Clinical Trial of OMTX705 in Combination With Gemcitabine/Nab-Paclitaxel and Tislelizumab in Patients With Advanced/Metastatic Pancreatic Adenocarcinoma

Inclusion Criteria: 1. Capable of giving signed informed consent. 2. Male and female participant aged 18 years and older. 3. Participants must have histologically or cytologically confirmed PDAC: a) Metastatic PDAC who have not received therapy or received 1 prior line of systemic cytotoxic therapy (Part 1 and Part 2) and if trial treatment is given in the second line setting; b) Non-resectable locoregional PDAC who have not received therapy or received 1 prior line of systemic cytotoxic therapy (Part 1 only); c) A previous treatment with a targeted agent (for example KRAS inhibitor in the context of a clinical trial) without chemotherapy not counted as previous line of therapy. This situation should be discussed with the medical monitor. 4. Participants should have documented disease progression if previously locally advanced disease or be in 2nd line for stage IV or, in the opinion of the investigator, despite of lack of documented PD per image, require a change in the therapy. 5. Participants should be considered in general eligible for standard GA, for first or second line for metastatic disease (Part 1 and 2) or as palliative therapy for non-resectable locoregional cancer (Part 1 only). Patients who received polychemotherapy (FOLFIRINOX or similar) as neoadjuvant/adjuvant treatment and recur locally or distant \<6 months after the completion of systemic therapy, will be classified as second line. 6. Measurable disease by RECIST v1.1 on CT PET/CT or magnetic resonance imaging (MRI) scan. 7. Eastern Cooperative Group Performance (ECOG) performance status 0-1. 8. Adequate bone marrow, hepatic and renal function: a) Total bilirubin ≤1.5 times upper limit of normal (ULN) or total bilirubin n \<3.0 × ULN with direct bilirubin within normal range in participants with documented Gilbert's syndrome; b) AST and ALT ≤3 times ULN, (if liver metastases are present, then ≤5 times ULN is allowed); c) Serum creatinine ≤1.5 x ULN or creatinine clearance ≥40 mL/min (measured or calculated using the Cockroft-Gault formula); d) Hemoglobin ≥9.0 g/dL (whole or partial blood transfusions not allowed in the two previous weeks); e) ANC ≥1.5 x 109/L (growth factors like granulocyte-colony stimulating factor are not allowed in the two previous weeks); f) Platelet count ≥100 x 109/L (platelet in the two previous weeks transfusions not allowed). 9. Women of childbearing potential (WOCBP) and men with sexual partners who are WOCBP must be willing to adhere to highly effective contraceptive requirements and must agree to avoid impregnating a partner or becoming pregnant, respectively, during the study, and for at least 90 days after the last dose of any IMP. Men with sexual partners who are WOCBP should adhere to contraception requirements for 180 days after the last dose of any IMP. 10. Suitable venous access for safe drug administration and the study-required drug concentration and pharmacodynamics sampling. 11. A valid archival tumor sample. 12. Pretreatment fresh biopsy is optional in Part 1 dose escalation. In Part 2, a fresh pretreatment biopsy and on-treatment is required unless biopsy is associated with significant risk and per discussion with the sponsor medical monitor (or designee). Exclusion Criteria: 1. Prior treatment with OMTX705 or nab-paclitaxel for the locally advanced (adjuvant or neoadjuvant) for metastatic disease. Previous use of gemcitabine as radiosensitizer or as part of neoadjuvant/adjuvant therapy is allowed if the treatment was completed 6 months before consent signature. Prior treatment with T-cell co-stimulating or immune checkpoint blockade therapies including anti-cytotoxic T-lymphocyte associated protein 4, anti-PD-1, and anti-PD-L1 therapeutic antibodies or any immune checkpoint inhibitor (except for participants to be enrolled in Part 1A). 2. Treatment with systemic anticancer treatments, investigational products, or major surgery within 4 weeks before the first dose of study drug or 5 half-lives, whichever is shorter. Participants should have recovered from previous treatment toxicity to Grade 1, baseline (excluding anemia, lymphopenia, alopecia, and skin pigmentation). Participants with endocrinopathies should have the replacement treatment in stable dosing. 3. History of uncontrolled brain metastasis. Participants with brain metastases are allowed if they are previously treated with surgery, whole-brain radiation, or stereotactic radiosurgery and have brain imaging during screening confirming that brain metastasis are stable (without evidence of progression by imaging using the identical imaging modality for each assessment, either MRI or CT and considered controlled with ≤10 mg/day prednisone equivalent at the time of receiving the first dose of OMTX705). For asymptomatic participants, screening brain imaging is not required. 4. Participant has received extended field radiotherapy ≤4 weeks before the start of treatment (≤1 week for limited field radiation for palliation), and who has not recovered to Grade 1 or better from related side effects of such therapy (except for alopecia). 5. Major surgical procedure or significant traumatic injury ≤21 days prior to ICF signature. 6. Cardiac arrhythmias requiring anti-arrhythmic therapy. Note: pacemakers, beta blockers, or digoxin are permitted. 7. Active infection requiring parenteral or oral antibiotics. Antibiotics given for prophylaxis are allowed. They are also allowed for minor localized infections like cystitis, amygdalates or localized skin infections. 8. Evidence of serious uncontrolled medical disorder that, in the opinion of the investigator or medical monitor, makes it unwise for the participant to participate in the study or that might jeopardize compliance with the protocol. 9. Drainage of ascitic or pleural fluid two or more times in the four weeks prior to the first dose of study drug or permanent drain in place (e.g., PleurX®) for ascites or pleural effusion symptom management. 10. Placement of a biliary stent, e