Preclinical and Nonclinical Characterization of HPN217: A ... · Preclinical and Nonclinical...
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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
aGFP TriTAC Donor 81
aGFP TriTAC Donor 86
-14 -12 -10 -8 -60
50
100
H929 TDCC Assay with HSA
TriTAC log(M)
Norm
aliz
ed V
iabi
lity
(%) HPN217 Donor 02
aGFP TriTAC Donor 02
HPN217 Donor 35
aGFP TriTAC Donor 35
HPN217 Donor 81
aGFP TriTAC Donor 81
HPN217 Donor 86
aGFP TriTAC 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
aGFP TriTAC 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
aGFP TriTAC 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
anti-GFP TriTAC Donor 81
HPN217 Donor 81
anti-GFP TriTAC Donor 02
HPN217 Donor 02
anti-GFP TriTAC Donor 86
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
anti-GFP TriTAC Donor 35
anti-GFP TriTAC Donor 02
HPN217 Donor 02
anti-GFP TriTAC Donor 81
HPN217 Donor 81
anti-GFP TriTAC Donor 86
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