Slide 1: AAV8 Empty Capsid plus ImmTOR (SEL-399) Human Proof-Of-Concept Study
Exhibit 99.1 SELB AAV8 Empty Capsid plus ImmTOR™ (SEL-399) Human Proof-Of-Concept Study* T op Line Data Report of a Phase 1 Clinical Study in Healthy Volunteers November 8, 2021 * Joint study with AskBio
Slide 2: Safe Harbor / Disclaimer
Safe Harbor / Disclaimer Any statem ents in this presentation about the future expectations, plans and prospects of Selecta Biosciences, Inc. (“the company”), including without lim itation, statem ents regarding the pre-clinical and clinical development of gene therapy product candidates b y the com
Slide 3: Inhibiting AAV-Specific Antibodies Could Enable Re-Dosing of AAV Gene Therapy
The Ability to Inhibit The Development of AAV-Specific Antibodies Has The Potential to Enable Re-Dosing of AAV Gene Therapy • Adeno-associated virus (AAV) vectors are the most widely used in-vivo gene therapy vectors • AAV is non-self replicating and over time transgene expression may wane, particul
Slide 4: AAV Gene Therapy Induces an Immune Response That Precludes Redosing
AAV Gene Therapy Induces an Immune Response That Precludes Redosing, Inhibits Efficacy, And Causes Adverse Events • Lower efficacy • Prevention of re-dosing • Adverse events • Loss of efficacy 4
Slide 5: Potential for ImmTOR to Enhance AAV Gene Therapy
Potential for ImmTOR to Enhance AAV Gene Therapy Potential to enable re-dosing of AAV gene therapy • Prevention of AAV antibody production • Potential to re-dose • Inhibition of liver inflammation • Enhanced efficacy • More durable efficacy • Improved safety 5
Slide 6: Long-Term Inhibition of Anti-AAV8 Antibodies With Monthly ImmTOR Doses in Animals
Long-Term Inhibition of Anti-AAV8 Antibodies With 3 Monthly Doses of ImmTOR in Animals Single And Multiple Dose ImmTOR Data AAV-EC + AAV-EC + 1 Mice AAV8 Empty capsid 2e13 vp/kg Single dose ImmTOR 3 monthly doses ImmTOR 2.0 2.0 1.5 1.5 1.5 1.0 1.0 1.0 0.5 0.5 0.5 0.0 0.0 0.0 Day Day Day BL = baselin
Slide 7: Study Design
Study Design 7
Slide 8: SEL-399 Phase 1 Dose-Escalation Study: Objectives and Endpoints
SEL-399 Phase 1 Dose-Escalation Study: Objectives and Endpoints § General Objectives § To determine the immune response to AAV8 empty capsids (EMC-101), which contain no DNA payload, in healthy volunteers § To determine whether single escalating doses of ImmTOR can reduce the immune response to AAV8
Slide 9: SEL-399 Phase 1 Dose-Escalation Study: Subjects and Design
SEL-399 Phase 1 Dose-Escalation Study: Subjects and Design § Total healthy volunteers enrolled: 23 (14 males and 9 females) § All subjects with anti-AAV8 NAb titers <1:5 at baseline § Randomized, placebo controlled and double-blind study Drug Infusions 30 45 60 75 90 Study Day 0 15 Placebo* + Empty
Slide 10: SEL-399 Phase 1 Dose-Escalation Study
SEL-399 Phase 1 Dose- Escalation Study 10
Slide 11: Single Dose ImmTOR Inhibited Formation of Anti-AAV8 NAb at Day 30
Single Dose ImmTOR Inhibited Formation of Anti-AAV8 NAb at Day 30 100% of subjects dosed with 0.3 mg/kg ImmTOR had NAb titers ≤1:25 at Day 30 67% of subjects dosed with 0.3 mg/kg ImmTOR had NAb titers ≤1:5 at Day 30 Linear Scale Log Scale 10 2000 2000 1000 1500 100 1000 Titer 1:25 10 500 Titer 1:5 1
Slide 12: Single Dose ImmTOR Inhibited Median Anti-AAV8 NAb in a Dose-Dependent Manner
Single Dose ImmTOR Inhibited Formation of Median Anti-AAV8 NAb in a Dose- Dependent Manner at Day 30 1:5 Median NAb titers in subjects dosed with 0.3 mg/kg ImmTOR at Day 30 250-fold lower median NAb titers in subjects dosed with 0.3 mg/kg ImmTOR at Day 30 100000 Median 10000 Titer 1:1250 1000 50-Fol
Slide 13: Single Dose Subjects Developed Delayed NAb Formation by Day 90
Subjects Treated With a Single Dose of ImmTOR Developed Delayed NAb Formation by Day 90 Two additional doses of ImmTOR may be required to maintain control beyond Day 30 2 of 6 subjects dosed with 0.3 mg/kg ImmTOR had NAb titers ≤1:25 at Day 90 1 of 6 subjects dosed with 0.3 mg/kg ImmTOR had NAb tite
Slide 14: Empty Capsid Data In-Line With Single Dose ImmTOR NHP Data at Day 90
Empty Capsid Data In-Line With Single Dose ImmTOR NHP Data at Day 90 1 Human Nonhuman Primate Target For Redosing Single dose Single Dose Three Doses 1000000 100000 Titers too high for re-dosing 100000 10000 200+ 10000 Failure 1000 1000 Antibody levels may interfere 50-200 Intermediate with efficien
Slide 15: Safety
Safety All treatment-related adverse events were expected for ImmTOR, readily monitorable, and transient § There were no Serious Adverse Events (SAEs) § Adverse events related to ImmTOR were expected based on previous clinical trials § Stomatitis (mouth ulcers, redness, or pain) was most common § 3
Slide 16: Summary
Summary 16
Slide 17: Summary and Conclusions
Summary and Conclusions § AAV8 empty capsids elicited a strong immune response with peak median anti-AAV8 NAb titers of 1:6875 § ImmTOR inhibited the formation of anti-AAV8 NAb in a dose-dependent manner at Day 30 § After Day 30, 2 of 6 subjects treated with 0.3 mg/kg ImmTOR maintained NAb titers ≤
Slide 18: Q&A
Q&A 18