Kofoed C, Erkalo G, Tay NES, Ye X, Lin Y, Muir TW (2025) Programmable protein ligation on cell surfaces. Nature 10.1038/s41586-025-09287-2. doi: 10.1038/s41586-025-09287-2 PMID: 40739351
Objective: To describe an autonomous decision-making device driven by proximity-gated protein trans-splicing that allows local generation of an active protein from two otherwise inactive polypeptide fragments
Summary: Authors showed that this protein-actuator platform can perform convergent protein ligation on designated cell surfaces, allowing highly selective generation of active proteins, which can either remain physically associated with the cell surface on which they were manufactured or be released into the surrounding milieu.
Usage: Flow cytometry: Mixed K562 cells (phenotypes indicated) were treated with a two-dose regimen of SMART-SpyCatcher/SpyTag003-biotin ([HER2 AND EGFR] logic,100 nM each) and Streptavidin–ZAP (20 nM) at a 24-h interval. Cell viability was assessed after 72 h by flow cytometry and normalized to untreated wild-type cells.
Ren X, Wang Y, Zhang Y (2025) Targeted depletion of dysfunctional hematopoietic stem cells mitigates myeloid-biased differentiation in aged mice. Cell Discov 11:56. doi: 10.1038/s41421-025-00810-3 PMID: 40490480
Objective: To develop and evaluate a targeted strategy for depleting dysfunctional, myeloid-biased CD150-high hematopoietic stem cells (HSCs) in aged mice to restore balanced hematopoiesis and mitigate aging-related blood disorders.
Summary: The study used an antibody-toxin conjugate to selectively eliminate CD150-high HSCs, improving lymphoid-to-myeloid ratios, reducing platelet hyperproduction, and restoring hematopoietic balance in aged mice. Treatment preserved functional CD150-low HSCs and showed minimal off-target or systemic toxicity.
Usage: Streptavidin-ZAP (IT-27) was combined with a biotinylated anti-CD150 antibody to generate Anti-CD150-SAP (IT-103). This conjugate was used at doses of 1–2 mg/kg in vivo and as low as 0.01 nM in vitro to specifically deplete CD150-high HSCs while sparing CD150-low populations.
Movahed AY, Bagheri R, Savatier P, Šarić T, Moradi S (2025) Elimination of tumorigenic pluripotent stem cells from their differentiated cell therapy products: An important step toward ensuring safe cell therapy. Stem Cell Reports 102543. doi: 10.1016/j.stemcr.2025.102543 PMID: 40541178
Objective: To review and evaluate current strategies for eliminating tumorigenic pluripotent stem cells (PSCs) from differentiated cell therapy products to improve the safety of PSC-based regenerative therapies.
Summary: Residual undifferentiated PSCs pose a tumorigenic risk in cell therapies. This review outlines genetic, antibody, toxin, and small molecule strategies for selectively removing PSCs, emphasizing the need for efficient, selective methods to ensure safety in regenerative medicine.
Usage: References a previous study that used Fab-ZAP to eliminate pluripotent stem cells by targeting specific surface markers, demonstrating its application as a targeted immunotoxin for PSC depletion.
Konturek-Ciesla A, Zhang Q, Kharazi S, Bryder D (2025) A non-genotoxic stem cell therapy boosts lymphopoiesis and averts age-related blood diseases in mice. Nat Commun 16(1):5129. doi: 10.1038/s41467-025-60464-3 PMID: 40456713
Objective: Application of Hematopoietic stem cell (HSC) transplantation leads to treatment toxicity. Therefore, authors employed a murine transplantation model based on low-intensity conditioning protocols using antibody-mediated HSC depletion to improve hematopoietic output and ameliorate age-compromised lymphopoiesis.
Summary: Authors demonstrate that young HSCs, once effectively engrafted in aged hosts, improve hematopoietic output and ameliorate age-compromised lymphopoiesis. This culminated in a strategy that robustly mitigates disease progression in a genetic model of myelodysplastic syndrome. These results suggest that non-genotoxic HSC transplantation could fundamentally change the clinical management of age-associated hematological disorders, offering a prophylactic tool to delay or even prevent their onset in elderly patients.
Usage: CD45-SAP (3 mg/kg) was administered to young (2 months) and aged (16 months) C57BL/6-CD45.2 mice
Nakano T, Okita K, Okazaki S, Yoshimoto S, Masuko S, Yagi H, Kato K, Tomioka Y, Imai K, Hamada Y, Masuko K, Shimada-Takaura K, Nagai N, Saya H, Arai T, Ishiwata T, Masuko T (2025) CD44v, S1PR1, HER3, MET and cancer-associated amino acid transporters are promising targets for the pancreatic cancers characterized using mAb. FEBS Open Bio 15(5):867-884. doi: 10.1002/2211-5463.13963 PMID: 39757718
Objective: To analyze pancreatic ductal adenocarcinomas (PDAC) using novel rat mAbs against membrane proteins in conjunction with flow cytometry and immunohistochemistry
Summary: Internalization of membrane proteins by mAbs and growth inhibition by toxin-linked mAbs were demonstrated in many PDAC cell lines, and mAbs against S1PR1, ASCT2, HER3 and CD44v inhibited the growth of xenografted MIA PaCa-2PDAC cells. Furthermore, CD44v-high PDAC showed high mRNA expression of HER1–3, MET and CD44v, and was correlated with poor prognosis. Taken together, the results suggest that CD44v, S1PR1, HER3, MET and the above-mentioned cancer-associated amino acid transporters might be promising targets for the diagnosis and treatment of PDAC.
Usage: Growth inhibition by rat mAbs against PDAC cell lines with secondary antibodies conjugated to saporin (PR-01). Rat mAb solution (4 ug/mL), a PDAC cell suspension and Saporin-conjugated goat anti-rat IgG pAb (Rat-ZAP, IT-26 at 4 ug/mL) were added to each well of 96-well plates.
Park HB, Kim KH, Kim JH, Kim SI, Oh YM, Kang M, Lee S, Hwang S, Lee H, Lee T, Park S, Lee JE, Jeong GR, Lee DH, Youn H, Choi EY, Son WC, Chung SJ, Chung J, Choi K (2024) Improved safety of chimeric antigen receptor T cells indirectly targeting antigens via switchable adapters. Nat Commun 15(1):9917. doi: 10.1038/s41467-024-53996-7 PMID: 39557825
Objective: To show that switchable CAR-T cells with a tumor targeting adaptor can mitigate on-target off-tumor toxicity against a low selectivity tumor antigen that cannot be targeted by conventional CAR-T cells, such as CD40.
Summary: The system is composed of anti-cotinine murine CAR-T cells and cotinine-labeled anti-CD40 single chain variable fragments (scFv), with which the authors show selective tumor killing while sparing CD40-expressing normal cells including macrophages in a mouse model of lymphoma. The authors evaluated whether Cot CAR-T cells could be depleted by Cot-saporin in vivo in an allogeneic CAR-T cell transfer model. When Balb/C mice transplanted with B6 bone marrow cells were injected with B6 Cot CAR-T cells, the transferred Cot CAR-T cells expanded in the peripheral blood in response to Balb/C alloantigen. However, when Cot-saporin was administered during this expansion phase, the Cot CAR-T cells failed to expand and were subsequently eliminated in the blood. Thus, Cot-saporin-mediated CotCAR-T cell suicide was confirmed in vitro and in vivo.
Usage: in vitro Cot CAR-T cell depletion by cotinine-drug conjugates: Peptides were incubated with saporin-labeled streptavidin (IT-27) at a molar ratio of 4:1 to generate cotinine-saporin conjugate (Cot-saporin). For Cot-saporin-dependent cytotoxicity assays on Cot CAR-T cells, a 1:1 mixed population (50,000 cells each) of Cot CAR-T cells (target cells) and control T cells (bystander non-CAR-T cells) were incubated with various doses of Cot-saporin for 48 h in medium containing human IL-2. Seven days after CAR-T cell transfer, Cot-saporin was administered intraperitoneally three times at 3-day intervals.
Jiang H, Cui H, Chen M, Li F, Shen X, Guo CJ, Hoekel GE, Zhu Y, Han L, Wu K, Holtzman MJ, Liu Q (2024) Divergent sensory pathways of sneezing and coughing. Cell 187(21):5981-5997. doi: 10.1016/j.cell.2024.08.009 PMID: 39243765
Objective: To study the difference in sensory receptors and neurotransmission/modulation mechanisms between sneezing and coughing.
Summary: Sneezing and coughing are frequently associated with allergies and respiratory viral infections and it’s assumed both involve common sensory receptors and neurotransmission mechanisms. The author’s work show that the nasal mucosa is innervated by several discrete populations of sensory neurons, but only one population (MrgprC11+MrgprA3−) mediates sneezing. Although this same population innervates the trachea, it does not mediate coughing, and instead, a distinct sensory population (somatostatin SST) mediates coughing but not sneezing. NMB-SAP was used to ablate neruomedin B (NMB) receptor expressing and nucleus tractus solitarius (NTS) neurons. Deletion of these neurons did not affect the coughing responses to Ly344864 and IL-31 (agonists to SST neurons) suggesting that NMB-sensitive NTS neurons do not mediate coughing.
Usage: Neuronal ablation by SST-saporin and NMB-saporin. SST-saporin was made by mixing biotin-labeled somatostatin and Streptavidin-ZAP (IT-27) at a 1:1 molar ratio at room temperature for 20 minutes. SST-Saporin (10 μM, 50 nL), NMB-saporin (#IT-70; 50 ng in 50 nL) or Blank-SAP (#IT-21; 10 μM in 50 nL or 50 ng in 50 nL) was injected into the NTS region.
O’Sullivan JA, Youngblood BA, Schleimer RP, Bochner BS (2024) Siglecs as potential targets of therapy in human mast cell- and/or eosinophil-associated diseases. Semin Immunol 69:101799. doi: 10.1016/j.smim.2023.101799 PMID: 37413923
Objective: To review a subset of Siglecs and their various endogenous or synthetic sialoside ligands that regulate eosinophil and mast cell function and survival.
Summary: Sialic acid-binding immunoglobulin-like lectins (Siglecs) are vertebrate glycan-binding cell-surface proteins. Many Siglecs mediate cellular inhibitory activity and are of interest as part of a strategy to therapeutically lessen unwanted cellular responses. Human eosinophils and mast cells express overlapping but distinct patterns of Siglecs, and certain Siglecs have become the focus of novel therapies for allergic and other eosinophil and mast cell-related diseases.
Usage: Saporin in conjunction with CD22 glycomimetic ligand BPCNeuAc leads to cells death induction in a ligand-dependent manner on B-lymphoma cells (Collins et al.). Incubation with anti-Siglec-8 monoclonal antibody conjugated to saporin led to the death of malignant mast cells and eosinophils (O’Sullivan et al.)
Bryder D, Konturk-Ciesla A, Zhang Q, Kharazi S (2024) A non-invasive stem cell therapy boosts lymphopoiesis and averts age-related blood diseases in mice. Research Square doi: 10.21203/rs.3.rs-4528815/v1
Objective: To develop a murine transplantation model based on low-intensity conditioning protocols using antibody-mediated Hematopoietic stem cell.
Summary: Authors demonstrate that young HSCs, once transplanted, survive and thrive in aged hosts, dramatically improving hematopoietic output and ameliorating age-compromised lymphopoiesis.
Usage: Intravenous injection of CD45-SAP (3 mg/kg, IT-91). Biotinylated anti-CD45.2 antibodies were mixed with streptavidin-saporin conjugate at a 1:1 molar ratio (IT-27).
Garaudé S (2024) Engineering an antibody-discernible and functional CD45 variant on hematopoietic stem and progenitor cells via base editing. Univ Basel Thesis.
Objective: To develop a system for a cell surface marker present on all hematopoietic cell to deplete malignant cells. Authors screened CD45’s extracellular domain regions with base editors and generated multiple CD45 protein variants altering the binding of antibodies.
Summary: Authors selected the CD45 K352E/G variant profile and improved its base editing rate as it showcased loss of binding of a unique anti-CD45 antibody while still maintaining the surface marker’s expression, stability, and function in human hematopoietic stem and progenitor cells (HSPCs). The resulting loss of antibody binding prompted the modification and humanization of the anti-CD45 antibody, culminating in the development of an anti-CD45 antibody-drug conjugate (CD45-ADC; CIM053-SG3376). In an AML mouse models xenografted with HSPCs, administration of the CD45-ADC selectively depleted human leukemia and HSPCs wt cells while preserving the healthy hematopoietic system derived from the transplanted base edited HSPCs.
Usage: In vitro antibody-drug-conjugate (ADC) mediated killing assays. For ADC killing assays involving saporin, a 100 nM stock was prepared by incubating the biotinylated antibody and Streptavidin-ZAP at a 1:1 molar ratio for 30 min at room temperature
