0 7 1 4 2 1 2 8 3 5 4 2 4 9 5 6

0

2 0 0

4 0 0

6 0 0

8 0 0

1 0 0 0

1 2 0 0

1 4 0 0

1 6 0 0

D a y s P o s t T u m o r C e ll C h a lle n g e

Me

an

Tu

mo

r V

olu

me

(m

m3)

P B S

20 g

90 g

30 g

10 g

Michelle Nelson, Robert Miller, Secil Franke-Welch, Ruth Chenault, Hang Fang, Allison Chunyk, Gabriela Hernandez-Hoyos, Hilario Ramos, David Bienvenue, Jane Gross, Catherine McMahan

APVO603: A dual 4-1BB and OX40 bispecific approach utilizing ADAPTIRTM platform

technology designed to deliver a conditional T cell/NK response against solid tumors

Seattle, WA, USA

Potential Key Advantages for APVO603

• APVO603 is a novel ADAPTIR bispecific with a

unique mechanism of action (MOA) that may boost

natural antitumor responses by activating two

different costimulatory receptors

• APVO603 enhances effector lymphocyte populations

(CD4, CD8 & NK cells) via increased proliferation,

amplified cytokine production and cytolytic capacity

• APVO603, was designed as a conditional activator

with potential to reduce toxicities observed for

competitor 4-1BB mAbs with the potential to

reinvigorate immune responses and enhance

prolonged tumor rejection in multiple solid tumor

indications

Fig. 5 APVO603 Elicits an OX-40/4-1BB Associated PD Response in NHP

APVO603 is Designed to Potentiate Memory

Generation & Tumor Lysis in Recently Activated TIL

APVO603 (α4-1BB x αOX40), a Dual Costimulatory

Molecule Designed to Treat

Multiple Solid Tumors

Fig. 2 APVO603 Augments Rejection of Established Tumors & Enhances Survival

Fig. 3 APVO603 has a Favorable Antibody-Like Half-Life in Non-Human Primates

Therapeutic

Candidate

• Next generation ADAPTIR for T-cell and NK-cell

costimulation

• Mutated IgG1 Fc; No ADCC or CDC; retains FcRn binding

Mechanism of

Action

Benefits

• Activity non-dependent on direct engagement of a tumor

antigen

• Potential to enhance the tumor microenvironment (TME)

responses: Reduction/reversal of suppressive environment;

Limitation or reversal of T cell exhaustion

• Designed for enhanced effector function and survival of pre-

existing TIL and NK cells

Potential

Safety

Benefits

• Requires engagement of both 4-1BB and OX40 in cis or

trans to induce downstream signaling (tumor-dependent

response)

• 4-1BB and OX40 are expressed on activated lymphocytes

and relatively few peripheral lymphocytes. Increased

potential to target tumor infiltrating lymphocytes (TIL)

Indications

• Multiple inflamed solid tumor types with resident tumor

infiltrating T cells (such as NSCLC, RCC)

• Potential to combine with checkpoint inhibitors

Half-life• 5.5 days in mice; up to 4.8 days in NHP

• Fully cross-reactive with cynomolgus macaque

Development

Stage

• Preclinical; IND-enabling studies underway

• CMC activities in progress to support IND filing in 20225e5 MB49 (SQ)

D0 D6 21

Therapy (IP)

Hu 4-1BB KI;

Hu OX40 KI

APVO603 induced proliferation of T cells and NK cells in NHP on Day 14

following dosing. Flow cytometry panels were used to evaluate immune cell

populations. By Day 28, proliferating cells were trending toward baseline in

most groups. Observations are consistent with elevated Ki-67 expression inNHP following α4-1BB (Fisher et al., CII 2012) or αOX40 (Oberst et al., Mol Cancer Ther

2018) treatment. No corresponding increases in cell populations were

observed. Displayed as fold change compared to pre-dose levels.

These PD results demonstrate a transient increase in the number of

proliferating lymphocytes following APVO603 treatment and are comparable

with trends seen with monotherapies.

In vitro human T cell cultures were activated with

αCD3/αCD28 on days 0, 2, 6, 9, 12 and 15 along

with a titration of APVO603 or a control ADAPTIR

and evaluated for surface markers of exhaustion

(A) or cytokine secretion (B). APVO603 reduces

surface marker expression associated with T

cell exhaustion. For surface marker expression,

activated CD4+ or CD8+ T cells were analyzed on

day 17 for co-expression of LAG3 and PD-1 by

flow cytometry.

APVO603 significantly reduces MB49 tumor burden in vivo. Human 4-1BB

/Human OX40 knock-in mice were implanted with the human bladder cancer line,

MB49, and tumors allowed to establish for 6 days prior to twice-weekly therapeutic

treatment. Mean tumor volume for each group is plotted + SEM. Compared toPBS, APVO603 at 90 & 30 μg was significant. Mean 8 mice/ group.

These data demonstrate that MB49-specific lymphocytes gain cytolytic capacity

following APVO603 treatment that leads to reduced tumor burden and prolonged

animal survival. These effects were significantly better when compared to the 4-

1BB monospecific urelumab analog.

NHP pharmacokinetic data for APVO603 had dose proportional

concentrations. APVO603 serum concentrations were measured in

cynomolgus monkeys (n=3 per group) following single or multiple

weekly doses. Based on non-compartmental analysis (NCA), the

serum half-life of APVO603 was in the range of 64 - 114 hr. Mean

systemic exposure increased with dose in a dose-proportional

manner, based on Cmax and AUC, and no significant accumulation

was observed after repeat dosing (Day 22) compared to a single dose

(Day 1). NCA was conducted using data through 168 hr post-dose.

The PK profile of APVO603 in NHP supports clinical dosing.

Fig.1 APVO603 Reduces T Cell Exhaustion Markers & Prolongs Cytokine Secretion

Cytokine Secretion

APVO603

Control

ADAPTIR

αCD3/αCD28

AACR Annual Meeting 2021Poster LB173

ModifiedIgG1 Fc

No ADCCNo CDCBinds FcRn

α4-1BB scFv

αOX40 scFv

MB49 Tumor Growth

0 2 4 4 8 7 2 9 6 1 2 0 1 4 4 1 6 8

1

1 0

1 0 0

1 0 0 0

1 0 0 0 0

T im e (h r )

AP

VO

60

3 C

on

c (

g/m

L)

1 5 m g /k g , D a y 1

4 9 .5 m g /k g , D a y 1

1 m g /k g

5 m g /k g

4 9 .5 m g /k g , D a y 2 2

1 5 m g /k g , D a y 2 2

D a y 2 D a y 1 4 D a y 2 8

-0 .2 5

0 .0 0

0 .2 5

0 .5 0

Fo

ld c

ha

ng

e K

i-6

7+

(L

og

)

V e h ic le

1 5 m g /k g

4 9 .5 m g /k g

1 m g /kg

5 m g /kg

Repeat Dosing

Single Dose

CD8+ T cells

D a y 2 D a y 1 4 D a y 2 8

-0 .2

0 .0

0 .2

0 .4

0 .6

Fo

ld c

ha

ng

e K

i-6

7+

(L

og

)

CD4+ T cells

D a y 2 D a y 1 4 D a y 2 8

-0 .2 5

0 .0 0

0 .2 5

0 .5 0

0 .7 5

Fo

ld c

ha

ng

e K

i-6

7+

(L

og

)

NK cells

Repeat Dosing

Single Dose

Mouse Survival

TCR

CD4/8+ T cell

Tumor

Tumor

OX40

Upregulation

4-1BB

Upregulation

CD4

NK

CD4, CD8 and NK

cells cooperate to

induce tumor lysis

Cytokines

Granzymes

Increased number and

potency of tumor-

specific cells with

effector function

Urelumab

Analog

APVO603

D 9 D 1 5 D 9 D 1 5 D 9 D 1 5 D 9 D 1 5 D 9 D 1 5

0

2 0

4 0

6 0

8 0

1 0 0

% o

f M

ax

Re

ad

Ou

t

0 . 0 5 0 .5 5

0

1 0

2 0

3 0

4 0

5 0

n M C o n s tru c t

Fre

qu

en

cy

PD

1+

LA

G3

+

0

CD4+ T cells

0 .0 5 0 .5 5

0

1 0

2 0

3 0

4 0

5 0

n M C o n s tru c t

Fre

qu

en

cy

PD

1+

LA

G3

+

0

CD8+ T cells

Control

ADAPTIR

APVO603

Granz APerforinTNF-αIFN-γ Granz B

Serum half-life ranged

from 64-114 hours

0 1 4 2 8 4 2 5 6 7 0 8 4 9 8 1 1 2 1 2 6

0

2 0

4 0

6 0

8 0

1 0 0

D a y s P o s t T u m o r C e ll C h a lle n g eT

ime

to

Tu

mo

r P

ro

gre

ss

ion

( >

15

00

mm

3)

APVO603 costimulation treatment

augments cytokine secretion in

restimulated cells. Sups from D9 or

D15 reactivated cells were analyzed

for cytokine secretion via multiplex-

based assay (Milliplex). 0.5 nM of

control or APVO603 were compared

to αCD3/ αCD28 treatment only.

These data suggest that the

costimulatory effects of APVO603

may diminish the detrimental &

exhaustive effects of repeated

stimulation within the TME.

Fig. 4 APVO603 Has a Favorable Safety Profile in Non-Human Primates

The preliminary safety of APVO603 was evaluated in a

non-GLP toxicology study performed in cynomolgus

monkeys. Single dose and repeat-dose groups were

included in the study. APVO603 was administered by

intravenous bolus infusion. Samples were collected

throughout the study for clinical pathology, PK, ADA, and

immunophenotyping by flow cytometry. Repeat-dose

animals were evaluated at necropsy following Day 28 for

histopathology with no evidence of liver toxicity.

Liver enzyme levels were not impacted by APVO603. Samples were collected pre and 24 hours post relative to dosing on Day 1

and 15 and then on Day 25. No general elevation in liver enzymes by single dose (A) or repeat-dose (B) were observed during

treatment. The observed changes were not considered dose-dependent for APVO603 and were similar to the vehicle control group.

Dotted line is the range for Cambodian Male NHP (Wilcox, et. al., SOT 2015).

These data demonstrate that APVO603 treatment does not induce hepatotoxicity and did not induce adverse reactions in NHP.

A

BFindings from the non-GLP toxicology study

• APVO603 administration was well tolerated in

animals at all dose levels.

• Clinical pathology evaluations included all

standard hematology, coagulation and clinical

chemistry parameters, with no indication of

adverse reactions based on the MOA.

• No cytokines were detected following the first

dose for any animal in single or repeated-dose

groups.

A

B

Cis

Crosslinking

Trans

Crosslinking

Summary and Potential Advantages of APVO603

4-1BB mAb OX40 mAb APVO603 Bispecific

SafetyLiver toxicity (4-1BB superagonist)

Good safety profile in NHP and Humans

Bispecific targeting requires dual 4-1BB and OX40 expression and limits on target toxicity

EfficacyPotent agonist, limited by therapeutic index

Lack of clinical response as single agent

Bispecific targeting allows for cis/trans engagement of T cells for enhance potencyWebsite: www.aptevotherapeutics.com; Contact: IR@apvo.com, nelsonm@apvo.com

ALT

Single Dose

AST

Single Dose

Repeat Dose Repeat Dose

0 7 14 21 280

50

100

Time (day)

Measu

rem

en

t (U

/L)

0 7 14 21 280

50

100

Time (day)

Measu

rem

en

t (U

/L)

0 7 1 4 2 1 2 8

0

5 0

1 0 0

1 5 0

2 0 0

T im e (d a y )

V e h ic le

1 5 m g /k g

4 9 .5 m g /k g

0 7 1 4 2 1 2 8

0

5 0

1 0 0

1 5 0

2 0 0

T im e (d a y )

V e h ic le

1 m g /kg

5 m g /kg

• APVO603 may reduce or reverse negative effects

of T-cell exhaustion and suppressive immune

responses by augmenting cytokine production and

reducing markers of T cell exhaustion following

repeat stimulation in vitro

• APVO603 therapy induces a dose-dependent in vivo

antitumor responses and significantly increases the

survival in MB49-inoculated mice

• APVO603 was well tolerated in NHP with a favorable

safety profile (up to 50 mg/kg) without liver toxicity