31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Ruthenium(II) cis-triaminocyclohexane complexes as anti-cancer compounds

Ruthenium complexes are promising candidates for the treatment of cancers. Two ruthenium(III) complexes have previously completed phase I clinical trials and half-sandwich ruthenium(II) η6-arene complexes are receiving much interest as anti-cancer agents. A range of new ruthenium(II) complexes have been prepared with a κ3-N fac-coordinating six electron donor, cis-1,3,5-triaminocyclohexane (cis-tach), replacing the η6-arene ligand. It is hypothesised that the cis-tach ligand will allow highly active complexes with good water solubility. Initial access to ruthenium(II) cis-tach complexes was established with triphenylphosphane ligands, yielding the complexes [RuCl(cis-tach)(PPh3)2]Cl and [RuCl2(cis-tach)(PPh3)]. The complexes adopt a piano-stool type structure, similar to η6-arene complexes. Use of labile dmso ligands in [RuCl(dmso-S)2(cis-tach)]Cl permitted the preparation of a range of complexes. Those with N–N and P–P bidentate chelating ligands, following the formula [Ru(dmso-S)(N–N)(cis-tach)]2+ and [RuCl(P–P)(cis-tach)]+ were studied. Complexes with N–N chelating ligands were found to be inert to substitution in aqueous solution compared to the bis-dmso complex, and were inactive in tumour growth inhibition. The complexes with chelating diphosphane ligands are highly water-soluble, with excellent in vitro activity in the inhibition of tumor cell growth; two of which were found to exceed that of cisplatin. A structure-activity relationship is discussed, and two compounds were selected for further study for their good water solubility and high activity respectively. The aqueous chemistry and the interaction of two of these complexes with small models of biomolecules and DNA was also investigated

<i>cis</i>-1,3,5-Triaminocyclohexane as a Facially Capping Ligand for Ruthenium(II)

Reaction of <i>cis-</i>[RuCl₂(DMSO-<i>S</i>)₃(DMSO-<i>O</i>)] with <i>cis</i>-1,3,5-triaminocyclohexane (tach) results in the formation of [RuCl­(tach)­(DMSO-<i>S</i>)₂]­Cl, a valuable precursor for a wide range of other tach-containing Ru complexes. Reaction of [RuCl­(tach)­(DMSO-<i>S</i>)₂]Cl with the chelating nitrogen-based ligands (N–N = bipyridine, phenanthroline, and ethylenediamine) affords [Ru­(N–N)­(DMSO-<i>S</i>)₂(tach)]­[Cl]₂. A similar reaction between [RuCl­(tach)­(DMSO-<i>S</i>)]Cl with the chelating phosphorus-based ligands (P–P = dppm, dppe, dppp, dppb, dppv, and dppben) leads to the formation of [RuCl­(P–P)­(tach)]­Cl. The structures of 10 examples of the tach-containing complexes have been determined by single crystal X-ray diffraction. An examination of the structural metrics obtained from these studies indicates that the tach ligand is a strong sigma donor. In addition, the presence of the NH₂ groups in the tach ligand allow for participation in hydrogen bonding further modulating the coordinative properties of the ligand

<i>cis</i>-1,3,5-Triaminocyclohexane as a Facially Capping Ligand for Ruthenium(II)

Reaction of <i>cis-</i>[RuCl₂(DMSO-<i>S</i>)₃(DMSO-<i>O</i>)] with <i>cis</i>-1,3,5-triaminocyclohexane (tach) results in the formation of [RuCl­(tach)­(DMSO-<i>S</i>)₂]­Cl, a valuable precursor for a wide range of other tach-containing Ru complexes. Reaction of [RuCl­(tach)­(DMSO-<i>S</i>)₂]Cl with the chelating nitrogen-based ligands (N–N = bipyridine, phenanthroline, and ethylenediamine) affords [Ru­(N–N)­(DMSO-<i>S</i>)₂(tach)]­[Cl]₂. A similar reaction between [RuCl­(tach)­(DMSO-<i>S</i>)]Cl with the chelating phosphorus-based ligands (P–P = dppm, dppe, dppp, dppb, dppv, and dppben) leads to the formation of [RuCl­(P–P)­(tach)]­Cl. The structures of 10 examples of the tach-containing complexes have been determined by single crystal X-ray diffraction. An examination of the structural metrics obtained from these studies indicates that the tach ligand is a strong sigma donor. In addition, the presence of the NH₂ groups in the tach ligand allow for participation in hydrogen bonding further modulating the coordinative properties of the ligand