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Mannose in Targeted Immunotherapeutic Endeavors

Mannose on the surface of many common pathogens serves as a "danger signal" that, not found on healthy human cells and tissues, activates lectin activation pathway of complement system to "bomb" pathogen invaders.

In addition to complements, macrophages are able to sense the invasion as well. When capturing mannose through receptor, the macrophage turns itself from a bored "garbage collector" to a "professional eater" or an "angry killer" against microbial attacks.

Mannose glycosylation is also found to be a “hallmark” in cancer cells.

The mannose characteristics has been evaluated for the potential in targeted and broad-spectrum microorganism inhibition and cancer diagnosis or therapy. Some of research endeavors are listed and discussed below.

• High mannose-specific aptamers for broad-spectrum virus inhibition and cancer targeting.

The aptamers tested exhibited high affinity toward spike protein of SARS-CoV-2 & envelope protein GP120 of HIV and a certain inhibition effect. Meanwhile, they specifically recognized cancer cells over normal cells.



Figure 1. Mannose-specific aptamers for broad-spectrum virus inhibition and cancer targeting

• Mannose modification for targeted photothermal therapy

Photothermal therapy is promising to conquer cancer resistance. To arm it with cancer selectivity, nanoparticle used in the therapy was equipped with mannose as targeting unit. Data indicated the potential application of photothermal therapy of tumor for accurate diagnosis.

• Mannose-modification for targeting TAMs

Tumor-associated macrophages (TAMs) are a class of immune cells that amount to substantial tumor mass. They contribute significantly to immunosuppressive TME and the resistance to chemotherapy drugs and nano-medicine, and therefore are rising as targets in cancer treatment, via either polarization into M1-like phenotype or depletion.

A study with mannose-modified nanocarriers displayed TAM-targeting delivery in solid tumors.

If loaded with proper cargo, these carriers could be used for prognosis or therapeutic purposes.

Here comes the one that’s loaded with therapeutic cargo. In order to endow chemotherapy with tumor precision, a research group developed mannose-modified liposomes co-loaded with ZOL and DOX, and offered results indicating remarkably enhanced anticancer effects via depleting TAMs.



Figure 2. Man-LP@ZOL/DOX developed by Cai. could deplete M2-tumor-associated macrophages to enhance anti-tumor effect of doxorubicin on TNBC

• Lectibody that targets mannose for pan-tumor treatment.

As discussed, cancer-related glycomics, including mannose glycosylation, is found to be a “hallmark” in cancer cells, and now is a treasure waiting to be mined for pan-tumor drug development.

AvFc, a lectibody constructed by fusing glycan-binding lectin to human IgG1, was found to significantly restrict tumor growth in models, which provides POC evidence that mannose glycans in the glycocalyx of cancer cells can be a pan-tumor, druggable target.



Figure 3. AvFc, a lectibody that targets mannose for pan-tumor treatment

Mannose is rarely used for glycolysis in the normal tissues of mammals, which makes it a “sweet” option in cancer treatment as in pathogen fighting, so sweet as to make “one-therapeutic-fit-all” therapies expected.

Reference

1. Bangarh, Rashmi, et al. "Aberrant protein glycosylation: Implications on diagnosis and Immunotherapy." Biotechnology Advances (2023): 108149.

2. Li, Wei, et al. "High mannose-specific aptamers for broad-spectrum virus inhibition and cancer targeting." CCS Chemistry 5.2 (2023): 497-509.

3. Li, Jiaxu, et al. "Mannose modified zwitterionic polyester-conjugated second near-infrared organic fluorophore for targeted photothermal therapy." Biomaterials Science 9.13 (2021): 4648-4661.

4. Fernández-Mariño, Iago, et al. "Mannose-modified hyaluronic acid nanocapsules for the targeting of tumor-associated macrophages." Drug Delivery and Translational Research 13.7 (2023): 1896-1911.

5. Wendong, Yao, et al. "Mannose modified co-loaded zoledronic liposomes deplete M2-tumor-associated macrophages to enhance anti-tumor effect of doxorubicin on TNBC." Journal of Drug Delivery Science and Technology 74 (2022): 103551.

6. Oh, Young Jun, et al. "Antitumor activity of a lectibody targeting cancer-associated high-mannose glycans." Molecular Therapy 30.4 (2022): 1523-1535.

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With its unparalleled single B antibody discovery approach and unique antigen design strategy, Detai Bioscience, Inc. is overcoming the low immunogenicity of vitamins, toxins, and glycans, and is discovering high-quality antibodies against these haptens to enable alternative cancer therapies and upgraded in vitro diagnosis (IVD). Contact us for details of how we can help.

Tumor Microenvironment Responsive Therapeutic Antibodies

The efficacy of immunotherapies for solid tumor has been heavily hampered by the hostility of tumor microenvironment (TME). TME is a complex and dynamic milieu, and tumor cells often undergo metabolic reprogramming to support their growth, survival, and proliferation within this microenvironment. While driving cancer development, TME-specific metabolite composition also contributes to the immunosuppressive nature and metabolic barriers of TME.

The specific metabolism of the TME has in recently years been leveraged to design therapeutic antibodies of precision tumor targeting

• pH-selective antibody drugs

Due to glycolysis, hypoxia, and deficient blood perfusion, acidosis is a hallmark of TME. This feature has been leveraged to design pH-selective antibodies of precision tumor targeting that remain inactive in bloodstream but become active when encountering an acidic environment in cancer.

The pH difference has also been utilized as switch of releasing therapeutic payload, as seen in the case of ADCs.



Figure 1. Designs for antibody-drug conjugate (ADC) and antibody-drug-inspired conjugates can facilitate 1) multivalent interaction with cancer cell receptors, promoting internalization. 2) Controlled cargo release is achieved through a pH-responsive or oxidative cleavage linker.

• proteolysis-responsive antibody drugs

Dysregulated (specific or elevated) proteolysis in TME has become recognized as another important hallmark of cancers.

Exploiting the unique TME characteristic, scientists have designed protease-activated T cell engager antibodies to fulfill site-specific and controlled drug delivery. Their activity is sealed with masking peptides fused to antibodies with tumor protease-cleavable linkers, and recovered by the removal of the mask in TME.

This class of antibodies are under investigation by Janux, CytomX, Roche, Amunix, Harpoon, and quite a few more.



Figure 2. Probody TCB (CI107) is a bispecific IgG designed for EGFR and CD3 binding, with a cleavable linker preventing normal tissue interaction. In the tumor microenvironment, linker cleavage enables specific binding to the target antigen and CD3+ T cells.



Figure 3. ProTriTACTM developed by Harpoon Therapeutics

Besides, Revitope's PrecisionGATE and Takeda's COBRA, platforms for the design of precision immunotherapies with separated, inactive constructs, leverage the proteolysis characteristic for better controlled immune activation. The constructs, upon proteolysis in TME, rearrange and become complete, active T cell engagers:

The disease specific protease-mediated cleavage, meanwhile, is also exploited in PAC-Ig platform of Chugai, where TME-targeted VHH release is designed to achieve site-specific antigen binding:



Figure 4. PAC-IgTM platform developed by Chugai

Last but not least, this TME-responsive mechanism is also utilized to deliver viral antigens to tumor surface for presentation, which in turn retargets specific CD8+ T cells against tumors:

TME-responsive precise therapeutic antibodies are an exciting and rapidly evolving area of cancer research. They hold great promise for improving the precision and effectiveness of cancer treatments, and are offering a promising avenue for more precise and personalized medicine in the future that is likely to produce better outcomes for cancer patients.

Reference

1. Sulea, Traian, et al. "Structure-based engineering of pH-dependent antibody binding for selective targeting of solid-tumor microenvironment." MAbs. Vol. 12. No. 1. Taylor & Francis, 2020.

2. Chang, Hwai Wen, et al. "Generating tumor-selective conditionally active biologic anti-CTLA4 antibodies via protein-associated chemical switches." Proceedings of the National Academy of Sciences 118.9 (2021): e2020606118.

3. Lee, Peter S., et al. "Improved therapeutic index of an acidic pH-selective antibody." MAbs. Vol. 14. No. 1. Taylor & Francis, 2022.

4.Raabe, Marco, et al. "Assembly of pH‐Responsive Antibody‐Drug‐Inspired Conjugates." Macromolecular Bioscience 22.2 (2022): 2100299.

5.Migliorini, Francesca, et al. "A pH-responsive crosslinker platform for antibody-drug conjugate (ADC) targeting delivery." Chemical Communications 58.75 (2022): 10532-10535.

6.Boustany, Leila M., et al. "A Probody T Cell–engaging bispecific antibody targeting EGFR and CD3 inhibits colon cancer growth with limited toxicity." Cancer Research 82.22 (2022): 4288-4298.

7.Geiger, Martina, et al. "Protease-activation using anti-idiotypic masks enables tumor specificity of a folate receptor 1-T cell bispecific antibody." Nature communications 11.1 (2020): 3196.

8.Cattaruzza, Fiore, et al. "Precision-activated T-cell engagers targeting HER2 or EGFR and CD3 mitigate on-target, off-tumor toxicity for immunotherapy in solid tumors." Nature Cancer 4.4 (2023): 485-501.

9.Lin, Regina J., et al. "ITGB6 ProTriTAC™, a protease-activated T cell engager prodrug targeting Integrin-β6 for the treatment of solid tumors." Cancer Research 83.7_Supplement (2023): 2927-2927.

10.Panchal, Anand, et al. "COBRA™: a highly potent conditionally active T cell engager engineered for the treatment of solid tumors." MAbs. Vol. 12. No. 1. Taylor & Francis, 2020.

11.Millar, David G., et al. "Antibody-mediated delivery of viral epitopes to tumors harnesses CMV-specific T cells for cancer therapy." Nature biotechnology 38.4 (2020): 420-425.

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Understanding the specific metabolic characteristics of TME is essential for developing targeted therapies that exploit metabolic vulnerabilities in cancer cells while potentially sparing normal cells. At DetaiBio, we understand how essential it is to tailor antibody discovery and drug design strategy according to target product profile, and, with our cutting-edge single B antibody discovery approach, are dedicated to finding antibody candidates of desired properties to meet challenging but urgent medical needs.

Fine-tuned CD3 Affinity: Desired Balance between Antitumor Activity and Safety Drives the Design of Next-generation T Cell-engagers

Cytokine release-related syndrome (CRRS) is commonly observed in T cell engagers (TCEs) clinical trials. It is triggered often by excessive T cell activation, which in turn impairs desirable drug distribution and long-term efficacy.

Is cytokine production a hallmark of T cell activation? Or, in clinical setting, are high levels of cytokine production necessary for TCE efficacy?

The answer is NO, for both questions.

Studies unveiled that activation of biological functions in CTLs is determined by the molecular dynamics between CTLs and targets, and there exists an activation THRESHOLD for cytotoxicity advancing to full activation.

These seminal findings indicated that T cell killing does NOT require the formation of a stable mature immunological synapse, and have formed rationale underlying decoupling cytotoxicity from toxicity-triggering T cell stimulation in the development of next-generation TCEs, where CD3-binding affinity is finely tuned (generally, attenuated) to reach a "sweet spot" of signal that drives anti-tumor cytolytic activity without generating excessive cytokine release and/or T-cell exhaustion.

Figure 1.Fine-tuning CD3-binding affinity strikes a balance for optimal anti-tumor cytolytic activity, minimizing cytokine release and T-cell exhaustion

To date, quite a lot of novel TCEs have been built and investigated relying on the concept, and data produced so far support the "decoupling" theory, as exemplified by the developers and their candidate TCE drugs below.

• TeneoBio (TNB-486)



Figure 2. Structure of TNB-486

This CD19xCD3 bispecific antibody was designed for the treatment of B-NHL. Although its low affinity CD3-targeting arm lowered its in vitro killing potency, but it achieved the same maximum killing, and stimulated significantly less cytokine release. Amazingly, robust and long-term in vivo tumor cell killing occurred at low dose only. Favorable biodistribution or less propensity for inducing T-cell exhaustion or activation-induced cell death (AICD) resulting from low CD3 affinity may be responsible for its improved in vivo function.

This new TCE represented a novel therapeutic that induces potent T cell-mediated tumor-cell cytotoxicity uncoupled from high levels of cytokine release, making it an attractive candidate for B-NHL therapy.

• Genentech (HER2 TDB 1)



Figure 3.Structure of HER2 TDB 1

Bulit to lower systemic cytokine release and on-target/off-tumor toxicity to normal tissues of TCEs, this HER2/CD3 TCE of low binding affinity for CD3 proved that low affinity led to better overall tolerability in animal model, while T cell binding affinity had but very limited impact on in vitro and in vivo antitumor activity. The data indicated that fine-tuned affinity for CD3 as well as tumor target is a promising strategy for achieving maximal therapeutic index of CD3 TCEs.

• Amgen (AMG 424)



Figure 4. Structure of AMG 424

This CD3 affinity-optimized TCE showed ability to kill cancer cells and trigger T-cell proliferation, but with attenuated cytokine release, and its potential to elicit significant clinical activity in patients with multiple myeloma.

• Regeneron (REGN4018)



Figure 5. Structure of REGN4018

This CD3 affinity -customized MUC1xCD3 TCE for the treatment of ovarian cancer indicated attenuated profiles of cytokine release and favorable biodistribution, while its tumor killing potency remained, demonstrating potent antitumor activity and good tolerability of REGN4018, and is now under clinical evaluations.

• AbCellera

This biotech is Identifying TCEs with balanced anti-tumor potency and toxicities, mostly CRRS by fine-tuning CD3-binding affinity as well as disease target-binding moieties. Its proof-of-concept TCEs have showed high potency with low cytokine release.

Reference

1.Faroudi, Mustapha, et al. "Lytic versus stimulatory synapse in cytotoxic T lymphocyte/target cell interaction: manifestation of a dual activation threshold." Proceedings of the National Academy of Sciences 100.24 (2003): 14145-14150.

2.Riquelme, Erick, et al. "The duration of TCR/pMHC interactions regulates CTL effector function and tumor‐killing capacity." European journal of immunology 39.8 (2009): 2259-2269.

3.Malik-Chaudhry, Harbani K., et al. "TNB-486 induces potent tumor cell cytotoxicity coupled with low cytokine release in preclinical models of B-NHL." MAbs. Vol. 13. No. 1. Taylor & Francis, 2021.

4.Staflin, Karin, et al. "Target arm affinities determine preclinical efficacy and safety of anti-HER2/CD3 bispecific antibody." JCI insight 5.7 (2020).

5.Zuch de Zafra, Christina L., et al. "Targeting multiple myeloma with AMG 424, a novel anti-CD38/CD3 bispecific T-cell–recruiting antibody optimized for cytotoxicity and cytokine release." Clinical Cancer Research 25.13 (2019): 3921-3933.

6.Crawford, Alison, et al. "A Mucin 16 bispecific T cell–engaging antibody for the treatment of ovarian cancer." Science translational medicine 11.497 (2019): eaau7534.

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Molecular Construction of T Cell Engagers: Formats Matter

T cell engagers (TCEs) are artificial, multi-specific therapeutic antibodies for cancer treatment, engineered to redirect the immune system's T cells to recognize and kill cancer cells. They are designed to bind to a target antigen expressed on a cancer cell and to a trigger molecule on T cells, generally CD3. Formats of TCEs, as to other multi-specifics, matter a lot for their manufacturability and PK/ADA property as well as efficacy. Different formats have been developed, each with ads and drawbacks. Representatives of some significantly developed TCEs, either preclinically or clinically, are illustrated in this review.

IgG-like TCEs

IgG-like TCEs, due to limited mutations introduced, retain many of the favorable traits of conventional IgGs.

Unlike the generation of Catumaxomab (Epcam/CD3 TCE), specific and smart strategies to encourage desirable LC/HC and/or HC/HC pairing and to facilitate purification are essentially required and actually utilized to successfully construct the new-generation, premium format, as exemplified below.

• Mosunetuzumab by Genentech

Mosunetuzumab is constructed with knobs-into-holes technology for desired HC pairing while in vitro annealing for HC/LC pairing, and was approved for the treatment of R/R follicular lymphoma.

• Teclistamab by JNJ

It's a BCMA-targeting DuoBody that has been marketed for Relapsed/Refractory Multiple Myeloma (R/R MM) treatment

• DuoBody

A controlled Fab-arm exchange technology developed by Genmab, enables efficient generation of bsAbs with normal IgG structures.

• Epcoritamab

It's another DuoBody co-developed by AbbVie and Genmab, and was recently approved for Relapsed/Refractory diffuse large B-cell lymphoma (R/R DLBCL) treatment.

• ERY974 by Chugai (ART-Ig)

ERY974 is an anti–GPC3/CD3 TCE for treatment of solid tumors under development preclinically. Its construction is achieved through introduction of electrostatic steering mutations in the CH3 domain to drive heterodimerization of the heavy chains and utilization of a common LC to avoid LC mispairing.

• REGN1979 by Regeneron

This CD20/CD3 TCE, now in clinical trials for B-NHL, is a devised format via the introduction of local isotype chimera of IgG1/G3 in CH3 in addition to the utilization of a common LC.

This format promises to be a more native one since it avoids Fc-Fc interface engineering, therefore further reducing PK/ADA and manufacturability risks.

Based on this technology, a few more TCEs for solid tumors, including REGN4018, REGN4336(PSMA/CD3 for mCRPC), are under clinical evaluations.

Fugure 1. Fragment-based TCEs

While IgG-like formats hold traits of native IgG favorable for manufacturability and PK/ADA property of antibody drugs, fragment-based T cell engagers (TCEs) have been developed anyway, although immunogenicity and instability result due to unnatural mutations or fragments introduced, for achieving unique medical purposes, or due to the unavailability of constructing technology, or commercial limitations.
Fragment-based TCEs are generally

• Simple structures comprised of linked scFvs, scFabs or sVDs, et al.
• Lacking half-life extending (HLE) part.
• Challenging to produce, prone to aggregate/fragment.
• Of small size with short half-life.

Representative TCE of this kind is blinatumomab(CD19/CD3 BiTE, two linked, independent scFvs) by Amgen approved for treatment of BCP-ALL and more later on.

In order to prolong half-life and allow less frequent dosing, BiTE molecules have been genetically fused to an Fc domain, resulting in a series of HLE BiTE molecules (MW around106 kD) in Amgen.

AMG757, one of HLE BiTEs by Amgen targeting DLL3, is under investigation for SCLC treatment.

In a similar fashion, MacroGenics DART platform designs therapeutic molecules that combine two independent Fabs in a diabody-like structure with or without Fc domain tailored to have a long or short half-life, respectively.

MGD024, a CD123 x CD3 Dart TCE for patients with R/R CD123(+) hematologic malignancies, has entered clinical investigation.

Meanwhile, with its TriTAC and ProTriTAC(prodrug) TCE platforms, Harpoon has created fragment-based TCEs that incorporate single domain antibodies and use albumin binding for half-life extension.

Furthermore, tebentafusp-tebn(KIMMTRAK), the first and only approved TCE for solid tumor treatment (mUM) developed by Immunocore, is composed of a TCRm and a CD3-targeting scFv. It has an acceptable PK profile due to its increased size (77KD).

Figure 2. TCEs Other Than Above Discussed

In order to acquire improved efficacy/safety profile or to further enhance clinical significance, numerous differentiated formats in addition to fragment-based and IgG-like ones have been designed and tested, some of which are discussed below.

• EMB-07.

This TCE (ROR1/CD3) is an appended-IgG of symmetrical structure (2:2) designed with FIT-Ig platform of EpimAb for solid tumors, and is now in clinical evaluation.

Appended-IgGs are conventional IgGs appended with scFv, Fab, or nanobody, et al. They have half-life comparable to parental ones. However, non-natural structures might give rise to increased aggregation, instability and ADA risk. FIT-Ig platform generates bispecific antibodies without introducing mutations or linkers, favoring their manufacturability and stability.

EMB-06, another FIT-Ig generated TCE targeting BCMA, is also under clinical evaluation.

• BA1202.

This CEA/CD3 symmetrical (2:2) TCE by Boan Biotech is of a butterfly-shaped antibody structure: Fab ends bind bivalently to CEA while LC-NT linked bivalent scFvs bind to CD3 monovalently (possibly due to altered spatial constructure and impaired affinity compared to Fc-hinge linked one), and has entered clinical trial.

• Cibisatamab (RG7802).

It's a 2:1 format CEA/CD3 TCE by adding a second CEA-binding Fab to asymmetrical 1:1 format to enable a "low affinity but high avidity" binding to disease targets. It presumably will achieve optimized efficacy and safety by decreasing "on-target-off-tumor toxicity", and is now under development by Roche in clinical trials.

• CX-904.

Designed by Cytomx for precision targeting, this clinical-stage 2:2 EGFR/CD3 TCE prodrug is conditionally activated in tumor microenvironment upon specific proteolysis.

• Imvotamab (IGM-2323).

This TCE of IgM isotype by IGM targets CD20 and CD3. With 10-valency units for CD20, it’s proposed to bind to CD20 with more power (avidity) than IgG format, therefore overcoming target decrease-induced drug resistance, and achieving deeper depletion than currently approved antibody therapies.

More IgM TCE drugs from this company include IGM-2644 (CD38/CD3) and IGM-2537 (CD123/CD3).

• TNB-486.

This CD19-targeting TCE’s asymmetrical format by Teneobio falls kind of between the fragment-based and the IgG-like. It’s comprised of a CD3-binding half IgG and a CD19-binding HcAb, and is now under clinical evaluation for relapsed/refractory (R/R) B-lymphoma.

• YBODY.

Similar with the format of TNB-486, YBODY platform by YZYBio designs TCE that is composed of disease target-binding half IgG and CD3-binding scFv.

A few YBODY TCEs are now in clinical trials, such as M802 (HER2/CD3).

Figure3. IgG-like TCEs in differentiated formats

Reference

1.Giese, Glen, et al. "Bispecific antibody process development: Assembly and purification of knob and hole bispecific antibodies." Biotechnology progress 34.2 (2018): 397-404.

2.Pillarisetti, Kodandaram, et al. "Teclistamab is an active T cell–redirecting bispecific antibody against B-cell maturation antigen for multiple myeloma." Blood advances 4.18 (2020): 4538-4549.

3.Labrijn, Aran F., et al. "Efficient generation of stable bispecific IgG1 by controlled Fab-arm exchange." Proceedings of the National Academy of Sciences 110.13 (2013): 5145-5150.

4.Zhang, Jimin, et al. "Pharmacodynamic activity of epcoritamab (GEN3013; CD3xCD20) as monotherapy is maintained in combination with standard of care therapies in patients with diffuse large B-cell lymphoma." Cancer Research 83.7_Supplement (2023): 3248-3248.

5.Shiraiwa, Hirotake, et al. "Engineering a bispecific antibody with a common light chain: Identification and optimization of an anti-CD3 epsilon and anti-GPC3 bispecific antibody, ERY974." Methods 154 (2019): 10-20.

6.Ishiguro, Takahiro, et al. "An anti–glypican 3/CD3 bispecific T cell–redirecting antibody for treatment of solid tumors." Science translational medicine 9.410 (2017): eaal4291.

7.Smith, Eric J., et al. "A novel, native-format bispecific antibody triggering T-cell killing of B-cells is robustly active in mouse tumor models and cynomolgus monkeys." Scientific reports 5.1 (2015): 17943.

8.Leung, Shuk on Annie, and Panagiotis A. Konstantinopoulos. "Advances in the treatment of platinum resistant epithelial ovarian cancer: an update on standard and experimental therapies." Expert Opinion on Investigational Drugs 30.7 (2021): 695-707.

9.Kelly, William Kevin, et al. "A phase 1/2 study of REGN4336, a PSMAxCD3 bispecific antibody, alone and in combination with cemiplimab in patients with metastatic castration-resistant prostate cancer." (2022): TPS5105-TPS5105.

10.Portell, Craig A., Candice M. Wenzell, and Anjali S. Advani. "Clinical and pharmacologic aspects of blinatumomab in the treatment of B-cell acute lymphoblastic leukemia." Clinical pharmacology: advances and applications 5.sup1 (2013): 5-11.

11.Jen, Emily Y., et al. "FDA approval: blinatumomab for patients with B-cell precursor acute lymphoblastic leukemia in morphologic remission with minimal residual disease." Clinical Cancer Research 25.2 (2019): 473-477.

12.Giffin, Michael J., et al. "AMG 757, a half-life extended, DLL3-targeted bispecific T-cell engager, shows high potency and sensitivity in preclinical models of small-cell lung cancer." Clinical Cancer Research 27.5 (2021): 1526-1537.

13.Huang, Ling, et al. "Multispecific, Multivalent Antibody‐Based Molecules Engineered on the DART® and TRIDENTTM Platforms." Current Protocols in Immunology 129.1 (2020): e95.

14.Winer, Eric S., et al. "A Phase 1, First-in-Human, Dose-Escalation Study of MGD024, a CD123 x CD3 Bispecific Dart® Molecule, in Patients with Relapsed or Refractory CD123-Positive (+) Hematologic Malignancies." Blood 140.Supplement 1 (2022): 11753-11754.

15.Hua, Gwen, Daniel Carlson, and Jacqueline R. Starr. "Tebentafusp-tebn: A Novel Bispecific T-Cell Engager for Metastatic Uveal Melanoma." Journal of the Advanced Practitioner in Oncology 13.7 (2022): 717.

16.Bacac, Marina, et al. "A novel carcinoembryonic antigen T-cell bispecific antibody (CEA TCB) for the treatment of solid tumors." Clinical Cancer Research 22.13 (2016): 3286-3297.

17.Boustany, Leila M., et al. "A Probody T Cell–engaging bispecific antibody targeting EGFR and CD3 inhibits colon cancer growth with limited toxicity." Cancer Research 82.22 (2022): 4288-4298.

18.Hart, Kevin C., et al. "High valency of IGM-2323, a CD20xCD3 IgM bispecific T cell engager, displaces rituximab binding and induces potent B lymphoma cell killing." Cancer Research. Vol. 82. No. 12. 615 CHESTNUT ST, 17TH FLOOR, PHILADELPHIA, PA 19106-4404 USA: AMER ASSOC CANCER RESEARCH, 2022.

19.Malik-Chaudhry, Harbani K., et al. "TNB-486 induces potent tumor cell cytotoxicity coupled with low cytokine release in preclinical models of B-NHL." MAbs. Vol. 13. No. 1. Taylor & Francis, 2021.

20.Hou, Jing-Zhou, et al. "Interim Results of the Phase 1 Study of Tnb-486, a Novel CD19xCD3 T-Cell Engager, in Patients with Relapsed/Refractory (R/R) B-NHL." Blood 140.Supplement 1 (2022): 1474-1475.

21.Jacobs, R., R. Nair, and S. G. Cho. "High complete response rate with TNB-486 in relapsed/refractory follicular lymphoma: Interim results from an ongoing Phase I study." European Hematology Association (EHA) (2023): 8-11.

22.Yu, Shengnan, et al. "A novel asymmetrical anti-HER2/CD3 bispecific antibody exhibits potent cytotoxicity for HER2-positive tumor cells." Journal of Experimental & Clinical Cancer Research 38 (2019): 1-16.

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Emerging Antibody Therapies Targeting B Cell Lymphomas

Since rituximab, novel modalities of highly potent immunotherapies have been investigated and/or marketed to lift the limits on treatment of B cell lymphomas, including NHLs. The past decade has witnessed the approval of plenty of antibody-based, potent therapies of B cell lymphomas, that, along with CAR -Ts, have tremendously changed the therapeutic landscape, including:

1. T Cell Engagers (TCEs)

• 1) Blinatumomab: CD19/CD3 TCE of BiTE format, by Amgen.
• 2) Mosunetuzumab: first ever approved CD20/CD3 TCE, by Roche.
• 3) Epcoritamab: a CD20/CD3 TCE by Abbvie and Genmab; subcutaneously. administrated for better patient compliance and lower CRS liabilities.
• 4) Glofitamab: a 2:1 format CD20/CD3 TCE by Roche; dual-targeting brings T cells in closer proximity for potent target-killing.

2. Antibody-drug conjugates (ADCs)

• 1) Brentuximab vedotin (anti-CD30-MMAE by Seagen/Takeda).
• 2) Polatozumab vedotin (anti-CD79b-MMAE by Genentech).
• 3) Loncastuximab tesirine (anti-CD19-PBD by ADC/Sobi).

However, the clinical effectiveness of approved ones has been impaired by inadequate treatment efficacy, intolerable toxicities, and the development of treatment resistance.

Fortunately, novel antibody therapeutics inspired by unmet medical needs are emerging that, either at early or POC stages or late stage of clinical tests, seem promising for combatting limitations currently seen in clinical practices, as exemplified below.

1. IGM-2323 (Imvotamab) by IGM Biosciences

This TCE of IgM isotype targets CD20 and CD3. With 10-valency units for CD20, it’s designed to bind to CD20 with more power (avidity). Preclinical research demonstrates that it may have advantages over IgG bispecific antibodies, therefore more likely to overcome CD20 low abundance or loss-induced drug resistance, and achieve deeper depletion than currently approved antibody therapies.

Data generated from its Phase 1 clinical trials provide evidence that Imvotamab exhibits a favorable safety and tolerability profile with encouraging activity in refractory or relapsed NHL patients.

2. Odronextamab by Regeneron

This CD20/CD3 TCE is a devised format via the introduction of local isotype chimera of IgG1/3, and promises to be of native format with improved PK property.

Figure 1. Structure of Odronextamab

Odronextamab has reported new data from its pivotal Phase II study, and is now under FDA priority review.

If approved, odronextamab would be the first and only bispecific antibody approved in both FL and DLBCL – the two most common subtypes of NHL.

3. GB261 (by Genor)

This CD20/CD3 TCE is of ultra-low affinity to bind CD3 and, RARELY, keeps Fc functions (ADCC and CDC). By its designed MOAs, Fc-mediated cytolysis and T cell-mediated killing dominates in according to the change of T/B cell ratios from initial stage of treatment towards late stage.

GB261 significantly inhibited rituximab-resistant cancer cell proliferation and induced but less cytokine release, and, now in clinical trial, promises to be a highly potent TCE for B cell malignancies.

Figure 2. Efficacy of GB261 on CD20+, CD3+ lymphocytes in Cynomolgus monkeys

4. CX-2029 (by CytomX)

This probody drug conjugates directed against CD71 that contains MMAE are conditionally activated, masked ADC, whose activity would be restored by tumor-associated proteases, thereby restricting target engagement to the tumor, creating a therapeutic window for this previously undruggable target.

Now under phase 1/2 evaluation in patients with some solid tumors and DLBCL,
This prodrug showed clinical activity at tolerable doses.

Figure 3. Structure of CX-2029 drug conjugates

5. CH2-aIgM-MMAE (by Technical University of Darmstadt)

When targeting such antigens as mentioned above, while failing to cover all target disease cells, it’s hard to distinguish cancerous B cells from their non-malignant counterparts, leading to on-target toxicities.

An amazing work on CH2-aIgM-MMAE, a human IgM-targeting prodrug ADC, provided a novel mechanism for NHL treatment.

In this excellent POC research:

• 1) Human IgM (constant domain), rather than any CD markers, was targeted for clonal B cell lymphoma eradication. Immunization of chicken instead of mammals, was used to get desired immune response.
• 2) Chicken-derived aIgM was fused to and masked by the epitope-holding IgM domain CH2 via a dual tumor-protease cleavable linker.
• 3) The prodrug was ultimately equipped with MMAE.
• 4) Binding capacity of the prodrug was restored upon conditional protease-mediated demasking which consequently enabled target-dependent antibody internalization and subsequent induction of apoptosis in malignant B cells.

Figure 4. Design and mode of action of masked aIgM ADC.

Limitations on clinical practice are being updated as its boundary are pushed. So are the therapeutic approaches for them. As they are evolving, these approaches will definitely further enhance the chance of cure for B cell malignancies.

Reference

1. Hart, Kevin C., et al. "High valency of IGM-2323, a CD20xCD3 IgM bispecific T cell engager, displaces rituximab binding and induces potent B lymphoma cell killing." Cancer Research. Vol. 82. No. 12. 615 CHESTNUT ST, 17TH FLOOR, PHILADELPHIA, PA 19106-4404 USA: AMER ASSOC CANCER RESEARCH, 2022.

2. Cai, Wenyan, et al. "Biological activity validation of a computationally designed Rituximab/CD3 T cell engager targeting CD20+ cancers with multiple mechanisms of action." Antibody Therapeutics 4.4 (2021): 228-241.

3. Johnson, Melissa, et al. "P01. 06 CX-2029, a probody drug conjugate targeting CD71 in patients with selected tumor types: PROCLAIM-CX-2029 dose expansion phase." Journal of Thoracic Oncology 16.3 (2021): S238.

4. Johnson, Melissa, et al. "Phase I, first-in-human study of the probody therapeutic CX-2029 in adults with advanced solid tumor malignancies." Clinical Cancer Research 27.16 (2021): 4521-4530.

5. Schoenfeld, Katrin, et al. "Conditional activation of an anti-IgM antibody-drug conjugate for precise B cell lymphoma targeting." Frontiers in Immunology 14 (2023): 1258700.

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