Inclusion Criteria:

Histologically confirmed extracranial solid tumors that are relapsing or refractory including locally advanced pancreatic cancer, unresectable soft tissue sarcomas, hepatic metastases due to colorectal cancer
At least one measurable disease per Response Evaluation Criteria in Solid Tumors v. 1.1 (RECIST 1.1) with a non-nodal lesion with longest diameter ≥ 10 mm or nodal lesions with short diameter ≥ 15 mm
Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 2
As assessed by the investigator, ≥ 3 month life expectancy
Adequate hematologic, liver and renal function at Screening as determined by lab criteria
Recovered < Grade 2 from all acute toxicities from previous therapy Has not had prior treatment with high dose corticosteroids within the 2 weeks of screening Is willing and able to comply with the study schedule and other protocol requirements Willing to follow contraception guidelines Exclusion

Exclusion Criteria:

Have a primary brain tumor Use of an investigational drug or local therapy or agent within 2 weeks of first dose of study drug. Current systemic chemotherapy per investigator's discretion is allowed, but no immune checkpoint inhibitors or immune modulators Use of anticoagulants or anti-platelet agents unless subject can safely start/stop to allow intratumoral injections Use of bevacizumab (Avastin) within 28 days of the STI-1386 injection Diagnosis of other malignancies that have required therapy in the last year or are not in complete remission. Exceptions include non-metastatic basal cell or squamous cell carcinomas of the skin, prostate cancer or cancer in situ that does not require treatment currently or is otherwise under control Requiring chronic systemic immunosuppressants, including steroids > 20 mg/day
Presence of bulky disease defined as any single mass > 5 cm in greatest dimension will trigger a discussion to determine eligibility
New York Heart Association (NYHA) Class >3 of left ventricular ejection fraction (LVEF) < 50% Prolonged corrected QT interval as determined by 12-lead electrocardiogram Has spinal cord compression or clinically unstable brain metastases within 4 weeks of first dose of study drug Evidence of active herpes infection and/or chronic herpes infection requiring prophylactic antiviral medication that may not be discontinued Has an active or recent COVID-19 infection, must have a negative RT-PCR test and not have had symptoms within 4 weeks of day 1 of study drug administration Any active infection requiring systemic therapy within 72 hours of injection of STI-1386, excluding anti-viral maintenance therapy for HIV Moderate to severe chronic obstructive pulmonary disease or other moderate to severe chronic respiratory conditions unless under treatment and stable for the 3 months of screening Have active human immunodeficiency virus (HIV) infection, human T-cell leukemia virus type 1 (HTLV1) infection, or hepatitis B virus (HBV) or hepatitis C virus (HCV) viremia Pregnant or lactating or up to 3 months post last dose Underlying medical conditions that, in the opinion of the investigator and/or medical monitor will prevent the subject from participating Allergy to acyclovir and related anti-HSV antiviral agents