Preclinical and Nonclinical Characterization of HPN217: A ... · Preclinical and Nonclinical Characterization of HPN217: A Tri-Specific T Cell-Activating Construct (TriTAC) Targeting

Preclinical and Nonclinical Characterization of HPN217: A Tri-Specific T Cell-Activating Construct

(TriTAC) Targeting B Cell Maturation Antigen (BCMA) for the Treatment of Multiple MyelomaChe-Leung Law, Wade Aaron, Rick Austin, Manasi Barath, Evan Callihan, Thomas Evans, Maria Gamez Guerrero, Golzar Hemmati, Adrie Jones, Kathryn Kwant, Llewelyn Lao, Bryan Lemon,

Katrine Moldt, Purbasa Patnaik, Kenneth Sexton, Holger Wesche, Shelly Xiao, Stephen Yu and Tim Yu. Harpoon Therapeutics, South San Francisco, CA 94080

Abstract 3225 ASH Annual Meeting 2018

IN VITRO PHARMACOLOGY

HPN217: BCMA-TARGETING TriTAC

• B cell maturation antigen (BCMA), also

known as TNFRSF17 and CD269, is

expressed on B lineage cells including

memory B cells, plasmablasts and plasmacells

• TNFSF13/APRIL and TNFSF13B/BAFF areligands for BCMA that activate the MAP

kinase and Bcl-2/XL pathways to promote

proliferation and survival

• Expression of BCMA is maintained

subsequent to plasma cell transformation

into multiple myeloma (MM)

• BCMA has been explored as a target for

antibody-based therapeutic modalities

including CAR T cells, effector function-

RATIONALE

HPN217 SUMMARY• Binds to human BCMA, CD3ε, and albumin; cross reacts to cyno CD3ε and

albumin but not to cyno BCMA

• Redirects T cells to kill BCMA expressing cells in vitro

• Inhibits tumor growth in models of multiple myeloma and mantle cell

lymphoma

• Has a terminal serum half-life of 70-84 hrs and stability of ≥ 1 week in

circulation in cyno monkeys

• Designed to be an efficacious, safe, and convenient therapeutics for patients

with BCMA expressing malignancies

• Projected to enter a first in human clinical trial in the second half of 2019

αBCMA

αCD3ε

αALB

anti-BCMA single domain antibody

targets cells expressing BCMA

anti-albumin single domain antibody

extends half-life

anti-CD3ε scFv engages T cells

molecular weight of ~54 kDa

IN VITRO PHARMACOLOGY

Secondary controlHPN217Anti-GFP TriTACHPN217

Alexa fluor 647

Effects of Human Serum Albumin on the Potency of HPN217 in

T Cell-Dependent Cellular Cytotoxicity (TDCC)

enhanced antibody, antibody-drug conjugates, CD3-based bi-specific T cell engaging

molecules, and CD16A-based bi-/tri-specific molecules

• HPN217 is a novel Tri-specific T Cell-Activating Construct (TriTAC) engineered to have

long circulating half-life that re-directs T cells to kill BCMA positive cancer cellsCell Line EC50 (pM) EC50 + ALB (pM) ALB Shift

EJM 9.6 149 15

OPM2 6.5 328 50

MOLP8 2.5 388 154

RPMI8226 4.8 194 89

EJM Cells

BINDING & SPECIES CROSS-REACTIVITY

BCMA positiveNCI-H929

BCMA negativeDMS 153

Re

lati

ve C

ell

Co

un

t

Normal T cellsDonor 02

Normal T cellsDonor 35

HPN217 does not cross-react with cyno BCMA

BCMA CD3 ALB

human KD (nM) 2.4* 7.9* 6

cyno KD (nM) No binding* 7.8* 7.5

KD Determined by Biolayer Interferometry

Re

lati

ve C

ell

Co

un

t

IN VIVO PHARMACOLOGY

PHARMACOKINETICS & IN VIVO STABILITY

Sample EC50 (pM)

HPN217 purified protein 440

168 h (Day 7) PK serum sample 580

BCMA

(receptors/cell)

BCMA

Transcript

(FPKM)

EC50 (pM)

Donor 02 Donor 35 Donor 81 Donor 86

EJM 15900 607 151 121 143 191

NCI-H929 8160 1931 169 113 124 239

OPM2 7072 358 250 199 265 416

RPMI-8226 4308 35 275 371 211 543

Dose

(mg/kg)

Terminal

T1/2 (hr)

Cmax

(ng/mL)

AUC0-168h

(h*ng/mL)

AUC0-inf

(h*ng/mL)

CL

(mL/h/kg)

Vi

(L/kg)

0.01 69.5 604 23400 28200 0.359 16.7

0.1 79.0 4650 251000 306000 0.328 21.5

1 84.4 61700 1560000 2130000 0.470 16.4

Flow Cytometric Analysis on HPN217 Binding to Target Cells

TDCC Activity of HPN217 Measured in the Absence or Presence

of 15 mg/mL Human Serum Albumin (ALB)

HPN217-Mediated TDCC against BCMA Positive NCI-H292 (Upper

Panel) and BCMA Negative NCI-H510A Cells (Lower Panel)

Potent Cytotoxicity against Multiple Myeloma Cells with > 4,300

Surface BCMA Receptors/Cell

HPN217- and BCMA-Dependent Activation of Normal T Cells:

Upregulation of CD69 & CD25; Secretion of TNFα & IFNγ

HPN217-Mediated Tumor Growth Suppression in the RPMI-8226

MM Model (BCMA RNA/FPKM: 35, BCMA/Cell: ~4,308)

HPN217-Mediated Tumor Growth Suppression in the Jeko-1 MCL

Model (BCMA RNA/FPKM: 16, BCMA/Cell: ~2,200)

Serum Concentration-Time Profiles of HPN217 in Cyno Monkeys

Following A Single, Intravenous Bolus Dose of HPN217

HPN217 Single Dose PK Parameters in Cyno Monkeys

(Measured by Anti-Idiotype Assay)

HPN217 Remained Functionally Intact after One-Week Circulation

in Cyno Monkeys: TDCC Assay Using EJM as Target Cells

• Anti-idiotype: anti-id mAbs against

the ALB binding domain to capture &

CD3ε binding domain to detect

• Functional: recombinant CD3ε to

capture and recombinant BCMA to

detect

*measured in the presence of 15 mg/mL human serum albumin

-16 -14 -12 -10 -8 -60

50

100

150

normalized EJM

TriTAC log(M)

Norm

aliz

ed V

iabi

lity

(%) HPN217

anti-GFP TriTAC + ALB

HPN217 + ALBanti-GFP TriTAC

-14 -12 -10 -8 -60

50

100

TriTAC log(M)

Norm

aliz

ed V

iabi

lity

(%) HPN217 Donor 2

HPN217 Donor 35

HPN217 Donor 81

HPN217 Donor 86

aGFP TriTAC Donor 2

aGFP TriTAC Donor 35



-14 -12 -10 -8 -60

50

100

H929 TDCC Assay with HSA

TriTAC log(M)

Norm

aliz

ed V

iabi

lity

(%) HPN217 Donor 02


HPN217 Donor 35


HPN217 Donor 81


HPN217 Donor 86


-14 -12 -10 -8 -60

1

2

3

4

TriTAC log(M)

TNFa

(ng/

mL) HPN217 Donor 2

aGFP TriTAC Donor 2

HPN217 Donor 35


-14 -12 -10 -8 -60

10

20

30

40

TriTAC log(M)

IFNg

(ng/

mL) HPN217 Donor 2

aGFP TriTAC Donor 2

HPN217 Donor 35


-14 -12 -10 -80

20

40

60

EJM CD69

TriTAC Concentration log(M)

% C

D69

Posi

tive

Cells HPN217 Donor 35

anti-GFP TriTAC Donor 35


HPN217 Donor 81


HPN217 Donor 02


HPN217 Donor 86

-14 -12 -10 -80

10

20

30

40

EJM CD25+

TriTAC Concentration log(M)

% C

D25

Pos

itive

Cel

ls

HPN217 Donor 35



HPN217 Donor 02


HPN217 Donor 81


HPN217 Donor 86

EJM CD69 EJM CD25

EJM TNFα EJM IFNγ

-16 -14 -12 -10 -8 -60

50

100

Normalized data 100% serum/net 10% serum

TriTAC log(M)

Norm

aliz

ed V

iabi

lity

(%)

HPN217 purified protein168 h serum sampleanti-GFP TriTAC

• RPMI-8226 cells implanted s.c.

on day 0

• Normal PBMC implanted i.p. on

day 0• Treatment started on day 0 (¿,

preventive) or day 7 (l,

therapeutic), qdx10

• Jeko-1 cells implanted s.c. on

day 0

• Normal PBMC implanted i.p. on

day 3• Treatment started on day 3 (¿,

preventive) or day 10 (l,

therapeutic), qdx10

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Preclinical and Nonclinical Characterization of HPN217: A ... · Preclinical and Nonclinical Characterization of HPN217: A Tri-Specific T Cell-Activating Construct (TriTAC) Targeting