1. Recombinant XTEN Products
XTEN fused to Human Proteins or Peptides
• Long, tunable PK enables up to once-a-month dosing
• Long PK maximizes efficacy and minimizes toxicity
• Clinically validated in 2 products
Protein or
• Genetic fusion (no chemical conjugation step) DNA Peptide XTEN
• Manufactured in E. coli or mammalian cells
Expression
• Non-immunogenic
• Biodegradable (safer than PEG) Payload XTEN
• 3 publications
Products with Completed POC Trials
• Exenatide-XTEN Diartis Inc. Ph.I in patients completed Long tail of natural hydrophilic amino acids
• hGH-XTEN Versartis Inc. Ph.I in patients completed
Preclinical Products
• GLP2-XTEN Short Bowel Syndrome; Pre-clinical
• AAT-XTEN AAT deficiency, Diabetes; Preclinical
• Glucagon-XTEN 4 Diabetes indications; Preclinical
• C-peptide-XTEN Diabetes complications; Preclinical
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2. Advantages of Long Half-life
Dosing Frequency
Cmax: Toxicity
Serum Concentration of Drug
Toxic dose
Therapeutic Window
Peak-Trough Ratio:
Toxicity
Therapeutic dose
AUC: Efficacy
Time
• Maximizes Efficacy (AUC) • Improves Dosing Frequency
• MinimizesToxicity (Cmax, P/T ratio) • Improves Compliance
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3. XTEN Concept
O O O
O O O O PEG
O O O
N N N
N N N N Polypeptide
O O O
O
O O O
N XTEN N Drug
N
N N N N
O O O
O
Promoter O
XTEN
PEG and XTEN are linear polymers with large apparent molecular weight
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4. PEG versus XTEN
DNA Drug DNA Drug XTEN
Expression
Expression
GMP PEG XTEN
K
Unstructured polymer with
large hydrodynamic radius
K K
K N
K
+ Half-life
extension + Half-life
extension (Tunable)
+ Low immunogenicity + Low immunogenicity
 Complicated manufacturing + Improved manufacturing
 Heterogeneous product + Homogeneous product
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5. XTEN Design and Properties
Goals
Long Serum Half-life
Stable in Plasma Composition G, E, S, T, A, P
Degraded Intracellularly Size 864 AA = 75 kDa
High Expression Level Expression E. coli & Mammalian
Genetically Stable
No Non-specific Binding SDS-PAGE, SEC, MS Homogeneous
No Aggregation
Solubility >130 mg/ml
Non-Immunogenic
Viscosity Same as PEG
Solution Plasma Stability >30 days
No unstable AA Biodegradable Yes
No hydrophobic AA
Endotoxin/DNA/HCP All easily removed
Multiple AA types
Not Repetitive
Evolutionary Process
Current XTEN meets all goals and requirements
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6. XTEN Technology
Natural Peptide Structure Monodisperse by ESI-MS
…GSTSESPSGTAPGTSPSGESSTAP
GSTSESPSGTAPGSTSESPSGTAPGT
STPESGSASPGTSTPESGSASPGST
SESPSGTAPGSTSESPSGTAPGTSPS
GESSTAPGSTSESPSGTAPGTSPSG
ESSTAPGTSPSGESSTAPGSTSSTAE
SPGPGTSPSGESSTAPGTSPSGESS
TAPGSTSE…
Unstructured by CD Large Hydrodynamic Radius by SEC
XTEN
XTEN is a polymer with similar properties as PEG, but is a protein
6 Schellenberger et al., (2009) Nature Biotechnology, 27, 1186-90

7. XTEN Immunogenicity Summary
- Zero hydrophobic residues
- Zero epitopes by Tepitope prediction
- Zero epitopes by Epivax prediction
- Morphosys panned 4 times – no binders
- Non-immunogenic in in-house animal studies
- Mice, rats, rabbit, cyno: 439 epitopes; 67 animals; <10 sc injections
- Non-immunogenic in 2 toxicology studies
- Mice: 14 SC injections; Monkeys: 5 SC injections
- Monkeys: 7 SC injections
- Non-immunogenic in 2 clinical trials (120 patients)
- 1 monthly dose, but Exenatide payload shows response after 10 days
- Non-immunogenic even with Freund’s adjuvant
- 20 mice, 6 rabbits: antibody titer too low to be useful
• All data suggest that XTEN is non-immunogenic in animals
• Because XTEN is as foreign to animals as to humans,
XTEN is expected to be non-immunogenic in humans
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• Initial clinical results support this conclusion

8. Immunogenicity of XTEN
Response
XTEN N Species Injections XTEN Control Length
XTEN_A 10 mouse 10, sc weak strong 576
- 10 different XTENs XTEN_A 3 mouse 9, sc none strong 576
- All 100% G,E,S,T,A,P XTEN_A 3 cyno 3, iv none NA 576
XTEN_C 4 rabbit 3, sc none weak 288
- Different ratios XTEN_C 4 mouse 3, sc none weak 288
- Comprising 436 9-mers XTEN_C 4 rat 3, sc none weak 288
- Non-repetitive XTEN_F 3 mouse 9, sc none strong 875
- No T-cell epitopes XTEN_G 3 rat 4, sc/ip none strong 288
- Immunized 67 animals XTEN_H 3 rat 4, sc/ip none strong 288
- 4 species XTEN_I 3 rat 4, sc/ip none strong 288
- Up to 10 SC injections XTEN_K 3 mouse 9, sc none strong 875
XTEN_L 5 mouse 9, sc none strong 144
XTEN_L 3 mouse 3, sc none strong 144
Immune Response Rating:
Weak < 0.3OD at 1:100 XTEN_M 5 mouse 9, sc weak strong 144
Moderate >1.0OD at 1:100; XTEN_M 3 mouse 3, sc none strong 144
<0.3OD at 1:1000 XTEN_N 5 mouse 9, sc none strong 144
Strong > 0.3OD @ 1:1000
XTEN_N 3 mouse 3, sc none strong 144
• No significant immune responses to any XTEN sequences tested
• No response to the clinical XTEN sequence
• Even with adjuvant generally no immune response
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9. XTEN Safety Advantages over PEG
• PEG is not biodegraded
• PEGylated proteins can accumulate in the kidneys, causing vacuolation
Bendele, A., et al. (1998) Toxicol Sci, 42: 15
• Products are routinely tested for vacuolation – and have failed for this reason
• “The non-biodegradable nature of PEG may become a limiting factor
for the next generation of protein pharmaceuticals”
Gaberc-Porekar, V., et al.(2008) Curr Opin Drug Discov Devel, 11: 242
• XTEN is fully biodegradeable
• Stable in serum, but rapidly degraded by intracellular and lysosomal proteases
• No kidney vacuolation (or other toxicities) observed
• Single dose of 200 mg/kg
• Multiple doses of 50 mg/kg
The accumulation of PEG in all tissues has become a serious concern
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10. Biodegradation of XTEN vs PEG
• PEG is not biodegraded
• PEGylated proteins can accumulate in the kidneys, causing vacuolation
Bendele, A., et al. (1998) Toxicol Sci, 42: 15
• Products are routinely tested for vacuolation – and have failed for this reason
• XTEN is fully biodegradeable
• Stable in serum, but rapidly degraded by lysosomal proteases
• No kidney vacuolation (or other toxicities) observed
• Single dose of 200 mg/kg; Multiple doses of 50 mg/kg
In Monkey Plasma In Monkey In vivo In Kidney Homogenate
Time (days) Time (days) Time (days)
0 1 7 0 1 7 0 1 7
Detection:
Anti-GFP Western
of blood samples
Incubated @ 37C in 50% plasma. Injected into a cynomolgus monkey Incubated @ 37C in rat kidney homogenate
XTEN is stable in blood, but rapidly degraded intracellularly, as desired
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11. Process Advantage over PEG
XTEN PEG
GLP2-XTEN880 G-CSF-PEG20 (Neulasta)
Calc. 84,830 Da
Exp. 84,831 Da
Intensity
82000 84000 86000 88000
Mass Mass
Bagal, D., et al. (2008) Anal. Chem., 80: 2408-18
1 Species >100 Species
Homogeneity of XTEN is a major advantage
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12. 6-Month Stability of XTEN
-80’C, 4’C and 25’C
SEC
670kD 44kD
17kD
150kD
1.3kD
SDS-PAGE
Temp (°C) -80 4 25 37
37’C
-80’C, 4’C
RPC18
25’C
37’C
Degraded
XTEN
37’C
25’C
XTEN is stable in water for 6 months at 25C, pH 6.2
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13. Lot Release Methods
Property Methods Performed at Amunix Status
Purity SDS-PAGE Developed
Reverse Phase HPLC – Intact protein Developed
Analytical SEC Developed
Analytical IEX Developed
Concentration A280 Developed
Identity Intact Mass Determination – ESI mass spectrometry Developed
Peptide Mapping – Tryptic digest, RP-C18 and MALDI Developed
Safety Endotoxin – Endosafe cartridges Developed
Host Cell Protein – Cygnus ELISA kit Developed
Host Cell DNA – qPCR Developed
Potency Payload Specific assays: enzymatic, cell based, binding Developed
Outsourced Methods: CD, MALS, AA sequence, AA composition
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14. GLP2-XTEN PK in Cynos: SC vs IV
2 mg/kg, 3 cynos/group; XTEN/GLP2 ELISA
IV = 118 hrs
SC = 125 hrs
ng/ml
hours
Cyno T½ is ~125 hr Bioavailability is 93%
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15. Cyno PK of AAT-XTEN
Alpha1-anti-Trypsin-XTEN, IV, 2 cynos/group
Concentration (ng/ml)
T1/2= 130 hrs
T1/2= 111 hrs
Time (hours)
Cyno T1/2 at expected dosing is 130 hrs
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16. hGH-XTEN PK in Cynos: SC, IV, IM
1000000
2 cynos/arm
1.5 mg/kg SC
1.5 mg/kg IV
1.5 mg/kg
1.5 mg/kg IM
Total Protein Conc. (ng/ml)
100000
10000
IM
T1/2 = 110 hrs SC
IV
1000
100
0 50 100 150 200 250 300 350 400
Time (hours)
IV, SC and IM are nearly identical - very high bioavailability
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17. Allometric Scaling of XTEN PK
300 XTEN Product
GLP2-XTEN
Ex4 hGH GLP2G (267 hrs)
250 aaT FVII FIX
200
Half-Life (hours)
Exenatide-XTEN
150 130 hrs
100
50
0
Mouse Rat Monkey Dog Human
XTEN extends half-life proportional to species size
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18. XTEN Publications
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