Drug-free macromolecular therapeutics – a new paradigm in polymeric nanomedicines

The tumor microenvironment in the majority of cancers is known to favor polarization of tumor-associated macrophages (TAMs) to alternatively activated M2 phenotype, promoting disease progression and reducing patient survival. Effective therapy targeting this M2 macrophage population is thus a promising adjuvant to approved cancer therapies. One of the challenges in targeting M2-like TAMs is a lack of high affinity targeting ligand with good selectivity over anti-tumor M1-like TAMs. We have previously identified an M2 macrophage-targeting peptide (M2pep) that binds preferentially to murine M2 macrophages and M2-like TAMs. A fusion peptide of M2pep with pro-apoptotic peptide KLA (M2pepKLA) was further used to reduce TAM population in vivo but high concentrations and frequent dosing were required due to low binding affinity of M2pep for M2 macrophage. The goal of this study was to develop more potent TAM depletion constructs by increasing the valency of both the M2pep targeting and KLA drug domains. Divalent and tetravalent displays of M2pep ([M2pep]2-Biotin and [M2pep]4-Biotin) were synthesized and evaluated for improvement in binding avidity to the murine macrophages. High avidity and selective binding of [M2pep]2-Biotin to M2 macrophages was achieved with at least 10-fold lower concentration than required for monovalent M2pep activity. Increasing M2pep valency to four, however, resulted in a reduction in both binding activity and selectivity. Surprisingly, both divalent and tetravalent M2pep, without conjugation of any cytotoxic drug cargo, exhibited M2 macrophage-selective toxicity not observed in monovalent M2pep treatment. We next synthesized divalent M2pep with monovalent and divalent KLA ([M2pep]2-[KLA] and [M2pep]2-[KLA]2) to evaluate its enhanced potency compared to M2pepKLA. While both constructs were significantly more toxic than M2pepKLA to primary, bone marrow-derived M2 macrophage, desired selectivity was retained only with [M2pep]2-[KLA]. Finally, we evaluated all multivalent M2pep and M2pepKLA analogs using a syngeneic CT-26 tumor cell suspension. In this setting, [M2pep]4-Biotin and [M2pep]2-[KLA]2 exhibited selective toxicity to both M2-like TAMs and malignant cells but not to M1-like TAMs. Therefore, these constructs are promising anti-cancer constructs with dual-modality mechanisms: malignant cell killing and TAM-based immunomodulation.

Section: Resultsmentioning

confidence: 99%

Synthesis and evaluation of multivalent M2pep peptides for targeting alternatively activated M2 macrophages

Ngambenjawong

Cieslewicz

Schellinger

et al. 2016

“…Macromolecular therapeutics employ biomimetic strategies to stimulate or control specific cellular activities [36,37]. The research presented here is based on a novel paradigm in the nanomedicine research area – drug-free macromolecular therapeutics [9]. The basic idea is to induce apoptosis by crosslinking of cell-surface (slowly internalizing) receptors mediated by the biorecognition of high-fidelity natural binding motifs, such as antiparallel coiled-coil peptides [10] or complementary oligonucleotides [12].…”

Section: Introductionmentioning

confidence: 99%

Drug-free macromolecular therapeutics: Impact of structure on induction of apoptosis in Raji B cells

Zhang

Fang

Yang

et al. 2017

Self Cite

Recently, we developed a new paradigm in macromolecular therapeutics that avoids the use of low molecular weight drugs. The activity of the “drug-free macromolecular therapeutics” is based on the biorecognition of complementary motifs at cell surface resulting in receptor crosslinking and apoptosis induction. The system is composed of two nanoconjugates: (1) a single-stranded morpholino oligonucleotide (MORF1) attached to an anti-CD20 Fab′ fragment (Fab′-MORF1); (2) multiple copies of complementary oligonucleotide MORF2 grafted to a linear polymer of N-(2-hydroxypropyl)methacrylamide (HPMA) – P-(MORF2)x. The two conjugates crosslink CD20 antigens via MORF1-MORF2 hybridization at the surface of CD20+ malignant B-cells and induce apoptosis. Preclinical studies in a murine model of human non-Hodgkin’s lymphoma showed cancer cells eradication and long-term survivors. The aim of this study was to determine the relationship between the detailed structure of the nanoconjugates and apoptosis induction in Raji cells to allow system optimization. The factors studied include the length of the MORF sequence, the valence of P-(MORF2)x (varying x), molecular weight of P-(MORF2)x, incorporation of a miniPEG spacer between Fab′ and MORF1 and between polymer backbone and pendant MORF2, and comparison of two Fab′ fragments, one from 1F5 antibody (Fab′1F5), the other from Rituximab (Fab′RTX). The results of apoptosis induction in human Burkitt’s B-cell non-Hodgkin’s lymphoma (NHL) Raji cells as determined using three apoptotic assays (Annexin V, Caspase 3, and TUNEL) indicated that: a) An improvement of apoptotic activity was observed for a 28 base pair MORF sequence when compared to MORFs composed of 20 and 25 base pairs. The differences depended on type of assay, concentration and exposure schedule (consecutive vs. premixed). b) The higher the valence of P-(MORF2)x the higher the levels of apoptosis. c) Higher molecular weight of P-(MORF2)x induced higher levels of apoptosis. d) A miniPEG8 spacer was effective in enhancing apoptotic levels in contrast to a miniPEG2 spacer. e) There was not a statistically significant difference when comparing Fab′1F5-MORF1 with Fab′RTX-MORF1.

“…Thus we hypothesized that if we can crosslink graft copolymers with concomitant formation of hydrogels, we could crosslink cell surface (non-internalizing) CD20 receptors with simultaneous apoptosis induction. Indeed, we succeeded and the activity of this system both in vitro and in vivo was far better than we expected [reviewed in 200]. …”

Section: New Paradigm: Drug-free Macromolecular Therapeuticsmentioning

confidence: 93%

“…In addition to NHL therapy, it may be used for the treatment of other B cell related diseases – rheumatoid arthritis, idiopathic thrombocytopenic purpura, hemolytic anemia [246–247], and multiple sclerosis [249]. Moreover, in addition to CD20, other slowly internalizing receptors may be used as targets, such as CD45, death receptor 4, prostate cell antigen, and carcinoembryonic antigen [200]. …”

Section: Conclusion and Future Prospectsmentioning

confidence: 99%

Design of smart HPMA copolymer-based nanomedicines

Yang

Kopeček

2016

Self Cite

The state-of-the art in water-soluble macromolecular therapeutics has been reviewed. First the design principles for polymer-drug conjugates are discussed followed by two recent developments in the field: a) The design, synthesis and properties of backbone degradable N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-drug conjugates. The enhanced intravascular half-life of such conjugates creates a concentration gradient (blood vs. tumor) for an extended time interval resulting in increased solid tumor accumulation by enhanced permeability and retention (EPR) effect with concomitant increase in efficacy. b) Drug-free macromolecular therapeutics is a new paradigm in macromolecular therapeutics. Apoptosis in malignant cell is induced by crosslinking of cell surface non-internalizing receptors. Crosslinking of receptors is mediated by the biorecognition of two nanoconjugates containing high-fidelity complementary motifs (peptides or oligonucleotides). Results for the treatment of B cell lymphomas in animal models and patient cells demonstrate the high translational potential of this aproach.