ALX148 is a High Affinity SIRPα Fusion
Protein that Blocks CD47, Enhances theActivity of Anti-Cancer Antibodies andCheckpoint Inhibitors, and Has a Favorable
Safety Profile in Preclinical Models
Steven E Kauder, Tracy C Kuo, Amy Chen, Ons Harrabi, SonyS Rocha, Laura Doyle, Sangeetha Bollini, Bora Han, EmmaSangalang, Janet Sim, Sophia Randolph, Jaume Pons, andHong I Wan
Alexo Therapeutics
South San Francisco, CA USA
Dublin, Ireland

The CD47-SIRPα Interaction Regulates
Myeloid Cell Function• CD47
Myeloid CellTumor CellCD47

Phagocytosis

SIRPαInflammation
Activation– Broadly expressed cellsurface protein– Overexpressed on tumor cells• SIRPα– Receptor for CD47 on myeloidcells– Inhibitory signaling upon
CD47 binding• CD47-SIRPα is an immune
checkpoint• CD47 is a promisingtherapeutic target

Unique Design of ALX148 is Responsible for
Improved Safety
ALX148• Engineered SIRPα domain binds CD47
with picomolar affinity• Blocks CD47-SIRPα interaction• Binds CD47 from humans, non-humanprimates, and mice
• Fc domain does not bind Fcγ receptor,binding to neonatal Fc receptor ismaintainedHigh Affinity
SIRPα Domain
S-SS-S

InactiveFc Domain

Platelets

Red Blood Cells
ALX148% of Predose (Day -5)% of Predose (Day -5)100755025125

3512Day-5

3512****

10075
50
250-5Control, active Fc

150*******

1250

ALX148Control, active Fc-53512Day-5CD-1 mice
30 mg/kg x1
35 12****p<0.0001, ***p<0.001

ALX148 Enhances Activity of Targeted
Antitumor Antibodies
Inhibition of Z138 Xenograft
Tumorigenesis

Phagocytosis of Daudi
Tumor Cells in vitro

2000Tumor Volume, mm3 + SEM

Phagocytosis, percent

1510

50-2-10123ALX protein, nM (log10)
No antibody
obinutuzumab
ALX148
ALX148 + obinutuzumab

1500

****

1000
500014 16 18 20 22 24 26 28 30 32 34
Day post implant
PBS
obinutuzumab
ALX148
ALX148 + obinutuzumab

Similar results with rituximab, trastuzumab
NOD SCID Mice
0.05 mg/kg obinutuzumab 2x/week
10 mg/kg ALX148 2x/week****, p<0.0001

ALX148 Enhances Efficacy of Checkpoint
Inhibitors in Multiple Syngeneic Models
Combination WithαPD-L1 in MC38 Model**Tumor volume, mm3 ± SEM

Combination WithαPD-1 in CT26 Model
800600400****200
05101520Days post implantation
PBSanti-PD-L1ALX148
ALX148 + anti-PD-L1BALB/c mice
αPD-1 5 mg/kg 3q5d
ALX148 10 mg/kg 2q10d**p<0.01

C57BL/6 mice
αPD-L1 2 mg/kg 2q7d
ALX148 30 mg/kg 2q10d****p<0.0001

ALX148 Activates Splenic Dendritic Cells inTumor-Bearing Mice500
450400/anti-P
D-L
1-L
1PBS ALX148 αPD-L1 ALX148+αPD-L148LX
1PBS ALX148 αPD-L1 ALX148+αPD-L1A350

antiPD300

55030

PBS ALX148 αPD-L1 ALX148+αPD-L1350***

480.0400*

600

20.1450650

LX10.2**A

0.3**

S*30**CCR7 Expression

PB

0.4**

500

Spleen CCR7 CD8+ DC of CD45

GeoMean(MFI)
Geometric
Mean(MFI)

0.5

CD86 Expression
Geo Mean (MFI)

Percent of CD45+

CD8+ Dendritic Cells

C57BL/6 mice
αPD-L1 2 mg/kg 2q7d
ALX148 30 mg/kg 2q10d**p<0.01, *p<0.05

ALX148 and Anti-PD-L1 Cooperatively
Increase CD8+ T Cell Function in the Tumor

PBS ALX148 αPD-L1 ALX148+
αPD-L10.8***0.60.4
0.20.0PBS ALX148 αPD-L1 ALX148+
αPD-L1Granzyme B+ CD8+ T Cells
Percent of CD45+

****
****
****

IFNγ+ CD8+ T Cells
Percent of CD45+

Percent of CD45+

Infiltrating CD8+ T Cells

****
****
****

PBS ALX148 αPD-L1 ALX148+
αPD-L1C57BL/6 mice
αPD-L1 2 mg/kg 2q7d
ALX148 30 mg/kg 2q10d****p<0.0001, **p<0.01, *p<0.05

ALX148 Reduces Immunosuppressive
Populations in the Tumor Microenvironment
Myeloid-Derived
Suppressor Cells

M1/M2 Ratio
M1/M2ratio

15*****1050PBS ALX148 αPD-L1 ALX148+
αPD-1

BALB/c mice
CT26 tumor
αPD-1 5 mg/kg x1
ALX148 30 mg/kg x1*p<0.05, **p<0.01

Percent of CD45+

Tumor-AssociatedMacrophages***

PBS ALX148 αPD-L1 ALX148+
αPD-L1C57BL/6 mice
MC38 tumor
αPD-L1 2 mg/kg 2q7d
ALX148 30 mg/kg 2q10d*p<0.05, **p<0.01

ALX148 Has a Favorable Safety Profile inNonhuman Primates

CD47 Occupancy on CD4+ T Cells101141822

DD9D127

D5DDayDD4hDr2
D3

D1-20.175
50250

Group 1: Rituximab
Group 1: Rituximab

DayDaysGroup 2: Rituximab + ALX148 10mg/kg

Groupmg/kg
2: Rituximab + ALX148 10mg/kg
Groupmg/kg
3: Rituximab + ALX148 30mg/kg
1030
Group 3: Rituximab + ALX148 30mg/kg
Group 4: Rituximab + ALX273 30mg/kg

Group 5: Rituximab + ALX274 30mg/kg
Group 4: Rituximab + ALX273 30mg/kg
Group 5: Rituximab + ALX274 30mg/kg

D2210013, 1

14, 315, 3100

D181000

125

D12D14CD47Occupancy (%) %CD47
Occupancy,Concentration - Time ProfileDD8710000

DD1 -24hr
D2D3D5Pharmacokinetics

D•Four week repeat dose toxicity study
No ALX148 mechanism-related toxicity or adverse events up to 100
mg/kg
Separate PK/PD study: PK profile similar to CD47 antibody;
Sustained CD47 target occupancy
12, 10
ALX148 (ug/ml)
ALX148,μg/ml••

Summary
ALX148 Inhibits the CD47-SIRPα Checkpoint
ALX148 activatesDCs, enhancing
T cell priming
ALX148 decreases
suppressive cells

ALX148 enhances
macrophage
phagocytosis

ALX148 increases
cytotoxic T cellfunction
After Chen and Mellman, 2013••

ALX148 enhances the efficacy of antitumor and checkpoint
inhibitor antibodies
ALX148 has a favorable preclinical toxicity profile

Summary
ALX148 Inhibits the CD47-SIRPα Checkpoint
ALX148 activatesDCs, enhancing
T cell priming
ALX148 decreases
suppressive cells

ALX148 enhances
macrophage
phagocytosis

ALX148 increases
cytotoxic T cellfunction
After Chen and Mellman, 2013

•ALX148 is currently being investigated in a Phase 1 clinical trial(NCT03013218)– Clinical safety profile consistent with preclinical studies– Clinical data presented at 2017 SITC Annual Meeting