flexible by design ProTIA Bispecific T cell engagers designed for local activation in the tumor environment

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1 flexible by design ProTIA Bispecific T cell engagers designed for local activation in the tumor environment 1

2 Cancer Therapeutics With Best-in-Class Therapeutic Index XTEN Protein Polymers The Problem with T Cell Engagers ProTIA Provides a Solution Lead Program AMX-268 2

3 XTEN Brings the Precision of Recombinant Production to Polymer Chemistry Chemical Polymer XTEN Protein Polymer Typical Protein Chemical Reactor Live Cells Live Cells Monomers Random Polymerization Ribosomal Biosynthesis Ribosomal Biosynthesis RANDOM LENGTH RANDOM SEQUENCE UNDEFINED STRUCTURE 1-3 MONOMERS DEFINED LENGTH DEFINED SEQUENCE UNDEFINED STRUCTURE 6-7 MONOMERS DEFINED LENGTH DEFINED SEQUENCE DEFINED STRUCTURE 2 MONOMERS 3

4 XTEN Offers Superior CMC Properties Versus Chemical Polymers such as PEG Peptide-XTEN G-CSF-PEG (Neulasta) Intensity Mass Mass (Da) (Da) Mass Mass (Da) (Da) XTEN PEG, Chemical Polymers Homogeneity 1 Species >1 Species Chromatography Sharp peaks Broad peaks Polymer purification Ion exchange, scalable Size exclusion, not scalable Recombinant Fusion Yes No Cleavage Site Insertion Yes No 4

5 Amunix Developed XTEN Protein Polymer Technology Growth Hormone Exendin-4 Recombinant Fusion Chemical Conjugation Undisclosed Factor VIII Factor IX XTEN Protein Polymer Highly soluble, stable Fully biodegradable Defined chemical composition Long in vivo half-life Low immunogenicity Well tolerated (>3 patients) Undisclosed Partner AMX-268 Additional ProTIAs XTEN-Drug Conjugates Immune Activators (ProTIA) ProTIA XTEN platform has been optimized and validated through many successful partnerships XTEN polymers are a key component of ProTIA therapeutics 5

6 Cancer Therapeutics With Best-in-Class Therapeutic Index XTEN Protein Polymers The Problem with T Cell Engagers ProTIA Provides a Solution Lead Program AMX-268 6

7 Toxicity Efforts to Increase Antibody Potency Have Resulted in Concomitant Increases in Toxicity T Cell Engagers (BiTE, DART, bsigg) CAR-T Class Drug Dose Range (mg per patient) Low High Herceptin 14, 42, ADCs Checkpoint Inhibitors IgG Erbitux 45, 72, Rituxan 45, 1, Naked Antibodies ADC Kadcyla 252, 252, Adcetris 126, 126, T Cell Engager Revomab 1 15 Blincyto 9 28 Potency T cell engagers require very low dosing to mitigate systemic toxicity 7

8 Example of On-Target but Off-Tumor Toxicity Before treatment After treatment Eyes (MART1+) Tumor (MART1+++) Skin (MART1+) Patient treated with adoptive T-cell therapy Target MART1 is expressed at low level in eyes and skin Severe on target toxicity was observed Source: Nat. Biotechnol. (213) 31, Most tumor antigens show low-level expression in healthy tissues Additional mechanisms are required to limit toxicity in healthy tissues 8

9 Cancer Therapeutics With Best-in-Class Therapeutic Index XTEN Protein Polymers The Problem with T Cell Engagers ProTIA Provides a Solution Lead Program AMX-268 9

10 Toxicity Three Targeting Mechanisms for Class-Leading Therapeutic Index ProTIA Combines 3 Targeting Mechanisms Administration as Prodrug ADCs T Cell Engagers CAR-T 1 Tumor antigen binding 2 Localized activation 3 EPR effect Low activity Long half-life Limited uptake by health tissues 3 EPR effect Naked Antibodies ProTIA 2 Localized Activation Potency High activity Short half-life Rapid tissue uptake 1 Tumor antigen binding 1

11 ProTIA: Rapidly Assembled from Standard Domains Building Blocks acd3 IgG atumor IgG Trigger Site XTEN ProTIA-X (Administered Form) ProTIA activation by tumorassociated proteases XTEN is a Key Component of ProTIA Blocks T-cell activation of prodrug form Provides long circulation half-life Reduces uptake by healthy tissues Minimizes aggregation risk Facilitates manufacturing ProTIA-A (Activated Form) 11

12 ProTIA Combines 3 Mechanisms to Achieve Best-In-Class Therapeutic Index Tumor Tissue Normal Tissue Blood Vessel Blood Vessel EPR effect Vascular Endothelium Vascular Endothelium Localized activation Protease-rich tumor environment Tumor antigen binding Low tumor antigen T Cell Tumor Cell T Cell Normal Cell 12

13 buffer Robust and Scalable Manufacturing Platform Rapid E. coli Manufacturing Defined Chemical Structure aepcam ORI acd3 XTEN Expression Plasmid Selection ESI-MS MW calc 138,649 MW exp 138,66 E. Coli XTEN Prevents Aggregation Single protein chain Soluble production No refolding No cell line development One week fermentation time Size Exclusion Chromatography. 2. Time, min 13

14 ESI-MS Analysis of Herceptin and ProTIA Herceptin ProTIA MW calc 138,649 Da MW exp 138,66 Da Antibodies are produced in cell culture Glycosylation results in heterogeneity ProTIA is produced in E. coli No post-translational modifications Defined chemical structure 14

15 Significant Improvement vs Competing T Cell Engagers Property ProTIA Probodies, Bispecific Bispecifc Fragments IgG-Like Companies Amunix (ProTIA) Cytomx (Probodies) Akriveia (Akluded) Amgen (BiTE) MacroGenics (DART) Affimed (TandAbs) Immunocore (ImmTAC) Xencor (XmAb) Regeneron (BiAb) Roche (TCB) Janssen (FynomAb) Emergent (ADAPTIR) Binding to tumor antigen Localized activation EPR Effect ProTIA vs Bispecific Probodies: Activated Probodies have long circulation half-life Accumulation in circulation? Activated ProTIA has very short half-life No accumulation in circulation 15

16 Marker (kda) Before cleavage Protease A Protease B Protease C Protease D ProTIA Therapeutics are Designed for Activation by Multiple Tumor-Associated Proteases Tumor protease digests analyzed by electrophoresis ProTIA-X (Injected form) Experiment AMX-168 was incubated with tumorassociated proteases Reactions were analyzed by electrophoresis ProTIA-A (Activated form) Released XTEN Proteases A, B, and C cleave at ProTIA-X at the trigger site releasing active ProTIA-A Protease D degrades XTEN polymer releasing ProTIA-A but no intact XTEN 16

17 Impact of XTEN on T Cell Activity Cell line: SKOV-3 Cell line: OVCAR3 8 ProTIA-A ProTIA-X ProTIA-B 8 ProTIA-A ProTIA-X ProTIA-B % Specific Lysis x % Specific Lysis x Log Concentration (nm) SKOV-3 cells partially convert ProTIA-X to ProTIA-A during in vitro assay Log Concentration (nm) OVCAR3 cells convert ProTIA-X to ProTIA-A during in vitro assay ProTIA-A is highly active (similar to BiTE) with both cell lines ProTIA-B is 3-1x less active than ProTIA-A XTEN blocks T cell activation ProTIA-X is partially activated during assay by proteases produced by target cell line 17

18 XTENylation Prevents Non-Specific T Cell Activation anti-cd3 IgG (Positive control) ProTIA-X (Injected form) ProTIA-A (Activated form, similar to BiTE) IL-6 pg/ml Untreated 1 nm anti-cd3 1 nm 1 nm 1 nm acd3 ProTIA-X 1 nm 1 nm 2 nm ProTIA-X 1 nm 1 nm ProTIA-A 1 nm 2 nm ProTIA-A TNFa pg/ml anti-cd3 Untreated 1 nm 1 nm ProTIA-X does not induce any significant cytokine response ProTIA-A (structure similar to BiTE) triggers cytokine release acd3 ProTIA-X 1 nm 1 nm 1 nm 1 nm ProTIA-X 2 nm 1 nm 1 nm ProTIA-A 1 nm 2 nm ProTIA-A 18

19 Plasma Concentration (%ID/g) Trigger Site is Stable in Tumor-Bearing Mice Implant tumor cells Intraperitoneal Inject mixture ProTIA-A ProTIA-X ProTIA-B Collect Plasma 4h 8h 24h 2d 3d 5d 7d ProTIA-A ProTIA-X ProTIA-B ProTIA-X ProTIA-B.1 ProTIA-A Time (h) Trigger site is stable in tumor-bearing mice Plasma half-lives: 2hr for ProTIA-X and ProTIA-B; <2hr for ProTIA-A 19

20 ProTIA Provides 1x Improved Therapeutic Index vs BiTEs Target+ expression in multiple organs Tumor (Target+++) ProTIA is 1x Less Toxic vs BiTE ProTIA Matches Efficacy of BiTE 8 Percent survival x dose 1x dose ProTIA-X 3x dose 1x dose 3x dose 1x dose ProTIA-A ~ BiTE ProTIA-A ~ BiTE ProTIA-X Prodrug Mouse specific surrogate Human xenograft model 2

21 ProTIA-B ProTIA-X ProTIA-A AMX-N68 in Platinum-Resistant Ovarian Ascites Model Implant OVCAR-3 (IP) CA125 Inject PBMC Inject test article (2x per week, IP) 21 5 Animals: NOG 6 per group Target: OVCAR-3 Effector: PBMC Route: OVCAR-3 = IP PBMC = IV Test articles = IP Endpoints: CA125 profile Ascites volume, Tumor nodules Measure Body Weight 2x/week Vehicle Low dose 3.6 nmol/kg (.5 mg/kg ProTIA-X) High dose 18 nmol/kg (2.5 mg/kg ProTIA-X) Low dose intraperitoneal ProTIA-X and ProTIA-A eliminates most/all CA-125 secretion ProTIA-B has minor(no) impact on CA-125 secretion even at 5x increased dose level Study: AX

22 ProTIA-B ProTIA-X ProTIA-A Implant HCT-116 (SC) AMX-N68: Efficacy in Established Lung Tumor Model Inject PBMC Inject test article (3x per week, IV, 4 wks) Animals: NOG 5 per group Target: HCT-116 Effector: PBMC Route: HCT-116 = SC PBMC = IV Test articles = IV Endpoints: BW Tumor volume Measure Tumor Volume & Body Weight 2x/week Vehicle Vehicle s Low dose 2.16 nmol/kg (.3 mg/kg ProTIA-X) s ProTIA-X and ProTIA-A showed strong efficacy over a wide range of concentrations ProTIA-B resulted in limited activity (>1x weaker than ProTIA-X) s s s s s s s s High dose 21.6 nmol/kg (3. mg/kg ProTIA-X) s 2 Study: AX

23 Cancer Therapeutics With Best-in-Class Therapeutic Index XTEN Protein Polymers The Problem with T Cell Engagers ProTIA Provides a Solution Lead Program AMX

24 EpCAM+ Expression/Cancer Incidence/Market Potential Global assessment of potential patient populations for AMX-268 EpCAM Overexpression (TIS >4) Cancer ESTIMATED CANCER INCIDENCE, WORLD New Cases per Year 75% (including SCLC) Lung 1,824,71 46% (~75% TNBC) Breast 1,671,149 94% Colorectum 1,36,62 89% Prostate 1,94,916 74% Stomach 951,594 65% Oesophagus 455,784 63% Pancreas 337,872 Very large therapeutic potential No competitive therapies in this space Multibillion dollar market potential $5,/treatment x 1, patients = $5 BB 55% Kidney 337,86 87% Thyroid 298,12 73% Ovary 238,719 66% Gallbladder 178,11 Sources: GLOBOCAN 212 IARC Spizzo et al., J Clin Pathol 211;64:415 24

25 Differentiating Properties AMX-268 Versus Other EpCAM Targeting Agents acd3 aepcam acd3 aepcam acd3 aepcam Name Administration Route Administration Schedule Revomab (Catumaxomab) IP, requires catheter 4 doses in 12 days MT11 AMX-268 AMX-268 Potential Benefit Continuous IV IV Convenience Safety (avoid IP injection) 28 days Weekly Enables long-term treatment Immunogenicity Very high Low Low Enables long-term treatment Toxicity Profile Moderate High Low Safety Potency (higher dosing) 25

26 Highlights Innovative ProTIA Format Combines Three Targeting Modes Strong Validation Proven Partnering Administered as inactive prodrugs (ProTIA-X) with long circulation half-life Converted at the tumor site into highly active T cell engager (ProTIA-A) Activated form has short half-life to minimize risk of systemic exposure Binding to tumor antigen Localized protease activation EPR effect (Limited permeation of healthy tissues) 1X widened therapeutic window demonstrated Sub nanomolar activity against multiple targets XTEN component of ProTIA validated in multiple clinical trials >$8 million in non dilutive revenue to date Multiple XTEN-based partnerships: Genentech, Bioverativ, Lilly, Roche, Janssen, Versartis, Naia Please contact us with questions about ProTIA or our XTEN for half-life extension Partnering/licensing requests: matt@gellerbp.com 26