Sonnet Biotherapeutics Based on Management’S Current Expectations Which Are Subject to Known and Unknown Uncertainties and Risks

SONNET BIO Digital Presentation BioTherapeutics June 2020

This presentation contains forward looking statements that do not guarantee future performance Forward Looking Statements

This presentation contains forward-looking statements about Sonnet BioTherapeutics based on management’s current expectations which are subject to known and unknown uncertainties and risks. Words such as “anticipated,” “initiate,” “expect,” “intend,” “plan,” “believe,” “seek,” “estimate,” “may,” and variations of these words or similar expressions are intended to identify forward-looking statements. Our actual results could differ materially from those discussed due to a number of factors, including, but not limited to, our ability to raise additional equity and debt financing on favorable terms, the success of our R&D programs, our ability to obtain regulatory approval of our clinical assets and other risk factors.

We are providing this information as of the date of this presentation and do not undertake any obligation to update any forward-looking statements contained in this presentation as a result of new information, future events or otherwise. Unless the context requires otherwise, references to “Sonnet,” “Company,” “we,” “us” and “our” refer to Sonnet BioTherapeutics.

2 Pipeline: Multiple Points of Intervention

Naïve IL-18 Antigen T-cell Antigen Lymph Tumor Mature Dendritic Fragments Cell (antigen Antigen presenting) receptors Effector cells: 1. Activate other immune cells 2. Kill “target cells”

Activated T-cell Memory cells: Immature 1. Circulate months → years Dendritic Cell 2. Ready to rapidly respond to same antigen again Replication of Antigen Activated T-cell T-cell antigen-specific T-cells become Recognition APC Interaction Activation T-cells specialized

GM-CSF IL-12 IL-15

3 Sonnet’s Technology Advantage

Sonnet’s Fully Human Albumin Binding KEY FEATURES Flexible Linkers (FHAB) technology utilizes a single chain Fully Human Construct antibody fragment (scFv) capable of Therapeutic • Low/No immunogenicity delivering one or two active drug Payload B • Single- or Bi-specific design compounds • Therapeutic payloads attached via Targeted Delivery flexible linker peptides • High efficacy with low side effects Therapeutic • GP60- and SPARC-driven uptake Payload A Following administration, Sonnet’s FHAB- Enhanced pK derived candidates bind to and “hitch- • Extended dosing intervals hike” on endogenous human serum • FcRn binding albumin (HSA) for transport to target Human Serum tissues Albumin Small Size with Linear Flexibility • Optimized tumor penetration • FHAB has been designed to bind, unbind and rebind to albumin in an Mammalian Cell Production (CHO) on-and-off fashion through a physical • Glycosylated bonding mechanism, obviating the Sonnet FHAB complex taken up through GP60- and Modular need for chemical conjugation SPARC-mediated binding • Off-the-shelf system • Rapid asset development

4 Molecular Biology of the FHAB Platform

IL-12-FHAB IL-12-FHAB-IL15

Interleukin 15 Flexible Linker Flexible Linkers Interleukin 12 Interleukin 12

GMcSF-FHAB-IL18 Anti-IL6-FHAB-Anti-TGFβ

GMcSF Flexible Linkers

VH VL

Interleukin 18 Anti-TGFβ scFv

Flexible Linkers Anti-IL6 scFv

5 Pipeline Overview

Program Indications Discovery Pre-Clinical Phase I Next Milestone:

Chemotherapy Induced Pilot Efficacy SON-080 (low dose IL-6) Peripheral Neuropathy Study Initiation

Phase 1b/2a SON-081 (low dose IL-6) Diabetic Peripheral Neuropathy Study Initiation

SON-1010 (IL12-FHAB) Lung, Head & Neck Solid Tumors GLP Tox

SON-1210 (IL12-FHAB-IL15) Colorectal Solid Tumors Non-GLP Tox

Preclinical

AB AB Platform SON-2014 (GMcSF-FHAB-IL18) Melanoma, Renal Cancers

H Efficacy F

Preclinical SON-3015 (Anti-IL6-F AB-Anti-TGFβ) Prostate, Breast & Lung Cancers H Efficacy

6 Functional Assays Demonstrate Biological Activity

 Used the PathHunter® eXpress Dimerization Assay with mIL12-FHAB IL12RB1/IL12RB2

 Recombinant hIL-8 (negative control) or test samples

)

U L

R 300,000 (

mGM-CSF Recombinant e

c Pool 1 n

e 200,000 Pool 2 c

s Pool 3

 Used proliferation assay with the JAWS II cell line e mGMcsf-F AB n mGM-CSF Recombinant + Buffer H i 100,000

m IL-8 u

 Recombinant hIL-8 (negative control) or test samples L 0 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 GM-CSF (nM)

 Used proliferation of the CTLL2 cell line over 24 hours of hIL15-FHAB culture in the presence of recombinant hIL-15 (positive control), recombinant hIL-8 (negative control) or test

samples

)

(

e 5000

c mIL-18AH/2

n 4000 mIL-18AH/3 e

 Used the PathHunter® eXpress IL18R1/IL18RAP c Recom mIL-18 mIL18-FHAB s 3000 e hIL-8

dimerization assay n

i 2000 m

u 1000

 Recombinant hIL-8 (negative control) or test samples L 0 0.0001 0.01 1 100 10000 Conc (nM)

7 IL-12 and IL-15 Cell-Based Activity for IL12-FHAB-IL15 IL-12 IL-15

CTLLmCTLL-2-2

hIL12 (R&D Systems)

mIL12-FHAB-hIL15 (batch: H-C-02/03) IL-12 activity based on proliferation CTLL-2 cytotoxic T lymphocytes are able to proliferate and IFN secretion in response to either human or mouse IL-15

Lymphoblast proliferationS a m p le 3 assay (IL-12) IFN- release (IL-12) CTLL-2 proliferation assay (IL-15)

400 2 . 5 hiL-15 hiLh IL --1122 (R & D S y s te m s ) hIL12hIL12 (R&D) h I L - 1 5 ( R & D S y s t e m s )

2 5 0 0 0 350 hIL15h I L 1-F5H-ABA B-mIL12D - m I L 1 2 mIL12h IL 1 5 R-AFH- AABB D-hIL15- m IL 1 2 b a tc h : H - C - 0 2 /0 3 hIL15RA-ABD-mIL12mIL12-FHAB-hIL15 300 batch: H-C-02/03 2 . 0 log(agonist) log(agonist) vs. hIL12 mL12-F AB- mIL12-FHAB vs. response H response hIL15 hIL15-FHAB- hIL15 )

2 0 0 0 0 Best-fit 250 Best-fit mIL12

m (pg/ml)

values n values γ

U 1 . 5

0 L

Bottom 12982 12867 9 Bottom 0.404 0.4036

4 R

200 .

Top 21276 21297 ( Top 1.947 1.937 hIFN

LogEC50 -0.5968 -0.5351 D LogEC50 1.261 1.01 HillSlope 0.8736 0.9478 . 1 5 0 0 0 1 . 0 HillSlope 4.968 4.694

150 O EC50 0.2530 0.2917 EC50 18.26 10.23 100 0 . 5 1 0 0 0 0 50

1 0 -1 0 1 0 -5 1 0 0 1 0 5 0 0 . 1 1 1 0 1 0 0 1 0 0 0 [A g o n is t] , p M 750 150 30 6 1.2 0 Dose (pM) [ A g o n i s t ] , p M

IL12-FHAB-IL15 cell-based assays show full bioactivity in the bispecific construct 8 FHAB: Enhanced Pharmacokinetics Comparing the pharmacokinetic (pK) behavior of naked IL-12 and IL-15 versus the same interleukins linked to Sonnet’s FHAB

Method: 8 mice C57B/ TP, Age 9.5 weeks dose IV, sacrificed @ 5, 15, 30 mins, 1, 2, 4, 8, 24 & 48 hrs. Serum tested by ELISA

IL12-F AB IL12 WT H IL15IL15 WT WT IL15-A10M3IL15-FHAB 10,000,000.00000 10,000,000.00000

1,000,000.00000 1,000,000.00000

100,000.00000 100,000.00000 Fusion to FHAB increased t β = 9.5 hrs 1/2 t β ~ 7.0 hrs the plasma half-life of IL-12 10,000.00000 10,000.00000 1/2 > 4x and IL-15 >10X

1,000.00000 1,000.00000 t1/2 β = 0.6 hrs IL-12 MW = 70kd vs IL-15 MW=13kd t1/2 β = 2.5 hrs*

100.00000 100.00000 Protein Protein Concentration ( pg/ml ) Protein Protein pg/mlConcentration ) ( 10.00000 10.00000 * IL12 pK in Mice ~ 3 hrs J. Immunol. 164, 839-847 * IL15 pK in Mice ~ 0.5 hrs 2012 PLoS ONE 7(2): * IL12 pK in Mice ~ 3 hrs J. Immunol. 164, 839–847 1.00000 1.00000 0 5 10 15 20 25 30 0 5 10 15 20 25 30 Time (Hours) Time (Hours)

9 FHAB: Superior Uptake and Retention in Tumor Tissue

An in vivo demonstration of SPARC-mediated binding with optimized retention using albumin

Western blot analysis of Mouse 4T1 (TGFβ-positive tumor @ ~150mm3) extracts from mice terminated at 0.5, 4, 12 and 24-hours post IV injection with 100 µg/mouse of FHAB, anti-TGFβ or anti-TGFβ-FHAB. Results show superior accumulation and

retention of FHAB in the tumor FHAB alone Anti-TGFβ, no FHAB Anti-TGFβ-FHAB • FHAB - Present at 0.5 hours, peaks at 4 50kD hours and detectable through 24 hours. • Anti-TGFβ - Present at 0.5 hours then

0.5 4 12 24 0.5 4 12 24 0.5 4 12 24 hours declines at 4 hours and undetectable at 12 and 24 hours.

• Anti-TGFβ-FHAB – Present at 0.5 hours. 25kD and detectable through 24 hours.

10 Tumor Weight ** 0.4 * I FN -

0.3 Spleen Weight

0.3 SON0.2 -1010: Extended IFN-γ Release With2500 Reduced

* Grams 0.2

0.1 Grams Tumor0.0 and Reciprocal 0.1Spleen Weight vs Naked IL-12 0.0 Placebo Tumor Weight Spleen Weight Placebo 2000 TumorIL12 (1 ug/mouse)IL12 (3 ug/mouse) Weight Spleen Weight I FN - IL12 (1 ug/mouse)IL12 (3 ug/mouse) IL12-ABD (1.5IL12-ABD ug/mouse) (4.5 ug/mouse)

IL12-ABD (1.5 IL12-ABD ug/mouse) (4.5 ug/mouse) ANOVA: P=0.0081 ** 0.3 IFN- 0.4 ANOVA: P=0.0061 2500 Placebo * 2500 P l a ce b o * 1500 IL12-FHAB 1µg 0.3 IL 1 2 -A B D (1 .5 g /m o u s e ) 0.2 2000 2000 IL12IL 1 2-FHAB -A B D (4 3µg .5  g /m o u s e ) 0.2 pg/ml 1000 IL-12 1µg Placebo

1500 IL 1 2 (1 g /m o u s e ) Grams Grams 0.1 IL12-ABDPlacebo (1.5 g/mouse) 1500 IL-12 3µg 0.1 IL 1 2 (3 g /m o u s e ) IL12-ABD (4.5 g/mouse) pg/ml IL12-ABD (1.5 g/mouse) 1000 IL12 (1 g/mouse) 500 IL12 (3 g/mouse)IL12-ABD (4.5 g/mouse) 0.0 0.0 pg/ml in AUC & Exposure 1000 500 IL12 (1 g/mouse) Placebo IL12-FHAB IL12-FHAB IL-12 IL-12 Placebo IL12-FHAB IL12-FHAB IL-12 IL-12 1µg 3µg 1µg 3µg 1µg 3µg 1µg 3µg IL12 (3 g/mouse) Placebo Placebo 0 0 0 500 2 0 4 2 6 4 6 Day 5 Day 5 Days IL12 (1 ug/mouse)IL12 (3 ug/mouse) IL12 (1 ug/mouse)IL12 (3 ug/mouse) D a y s IL12-ABD (1.5IL12-ABD ug/mouse) (4.5 ug/mouse) Summary: IL12-ABD (1.5 IL12-ABD ug/mouse) (4.5 ug/mouse) 0 • IL12-FHAB is more effective than naked IL-12 in reducing tumor weight, at equivalent0 doses2 4 6 ANOVA: •P=0.0081Reduction in tumor weight correlates withANOVA: increase P=0.0061 in spleen weight Days • IFN-γ levels are ~10x greater with longer pK

11 SON-1010 vs Naked IL-12: Dose Level Comparisons

Tumor Volume Changes Between Groups on Day 10 Post Treatment

3000 Single Dose IL-12 vs IL12-FHAB 2500 G1: Vehicle Dose-dependent reduction in tumor volume

2000 )

3 G2: IL-12 with improved survival * 3µg 1500 G3: IL12-FHAB Superior to naked IL-12 1000 G4: IL-12 * 10µg G5: IL12-FHAB Favorable toxicity as 500 measured through body G6: IL-12 20µg 0 * weight analysis G7: IL12-FHAB

Final Tumor Final(mm Volume * Equal molar IL-12 concentrations Markers of CRS showed no increase at doses <20µg

Treatment Groups All asterisks are compared to Vehicle group with one-way ANOVA analysis * <0.05 ** <0.01 *** <0.001

* Data Not Shown: Kaplan-Meier evaluation of mouse B16F tumor survivability

shows a marked increase in survival with IL12-FHAB treatment.

12 SON-1010: Reduces Tumor Volume

Single Dose IL12-FHAB (1.3µg) vs IL-12 (30µg) in B16F10 Melanoma

Tumor Volume 3000 3 0 0 0 PPlacebol a c e b o 2857

) 2500 3 2 5 0 0 IIL12L 1 2 - AFHBABD ( 1(1.3µg,. 3 u g , S SD)D ) = Molar 0.9µg of IL-12 IL-12 (1µg) and IL12-FHAB

) (1.3µg) are molar 3 m 2000 IILL -1122 ( (30µg,3 0 u g , S SD)D ) 1996

m 2 0 0 0 equivalent and have ( similar bioactivity, in vitro; e 1500

m however, in vivo, F AB is 1 5 0 0 H u 1:30 ratio of IL-12 l approximately 30-fold

o 1000

V more potent than IL-12 (at 1 0 0 0 1002 r Dose

Tumor (mm Volume day 10, 1.3µg IL12-F AB >

o H

500 IL-12 30µg). m u 5 0 0 T 0

0 00 2 2 4 4 6 6 8 8 10 1 0 D Daysa y s

13 Monospecific vs Bispecific: Bispecific is Better

IL12-FHAB-IL15 vs IL12-FHAB

m m

Sonnet Bispecific Construct (

IL12-FHAB-IL15 e Single I.V. Dose @ 100 mm3 SC B16F10

) 1500

m 1 5 0 0 3

u V e h ic le

Synergistic Biologic Activity: l Day 10 Tumor Volume (n=8)

)

3 o

I L 1 2 - A B D ( 5 u g ) V

IL-12: ↑ IL-15 alpha receptor, ↑ IFN, 1000 r 1 0 0 0 I L 1 5 - A B D - I L 1 2 ( 6 u g )

↑ NK/T cells, ↑ TH1 and ↓ T reg o m

IL-15: ↑ IL-12 beta 1 receptor, ↑ NK u 500

T 5 0 0

cells, ↓ CD8 memory loss by l

apoptosis a

n Final Tumor Final(mm Volume i 0

F 0

Vehicle IL12-FHAB (5µg) IL12-FHAB-IL15 (6µg) Molar = 5 µg IL12

IL12-FHAB-IL15 produced a greater reduction in tumor volume than the molar equivalent dose of IL12-FHAB. In vivo, IL12-FHAB-IL15 is more effective at reducing tumor growth than IL-12 alone.

14 Pipeline Drug Development Strategy

IL12-FHAB, IL12-FHAB-IL15 and IL-6

Accelerate development by incorporation of a platform cell line development process with perfusion manufacturing • CHO host cell line suitable for perfusion upstream process implementation • Same media/feed/purification processing wherever applicable, to simplify supply chain

• Manufacturability proven for IL12-FHAB with high yield process

• Manufacturability and productivity enhancements being developed for IL12-FHAB-IL15 cell line • IP- protected process under development • Accelerated speed-to-clinic by using early transfection pooled material for in vitro pharmacodynamics and SCID mouse studies • Incorporate a pre-IND meeting into the development plan to ensure FDA familiarity with the pipeline, company and clinical direction of programs on an ongoing basis

• First pre-IND expected with IL12-FHAB, followed by IL12-FHAB-IL15

15 CMC Status of Lead Molecules

SON-1010 (IL12-FHAB) SON-1012 (IL12-FHAB-IL15)

• CLD and MCB complete: ~350mg/L productivity in a 10-day • Cell line development at clone selection stage fed-batch process • Media selection / proprietary (IP process), manufacturing • Analytical methods qualification near completion process development underway with pooled transfections • First use of material • GLP 50L fed-batch upstream completed, downstream ongoing. Productivity >700mg/L – Assay set up for CPPs, CQA’s

• GMP 50L fed-batch start date 3Q20 – Purification process development first use of material

• Formulation developed through iterative DOE for lyophilized – Western Blot and cross-ELISA for IL-12 and IL-15 developed to verify intact molecule version • Final clone selection expected 4Q20 – DS stable at -80oC • First use of material generated from continuous process in – DP initial material for Phase I – liquid fill planned animal studies ~3Q20 • Availability of DS and DP not on critical path to product development plan

16 FHAB Platform Opens Up New I/O Drug Opportunities

Flexible Combinations - Innovative Therapeutic Options: Numerous scientific publications support the use of IL-12 in combination with PD-1/PD-L1 checkpoint inhibitors, thus:

 Combination products consisting of Sonnet’s IL12-FHAB immune system modulator and Collaboration Partner’s anti-PD-1 or anti-PD-L1; or

 Combination products consisting of Sonnet’s IL12-FHAB-IL15 immune system modulators and Collaboration Partner’s anti-PD-1 or anti-PD-L1

Innovative therapeutic options also exist:

 Innovative products consisting of Sonnet’s IL12-FHAB monospecific and Collaboration Partner’s target payload to create a novel bispecific; or

 Innovative products consisting of the FHAB delivery module and two payloads from Collaboration Partner to create a dual mechanism of action

17 Platform Technology Summary

Immuno-Oncology: Validated targets in concert with unique delivery using proprietary Fully Human Albumin Binding domain (FHAB) platform

Extended pK (T½) and tumor targeting Sonnet platform is fully human (produced in CHO cells and glycosylated): IL12-F AB addressed with FHAB H • Analytical methods development and qualification – Complete in time for GMP batch • Formulation development for Lyo DP – Completed In vivo POC of FHAB demonstrated in a Melanoma tumor mouse model: • Process development and GMP manufacturing – Targeted completion 2H20 • Enhanced pK • Selectivity to tumor Pipeline Expansion 2021: Several new, novel interleukin- • Superior efficacy of interleukins while growth factor combinations linked to F AB (Anti-IL6- attached to FHAB as compared to their H naked counterparts FHAB-anti-TGFẞ, GMcSF-FHAB-IL18, GMCSF-FHAB-IL12)

Intellectual Property: PCT and US Patents in prosecution, as well as 5 provisional patents filed (i.e., potential utility with Vaccines, ADCs, Checkpoint Inhibitors and CAR-Ts)

• Study exploring IL12-FHAB as a viral adjuvant in H1N1 mouse influenza challenge model initiated in May 2020