JTX-2011 Alone and in Combination With Anti-PD-1 or Anti-CTLA-4 in Subjects With Advanced and/or Refractory Solid Tumors

JTX-2011 is an agonist monoclonal antibody that specifically binds to the Inducible
CO-Stimulator of T cells (ICOS) to generate an anti-tumor immune response. This is a Phase
1/2, open label, multicenter, dose escalation and expansion, first-in-human (FIH) clinical
study to evaluate the safety and tolerability, PK, PD, and preliminary efficacy of the ICOS
agonist monoclonal antibody JTX-2011 alone and in combination with nivolumab, ipilimumab, or
pembrolizumab in adult subjects with advanced and/or refractory solid tumors. The study will
include a dose escalation phase for single agent and the combination therapies, followed by
an expansion phase in specified tumor types for single agent and the combination therapies.

Inclusion Criteria:

1. Must be willing and able to participate and comply with all trial requirements and
able to provide signed and dated informed consent prior to initiation of any trial
procedures

2. Evaluable or measurable disease, according to Response Evaluation Criteria in Solid
Tumors (RECIST) v1.1 criteria, and meet the requirements for the intended study cohort

3. Male or Female ≥ 18 years of age

4. Have an Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0-1.
Subjects with ECOG 2 may be considered for enrollment in Parts C, D, F, and H if
approved by Medical Monitor

5. Have a predicted life expectancy of ≥ 3 months

6. Have laboratory values (obtained ≤ 28 days prior to first infusion day) in accordance
with the study protocol

7. If medical history of the following, case should be reviewed by the Medical Monitor:
prior biliary tract disorders (as based on Hepatobiliary SOC high level terms of:
obstructive bile duct disorders, hepatic vascular disorders, structural and other bile
duct disorders) or portal hypertension and/or hepatic vascular disorders

8. Women of child-bearing potential (WOCBP) must have a negative serum pregnancy test at
screening and a negative urine pregnancy test prior to administration of each dose of
JTX-2011

9. WOCBP and males with partners of child-bearing potential must agree to use adequate
birth control throughout their participation and for 5 months following the last study
treatment

Exclusion Criteria:

1. Receiving concurrent anti-cancer treatment (excluding radiation therapy), either
approved or investigational

2. Have refused standard therapy

3. Have received anti-cancer therapies listed below within the specified timeframe, or
who have ongoing toxicity from prior therapy > Grade 1 according to the Common
Terminology for Adverse Events (CTCAE). Exceptions to this are: > Grade 1 toxicities
which in the opinion of the Investigator should not exclude the subject (e.g.
alopecia, Grade 2 neuropathy, hypo- or hyperthyroidism or other endocrinopathies that
are well-controlled with hormone replacement) and are approved by the Medical Monitor.

1. Have received biologic therapy, including immunotherapy, < 28 days prior to C1D1;

2. Have received CAR-T therapy;

3. Have received chemotherapy < 21 days prior to C1D1, or < 42 days for mitomycin or
nitrosoureas;

4. Have received targeted small molecule therapy < 14 days prior to C1D1;

5. Have undergone organ transplantation including allogeneic or autologous stem-cell
transplantation, at any time;

4. Have undergone a major surgery (excluding minor procedures, e.g. placement of vascular
access, biopsy, etc.) < 6 months prior to the first day of study treatment, C1D1

5. Have a history of intolerance, hypersensitivity, or treatment discontinuation due to
severe immune adverse events on prior immunotherapy, or documented presence of
neutralizing anti-drug antibody to nivolumab, ipilimumab, or pembrolizumab. Subjects
who discontinued prior immunotherapies for immune-related adverse events that are
well-controlled with appropriate treatment may be enrolled if approved by the Medical
Monitor.

6. Have a diagnosis of immunodeficiency, either primary or acquired, or treatment with
systemic steroids or any other form of immunosuppressive therapy within 7 days prior
to C1D1. Exception: inhaled or topical steroids and adrenal replacement doses are
permitted in the absence of active autoimmune disease as well as a one-time dose of
immunosuppressive agents used prophylactically for contrast allergies

7. Have any active disease requiring systemic immunosuppressive treatment

8. Have known severe intolerance to or life-threatening hypersensitivity reactions to
humanized monoclonal antibodies or intravenous immunoglobulin preparations; any
history of anaphylaxis; prior history of human anti-human antibody response; known
allergy to any of the study medications, their analogues, or excipients in the various
formulations of any agent

9. Are symptomatic or have uncontrolled brain metastases, leptomeningeal disease, or
spinal cord compression not definitively treated with surgery or radiation (brain
metastases that are stable and asymptomatic, either treated or untreated, will be
allowed)

10. Have current second malignancy at other sites, which requires treatment, or in the
judgement of the Investigator, may require treatment within the next year. Concurrent
malignancies that do not require treatment and are clinically stable are allowed. A
past history of other malignancies is allowed as long as the subject is not receiving
specific treatment other than hormonal therapy, and, in the judgement of the
Investigator, is unlikely to have a recurrence.

11. Have active and clinically relevant bacterial, fungal, or viral infection, including
known Hepatitis A, B, or C or human immunodeficiency virus (HIV) (testing not
required)

12. Have received live vaccines within past 30 days (inactivated vaccines are allowed;
seasonal vaccines should be up to date prior to first infusion day)

13. Women who are pregnant or breastfeeding

14. Have experienced symptomatic cardiac disease that is unresponsive to surgical or
medical management

15. Have any medical or social condition that, in the opinion of the Investigator, might
place a subject at increased risk, affect compliance, or confound safety or other
clinical trial data interpretation