Inclusion Criteria:

          1. Patient is at least ≥18 years of age (male or female).

          2. Disease characteristics for patients in Part 1:

             a. Patient with any histologically or cytologically confirmed solid tumor that is
             locally advanced or metastatic or unresectable tumor and has disease progression after
             treatment with available therapies that are known to confer clinical benefit or who
             are intolerant to treatment.

             Note: Tumor types of primary interest in Part 1 Dose Escalation include tumors which
             are relapsed or refractory after anti PD-1/PD-L1 therapy (include but not limited to
             malignant melanoma, HNSCC, renal cell carcinoma, hepatocellular carcinoma, Merkel cell
             carcinoma, urothelial, non-small cell lung cancer, gastric carcinoma, ovarian
             carcinoma, endometrial, TNBC, cervical cancer, and colorectal carcinoma)

          3. Disease characteristics and prior treatments for patients in Part 2:

               1. Cohort A (Melanoma): Patients with advanced or metastatic melanoma who have
                  progressed following treatment with an anti-PD-1 or anti-PD-L1 antibody. Patients
                  with BRAF mutated melanoma must have previously received BRAF/MEK targeted
                  therapy.

               2. Cohort B (Head and Neck): Patient has anti-PD-1/PD-L1 refractory metastatic or
                  recurrent HNSCC of the oral cavity, oropharynx, hypopharynx, or larynx.
                  Participants may not have a primary tumor site of the nasopharynx (any
                  histology).

             i. Has histologically confirmed Stage III, IVa, or IVb disease per TNM staging,
             American Joint Committee on Cancer (AJCC, 8th edition), with recurrent or persistent
             disease after definitive chemoradiation, deemed unresectable and considered refractory
             to both platinum-based combination chemotherapy and anti-PD-1/PD-L1 antibody therapy
             OR ii. Has histologically confirmed Stage IVc disease per TNM staging, AJCC 8th
             edition, considered refractory to platinum-based combination chemotherapy and
             anti-PD-1/PD-L1 antibody therapy.

             c. Cohort C: Tumor types not in Cohort A and B - Naïve or relapsed refractory to anti
             PD-1/PD-L1

          4. An Eastern Cooperative Oncology Group (ECOG) performance status ≤1

          5. Estimated life expectancy ≥3 months

          6. Measurable disease according to RECIST criteria v 1.1

          7. Patients must have recovered (ie, to NCI CTCAE grade ≤1) from all toxicity associated
             with previous treatments (exception: patients may enter with continuing alopecia
             irrespective of CTCAE grade).

          8. All women of childbearing potential must have a negative pregnancy test at Screening,
             prior to study drug administration

          9. Women of childbearing potential include any female who has experienced menarche and
             who has not undergone successful surgical sterilization (hysterectomy, bilateral tubal
             ligation, or bilateral oophorectomy) or is not postmenopausal. Postmenopausal is
             defined as: (1) Amenorrhea ≥12 consecutive months without another cause and a
             documented serum follicle stimulating hormone (FSH) level >35 mIU/mL; (2) Women with
             irregular menstrual periods and a documented serum FSH level >35 mIU/mL; or (3) Women
             on hormone replacement therapy (HRT)

         10. All patients, male and female, who are not surgically sterilized or postmenopausal as
             defined above, must agree to use dual effective birth control during the study and for
             at least 28 days after the last dose of study medication and 5 months after the last
             dose of atezolizumab.

             Highly effective methods of contraception are hormonal contraceptives (oral,
             injectable, patch, intrauterine devices), male partner sterilization, or total
             abstinence from heterosexual intercourse, when this is the preferred and usual
             lifestyle of the patient. Note: The double-barrier method (eg, synthetic condoms,
             diaphragm, or cervical cap with spermicidal foam, cream, or gel), periodic abstinence
             (such as calendar, symptothermal, post-ovulation), withdrawal (coitus interruptus),
             lactational amenorrhea method, and spermicide only are not acceptable as highly
             effective methods of contraception

         11. Patients has adequate hematologic and organ function, defined as:

               1. ANC ≥1500 mm3 without requiring G-CSF

               2. Platelets ≥100,000/mm3

               3. Hemoglobin ≥9 g/dL Note: Patients with Hb 7 to ≤9 g/dL (without bleeding)
                  transfused prior to dosing in order to meet eligibility criteria

               4. Serum creatinine ≤1.5× upper limit of normal (ULN) for the reference laboratory
                  or creatinine clearance ≥50 mL/min within the 28 days before enrollment
                  (calculated from Cockcroft-Gault formula or 24 hour urine collection).

               5. Alanine aminotransferase (ALT), aspartate transaminase (AST) ≤3.0× the upper
                  limit of normal (ULN) if no liver involvement or ≤5×ULN with liver involvement

               6. Adequate coagulation: prothrombin time (PT), an International Normalized Ratio
                  (INR) or activated partial thromboplastin time (aPTT) ≤1.5×ULN or for patients
                  requiring anticoagulant therapy, the PT/INR, aPTT should be within therapeutic
                  range of the given anticoagulant agent

               7. Total bilirubin ≤1.5×ULN (or total serum bilirubin ≤3×ULN for patients with
                  Gilbert's disease)

         12. Patients must be willing and able to provide written informed consent prior to the
             performance of any study-specific procedure

        Exclusion Criteria:

          1. Women who are pregnant or lactating or expecting to conceive a child within the
             projected duration of the study

          2. History or evidence of cardiovascular (CV) risk including any of the following: Recent
             (within the past 6 months) history of serious uncontrolled cardiac arrhythmia or
             clinically significant ECG abnormalities including second degree (Type II) or third
             degree atrioventricular block; Cardiomyopathy, myocardial infarction, acute coronary
             syndromes (including unstable angina pectoris), coronary angioplasty, stenting, or
             bypass grafting within the past 6 months before enrolment; Congestive heart failure
             (Class II, III, or IV) as defined by the New York Heart Association functional
             classification system (NYHA).

          3. Patients with marked Baseline QTc prolongation (QT interval corrected for rate by
             Fridericia's formula [QTcF] ≥470 msec for women and ≥450 msec for men on the ECG
             obtained at Screening by mean of three ECGs).

          4. Use of concomitant medications known to moderately or severly prolong QT interval.

          5. Patients with active or ongoing infection requiring systemic IV antibiotic therapy.
             Patients with active or ongoing Epstein-Barr virus, hepatitis B virus, or hepatitis C
             virus or with known human immunodeficiency virus (HIV) infection, tuberculosis, or
             other infections within 4 weeks.

          6. Clinically significant pulmonary disease, chronic or recurrent renal or urinary tract
             disease, liver disease, endocrine disorder, autoimmune disorder, or neuromuscular,
             musculoskeletal, or mucocutaneous conditions that, in the opinion of the Investigator,
             put the patient at additional risk by participating in the study or otherwise make the
             patient unsuitable for the study

          7. The patient has uncontrolled intercurrent illness including, but not limited to
             uncontrolled infection, including uncontrolled diabetes mellitus or decreased
             pulmonary function, or psychiatric illness/social situations that would limit
             compliance with study

          8. Has an active autoimmune disease that has required systemic treatment in the past 2
             years (ie, with use of disease modifying agents, corticosteroids, or immunosuppressive
             drugs) except vitiligo or resolved childhood asthma/atopy. Replacement therapy, such
             as thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal
             or pituitary insufficiency, is not considered a form of systemic treatment

          9. Patients with a history of or active pneumonitis Grade ≥ 2 (from any etiology).

         10. Patients who have discontinued prior immunotherapy due to immune-related adverse
             reaction(s)

         11. Is on chronic systemic steroid therapy in excess of replacement doses (prednisone ≤10
             mg/day is acceptable), or on any other form of immunosuppressive medication. Note: The
             use of physiologic replacement doses of corticosteroids may be approved after
             consultation with the Sponsor's Medical Monitor or designee

         12. Patients who have undergone major surgery within the last 4 weeks

         13. Patients with new brain metastasis. Patients with treated (surgically excised or
             irradiated) and stable brain metastases are eligible as long as the treatment was at
             least 4 weeks prior to initiation of study drug and baseline brain CT with contrast or
             MRI within 2 weeks of initiation of study drug is negative for new brain metastases

         14. Active malignant disease other than that being treated in this study. Exceptions:
             malignancies that were treated curatively and have not recurred within the past 2
             years; completely resected basal cell carcinoma and squamous cell carcinoma of the
             skin; and completely resected carcinoma in situ of any type.

         15. Patient- Prior treatment with the following agents:

               1. Stimulator of Interferon Genes (STING) agonist at any time.

               2. Anticancer therapy or investigational therapy within 28 days or 5 half-lives of
                  the drug, whichever is shorter; "Check-point inhibitors", including Programmed
                  death receptor-1 (PD-1), PD-L1 and Cytotoxic T-lymphocyte-associated antigen 4
                  (CTLA-4) inhibitors within 28 days (except part 2 Cohort C);

               3. Prior radiation therapy: permissible if at least 1 non-irradiated measurable
                  lesion is available for assessment according to RECIST version 1.1 or if a
                  solitary measurable lesion was irradiated, objective progression is documented. A
                  wash out of at least 28 days before start of study treatment for radiation of any
                  intended use to the extremities for bone metastases and 28 days for radiation to
                  the chest, brain, or visceral organs is required. Palliative radiation is
                  permissible at any time before or during the study.

         16. Receipt of any live vaccines within 4 weeks prior to the initiation of study drug and
             anticipation of need for such a vaccine during atezolizumab treatment or within 5
             months after the final dose of atezolizumab.

         17. Patients considered by Investigators for any other reason to be unsuitable for the
             study or unable to comply with all study procedures and follow-up examinations.