Brain Delivery of Macromolecular Therapeutics

Nanomedicines designed for brain delivery/action have a difficult hurdle to overcome; they need to cross the blood brain barrier (BBB). We focus on receptor binding peptides that transcytose bound cargo into the brain. In particular, angiopep-2 (AP-2; TFFYGGSRGKRNNFKTEEY) binds to LDLR (low-density lipoprotein receptor)-related protein 1(LRP-1) followed by transcytosis. N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer – AP-2 conjugates are evaluated for the treatment of primary central nervous system lymphoma (PCNSL) and Alzheimer disease (AD).

PCNSL: In collaboration with the Cedar-Sinai Medical Center in Los Angeles (Dr. V.A. Ljubimov) we developed a novel therapy for PCNSL by combining a targeted polymer therapy with an immune checkpoint inhibitor (anti-PD1 antibody). HPMA copolymer based nanoconjugate (P-AP2-H6-cMyc AON) was designed to block c-Myc expression mediated by an anti-sense oligonucleotide (AON). AP-2 was conjugated to the HPMA copolymer to facilitate the conjugate BBB crossing. The systemically administered nanoconjugate alone or in combination with anti-PD1 antibody was active in the treatment of syngeneic orthotopic mouse model of intracranial brain lymphoma (Fig. 7) [1].

Figure 7. Proposed mechanism of action of HPMA copolymer-based nanodrug in combination with aPD1. Orchestrated antitumor activities of the HPMA copolymer-drug conjugates through various functional moieties. (1) After intravenous administration, nanodrug molecules penetrate BBB via AP-2 peptide-mediated transcytosis. (2) AP-2 peptide binds to its receptor LRP-1 on B cell lymphoma cells and (3) leads to internalization of the nanodrug. (4) H6 peptide containing 6 histidine residues induces proton sponge effect to mediate endosomal escape and c-Myc AON is released into cytoplasm. (5) c-Myc AON binds to its mRNA and suppresses c-Myc expression, (6) which leads to inhibition of cell proliferation and apoptosis. (7) Simultaneously, two immune checkpoints, PD-L1 that sends to immune system a “don’t find me” signal and CD47 that sends “don’t eat me” signal, are suppressed in response to c-Myc inhibition. (8) In combination treatment, the addition of anti-PD-1 antibody blocks the immune checkpoint leading to activation of (9) T cells and (10) macrophages (MF).

AD:In collaboration with the Department of Radiology and Imaging Science, University of Utah (Dr. D.J. Cross) we designed HPMA copolymer-AP-2-paclitaxel (PTX) conjugates that cross the BBB and are efficient in the treatment of an animal model of AD. A hallmark of AD pathology is the accumulation of neurofibrillary tangles, primarily composed of hyperphosphorylated tau protein. Microtubule-stabilizing agents such as PTX bind to β tubulin on the inner surface of microtubules, and subsequently promote assembly, alter dynamics, and prevent depolymerization. Our design (Fig. 8) addresses the issues of BBB permeability and reduces systemic toxicity [2].

Figure 8. (A) Synthesis of P-PTX-AP2. (B) Cytotoxicity of PTX and P-PTX-AP2 toward SH-SY5Y cells. (C) Transport of Cy5.5 labeled P-(AP2)12 (precursor Mw=87 kDa) across the BBB following i.v. administration to mice. HPMA copolymer without AP2 (PHPMA) was used as control. (D) Testing spatial learning and memory with Radial Water Tread following P-PTX-AP2 treatment of aged 3xTg-AD mice (n=12). Saline (n=11) and wild type (WT) mice (n=12) were controls. Day 1-4 (learning and acquisition phase), Day 5 (short term), and Day12 (long term memory).

References

[1] Blood-brain barrier crossing biopolymer targeting c-Myc and anti-PD-1 activate primary brain lymphoma immunity: artificial intelligence analysis. V.A. Ljubimov, T. Sun, J. Wang, L. Li, P.Z. Wang, A.V. Ljubimov, E. Holler, K.L. Black, J. Kopeček, J.Y. Ljubimova, J. Yang. J. Controlled Release 381, 113611 (2025) [doi]

[2] Vector-guided Brain Delivery of Paclitaxel Mitigates Alzheimer’s-Related Pathology and Cognitive Decline in 3xTg-AD Mice. S. Li, A.D. Jensen, R.M. Aljassimi, H. Al Faruque, S. Pytlíková, M. Sima, D.G. Cook, J. Schmidt, S. Minoshima, J. Kopeček, J. Yang, D.J. Cross, In preparation