wide range of tumors while ensuring low collateral damage to nearby healthy tissues. This kind of cancer therapy exploits the radiation following the decay of a specific radionuclide to deliver a lethal dose to tumor tissues. In the framework of the ISOLPHARM project of INFN, ¹¹¹Ag was recently proposed as a promising core of a therapeutic radiopharmaceutical. In this paper, the production of ¹¹¹Ag via neutron activation of ¹¹⁰Pd-enriched samples inside a TRIGA Mark II nuclear research reactor is studied. The radioisotope production is modeled using two different Monte Carlo codes (MCNPX and PHITS) and a stand-alone inventory calculation code FISPACT-II, with different cross section data libraries. The whole process is simulated starting from an MCNP6-based reactor model producing the neutron spectrum and flux in the selected irradiation facility. Moreover, a cost-effective, robust and easy-to-use spectroscopic system, based on a Lanthanum Bromo-Chloride (LBC) inorganic scintillator, is designed and characterized, with the aim of using it, in the future, for the quality control of the ISOLPHARM irradiated targets at the SPES facility of the Legnaro National Laboratories of INFN. ^natPd and ¹¹⁰Pd-enriched samples are irradiated in the reactor main irradiation facility and spectroscopically characterized using the LBC-based setup and a multiple-fit analysis procedure. Experimental results are compared with theoretical predictions of the developed models, showing that inaccuracies in the available cross section libraries prevent an accurate reproduction of the generated radioisotope activities. Nevertheless, models are normalized to our experimental data allowing for a reliable planning of the ¹¹¹Ag production in a TRIGA Mark II reactor.

188Re DD-3B6/22 Fab' for use in therapy of ovarian cancer: labelling and animal studies

A fast and high yielding method of 188Re radiolabelling DD-3B6/22 Fab' is described. An inert atmosphere [N2(g)] and ascorbic acid was essential for preparation and storage of therapeutic levels (< or =2 GBq/mg) for up to 24 h. Immunoreactivity was greater than 75%. Pharmacokinetic studies in nu/nu mice demonstrated localisation of 188Re DD-3B6/22 Fab' was equivalent and correlated well with the behaviour observed for 99mTc DD-3B6/22 Fab' used to image ovarian cancer. Excellent stability at the target site in vivo supports the potential use of 188Re DD-3B6/22 Fab' in the therapy of ovarian cancer.

Silver(I) Complexes of the Derivatized Crown Thioether Ligands 3,6,9,12,15,18-Hexathianonadecanol and 3,6,9,13,16,19-Hexathiaicosanol. Determination of Stability Constants and the Crystal Structures of [Ag(19-aneS6-OH)][CF(3)SO(3)] and [Ag(20-aneS6-OH)][BF(4)]

The derivatized 19- and 20-membered macrocyclic thio crowns 3,6,9,12,15,18-hexathianonadecanol C(13)H(26)OS(6) (19-aneS6-OH) (1) and 3,6,9,13,16,19-hexathiacycloicosanol C(14)H(28)OS(6) (20-aneS6-OH) (2) have been synthesized by [1 + 1] cyclization in about 30% yield. The ligands 1 and 2 react readily at room temperature with different silver(I) salts in water and in organic solvents to form in quantitative yields the complexes [Ag(19-aneS6-OH)](+) (3) and [Ag(20-aneS6-OH)](+) (4) for which crystals of X-ray quality were grown by slow diffusion of diethylether into methanol. [Ag(19-aneS6-OH)][CF(3)SO(3)] crystallizes in the triclinic space group P&onemacr; with Z = 2, a = 10.760(1), b = 10.853(2) and c = 11.326(2)Å, and alpha = 78.73(1), beta = 73.47(1), and gamma = 74.99(1) degrees. [Ag(20-aneS6-OH)][BF(4)] also crystallizes in the triclinic space group P&onemacr; with Z = 4. The unit cell constants were determined with a = 10.076(4), b = 10.525(3), and c = 22.135(8)Å, alpha = 93.32(2), beta = 102.43(2), and gamma = 100.32(2) degrees. The complex cations [Ag(19-aneS6-OH)](+) and [Ag(20-aneS6-OH)](+) are coordinated through only four sulfur atoms; thus, a distorted tetrahedral coordination geometry is exhibited. In addition we found a highly asymmetric Ag-S bond lengths distribution throughout all complex cations. The stability constants of [Ag](+) with 1 and 2 and, for comparison with [18-aneS6] (5), have been determined in methanol by potentiometric [Ag](+) measurements. Log K values for the formation of 3, 4, and [Ag(18-aneS6](+) (6) are 12.04 +/- 0.19, 11.49 +/- 0.15, and 12.67 +/- 0.13 respectively. Owing to a comparable macrocyclic effect, the similar log K values are reasonable but, since 6 coordinates octahedrally, not expected. (1)H and (13)C NMR investigations at various temperatures give evidence for fluxional coordinative behavior between all six sulfur atoms in solution. Consequently [Ag(19-aneS6-OH)](+), [Ag(20-aneS6-OH)](+), and [Ag(18-aneS6](+) seem to exhibit principally the same solution structures although the solid structures are very different.