Pickering emulsions with ethiodized oil and nanoparticles for slow release of intratumoral anti-CTLA4 immune checkpoint antibodies.

BACKGROUND: Intratumorous immunotherapy for cancer is currently thriving. The aim of such local strategy is to improve the therapeutic index of these treatments, for higher on-target/on-tumor activity and less on-target/off-tumor adverse events. Strategies allowing for slow release of anti-CTLA4 in the tumor microenvironment could improve their clinical efficacy.The purpose of the study was to develop a radiopaque delivery platform to improve the targeting and exposure of intratumorous anti-CTLA4 antibodies for cancer immunotherapy. METHODS: Pickering emulsions of anti-CTLA4 antibodies were formulated with radiopaque ethiodized oil and poly-lactic-co-glycolic acid (PLGA) nanoparticles. We characterized the microscopic aspect and stability of such emulsions using Turbiscan. We monitored the release of anti-CTLA4 over time from these emulsions and evaluated their structure using mass spectrometry. We then tested the functionality of the released antibodies by preforming ex vivo competitive binding assays. Finally, we assessed the in vivo efficacy of intratumorous anti-CTLA4 Pickering emulsions. RESULTS: Pickering emulsions of ethiodized oil and PLGA nanoparticles (PEEPs) resulted in a radiopaque water-in-oil emulsion with average internal phase droplet size of 42±5 µm at day 7. Confocal microscopy showed that anti-CTLA4 antibodies were effectively encapsulated by ethiodized oil with PLGA nanoparticles located at the interface between the aqueous and the oily phase. Turbiscan analysis showed that emulsions were stable with continuous and progressive release of anti-CTLA4 antibodies reaching 70% at 3 weeks. Structural and functional analysis of the released antibodies did not show significant differences with native anti-CTLA4 antibodies. Finally, intratumorous anti-CTLA4 PEEPs were able to eradicate tumors and cure mice in a syngeneic immunocompetent preclinical tumor model. CONCLUSION: Pickering emulsions of ethiodized oil and PLGA is an innovative radiopaque delivery platform that does not alter the functionality of anti-CTLA4 immune checkpoint antibodies. Beyond local anti-CTLA4 applications, these emulsions might be used with other therapeutic molecules for optimal intratumorous or intra-arterial delivery of novel cancer immunotherapies.

CD34+ immunoselection of autologous grafts for the treatment of high-risk neuroblastoma.

BACKGROUND: Graft contamination has been blamed for causing relapse in children with high-risk neuroblastoma (HRNB) after autologous hematopoietic stem cell transplantation (HSCT). PROCEDURE: We report the long-term results of hematopoietic reconstitution, post-transplant complications, and clinical outcome of 44 children with HRNB treated with busulfan/melphalan high-dose chemotherapy followed by transplantation of purged CD34+ immunoselected autologous peripheral HSCT. Minimal residual disease (MRD) of grafts was evaluated by anti-GD2 immunofluorescence or tyrosine hydroxylase reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: Contaminating neuroblasts were found in 19/38 grafts (50%) before CD34+ positive selection, and none after (technique sensitivity of one cell in 10(5)). A median of 6.5 × 10(6) CD34+ cells/kg (range 0.8-23.7) were transplanted with only 2% of TRM. Neutrophils and platelet recovery occurred within a median of 12 days (range 9-47) and 44 days (range 12-259), respectively, without any secondary graft failure. Twenty-three percents of patients experienced a sepsis (10/44) and 14% a pyelonephritis (6/44). Recurrence of varicella zoster virus occurred in 21% of patients (9/44). Negative RT-PCR MRD within the leukapheresis product and cis-retinoic acid therapy were significantly and independently associated to a better survival (P < 0.05). Overall and event-free survivals at 5 years post-transplant were at 59.3% and 48.3% respectively. CONCLUSIONS: Besides high rates of manageable infections due to late immune recovery, transplantation with CD34+ immunoselected grafts in HRNB children was feasible and did not affect long-term hematopoiesis.