157 entries

Novel approaches towards cancer-directed immune checkpoint inhibition

Ploeg E (2023) Novel approaches towards cancer-directed immune checkpoint inhibition. Univ Groningen Thesis. doi: 10.33612/diss.737906343

Objective: To evaluate a novel bispecific antibody, bsAb CD73xEGFR, that inhibits the immunosuppressive enzyme CD73 on cancer cells in an EGFR-directed manner.

Summary: The researchers constructed a bispecific antibody, bsAb CD73xEGFR, that binds to both CD73 and EGFR on cancer cells. In preclinical studies, they found that bsAb CD73xEGFR was more effective than the monospecific anti-CD73 antibody oleclumab at reducing tumor growth and enhancing anti-tumor immune responses, likely due to its ability to direct CD73 inhibition specifically to cancer cells overexpressing EGFR.

Usage: Cancer cells were incubated with bsAb CD73xEGFR (1 μg/ml) (or controls) in the presence of Fab-ZAP human (Cat. #IT-51). Apoptotic cancer cell death was evaluated after 24 h by flow cytometry using Annexin-V/PI staining.

Related Products: Fab-ZAP human (Cat. #IT-51)

Pathophysiological roles and applications of glycosphingolipids in the diagnosis and treatment of cancer diseases

Jin X, Yang GY (2023) Pathophysiological roles and applications of glycosphingolipids in the diagnosis and treatment of cancer diseases. Prog Lipid Res 101241. doi: 10.1016/j.plipres.2023.101241 PMID: 37524133

Objective: The authors review the tumor-related biological functions of GSLs and recent progress in using GSLs and related enzymes to diagnose and treat tumor diseases.

Summary: Glycosphingolipids (GSLs) are glycolipids present on the surface of living cell membranes. Specific GSLs and related enzymes are abnormally expressed in many cancer diseases and affect the malignant characteristics of tumors. The regulatory roles of GSLs in signaling pathways suggest that they are involved in tumor pathogenesis. GSLs have therefore been widely studied as diagnostic markers of cancer diseases and important targets of immunotherapy.

Usage: The stage-specific embryonic antigen-4 (SSEA4) mAb, MC-813-70, was mixed with Mab-ZAP at a molar ratio of approximately 3:1 with the complex used at nanomolar concentrations on MDA-MB-231 cells, a triple negative breast cancer cell known to express SSEA-4. The conjugate was able to reduce tumor viability in vitro.

Related Products: Mab-ZAP (Cat. #IT-04)

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The bone marrow stroma in human myelodysplastic syndrome reveals alterations that regulate disease progression

Kfoury YS, Ji F, Jain E, Mazzola MC, Schiroli G, Papazian A, Mercier FE, Sykes DB, Kiem A, Randolph MA, Abdel-Wahab OI, Calvi LM, Sadreyev R, Scadden DT (2023) The bone marrow stroma in human myelodysplastic syndrome reveals alterations that regulate disease progression. Blood Adv bloodadvances.2022008268. doi: 10.1182/bloodadvances.2022008268 PMID: 37450380

Objective: Evaluate mesenchymal cell molecular features searching for modifications that could impact Myelodysplastic syndrome (MDS) and offer potential therapeutics.

Summary: MDS is a heterogenous group of diseases affecting hematopoietic stem cells and are curable only by stem cell transplantation. Animal models of MDS indicate that changes in specific mesenchymal progenitor subsets in the BM can induce or select for abnormal hematopoietic cells. The authors identified that osteopontin (SPP1) is overexpressed in human bone marrow mesenchymal cells. SPP1 expression in comparable mesenchymal stromal cell populations plays protective roles in disease progression in an MDS mouse model.

Usage: Streptavidin-ZAP was combined with biotinylated CD117 (cKit) Ab in a 1:1 molar ratio. Mice were dosed with the conjugate at 3 mg/kg. The authors used the antibody-drug conjugate as a conditioning strategy that spares the non-hematopoietic microenvironment in the BM from genotoxic injury. This approach has been shown to deplete host hematopoietic stem cells with minimal toxicity effectively.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Temporal multimodal single-cell profiling of native hematopoiesis illuminates altered differentiation trajectories with age

Konturek-Ciesla A, Dhapola P, Zhang Q, Säwén P, Wan H, Karlsson G, Bryder D (2023) Temporal multimodal single-cell profiling of native hematopoiesis illuminates altered differentiation trajectories with age. Cell Rep 42(4):112304. doi: 10.1016/j.celrep.2023.112304 PMID: 36961818

Objective: Using single-cell transcriptome and epitope profiling to study hematopoiesis and the effects from aging.

Summary: The contribution from Hematopoietic stem cells (HSCs) to mature blood cells decline with age. The authors used transcriptome and epitope profiling to reconstruct early hematopoiesis and assessed HSC-specific lineage tracing. Their analysis identified previously uncharacterized cell populations which included multipotent progenitor cells (MPP) Ly-1 and Ly-II. Flt3 is a marker indicative of early differentiation found on MPP cells and was targeted for elimination via an antibody to Flt3 combined with Streptavidin-ZAP. This cell depletion provided evidence for the lack of self-renewal of Ly-1 and Ly-II cells in a transplantation setting and suggests that they need to be continuously replenished by upstream HSPCs.

Usage: Biotinylated anti-CD135 (clone A2F10) was combined with Streptavidin-ZAP at a 1:1 molar ratio, diluted in PBS to 0.2 mg/ml and injected into mice at 3 mg/kg.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Streptavidin-saporin: Converting biotinylated materials into targeted toxins

Ancheta LR, Shramm PA, Bouajram R, Higgins D, Lappi DA (2023) Streptavidin-saporin: Converting biotinylated materials into targeted toxins. Toxins 15(3):181. doi: 10.3390/toxins15030181

Summary: This manuscript describes the myriad of ways Streptavidin-ZAP is used and how this technology supports the scientific process of ‘Molecular Surgery’ and progress in research and drug development. Insights from publications and research performed using Streptavidin-ZAP and its impact on academia and industry for research and drug development are presented.

Read the full article.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Equimolar mixing of Streptavidin-ZAP and Biotinylated Molecule

Question: I was wondering if you could elaborate on why the Streptavidin-ZAP product recommends to be used at an equimolar ratio with the targeting reagent, when it is capable of binding up to four biotins/molecule?

Answer: It’s a question we get asked sometimes and it’s a good question.

You are correct that streptavidin is capable of binding up to 4 biotin molecules.  However, when we created streptavidin-ZAP with the purpose of being a modular way of creating targeted toxins, we learned that the best general rule to follow was using a equimolar reaction.  In theory, it is a 1:1 ratio of targeting molecule to streptavidin-ZAP, where we are most likely seeing an average of 1:1, but there is also the possibility of mixed ratios.

The amount of publications using the equimolar approach gave the desired results whether they were using a small biotinylated peptide or whole IgG.  You’ll notice that depending on the MW of your biotinylated targeting agent, the amount of streptavidin-ZAP needed for the experiment can vary drastically and through in-house characterization, the equimolar approach still worked best. 

Another reason we recommend a 1:1 ratio is based on our experience with our other secondary conjugates. It may be intuitive to think that using a higher dose of targeting agent would induce more cell death, but we found the opposite effect, where the excess, un-reacted targeting agent competed with the conjugated material for surface binding sites, which in turn decreased the amount of saporin being delivered. We have a publication (PMCID: PMC8952126 ) that also describes this observation.  

Once you’ve created a baseline using the equimolar protocol and are more accustomed to how streptavidin-ZAP works in your application, please contact us if you feel more optimization is needed.  It will be easier to help trouble-shoot when we are all working off the same protocol.

Related Products: Streptavidin-ZAP


  1. Ancheta LR et al. Saporin as a commercial reagent: its uses and unexpected impacts in the biological sciences-tools from the plant kingdom. Toxins (Basel) 14(3):184, 2022.

Which type of RIP is saporin?

Q: I read on your website that, “There are two types of RIPs: type I, which are much less cytotoxic due to the lack of the B chain and type II, which are distinguished from type I RIPs by the presence of the B chain and their ability to enter cells on their own.”

In the IT-27 Streptavidin-ZAP product, which type of saporin is there? Is it both type I and type II because the saporin is purified from the plant, or is it one specific type only in the product.

A: All saporin molecules are Type I ribosome-inactivating proteins. We only use saporin. An example of a Type II RIP is ricin, which can enter a cell on its own and has been used throughout history as a method of assassination.

Streptavidin-ZAP is streptavidin attached to saporin. On its own it has no way to get inside a cell. By mixing Streptavidin-ZAP with a biotinylated molecule that is recognized on the cell surface, the resulting conjugate is able to bind and internalize saporin into a cell. Once inside saporin inactivates the ribosomes which causes cell death.

CD3e-immunotoxin spares CD62Llo Tregs and reshapes organ-specific T-cell composition by preferentially depleting CD3ehi T cells

Kim S, Shukla RK, Yu H, Baek A, Cressman SG, Golconda S, Lee GE, Choi H, Reneau JC, Wang Z, Huang CA, Liyanage NPM, Kim S (2022) CD3e-immunotoxin spares CD62Llo Tregs and reshapes organ-specific T-cell composition by preferentially depleting CD3ehi T cells. Front Immunol 13:1011190. doi: 10.3389/fimmu.2022.1011190

Objective: To use a new murine testing model to demonstrate a substantial enrichment of tissue-resident Foxp3+ Tregs following CD3e-IT treatment.

Summary: The multi-organ pharmacodynamics of CD3e-IT and potential treatment resistance mechanisms identified in this study may generate new opportunities to further improve this promising treatment.

Usage: Male C57BL/6J mice were injected into retro-orbital sinus with 15 μg S-CD3e-IT (Biotinylated Anti-CD3 mixed with Streptavidin-ZAP in sterile 200 μl PBS twice a day for four consecutive days.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

The role of macrophage scavenger receptor 1 (MSR1) in inflammatory disorders and cancer

Gudgeon J, Marin-Rubio JL, Trost M (2022) The role of macrophage scavenger receptor 1 (MSR1) in inflammatory disorders and cancer. Front Immunol 13:1012002. doi: 10.3389/fimmu.2022.1012002

Objective: Review the role of Macrophage scavenger receptor 1 (MSR1) in health and disease, focusing on the molecular mechanisms influencing expression, its effect on disease process, macrophage function and signaling pathways, and the therapeutic potential of targeting MSR1.

Summary: MSR1 is primarily found on the surface of various types of macrophages and affects processes such as astherosclerosis, innate and adaptive immunity, lung and liver disease and cancer. Recently, MSR1 has been implicated to trigger inflammatory and tumorigenic pathways. MSR1 is most often correlated with the anti-inflammatory M2 macrophage phenotype. Investigations into anti-inflammatory signalling downstream of MSR1 are vital to fully understand the influence of MSR1 expression in inflammatory disease. Manipulating M2 macrophages through MSR1 may represent a new targeted therapeutic approach for diseases such as cancer, arthritis, and other inflammatory diseases.

Usage: In reviewing therapeutic strategies, an antibody-based method was developed using the 2F8 anti-SR-A monoclonal antibody. The antibody conjugated to RAT-ZAP and unconjugated saporin was delivered to mice via intraperitoneal injection to deplete vascular leukocytes (VLCs) from the peritoneum to reduce the tumor burden. 4.8 μg of Rat-ZAP in the absence or presence of 4 μg of clone 2F8 antibody was incubated on ice for 30 min.

Related Products: Rat-ZAP (Cat. #IT-26)

Fab-ZAP Final Concentration

Q: When using any of your Fab-Zap product line, the recommended final concentration is 4.5 nM. Is this based on experiments you have done? I question if at 4.5 nM my primary antibody will be saturated with Fab-ZAP secondary conjugate?

A: Yes, the 4.5 nM concentration is what we use to quality-control test our Fab-ZAP conjugates and why we recommend it in the literature.  We also recommend only titrating your primary antibody.  The 4.5 nM of Fab-ZAP should be enough to saturate your primary antibody.  If you have a test of ~10 nM of primary antibody and you experience less cell death than ~1 nM, this will indicate “antibody competition” (i.e., your primary antibody is not saturated).  The data sheet shows a cytotox with a nice example of this. (Fab-ZAP data sheet)

See: Fab-ZAP human (Cat. #IT-51)

In vivo visualization and molecular targeting of the cardiac conduction system

Goodyer WR, Beyersdorf BM, Duan L, van den Berg NS, Mantri S, Galdos FX, Puluca N, Buikema JW, Lee S, Salmi D, Robinson ER, Rogalla S, Cogan DP, Khosla C, Rosenthal EL, Wu SM (2022) In vivo visualization and molecular targeting of the cardiac conduction system. J Clin Invest e156955. doi: 10.1172/jci156955

Objective: To engineer targeted antibody conjugates directed against the cardiac conduction system (CCS) to allow visualization of the CCS in vivo.

Summary: Accidental injury to the CCS, a specialized set of cells embedded within the heart and indistinguishable from the surrounding heart muscle tissue, is a major complication in cardiac surgeries. They generated a fully human monoclonal Fab (hCNTN2) that targets the CCS with high specificity.

Usage: Streptavidin-ZAP was reacted with biotinylated hCNTN2 Fab to create hCNTN2-SAP. 100 ug of either hCNTN2-SAP and control-SAP were injected into wild-type mice with a single tail-vein injection and hearts were harvested after 2 days.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Antibody-based preparative regimens for cell, tissue and organ transplantation

Van Hentenryck M, Li Z, Murphy PM, Czechowicz A (2022) Antibody-based preparative regimens for cell, tissue and organ transplantation. (eds. 162). OBM Transplantation 6(3):162. doi: 10.21926/obm.transplant.2203162

Objective: Provide a review of progress in the use of antibodies to support cell and tissue transplantation with a particular focus on induction of donor-specific tolerance for solid organ transplantation.

Summary: Antibody-based conditioning to prepare the recipient is a promising approach towards achieving transplant tolerance in both hematopoietic and solid organ transplant settings.

Usage: To enhance HSC depletion while avoiding bystander toxicity (neutropenia, lymphopenia, and thrombocytopenia) caused by CD45-radioimmunotherapy, Palchaudhuri et al. developed a saporin-based CD45 (CD45-SAP) immunotoxin using a biotinylated antibody and Streptavidin-ZAP.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

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Synchronous intracellular delivery of EGFR-targeted antibody-drug conjugates by p38-mediated non-canonical endocytosis

Takahashi JI, Nakamura S, Onuma I, Zhou Y, Yokoyama S, Sakurai H (2022) Synchronous intracellular delivery of EGFR-targeted antibody-drug conjugates by p38-mediated non-canonical endocytosis. Sci Rep 12(1):11561. doi: 10.1038/s41598-022-15838-8 PMID: 35798841

Objective: The binding of cetuximab to EGFR suppresses ligand-induced signaling events. The authors demonstrate that synchronous non-canonical EGFR endocytosis can increase the efficacy of EGFR-targeting ADCs.

Summary: Epidermal growth factor (EGFR) has been a popular target in the treatment of cancer via monoclonal antibodies, specifically cetuximab and panitumumab. They have been applied to antibody-drug conjugates (ADCs) and their clinical efficacy had been demonstrated, but this efficacy has also been limited by acquired resistance via secondary mutations or the activation of bypass pathways. To overcome these limiting factors, the authors investigated if non-canonical clathrin-mediated endocytosis (CME) of EGFR induced the internalization of membrane-bound EGFR-targeted mAbs. Their results show that tumor necrosis factor-alpha strongly induces endocytosis of the cetuximab-EGFR complex via the p38 phosphorylation of EGFR and that Hum-ZAP, a secondary antibody conjugated to saporin, will also undergo internalization with the complex and enhance anti-proliferative activity.

Related Products: Hum-ZAP (Cat. #IT-22)

Mab-ZAP binds to Fc portion of mouse IgG

Q: Does Mab-ZAP (Cat. #IT-04) bind to the FC portion of mouse IgG?

A: The antibody used to create our Mab-ZAP (IT-04), will react with whole molecule mouse IgG, which includes the Fc portion and the two antigen binding Fab portions.

Related Products: ZAP Conjugates

FabFc-ZAP cross-reaction with another species

Q: Can your FabFc-ZAP human (Cat# IT-65) bind to the Fc portion of another species, such as mouse IgG? It looks like it binds to mouse IgG in our assay.

A: The antibody used to create our FabFc-ZAP Human (IT-65), can react with the Fc (gamma) portion of human IgG heavy chain and should not react with the Fab portion of human IgG. However, there could be minimal cross-reaction with mouse, horse, or bovine serum proteins, and it is possible to see cross-reaction with immunoglobulins from other species. 

Related Products: ZAP Conjugates

Comparison of CD3e antibody and CD3e-sZAP immunotoxin treatment in mice identifies szap as the main driver of vascular leakage

Kim S, Shukla RK, Kim E, Cressman SG, Yu H, Baek A, Choi H, Kim A, Sharma A, Wang Z, Huang CA, Reneau JC, Boyaka PN, Liyanage NPM, Kim S (2022) Comparison of CD3e antibody and CD3e-sZAP immunotoxin treatment in mice identifies szap as the main driver of vascular leakage. Biomedicines 10(6):1221. doi: 10.3390/biomedicines10061221

Objective: Investigate and identify the toxicity profiles of a CD3e-mAb and an immunotoxin of this CD3e antibody conjugated to saporin via a biotin-streptavidin bond, S-CD3e-IT.

Summary: The two agents had opposite effects on T cells, with the antibody alone able to modulate CD3e on the cell surface while the S-CD3e-IT caused depletion of the cell. The immunotoxin increased the infiltration of polymorphonuclear leukocytes (PMNs) into the tissue parenchyma of the spleen and lungs, a sign of vascular permeability while the antibody alone showed no signs of vascular leakage.

Usage: S-CD3e-IT was prepared by reacting biotinylated CD3e antibody with Streptavidin-ZAP in a 1:1 molar ratio. C57BL/6J mice received 25 μg of S-CD3e-IT in sterile 200 μL PBS, twice a day via retro-orbital injection for four days.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Dosage of Fab-ZAP for antibody concentration

Q: Is the dosage of Fab-ZAP always enough for any level of antibody concentration?

A: The 4.5 nM dosage of Fab-ZAP is the recommended concentration.  We do not typically see unspecific killing at 4.5 nM on most cell lines.  If the concentration of Fab-ZAP is increased, it may undergo bulk-phase endocytosis and kill cells indiscriminately.  A lower concentration of Fab-ZAP may lead to antibody competition, resulting in a lack of killing of cells at the highest concentration of antibody.

Related Products: ZAP Conjugates

Recommended ratio between Fab-ZAP dosage and antibody concentration

Q: Is there a recommended ratio between Fab-ZAP dosage and antibody concentration?

A: A recommended good starting point is 4.5 nM of Fab-ZAP, with a titration of the antibody starting at a concentration of 10 nM.

Related Products: ZAP Conjugates

Fab-ZAP number of replications

Q: Each concentration is suggested to perform 6 replications, can it be adjusted more or less in practice?

A: Yes, the assay design is meant to be a thorough approach but can be adjusted by the user. We recommend 6 replications based on our 96-well plate template design. The concentration of Fab-ZAP is 4.5 nM in the suggested protocols.

Related Products: ZAP Conjugates

Detecting the targeted antibody in supernatant

Q: Can Fab-ZAP detect the targeted antibody still in supernatant?

A: As long as there is nothing in the supernatant inhibiting the reactivity of Fab-ZAP, it should work.  We do not typically recommend this, but in theory it should be possible.  I would be cautious of this approach based off of the presumed lack of established concentration of antibody.

Related Products: ZAP Conjugates

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