Antibody-Directed Polymersomal Nanomedicines For Targeted Chemotherapy Of Hematological Malignancies

Hematological malignancies(HM)are a serious threat to human health.Chemotherapy and small molecule targeted therapy,as the main therapeutic regimens,are perplexed with poor selectivity and short half-life in vivo,leading to severe adverse effects,drug resistance and high relapse rate that correlated with disappointing outcomes of patients.In the recent decade,antibodies and antibody-drug conjugates(ADCs)based targeted therapies have made clinical progress for HM patients.However,large antibody dosage and combination with chemotherapeutics are generally needed,inevitably facing the drawbacks of chemotherapy.Nanomedicines,particularly ligand-installed ones,are promising in improving the performance of chemotherapeutics.Nevertheless,the development of actively targeted nanomedicines for HM therapy lagged far behind,and most of them remain suboptimal with inadequate stability,mediocre HM selectivity,insufficient cellular uptake and uncontrollable drug release.To this end,via comparing different targets,antibody-modified polymersomal nanomedicines were designed in this thesis to combine the advantages of specific antibodies with robust yet reduction-sensitive disulfide-crosslinked polymersomes,thus efficiently delivering chemotherapeutics using a small amount of antibodies to potently treat disseminated HM.In Chapter 1,the status quo and frontline regimens for HM,in particular acute lymphoblastic leukemia(ALL)and multiple myeloma(MM)were summarized.The cutting-age development of monoclonal antibodies and ADCs as well as nanomedicines and actively targeted nanomedicines for ALL and MM therapy were also briefly discussed.In Chapter 2,daratumumab or anti-CD19 antibody-modified disulfide-crosslinked polymersomes were constructed for CD38 and CD 19 targeted delivery of vincristine sulfate(VCR),respectively,to compare their anti-B-ALL activity thus providing an optimized targeted therapy for B-ALL.VCR is an essential and first line chemotherapy drug for ALL patients.Antibody-modified polymersomal VCR was prepared via co-assembly of PEG-P(TMC-DTC)-KD5 and N3-PEG-P(TMC-DTC)with simultaneous VCR loading and post modification with antibodies.CD38-targeting DP-VCR and CD 19-targeting aCD19P-VCR both have tunable surface antibody density,small sizes(44-51 nm),high VCR loading and high stability.DP-VCR showed selective uptake in 697 B-ALL cells with higher endocytosis than aCD19P-VCR and induced strong anti-ALL activity(IC50:0.06 nM VCR),which was 4.0 and 13.7-fold more potent than P-VCR and free VCR,respectively.In contrast,no toxicity to human peripheral blood mononuclear cells(PBMC)was detected for DP-VCR even at 108.3 nM VCR.Moreover,DP-VCR also exhibited superior in vivo anti-ALL activity to aCD19P-VCR,displaying significant survival benefit and marked reduction of leukemia burden in both 697 and Nalm-6-Luc orthotopic B-ALL models as compared to all controls.Importantly,DP-VCR induced little side effects.Encouraged by the remarkable anti-ALL efficacy of CD38-directed chemotherapy,daratumumab-polymersome-mertansine conjugates(DP-DM1)were fabricated in Chapter 3 to compare the anti-ALL effect of DM1 and VCR to further optimize the CD3 8-targeted nanotherapy.DM1,as one of the most commonly used toxin warheads in ADCs,has potent antineoplasmic activity in both HM and solid tumors.DP-DM1 was engineered via co-assembly of PEG-P(TMC-DTC)and N3-PEG-P(TMC-DTC)with simultaneous DM1 conjugation into the hydrophobic membrane through disulfide linkages,followed by modification with daratumumab.DP-DM1 had a high drug-to-antibody ratio of 163-643,which was tens to hundred times higher than that of ADCs and could significantly reduce the use of antibodies.Similar as DP-VCR in Chapter 2,DP-DM1 enabled selective targeting to CD38-positive B-ALL cells and therefore effectively inhibited the progression of orthotopic 697 ALL bearing mice,showing significantly prolonged survival than P-DM1 and free DM1.The survival benefit of mice after treatment with DP-DM1 was overall comparable to that of DP-VCR,yet with higher leukemia burden in the liver.Unlike B-ALL,T-cell ALL(T-ALL)lacks mature targeting antigen and is more aggressive with higher relapse rate.Moreover,there is no effective therapeutic regimen for relapsed patients,leading to extremely low 5-year survival rate.It is therefore urgent to develop effective targeted therapies for T-ALL.In light of the overexpression of CD38 and CD7 in T-ALL patients,anti-CD7 nanobody-modified P-VCR(aCD7P-VCR)was constructed in Chapter 4 to compare its therapeutic efficacy with that of DP-VCR in orthotopic CCRF-CEM T-ALL model and investigate the effect of monovalent(mo)and bivalent(bi)nanobodies.Both aCD7P-VCR and DP-VCR exhibited selective targeting and uptake in CCRF-CEM T-ALL cells,inducing strong cytotoxicity with an IC50 of ca.0.1 nM.In contrast,aCD7P-VCR was non-toxic to human PBMC and T cells even at a VCR concentration of 10.8 nM.In orthotopic CCRF-CEM T-ALL bearing mice,aCD7moP-VCR and aCD7biP-VCR with different nanobody surface densities all significantly inhibited the proliferation and infiltration of T-ALL cells in other organs,thus markedly prolonged the survival time.Among which aCD7moP-VCR was more effective and its therapeutic benefits could be further improved via increasing the administration cycle and total dose.However,DP-VCR displayed limited anti-T-ALL efficacy,indicating the superiority of CD7-targeted nanotherapy for T-ALL.The significant anti-ALL efficacy of targeted VCR nanotherapies drive us to further expand the application of P-VCR nanoplatform to MM.In Chapter 5,anti-BCMA antibody-modified P-VCR(aBP-VCR)was designed for BCMA-targeted chemotherapy of orthotopic LP-1-Luc MM model.aBP-VCR with varying antibody surface densities could effectively target to BCMA-positive MM cells and showed a tumor inhibition rate of over 99.0%,which was 18-fold higher than P-VCR,thus relieved osteolysis and significantly prolonged the survival time.In Chapter 6,a summary of the thesis and prospects for following works were provided.