Agonist and Bispecific IgM:Nature’s Approach to Highly Avid, Multivalent Antibodies

Bruce Keyt, Ph.D.Chief Scientific Officer, IGM Biosciences 

Mountain View, CA7

PEGS EuropeNovember 22, 2019

IgM: Natural multi‐valent, high avidity antibody 

• IgM hexamer (minus J chain) IgM pentamer (plus J chain)

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J‐chain (joining chain)

HC, LC and J‐chains      10 binding sitesHC and LC      12 binding sites

IgM for high aviditytumor cell binding

IgM Structure: Hexamer and Pentamer’3D imaging’ with transmission electron microscopy 

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Hexamer (minus J chain) Pentamer (plus J chain)

Ramesh Baliga and NanoImaging

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Bispecific IgM: CD20 x CD3Highly Avid, Asymmetric IgM Antibodies

High AvidityEnhanced binding, to difficult or rare targets with high specificity, high affinity binding domains 

Rigid and polarized disc shape confers biophysical propertiesEnhanced control of T cell engagement

Platform for multi‐specific mAbsEnables construction of protein based ”nano‐machines”

Modified J‐chain bispecific IgM10:1 asymmetric binding of tumor cell and T cells, Rapid innovation with various J chain constructs

Conformational change upon bindingEnables specialized properties upon bindingCan be designed to drive forceful agonistic properties

Naturally occurring formatKey to minimize immunogenicity

Daniel Chen  PEGS Europe Nov 21, 2019

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Cross‐linking Receptors on Tumor CellsTrimerizing Death Receptor: DR5 / TNFrSF10

MULTIMERIZEDRECEPTOR

MULTIMERIZINGLIGAND

Goal: Destroy tumor cells by trimerizing death receptor 5

Gastric Adenocarcinoma

Colon Adenocarcinoma

DR5 Expression

Also: pancreatic, lung, breast andprostate tumors, leukemia and lymphoma

Trivalent binding required

• Must bind three or more DR5 receptors to send strong signal

Signals cell to commit suicide (apoptosis)

• May be used with many other drugs or checkpoint antibodies

• Cell debris may help immune system cells recognize cancer (APC)

IgGs are bivalent

• Multiple IgG DR5 antibodies tested in clinical trials

Safe, but not effective*

• IgGs can only bind two DR5 receptors

• Cellular cross-linking required for IgG to have any effect

• Breast

• Prostate

• Colon

• Pancreatic

• Leukemia

• Lymphoma

Tumor Expression

* Holland, Cytokine & Growth Factor Reviews, 25 (2014) pp. 185-193

Death Receptor 5 (DR5): Tumor Apoptosis

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TNFrSF Members IgG Antibodiesless effective

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Death Receptor 5: Broad Tumor Expression

Beatrice Wang, Tasnim Kothambalwala, etal

Surface DR5 expression across several tumor cell lines.  Cell lines were stained with 2 mg/ml      of anti‐DR5‐APC antibody and receptor expression levels were measured by flow cytometry.

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DR5 IgM: CHO cell derived antibody characterization

Beatrice Wang , etal

IgM

Superior Cross‐linking function: Antibody induced Apoptosis DR5 Binding DR apoptosis and cell death

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Antibody (ng/ml)

IgG

1000 x improved apoptosison TNFrSF tumor target

Percent V

iability 

1000x

Antibody (pg/ml)

100 x improved binding onlow expression tumor target

0.01 0.1 1 10 100  

Percent B

ound

 

IgGIgM100x

Superior agonist cross‐linking of receptors IgM: 1000 x more potent, multiple antibodies, different DR5 epitopes

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mAb 1

mAb 3

mAb 2

mAb 4

In Vitro Cytotoxicity KineticsIgM rapidly destroys tumor cells, direct apoptotic effect

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Untreated  Anti‐DR5 IgG  Anti‐DR5 IgM

0.001 0.01 0.1 1 10 100 1000 100000

20

40

60

80

100

120

Colo205 (colon)

[Anti-DR5] (ng/mL)

0.001 0.01 0.1 1 10 100 1000 100000

20

40

60

80

100

120

HCT-15 (colon)

[Anti-DR5] (ng/mL)0.001 0.01 0.1 1 10 100 1000 100000

20

40

60

80

100

120

Nalm-6 (B-ALL)

[Anti-DR5] (ng/mL)

0.001 0.01 0.1 1 10 100 1000 100000

20

40

60

80

100

120

MIA-PaCa-2 (pancreas)

[Anti-DR5] (ng/mL)

In Vitro Cytotoxicity: IgG, crosslinked IgG vs IgMIgM is potent on IgG insensitive cell lines

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IgG

Crosslinked IgGIgM

IgG, CrosslinkedIgG

IgM

IgG, CrosslinkedIgG

IgM

IgG

Crosslinked IgGIgM

IgG‐sensitive tumor cells:

IgG‐resistant tumor cells:

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In Vitro Cytotoxicity: IgG, crosslinked IgG vs IgM

Beatrice Wang, Tasnim Kothambalwala

Significantly Enhanced Efficacy: Tumor Killing vs. IgG in Mouse Models

Durable efficacy seen even in disseminated acute lymphoblastic leukemia

Anti‐DR5: IgM Superior In Vivo to IgG 

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Nearly complete tumor eradication in colorectal tumor model

Anti‐DR5 IgM

Anti‐DR5 IgG at 6 g/ml *

Resistant Colorectal Tumor Model (HCT15)

IgM slowed tumor growth better than chemotherapy IgG not synergistic with chemotherapy

Anti‐DR5 IgM Outperforms Standard of Care

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IgG drug exposure is 7x greater than IgM

Colorectal Tumor Model (HCT15 Tumor Cells)

IgM synergistic with chemotherapy and showed dramatically enhanced survival in xenograft tumor model

Anti‐DR5: IgM Synergistic With Irinotecan

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In vivo efficacy yields tumor eradicationIgM efficacy in larger established tumors

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Dosing (3 mg/kg) designed to achieve similar plasma levels of antibody, both for IgG and IgM.Treatment during the first week only

In Vivo EfficacyIgM efficacy in patient‐derived xenograft models

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VehicleAnti‐DR5 IgGAnti‐DR5 IgM

Anti‐DR5 IgG

Anti‐DR5 IgM

DR5: IGM‐8444 In vivo mouse xenograft study

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In Vivo EfficacyDR5‐IgM antibodies penetrate tumors and rapidly induce apoptosis after a single dose

DR5-IgM DR5-IgGCleaved Caspase-3 at 1 hourColo205 Tumors

IgG

OX40: modest efficacy reported with agonist monotherapyBivalent IgG has limited ability to crosslink OX40 cell surface receptors 

OX40 IgM Induces More Checkpoint Signaling

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1 10 100 1000      10000

Anti‐OX40 antibody (ng/mL)

600

400

200

0

NFkBactiv

ity(relative luminescence)

GITR IgM Inhibits Effect of Regulatory T Cells

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0

200

400

600

800

IFN- Production

In presence of Tregs: CD4+ proliferation, cytokine secretion

IGM Biosciences: Agonistic Anti‐DR5 IgM  • IgM is a naturally occurring multi‐valent, high avidity antibody• Potent cell surface receptor cross‐linking agent• Robust agonist activity with TNFrSF receptors• Strong apoptosis with potent tumor cell killing (EC50 = 1 pM)• DR5 IgM has good anti‐tumor activity, in vitro and in vivo models• Anti‐DR5 IgM effective in solid and liquid tumors• Additive or synergistic activity with chemotherapy• Safety demonstrated in non‐GLP studies with cyno monkeys• High yield cell line development, in progress• IND: in preparation for 2020

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Mode Target Indications

Phase of Development Anticipated MilestonesDiscovery Preclinical Phase 1 Phase 2 Phase 3

T cell EngagerIGM‐2323

(CD20 x CD3)NHL, CLL Phase 1 for R/R 

B cell NHL: 2019

Receptor Cross‐linking 

Agonist

IGM‐8444(DR5)

Solid andHematologicMalignancies

IND filing: 2020(anticipated)

Targeted Cytokines IL‐15 x  PD‐L1

Solid andHematologicMalignancies

IND filing: 2021(anticipated)

Lead Programs

IGM Biosciences: Oncology Pipeline

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Acknowledgments

325 East Middlefield Road     Mountain View, CA 94043 26

Immuno‐Oncology• Angus Sinclair• Beatrice Wang

‐ Tasnim Kothambawala ‐ Ling Wang 

• Dalya Rosner‐ Susan Calhoun

• Manal Amoury

Preclinical Sciences• Steve Carroll

‐Maya Leabman‐ Yuan Cai‐ Chitra Saraiya

Discovery Biology• Ramesh Baliga• Paul Hinton

‐ Kevin Carlin• Dean Ng

‐ Sachi Rahman‐ Yasinee Ng

• Keyu Li• Marigold Manlosuc

Process Sciences • Marvin Peterson

‐ Bing Shan‐ Avneesh Saini‐ Hongjun Yue‐Madeline Tran

Clinical R&D• Daniel Chen‐Wayne Godfrey‐ Iris Sison‐ Genevive Hernandez