Development of Small Molecule Checkpoint Inhibitors

David Tuck, M.D. CMO Curis Inc

Immune Checkpoint Inhibitors Symposium March 14-16 2017

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Small molecule PK profile allows optimization of dose and administration schedule Usually less than 24 hour half-life (T1/2) permits

flexibility with dosing schedule – daily or intermittent dosing

Permits flexible adjustment of exposure as measured by Cmax and AUC – both parameters can be adjusted to match mechanism-of-action

Flexibility to adjust dose and schedule to address emergent adverse events

Flexibility to adjust for combinations

Untether patient from infusion chair – cost, convenience, access

Typical Small Molecule Drug PK Profile

Typical Antibody Drug PK Profile

Why Small Molecule Immune Checkpoint Blockade?

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Structural Features of PD-1 / PD-L1 Interaction

mPD1 hPDL1 hPDL1 hPD1

Lin et.al., 2008; PNAS. 105: 3011 Zak et.al., 2015; Structure. 23: 2341

Structural Features of PD-1 / PD-L1 Interaction

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Unbound PD1 Bound PD1 PDL1 Zak et.al., 2015; Structure. 23: 2341

Compounds Mechanism Reference Source

ENUM-C8 PD1 Non-blocking antibody AACR 2016 Enumeral

MQ-209,MQ-210 Non-blocking (Allosteric) antibody

ASCO 2016 Fenwick Abstract 3072

Mabquest

NP12 Peptide targeting PDL1 AACR 2013 Aurigene

(D) PPA-1 D peptides blocking PDL1-PD1 interaction

Chang 2015 Tsinghua Univ

high-affinity PD-1 Small non-antibody peptides

Maute PNAS 2015 Stanford

Small molecule BMS-202, BMS-8

Small molecule targeting PDL1

Zak et al 2016 BMS

CA170,CA327 Small molecules targeting immune checkpoints

AACR 2016 SITC 2016

Curis/Aurigene

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Small molecules, peptides, non-blocking antibodies

Peptides, small molecule and mAbs ICI may have different mechanisms

3/22/2017 6

Discovery, Characterization and Development of a New Class of Therapeutic Anti-PD-1 Antibody - Amirinia-Nave et al AACR 2016

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Aurigene discovery platform Small molecule design based on structure

of interaction hotspots

Small molecule library

Functional screening to identify compounds capable of selectively rescuing T cell proliferation and

activation in the presence of inhibitory checkpoints

VISTA TIM3 PD-L1

PD-1 PD-L1

Discovery process for small molecule immune checkpoint blockade

Pharmacophore derived

small molecule mimics

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Antagonism of PD-L1 and VISTA by CA-170 Ex-vivo activation of human PBMC

Dose dependent activation of PD-L1 or VISTA-inhibited T cells ex-vivo

PD-L1

Res

cue

(%)

IFN-γ production used as a marker for T cell activation

CA-170 Concentration (log nM)

VISTA

No activation of CTLA4-inhibited T cells

No activation of TIM3-inhibited T cells

Potent and selective rescue of human T cell activation (proliferation or IFN-γ production) Dose-dependent activation of T cells inhibited by exogenous PD ligands or by VISTA

• Similar to that observed using anti-PD1 or anti-VISTA antibodies as control

No rescue of T cells inhibited by CTLA-4, TIM3, BTLA, LAG3

EC50 = 17nM EC50 = 37nM

Curis Confidential

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CA-170 is Orally Bioavailable Multiple species

Oral exposure in all non-clinical species examined At 10mg/kg: Cmax ~ 500ng/ml, AUC ~ 3,500ng*hr/ml in mouse (efficacy animal model)

Proportional increase in Cmax and AUC with increased oral dosing of CA-170 From 10mg/kg to 1000mg/kg dose tested in mouse and monkey (safety animal model)

Parameter Oral PK Profile

Species Mice Rat Dog Monkey

T1/2 (hr) 3.5 3.6 3.8 3.8

Tmax (hr) 1.0 1.0 1.0 3.3

Cmax (µg/ml) 0.52 0.59 4.3 0.86

AUC (0-t) (µg*hr/ml) 3.45 3.88 22.5 4.54

Single-dose Exposure in Mouse

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CA-170 Anti-Tumor Activity In Vivo Syngeneic mouse tumor models sensitive to anti-PD1 antibodies

CT26 Colon Carcinoma Model B16/F10 Melanoma Model MC38 Colon Carcinoma Model

* **

*** * *

* *

In vivo activity in tumor models grown in immuno-competent C57BL/6 mouse strain CT26 and MC-38 CRC tumors grown subcutaneously and change in tumor size measured B16/F10 melanoma tumor cells injected intravenously and number of lung metastatic nodules measured

Day 13 post tumor cell inoculation

*p<0.05

* p<0.05, **p<0.01, ***p<0.001 J43 at 100ug/animal, ip, q7d

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In vivo Activity Requires Intact Immune System

No anti-tumor activity observed in immune-deficient SCID/beige mice Provides evidence for immune response-mediated anti-tumor mechanism of CA-170

MC38 Model Syngeneic Mice

MC38 Model SCID/beige Mice

* **

* p<0.05, **p<0.01 J43 at 100ug/animal, ip, q7d

Vehicle CA-170 10mpk

Days

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CA-170 is Active In Vivo Syngeneic mouse tumor models where anti-PD1 antibodies are inactive

CA-170 Daily Oral Treatment Anti-PD1 Bi-weekly Injection Anti-VISTA Bi-weekly Injection

In vivo activity in 4T1 breast cancer tumor model Dose dependent response to CA-170

Tumor model is non-responsive to anti-PD1 antibody treatment

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CA-170 is Active In Vivo Syngeneic mouse tumor models insensitive to anti-PD1 antibodies

In vivo activity in B16/F1 melanoma tumor model Dose dependent response to CA-170

Tumor model is non-responsive to anti-PD1 antibody treatment

CA-170 Daily Oral Treatment Anti-PD1 Twice-weekly Injection

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Predictable Dose Exposure, T cell Activation and Efficacy in anti-PD-1 Non-responsive Mouse Models with CA-170

Mouse single dose exposure T Cell Activation – In Tumor

T Cell Activation – In Blood Efficacy in the B16/F1 Model

CA-170

CA-170 In vivo Effect on Immune Profile

Increased T cell activation in tumor-bearing animals following CA-170 administration Increase in CD8+ T cell activation markers (CD69) in tumor and in tumor draining lymph nodes

Increase in peripheral circulation of active CD4+ and CD8+ T cells

↑ Activation – Tumor Infiltrating CD8+ T cells

↑ Number – Peripheral Circulating CD8+ & CD4+ T cells

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Tumor CD69+ T cells

↑ Activation – Tumor-draining Lymph Node CD8+ T cells

Tumor CD69+/PD1+ T cells Lymph Node CD69+/PD1+ T cells

Cells

/ ml

Blood CD8+/CD69+ T cells

Cells

/ ml

Blood CD4+/CD69+ T cells

↑ Activation – Peripheral Circulating CD8+ & CD4+ T cells

Blood CD69 on CD4+ T cells Blood CD69 on CD8+ T cells

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CA-170 has Clean Preclinical Safety Profile GLP 28-day repeat oral dosing safety profile – mice and monkeys

Mortality : No mortality

Clinical Signs of Toxicity : No abnormalities detected

Body weight : No test item related changes

Food Consumption : No test item related changes

Hematology : No test item related changes

Clinical Chemistry : No test item related changes

Gross Pathology : No treatment related changes

Organ weights : No treatment related changes

Histopathology : No treatment related changes

NOAEL at over 1,000 mg/kg/day : In vivo active dose = 10 mg/kg/day

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CA-327 Selectively Inhibits PDL1 and TIM3 Activation of human T cells in culture

Activation of PD-L1 or VISTA-inhibited T cells ex-vivo

No activation of CTLA4-inhibited T cells

No activation of VISTA-inhibited T cells

Potent and selective rescue of human T cell activation ex-vivo (proliferation or IFN-γ production) Dose-dependent activation of isolated human T cells inhibited by exogenous PD-ligands or by TIM3

Specificity: no rescue of T cells inhibited by CTLA-4, LAG3, VISTA

Res

cue

(%)

PDL1 TIM3

uM CA-327 uM CA-327

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CA-327 is Orally Bioavailable Multiple species

PK parameters at 10 mpk PO dose using water as vehicle under fed condition

Parameters Units BALB/c Mouse Wistar Rat Beagle Dog

AUC0-LAST h*ng/ml 5069 4631 12568

AUC0-inf h*ng/ml 5178 4702 12721

Beta t1/2 h 4.49 3.9 3.5

Cmax ng/ml 755 481 1450

Tmax h 1.0 3.3 2.6

P K p ro f ile o f A U -B G D -1 2 8 9 2 a c ro s s s p e c ie sa t 1 0 m p k d o s e u s in g w a te r a s v e h ic le

T im e (h )

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0 4 8 1 2 1 6 2 0 2 41 0

1 0 0

1 0 0 0

1 0 0 0 0

B A L B /c m o u s e

W is ta r ra t

B e a g le d o g

CA-327 PK Profile

CA-327 can inhibit tumor growth of multiple syngeneic tumor models in an immune dependent manner

3/22/2017 19

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a T im 31 0 u g

1 0 m g /k gP M 3 2 7 , Q D , P O

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2 0 0 0

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p < 0 .0 5

B16F10 melanoma CT26 colon carcinoma

Tu

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V e h ic leC o n tr o l

J 4 31 0 0 µ g

1 0 m g /k gP M -3 2 7 , Q D , P O

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5 0 0

1 0 0 0

1 5 0 0

p < 0 .0 1

MC38 colon carcinoma

Tu

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V e h ic leC o n tr o l

J 4 31 0 0 µ g

1 0 m g /k gP M 3 2 7 , Q D , P O

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CA-327 Effect on Immune Profile In Vivo CT-26 syngeneic colorectal cancer mouse model

Increased T cell activation in tumor-bearing animals with oral CA-327 administration Increased percentage of activated (CD69+ marker) CD8+ and CD4+ T cells in circulation and in tumors

↑ Percent Active – Tumor Infiltrating CD8+ & CD4+ T cells

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↑ Percent Active – Circulating CD8+ & CD4+ T cells

Blood CD8+/CD69+ T cells Blood CD4+/CD69+ T cells Tumor CD8+/CD69+ T cells Tumor CD4+/CD69+ T cells

% C

D8+

T C

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D4+

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CA-327

Additional compounds with distinct targets in preparation for clinical study demonstrate the robustness of this discovery platform Potent and selective, oral small molecule immune checkpoint inhibitor ex-vivo Targets PDL1 and TIM3 immune checkpoints Activates isolated T cells that are inhibited by PDL1 or TIM3 in culture

Potent immune checkpoint inhibitor in vivo in mouse tumor models with oral dosing Biologically active in mouse: Oral administration results in T cell activation in circulation and in tumor tissue Significant anti-tumor activity in multiple syngeneic tumor models

IND-enabling studies ongoing

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CA-170 Phase 1 Trial (CA-170-101) Dose escalation design

Dose Level 1 50 mg QD

n=1

DLT or treatment-related Grade ≥ 2 AE

100%

33-40%

-50%

Dose Level -1 25 mg QD

Dose Level 2 100 mg QD

n=1

Dose Level 3 200 mg QD

n=1

100%

Dose Level 4 400 mg QD

n=1

100%

50% Dose Level 5 600 mg QD

n=3

Dose Level 6 800 mg QD

n=3

33% Dose Level 7 and beyond QD

n=3

33-40%

Standard 3+3 Dose Level X

QD

Open-label, dose escalation and dose expansion trial Up to 300 patients with advanced solid tumors

or lymphoma 6 centers in US enrolling patients for dose

escalation stage Currently in 3+3 stage of dose escalation

Objectives Safety, tolerability, PK, PD, clinical effects, and

recommended Phase 2 dose (RP2D)

Treatment Oral, once daily administration in continuous

21-day cycles

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CA-170 Oral Exposure in Patients Initial five dose cohorts – continuous once daily dosing

Dose proportional increase in exposure with increasing doses in patients Near-linear doubling in Cmax and AUC with dose doubling: 50mg – 400mg daily dose

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hr*

ng

/ml

D a y 1 C y c le 1

D a y 1 5 C y c le 1

Parameter Units 50 mg 100 mg 200 mg 400 mg (n=2)

600 mg (n=3)

Tmax hr 7.4 4.0 3.0 8.0 7.3

Cmax ng/mL 412.4 1107.2 1997.6 3522.3 8976.3

AUClast hr*ng/mL 5196.7 11018.7 27487.8 57342.1 123669.3

Parameter Units 50 mg 100 mg 200 mg 400 mg (n=2)

Tmax hr 7 7 7 7

Cmax ng/mL 724.6 1078.4 2337.1 7087.3

AUClast hr*ng/mL 7953.9 13652.9 33997.6 102392.9

Day 1

Day 15

PK parameters

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5 0 0 0

1 0 0 0 0

1 5 0 0 0

1 2 4 6 8 0 60 2 4 8 2 42 4

5 0 m g (N = 1 )

1 0 0 m g (N = 1 )

2 0 0 m g (N = 1 )

4 0 0 m g (N = 2 )

6 0 0 m g (N = 3 )

T im e (h r)

D a y 1 D a y 8 D a y 1 5

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First dose levels in patients are consistent with Preclinical Predictable Dose Exposure and T Cell Activation ( NCT02812875 )

CD69+ CD134+ Granzyme B+

Day 1 Day 15

CA-170 exposure in humans

Change in the percentage of circulating CD8+ T cells expressing:

Human PK (200 mg/day)

Summary

• CA170 is a potent and selective, oral small molecule checkpoint inhibitor, and the first to enter the clinic

• Preclinical data demonstrate dose-dependent oral exposure, immune modulation and anti-tumor activity

• Clinical PK profile is similar to non-clinical and human exposure appears predictable on oral dosing

• CA-170 appears to be biologically active in patients, supporting continued clinical development

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CA-170 (PD-L1 / VISTA Antagonist): Summary

First-in-Class orally available small molecule antagonist of PD-L1 and VISTA

Induces proliferation of T-cells and IFN-gamma production Selective rescue in response to PD-L1, PD-L2, and VISTA inhibition and not other immune

checkpoint molecules

Clean off-target profile (enzyme, receptors, ion channels, kinases)

Orally bioavailable with good PK properties in mice & monkeys

Anti-tumor activity in multiple syngeneic tumor models

Clean in vivo safety profile – GLP toxicology in mice and monkeys

Phase 1 trial underway

Summary

Immune checkpoints of the immunoglobulin superfamily are amenable to small molecule targeting Transient interaction, not pre-formed complexes Structural information for receptor-ligand interaction is available Defined regions provide contact sites for small molecule interaction

This chemistry has identified key interaction regions for targeting Proposed interaction model is consistent with the structure-based design

This chemistry appears to extend to multiple checkpoint inhibitors PDL1, VISTA and TIM3 targeting compounds identified

Chemistry has translated to multiple drug candidates Successful conversion of design to an orally available, active and safe molecule

END

Curis Confidential