A Phase 1 Dose-Escalation Study to Investigate the Safety, Efficacy, Pharmacokinetics, and Pharmacodynamic Activity of CLN-619 (Anti-MICA/MICB Antibody) Alone and in Combination with Pembrolizumab in Patients with Advanced Solid Tumors

CLN-619-001 is a Phase 1, open-label, multi-center study of CLN-619 alone and in
combination with pembrolizumab in patients with advanced solid tumors.

Inclusion Criteria:

1. Males or females aged ≥ 18 years.

2. Willing and able to give written informed consent and adhere to protocol
requirements; written informed consent and any locally required authorization must
be obtained from the patient prior to performing any protocol-related procedures,
including screening evaluations.

3. Module A Monotherapy Dose Escalation Cohort and Module B Combination Therapy Dose
Escalation Cohorts: Histologically or cytologically-confirmed metastatic or locally
advanced, unresectable solid tumors. For Module B, tumor type is listed as an
approved indication per the current prescribing information for pembrolizumab.

4. Module A Cohort Expansions:

1. Expansion A1: Histologically or cytologically-confirmed metastatic or locally
advanced, unresectable NSCLC;

2. Expansion A2: Histologically or cytologically-confirmed metastatic or locally
advanced, unresectable cervical cancer.

3. Expansion A3 and A4: Histologically or cytologically-confirmed metastatic or
locally advanced, unresectable endometrial cancer.

4. Eligibility for disease-specific expansion cohorts may be further refined by
histologic subtype, molecular features, or exposure to prior therapy based on
clinical, pharmacodynamic, or biomarker data emerging from the study.

5. Module B Cohort Expansions:

1. Expansion B1: Histologically or cytologically-confirmed metastatic or
locally-advanced, unresectable NSCLC.

2. Expansion B2: Histologically or cytologically-confirmed metastatic or
locally-advanced, unresectable endometrial.

3. Eligibility for disease-specific expansion cohorts may be further refined by
histologic subtype, molecular features, or exposure to prior therapy based on
clinical, pharmacodynamic, or biomarker data emerging from the study.

6. Prior treatment history as follows:

a) Patients should have received any other approved standard therapy that is
available to the patient, unless this therapy is contraindicated, intolerable to the
patient, or is declined by the patient. In the case of a patient declining such
therapy, documentation that the patient has been informed and declined should be
documented in the medical record.

7. Baseline measurable disease based on RECIST v1.1 for Module A escalation, Module B
escalation; and, both Module A and Module B expansion cohorts. Patients are required
to have one or more measurable lesions that meet RECIST v1.1 and meet the following
conditions:

1. A non-lymph node lesion that has a longest unidimensional measurement of ≥ 10
mm or a lymph node lesion that has a shortest unidimensional measurement of ≥
15 mm;

2. Lesions that have received previous local treatment, such as radiotherapy or
ablation, can also be used as measurable target lesions if progression has been
confirmed according to RECIST v1.1 prior to enrollment, and the longest
unidimensional measurement is ≥ 10 mm.

8. Performance status of 0 or 1 based on the Eastern Cooperative Oncology Group (ECOG)
performance scale.

9. Estimated life expectancy of 12 weeks or greater.

10. Prior palliative radiotherapy must have been completed 14 days prior to dosing on
C1D1.

11. Toxicities related to prior study therapy should have resolved to Grade 1 or less
according to criteria of NCI CTCAE v5.0, except for alopecia. Peripheral neuropathy
should be clinically stable or improving and be Grade 2 or less in severity.
Patients with chronic but stable Grade 2 toxicities may be allowed to enroll after
agreement between the Investigator and Sponsor.

12. Have adequate liver and kidney function and hematological parameters within a normal
range as defined by:

1. Total bilirubin ≤ 1.5x ULN. This does not apply for patients with confirmed
Gilbert's Syndrome, for whom total bilirubin must be less than 3.0 mg/dL with a
conjugated bilirubin less than 0.5 mg/dL;

2. AST and ALT ≤ 2.5x ULN or ≤ 5x ULN for patients with liver metastases;

3. Creatinine clearance (CrCl) ≥ 45 mL/min as measured or estimated using
Cockcroft-Gault formula;

4. Hemoglobin ≥ 8 g/dL without blood transfusions for at least two weeks prior to
dosing on C1D1;

5. Absolute neutrophil count ≥ 1500 cells/mm3 without growth factor support, three
days for filgrastim, 14 days for pegfilgrastim;

6. Platelet count ≥ 75,000 cells/mm3.

13. Patients in the Module A and Module B dose escalation cohorts must have archival
tissue for biomarker analysis. A fresh biopsy is required if archival tissue is
unavailable.

Exclusion Criteria:

1. Currently participating/previously participated in an interventional study and
received an investigational drug within 28 days (or five half-lives, whichever is
longer) of dosing on C1D1.

2. Patients with concomitant second malignancies (except adequately treated
non-melanomatous skin cancers, ductal carcinoma in situ, superficial bladder cancer,
prostate cancer or in situ cervical cancer) are excluded unless in complete
remission three years prior to study entry, and no additional therapy is required or
anticipated to be required during study participation.

3. Patients with any active autoimmune disease or a history of known or suspected
autoimmune disease, or history of a syndrome that requires systemic corticosteroids
or immunosuppressive medications, except for patients with vitiligo, resolved
childhood asthma/atopy or autoimmune thyroid disorders on stable thyroid hormone
supplementation.

4. A serious uncontrolled medical disorder that would impair the ability of the patient
to receive protocol therapy or whose control may be jeopardized by the complications
of this therapy. These criteria include, but are not limited to the following:

1. Uncontrolled airway hyper-reactivity;

2. Type 1 diabetes mellitus. Type 2 diabetes mellitus patients are allowed if they
are under stable glycemic control as per Investigator assessment;

3. Uncontrolled, clinically significant pulmonary disease;

4. Requirement for supplemental oxygen to maintain a pulse ox > 93%;

5. Symptomatic congestive heart failure as per Investigator assessment or
documented cardiac ejection fraction less than 45%;

6. Ejection fraction < 45% in patients with prior history of treatment with
anthracycline chemotherapy or with a prior history of cardiac ventricular
dysfunction. Patients with prior history of ventricular dysfunction or
anthracycline therapy are required to have an echocardiogram for assessment of
baseline cardiac function;

7. History of unstable angina or myocardial infarction within six months of dosing
on C1D1;

8. Unstable cardiac arrhythmia;

9. History of ventricular arrhythmia;

10. Uncontrolled hypertension: patients with sustained systolic blood pressure
readings greater than 150 or diastolic blood pressure greater than 100 should
have documentation by treating physician that the finding is not consistent
with uncontrolled hypertension;

11. History of stroke or cerebral hemorrhage within one year of dosing on C1D1;

12. Poorly controlled seizure disorder;

13. Active diverticulitis within one year prior to dosing on C1D1;

14. Recent major surgery within three months of dosing on C1D1 or major surgery
with unresolved complications that could interfere with study treatment.

5. Treatment with systemic antiviral, antibacterial or antifungal agents for acute
infection within ≤ 7 days of dosing on C1D1.

6. Has a history of, or a positive test for, HIV1/2 primary immunodeficiency disease
such as Human Immunodeficiency Virus (HIV).

7. Diagnosed with hepatitis B (with positive testing for either hepatitis B surface
antigen [HBsAg] or hepatitis B core Ab) or hepatitis C (HCV) infection (with
positive testing for HCV antibody and/or HCV ribonucleic acid [RNA] in serum) under
any of the following conditions:

1. Active disease for hepatitis B or hepatitis C and received antiretroviral
therapy within 4 weeks.

2. Blood hepatitis B DNA or HCV RNA are detectable.

8. Prior organ allograft or allogeneic hematopoietic transplantation.

9. History of the following events in conjunction with prior treatment with checkpoint
inhibitor immunotherapy: Grade 3 or greater neurotoxicity, ocular toxicity,
pneumonitis, myocarditis, or colitis; liver dysfunction meeting the laboratory
criteria for Hy's Law.

10. Active central nervous system metastases and/or carcinomatous meningitis. Patients
with brain metastases identified at Screening may be rescreened after they have been
appropriately treated. Patients with treated brain metastases should be
neurologically stable for 28 days post completion of treatment and prior to
enrollment, and on a stable regimen of steroid dosing (prednisone <10 mg or the
equivalent) for 14 days prior to dosing on C1D1.

11. Treatment with non-oncology vaccines for the control of infectious diseases (i.e.
HPV vaccine) within 28 days of C1D1. The inactivated seasonal influenza vaccine can
be given to patients before initiation of treatment, and while on study therapy
without restriction. Influenza vaccines containing live virus, or other clinically
indicated vaccinations for infectious diseases (i.e. pneumovax, varicella) may be
permitted, but must be discussed in advance with the Sponsor Medical Monitor and may
require a study drug washout period before and/or after administration of the
vaccine. Covid-19 vaccines may be administered according to institutional policy.

12. Active SARS-CoV-2 infection including history of positive SARS-CoV-2 testing without
subsequent documentation of negative test results, patients with results that are
pending but not yet known, or patients with suspected active infection based on
clinical features.

SARS-CoV-2 vaccination is permitted on treatment.

13. Has received immunosuppressive medications including but not limited to cellcept,
methotrexate, infliximab, anakinra, tocilizumab, cyclosporine or corticosteroids
(≥10 mg/day of prednisone or equivalent), within 28 days of dosing on C1D1.

14. Female of child-bearing potential (FOCBP) who is pregnant or breast-feeding, plans
to become pregnant within 120 days of last study drug administration, or declines to
use an acceptable method to prevent pregnancy during study treatment and for 120
days after the last dose of study drug administration.

a) A female of childbearing potential is defined as: i) Not surgically sterile, i.e.
bilateral tubal ligation, bilateral oophorectomy, or complete hysterectomy, or; ii)
Not post-menopausal, defined as amenorrhea for ≥ two years without an alternative
medical cause.

Note: Females with amenorrhea for < two years and who are not surgically sterile
i.e. tubal ligation, bilateral oophorectomy, or complete hysterectomy will only be
considered not to be of reproductive potential if they have a documented follicle
stimulating hormone (FSH) value in the postmenopausal range.

15. Male patient who plans to father a child or donate sperm within 120 days or 5
half-lives of CLN-619, whichever comes later, of last study drug administration, or
who has a partner who is a FOCBP, and declines to use acceptable method to prevent
pregnancy during study treatment and for 120 days or 5 half-lives of CLN-619,
whichever comes later, after the last dose of study drug administration.

16. QT interval corrected for heart rate using Fridericia's formula (QTcF) of ≥ 500
milliseconds.

17. Patient has history of drug-related anaphylactic reactions to any components of
CLN-619 (Module A and Module B patients) or pembrolizumab (Module B patients only).
History of Grade 4 anaphylactic reaction to any monoclonal antibody therapy.

18. Known active alcohol or drug abuse.

19. Inability to comply with the protocol and/or not willing or not available for
follow-up assessments.

20. Patients who are incapacitated or involuntarily incarcerated.

21. Patients who are unsuitable for participation based on the judgement of the
Investigator.

22. Treatment with any of the following:

1. Systemic anticancer treatment within 14 days prior to the first dose of study
drug on C1D1.

2. Immunotherapy ≤ 28 days prior to the first dose of study drug on C1D1.

3. Radiotherapy < 28 days and palliative radiation ≤ 14 days prior to the first
dose of study drug on C1D1. If irradiated, lesions must have demonstrated
clear-cut progression prior to being eligible for evaluation as target lesions.

4. Major surgery (excluding placement of vascular access) ≤ 28 days of the first
dose of study drug on C1D1.

23. Refractory disease will be defined as progressive disease at 16 weeks after
receiving at least three doses of PD-1 therapy (Expansion B2 and Expansion B3 only).