Preclinical Characterization of Vadadustat

Preclinical Characterization of Vadadustat (AKB-6548), an Oral Small Molecule Hypoxia Inducible Factor Prolyl-4-Hydroxylase Inhibitor, for the Potential Treatment of Renal Anemia

A. Zuk, Z. Si, S. Loi, S. Bommegowda, S. Danthi, G. Molnar, M. Rabinowitz Research and Development Akebia Therapeutics Cambridge, MA

PRESENTED AT ASN KIDNEY WEEK 2019 Disclosures • The authors are employees of Akebia Therapeutics, which funded the studies

Disclaimers • Vadadustat is an investigational drug. Vadadustat is not approved by the United States Food and Drug Administration or any regulatory authority.

Confidential – Not for Distribution Objective

• To summarize the preclinical pharmacological characterization of vadadustat HIF and the prolyl-4-hydroxylase domain enzymes

O2 O2 O2 Normal O 2 O PHD HIF-a is degraded by proteasome 2 O2 O2 O2 HIF- a HIF-a OH OH

HIF-a HIF-a HIF translocates to nucleus HIF-a Activates protein production HIF-a HIF-a Protects against low oxygen EPO Iron utilization/absorption Low O O2 O2 Abbreviations: 2 VadadustatPHD …combines Hepcidin O2 = oxygen with other PHD = prolyl-4-hydroxylase domain factors… HIF = hypoxia inducible factor EPO = erythropoietin Hb and RBC Hb = hemoglobin production RBC = red blood cell Vadadustat inhibits recombinant human PHD1, PHD2 and PHD3 at equivalent nanomolar concentrations*

PHD1 PHD2 PHD3

Expt #1 Expt #1 Expt #1 e

e 100 e 100 100

s s n

n Expt #2 n Expt #2 Expt #2

o o

p p s

s 75 s 75 75 e

e Expt #3 e Expt #3 Expt #3

R R

d d

e e z

z 50 z 50 50

i i

l l

a a

m m r

r 25 r 25 25

o o

N N

% % 0 % 0 0 -10 -9 -8 -7 -6 -5 -10 -9 -8 -7 -6 -5 -10 -9 -8 -7 -6 -5 Vadadustat Log [M] Vadadustat Log [M] Vadadustat Log [M]

*Measured by Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) Assay. Data represent Mean + SD.

Mean (95% Confidence Interval)

IC50 value (nM) pIC50 value PHD1 15.36 (11.96, 19.73) 7.81 (7.71, 7.92) PHD2 11.83 (8.20, 17.07) 7.93 (7.77, 8.09) Abbreviations: PHD = prolyl-4-hydroxylase domain PHD3 7.63 (7.21, 8.07) 8.12 (8.09, 8.14)

IC50 = half maximal inhibitory concentration pIC50 = negative log of the IC50 value in molar Vadadustat-O-glucuronide inhibits recombinant human PHD2 at micromolar concentration*

Vadadustat-O-glucuronide e

s E xp t # 1

n 1 0 0 o

p E xp t # 2

s Inhibition is approximately e

7 5 E xp t # 3

d e

z 200-fold less potent than the

i 5 0

a m r parent compound at the IC

o 2 5 50

% 0 -1 0 -9 -8 -7 -6 -5 V a d a d u s ta t-O -G lu c u r o n id e L o g [M ]

*Measured by TR-FRET Assay. Data represent Mean + SD.

IC50 value (μM) pIC50 value Mean (95% 2.31 (1.74, 3.08) 5.64 (5.51, 5.77) Confidence Internal)

Abbreviations: PHD2 = prolyl-4-hydroxylase domain 2

IC50 = half maximal inhibitory concentration pIC50 = negative log of the IC50 value in molar Vadadustat is a competitive inhibitor of 2-oxoglutarate for recombinant human PHD2*

[Vadadustat] Log [M]

) 6000 -5 m

n -6

5 1

6 -7 / 4000

m -8

n 5

6 -9

6 (

2000 o

i -10

t a

R -11 0 -12 -10 -9 -8 -7 -6 2-Oxoglutarate Log [M]

*Measured by TR-FRET Assay. Data represent Mean + SD.

Abbreviations: PHD2 = prolyl-4-hydroxylase domain 2 Vadadustat inhibition of recombinant human PHD2 is not

sensitive to iron concentration in vitro*

e s

n 100

o + 100nM Fe2+

p s

e 2+

R + 1M Fe

e 2+

z 50 + 10M Fe

o N

0 % -15 -10 -5 Vadadustat Log [M] *Measured by TR-FRET Assay. Data represent Mean + SD. Vadadustat + Vadadustat + Vadadustat + 100 nM Fe2+ 1 µM Fe2+ 10 µM Fe2+ IC (nM) 19.25 ± 5.74 3.91 ± 0.38 3.26 ± 0.24 Abbreviations: 50 PHD2 = prolyl-4-hydroxylase domain 2

IC50 = half maximal inhibitory concentration Vadadustat was shown to stabilize both HIF-1a and HIF-2a in Hep3B and HUVEC cell lines in a dose and time dependent manner*

HIF-1a Hep3B HIF-2a Hep3B )

) 6 Hours 6 Hours g g 10 (EC = 44 M) 1.0 (EC = 51 M)  50

 50

/ g

g 24 Hours 24 Hours

p p

( (EC = 54 M)

( (EC50 = 67 M) 50

a 5 0.5

H H 0 0.0 -6 -5 -4 -3 -6 -5 -4 -3 Log Vadadustat [M] Log Vadadustat [M]

HIF-1a HUVEC HIF-2a HUVEC

60 10 )

6 Hours ) g

(EC50 = 25 M) g



 /

24 Hours / g

40 g p

(EC50 = 71 M) p

(

5 a

20 a 6 Hours

2 F

F (EC50 = 21 M) I

I 24 Hours H Abbreviations: 0 H 0 (EC50 = 38 M) HIF1a = hypoxia inducible factor-1 alpha HIF2a = hypoxia inducible factor-2 alpha -6 -5 -4 -3 -6 -5 -4 -3 Hep3B = human hepatocarcinoma cell line Log Vadadustat [M] Log Vadadustat [M] HUVEC = human umbilical vein endothelial *Measured by Mesoscale Discovery (MSD) Electrochemiluminescence Assay. HIF1a and cell HIF2a were normalized to total cellular protein (pg/g). Data represent Mean + SD. Erythropoietin (EPO) secretion is increased in vitro after exposure of Hep3B cells to vadadustat*

30 Expt #1 + + Expt #2 25

) 20

/ U

I 15 + +

(

P + E 10

0 0.1% 0.1 0.3 1 3 10 0.3% 30M Medium DMSO Vadadustat (M) DMSO Vada EPO release EPO EC50 (M) (mIU/mL)/EC50

Abbreviations: Vadadustat 9.97 12.04 DMSO = dimethylsulfoxide vehicle *Measured by an Enzyme Linked ImmunoSorbent Assay (ELISA) after 24 hrs incubation. Data EC50 = half maximal effective concentration represent Mean + SD. + P < 0.05 vs respective DMSO Control, Tukey’s Multiple Comparisons Test Production of vascular endothelial growth factor (VEGF) was not observed to increase in vitro after exposure of Hep3B cells to vadadustat*

1000 Expt #1 + + Expt #2

800

) L

m 600

(

G 400

E V

200

0 0.1% 3 M 10 M 0.3% 30 M 1% O2 DMSO Vadadustat DMSO Vadadustat Hypoxia

*Measured by Enzyme Linked ImmunoSorbent Assay (ELISA) after 24 hrs incubation. Data represent Mean + SD. + P < 0.05 vs 0.1% DMSO, Tukey’s Multiple Comparisons Test. Abbreviations: DMSO = dimethylsulfoxide vehicle

11 Single-dose administration of vadadustat in rats was shown to increase the circulating levels of EPO in a time and dose dependent manner*

30000 50 mg/kg

150 mg/kg )

L 20000

(

P 10000 E

0 0 1 3 6 24 72 Hours Post Dose

*Measured by Enzyme Linked ImmunoSorbent Assay (ELISA). Data represent Mean + SD.

12 Multi-dose exposure to vadadustat in mouse, rat and dog demonstrated increases in hemoglobin and hematocrit

Hemoglobin Hematocrit

Duration of treatment of normal animals: • Mouse = up to 6 months • Rat = up to 2 years • Dog = up to 9 months In mouse, rat and dog, vadadustat had a relatively short half- life and did not accumulate after repeat dosing

Gender Gender Dose Level Combined Accumulation Species Day Combined (mg/kg) AUC Ratio T (h) last 1/2 (µg*h/mL) 1 2.40 234 NA Mouse 100 56 1.90 197 0.84 1 2.09 993 NA Rat 120 28 2.05 902 0.90 1 2.86 740 NA Dog 120 28 3.59 776 1.05

NA = Not Applicable Conclusions

• In the preclinical setting, vadadustat ‒ inhibited recombinant human PHD1, PHD2 and PHD3 isoenzymes at equivalent nanomolar concentrations ‒ stabilized both HIF-1α and HIF-2α in vitro ‒ stimulated EPO production in vitro and in vivo ‒ increased hemoglobin and hematocrit in multiple species ‒ did not stimulate VEGF production in vitro • The pharmacology of vadadustat support development for anemia of CKD and ESRD END

16 Possible backup slides Background and Mechanism of Action

• Vadadustat is an orally bioavailable HIFα hypoxia-inducible factor prolyl hydroxylase inhibitor (HIF-PHI) in HIFβ development for the potential

VADADUSTAT treatment of anemia due to chronic

O2 PHD kidney disease No No • The HIF-PH enzymes are also HIFβ referred to as EGLN proteins or HIFα prolyl 4-hydroxylase domains (PHDs) HIFβ VADADUSTAT • Pharmacological inhibition of PHD OPHD2 PHD HIFα HIFβ enzymes lead to the stabilization of VADADUSTAT hypoxia-inducible factor (HIF), a + transcription factor that activates target genes to improve the O2 Hb and RBC • EPO • Iron Utilization/Absorption carrying capacity of the blood production • Hepcidin

EPO, erythropoietin; Hb, hemoglobin; HIF, hypoxia-inducible factor, HIF-PHD, HIF prolyl-hydroxylase domain; RBC, red blood cell. 18