New amphiphilic monomers (OCA-DTPAGlu and OCA-DOTA) containing, in the same molecule, three different functions: (i) the chelating agent (DTPAGlu or DOTA) able to coordinate gadolinium ion, (ii) the octreotide bioactive peptide able to target somatostatin receptors, and (iii) a hydrophobic moiety with two 18-carbon atoms alkyl chains have been designed and synthesized by solid-phase methods. The novel amphiphilic monomers aggregate, in water solution, giving stable micelles at very low concentration (cmc values of 2.3 x 10(-6) mol kg(-1) and 2.5 x 10(-6) mol kg(-1) for OCA-DTPAGlu and OCA-DOTA, respectively) as confirmed by fluorescence spectroscopy. Fluorescence studies and circular dichroism experiments indicate, for the two compounds as well as for their gadolinium complexes (OCA-DOTA(Gd) and OCA-DTPAGlu(Gd)), the complete exposure of octreotide on the micelle surface, and the predominant presence of an antiparallel beta-sheet peptide conformation characterized by a beta-like turn. The high relaxivity value (r(1p) = 13.9 mM(-1) s(-1) at 20 MHz and 25 degrees C), measured for micelles obtained by the gadolinium complex OCA-DTPAGlu(Gd), indicates these aggregates as promising target-selective magnetic resonance imaging (MRI) contrast agents.

The present work describes new supramolecular aggregates obtained by co-assembling two different amphiphilic molecules, one containing the bioactive bombesin peptide (BN), or a scramble sequence, and the other, the DOTA chelating agent, (C18)(2)DOTA, capable of forming stable complexes with the radioactive (111)In(III) isotope. The peptide in the amphiphilic monomer is spaced by the lipophilic moiety through ethoxylic spacers of different length: a shorter spacer with five units of dioxoethylene moieties in (C18)(2)L5-peptide, or a longer spacer consisting of a Peg3000 residue in (C18)(2)Peg3000-peptide. Structural characterization by SANS and DLS techniques indicates that, independently from the presence of the peptide containing monomer in the final composition, the predominant aggregates are liposomes of similar shape and size with a hydrodynamic radius R(h) around 200 nm and bilayer thickness, d, of 4 nm. In vitro data show specific binding of the (111)In-(C18)(2)DOTA/(C18)(2)L5-[7-14]BN 90:10 liposomes in receptor expressing cells. However, the presence of the Peg3000 unit on the external liposomal surface, could hide the peptide and prevent the receptor binding. In vivo experiments using (111)In-(C18)(2)DOTA/(C18)(2)L5-[7-14]BN show the expected biological behavior of aggregates of such size and molecular composition, moreover there is an increase in concentration of the GRPR targeting aggregate in the tumors compared to control at the 48 h time point evaluated (2.4% ID/g versus 1.6% ID/g).

New mixed nanoparticles were obtained by self-aggregation of two amphiplic monomers. The first monomer (C18)(2) L5-Oct contains two C18 hydrophobic moieties bound to the N-terminus of the cyclic peptide octreotide, and spaced from the bioactive peptide by five units of dioxoethylene linkers. The second monomer, (C18)(2) DTPAGlu, (C18)(2) DTPA or (C18)(2) DOTA, and the corresponding Gd(III) complexes, contains two C18 hydrophobic moieties bound through a lysine residue to different polyamino-polycarboxy ligands: DTPAGlu, DTPA or DOTA. Mixed aggregates have been obtained and structurally characterized by small angle neutron scattering (SANS) techniques and for their relaxometric behavior. According to a decrease of negative charges in the surfactant head-group, a total or a partial micelle-to-vesicle transition is observed by passing from (C18)(2) DTPAGlu to (C18)(2) DOTA. The thicknesses of the bilayers are substantially constant, around 50 Å, in the analyzed systems. Moreover, the mixed aggregates, in which a small amount of amphiphilic octreotide monomer (C18)(2) L5-Oct (10% mol/mol) was inserted, do not differ significantly from the respective self-assembled systems. Fluorescence emission of tryptophan residue at 340 nm indicates low mobility of water molecules at the peptide surface. The proton relaxivity of mixed aggregates based on (C18)(2) DTPAGlu(Gd), (C18)(2) DTPA(Gd) and (C18)(2) DOTA(Gd) resulted to be 17.6, 15.2 and 10.0 mM(-1) s(-1) (at 20 MHz and 298K), respectively. The decrease in the relaxivity values can be ascribed to the increase in τ(M) (81, 205 and 750 ns). The presence of amphiphilic octreotide monomer exposed on mixed aggregate surface gives the entire nanoparticles a potential binding selectivity toward somatostatin sstr2 receptor subtype, and these systems could act as MRI target-specific contrast agent.

Tenarad RIT is effective in chemorefractory HL and resulted in objective responses or clinical benefit in the majority of patients. Toxicity was acceptable despite the high load of prior treatments, previous ASCT and multiple Tenarad administrations. Further studies are planned to define the most effective schedule for this type of RIT in HL patients.

Purpose: This study addresses novel peptide modified liposomal doxorubicin to specifically target tissues overexpressing bombesin (BN) receptors. Methods: DOTA-(AEEA)(2)-peptides containing the [7-14]bombesin and the new BN-AA1 sequence have been synthesized to compare their binding properties and in serum stabilities. The amphiphilic peptide derivative (MonY-BN-AA1) containing BN-AA1, a hydrophobic moiety, polyethylenglycole (PEG), and diethylenetriaminepentaacetate (DTPA), has been synthesized. Liposomes have been obtained by mixing of MonY-BN-AA1 with 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). Results: Both (111)In labeled peptide derivatives present nanomolar Kd to PC-3 cells. (177)Lu labeled peptide DOTA-(AEEA)(2)-BN-AA1 is very stable (half-life 414.1 h), while DOTA-(AEEA)(2)-BN, shows a half-life of 15.5 h. In vivo studies on the therapeutic efficacy of DSPC/MonY-BN-AA1/Dox in comparison to DSPC/MonY-BN/Dox, were performed in PC-3 xenograft bearing mice. Both formulations showed similar tumor growth inhibition (TGI) compared to control animals treated with non-targeted DSPC/Dox liposomes or saline solution. For DSPC/MonY-BN-AA1/Dox the maximum effect was observed 19 days after treatment. Conclusions: DSPC/MonY-BN-AA1/Dox nanovectors confirm the ability to selectively target and provide therapeutic efficacy in mice. The lack of receptor activation and possible acute biological side effects provided by using the AA1 antagonist bombesin sequence should provide safe working conditions for further development of this class of drug delivery vehicles.