A Study to Assess the Safety and Tolerability of Different Doses of AG019 Administered Alone or in Combination With Teplizumab in Participants With Recently Diagnosed Type 1 Diabetes Mellitus (T1D)

This Phase 1b/2a, multi-center study will be conducted in participants with clinical
recent-onset Type 1 Diabetes Mellitus (T1D).

The primary objective of this study is to assess the safety and tolerability of different
doses of AG019 alone as well as AG019 in association with teplizumab. The secondary
objectives of this study are: to obtain pharmacodynamic (PD) data of AG019 alone as well as
AG019 in association with teplizumab; and to determine the potential presence of AG019 in
systemic circulation (safety - systemic exposure) and the presence of L. lactis bacteria in
fecal excretion (local exposure): Pharmacokinetic (PK) profile.

This study consists of 2 phases:

Phase 1b: this open-label part of the study will investigate the safety and tolerability of 2
different doses of AG019 in 2 age groups (18-40 years of age and 12-17 years of age).

Phase 2a: this randomized, double-blind part of the study will investigate the safety and
tolerability of AG019, in association with teplizumab, in 2 age groups (18-40 years of age
and 12-17 years of age).

Inclusion Criteria:

- Male or non-pregnant, non-lactating females, 18 - 40 years of age (both inclusive) or
12-17 years of age (both inclusive)

- Diagnosis of diabetes according to the American Diabetes Association (ADA) recommended
criteria

- Evidence of auto-antibodies to at least 1 β-cell autoantigen

- Stimulated C-peptide measured during 4h Mixed Meal tolerance Test (MMTT) > 0.2 nmol/L

- The first administration of AG019 should occur no later than 150 days post diagnosis
of diabetes

- Body weight ≥ 33kg

- Written informed consent obtained and documented (participant, parent, guardian as
applicable)

Exclusion Criteria:

- Previous history of serious cytokine release syndrome to teplizumab or other humanized
anti-CD3 monoclonal antibodies with no or minimal capacity to bind Fc receptors.
(Participants enrolled in the second phase of the trial in either Combination Cohort 1
or Combination Cohort 2, only)

- Use of immunosuppressive or immunomodulatory therapies, including systemic steroids
within 1 month prior to randomization

- Participation in another investigational drug trial within 12 weeks prior to the first
study drug intake and during participation in this study

- History of recurrent infections, other autoimmune diseases, cardiac disease,
malignancy, or any other (chronic) medical condition which, in the investigator's
opinion, could compromise participant safety

- Documented history of human immunodeficiency virus (HIV), Hepatitis Virus Type C (HCV)

- Evidence of active infection with Epstein-Barr Virus (EBV) or cytomegalovirus (CMV)

- Evidence of active or latent tuberculosis (TB)

- Administration of anti-CD3 antibody in past year

- Current therapy with any other anti-diabetic agents other than insulin (MDI, CSII or
analogue). Current or planned therapy with experimental (i.e., unapproved) insulin.
Patients on therapy for type 2 diabetes (e.g. metformin) should stop their therapy in
order to be eligible for study participation.

- Use of medications known to influence glucose tolerance

- Daily use of non-steroidal anti-inflammatory agents

- Compromised GI mucosal integrity or motility, not attributable to T1D (i.e., recent
diarrhea, gluten sensitive enteropathy, inflammatory bowel disease, irritable bowel
syndrome), or current use of medications known to influence GI motility