Inclusion Criteria:  Males or females aged ≥ 18 years. 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. Module A Monotherapy Dose Escalation Cohort and Module B Combination Therapy Safety Cohorts: Histologically or cytologically-confirmed metastatic or locally advanced, unresectable solid tumors. Module A Cohort Expansions: Histologically or cytologically-confirmed metastatic or locally-advanced, unresectable select tumor types. Module B Cohort Expansions: Expansion B1 or B2: Histologically or cytologically-confirmed metastatic or locally-advanced, unresectable select tumor types.  Baseline measurable disease based on RECIST v1.1 for expansion cohorts. Patients with non-measurable disease are eligible for the dose escalation portion of the trial. Patients are required to have one or more measurable lesions that meet RECIST v1.1 and meet the following conditions:  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; 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. Performance status of 0 or 1 based on the Eastern Cooperative Oncology Group (ECOG) performance scale. Estimated life expectancy of 12 weeks or greater. Prior palliative radiotherapy must have been completed 14 days prior to dosing on C1D1. 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.  Have adequate liver and kidney function and hematological parameters within a normal range as defined by:  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; AST and ALT ≤ 2.5x ULN or ≤ 5x ULN for patients with liver metastases; Serum creatinine ≤ 1.5x ULN or ≥ 50 mL/min by estimated creatinine clearance (CrCl) using Cockcroft-Gault formula; Hemoglobin ≥ 8 g/dL without blood transfusions for at least two weeks prior to dosing on C1D1; Absolute neutrophil count ≥ 1500 cells/mm3 without growth factor support, three days for filgrastim, 14 days for pegfilgrastim; Platelet count ≥ 75,000 cells/mm3. Have archival tissue for biomarker analysis. The sample should preferably be from a sample obtained after the most recent therapy. For patients in the expansion cohorts for Module A and B a fresh biopsy is required if archival tissue (e.g., all tumor blocks are exhausted) is unavailable. If a biopsy cannot be performed with acceptable clinical risk in the judgment of the Investigator the Sponsor medical monitor must be contacted to approve enrollment. If no archival tissue is available for patients enrolled in the dose escalation or the safety assessment portion of Module B, the Sponsor medical monitor must approve enrollment.  Exclusion Criteria:  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. 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. 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.  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:  Uncontrolled airway hyper-reactivity; Type 1 diabetes mellitus. Type 2 diabetes mellitus patients are allowed if they are under stable glycemic control as per Investigator assessment; Uncontrolled, clinically significant pulmonary disease; Requirement for supplemental oxygen to maintain a pulse ox > 93%; Symptomatic congestive heart failure as per Investigator assessment or documented cardiac ejection fraction less than 45%; 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; History of unstable angina or myocardial infarction within six months of dosing on C1D1; Unstable cardiac arrhythmia; History of ventricular arrhythmia; 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; History of stroke or cerebral hemorrhage within one year of dosing on C1D1; Poorly controlled seizure disorder; Active diverticulitis within one year prior to dosing on C1D1; Recent major surgery within three months of dosing on C1D1 or major surgery with unresolved complications that could interfere with study treatment. Treatment with systemic antiviral, antibacterial or antifungal agents for acute infection within ≤ 7 days of dosing on C1D1. Has a history of, or a positive test for, HIV1/2 primary immunodeficiency disease such as Human Immunodeficiency Virus (HIV). History of hepatitis B (with positive testing for either hepatitis B surface antigen [HBsAg] or hepatitis B core Ag) or hepatitis C (HCV) infection (with positive testing for HCV antibody and/or HCV ribonucleic acid [RNA] in serum). Acute hepatitis A (with positive testing for hepatitis A IgM). Prior organ allograft or allogeneic hematopoietic transplantation. 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. 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. 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. Active SARS-CoV-2 infection including history of positive SARSCoV- 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. 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.  Woman of child-bearing potential (WOCBP) 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 woman 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: Women 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.  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 WOCBP, 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. QT interval corrected for heart rate using Fridericia's formula (QTcF) of ≥ 500 milliseconds. 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. Known active alcohol or drug abuse. Inability to comply with the protocol and/or not willing or not available for follow-up assessments. Patients who are incapacitated or involuntarily incarcerated. Patients who are unsuitable for participation based on the judgement of the Investigator.