A Phase 1/2, Open-label, Multi-center, First-in-human Study of the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Anti-tumor Activity of STX-001 Delivered by Intratumoral Injection in Patients With Advanced Solid Tumors as a Monotherapy or in Combination With Pembrolizumab

This open-label, Phase 1/2, first-in-human (FIH), multiple ascending dose and dose expansion study involves STX-001 administration, alone or in combination with pembrolizumab, to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary antitumor activity in patients with advanced cancers.

Phase 1 consists of 4 planned dose escalation cohorts of STX-001 delivered as a monotherapy (Cohorts 1m), 4 planned dose escalation monotherapy cohorts of STX-001 delivered as a combination therapy with pembrolizumab treatment given concurrently (Cohorts 1c), and an additional monotherapy cohort targeting visceral lesions (Cohort 1vm) that will be evaluated at 30ug, 100ug and 300ug. New patients will be enrolled in each dose escalation cohort.

Phase 2 consists of dose expansion cohorts in patients with 2 defined cancer types: triple-negative breast cancer (TNBC) and melanoma. There will also be a monotherapy cohort for advanced melanoma. Phase 2 will evaluate STX-001 in combination with pembrolizumab; the recommended Phase 2 dose (RP2D) will be selected based on analysis of the totality of data from Phase 1 safety, tolerability, PK, PD and preliminary efficacy data.

Sex: ALL
Minimum Age: 18 Years
Healthy Volunteers: No
Age Groups: ADULT, OLDER_ADULT

General Inclusion Criteria:

* ≥ 18 years of age at the time of screening.
* Mentally competent and able to understand and sign the informed consent form (ICF).
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
* Life expectancy of ≥ 12 weeks per the Investigator.
* Body weight ˃ 40 kg.
* At least 4 weeks from any prior major surgery.
* Willing and able to provide blood samples prior to the start of this study.
* Has a tumor lesion amenable to injection, must be accessible for pre and post injection biopsy, and the patient must be willing to consent to biopsy, if deemed safe by the Investigator.
* Laboratory values (Hematology): Absolute neutrophil count ≥ 1,000 cells/mm3; Platelet count ≥ 75,000 cells/mm3; Hemoglobin ≥ 8.0 g/dL.
* Laboratory values (Renal): Serum creatinine < 1.5 × upper limit of normal (ULN) or creatinine clearance ≥ 40 mL/min based on the Cockcroft-Gault glomerular filtration rate estimation
* Laboratory values (Coagulation): Prothrombin/International Normalized Ratio (PT/INR) or prothrombin time must be < 1.5 × ULN;
* Activated partial thromboplastin time (aPTT) ≤ 1.5 × ULN unless undergoing anticoagulation therapy.
* Laboratory values (Liver): Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) 470 ms in women and > 450 ms in men based on a 12-lead electrocardiogram (ECG) in triplicate using the Fridericia formula: QTc = QT / RR1/3.

Recent medical concerns exclusions:

* Prior direct radiation therapy to the tumor lesion to be injected.
* Active use of systemic anticoagulants
* Evidence of active infection requiring intravenous (IV) antibiotics during screening requiring therapy within 7 days prior to Cycle 1 Day 1.
* Active uncontrolled bleeding, or a bleeding diathesis within 7 days prior to Cycle 1 Day 1.
* Serious or non-healing wound, fistula, skin ulcer, or non-healing bone fracture within 7 days prior to Cycle 1 Day 1.
* Known human immunodeficiency virus (HIV) infection, active hepatitis B infection, or hepatitis C infection.
* Virology evaluation should be conducted at screening to include serum HIV antibody, HBc antibody, HBsAg antigen, and HCV antibody. Patients with a positive antibody evaluation for HCV and/or HBc should undergo evaluation to measure HCV RNA or HBV DNA, respectively.
* Untreated central nervous system tumor, epidural tumor or metastasis, or brain metastasis. Patients with any primary Central Nervous System (CNS) malignancy including glioma and current, active, progressing CNS malignancy, including carcinomatosis meningitis are excluded.
* Patients with treated brain metastases are eligible if there is no evidence of progression for at least 4 weeks after CNS-directed treatment, as ascertained by clinical examination and brain imaging (magnetic resonance imaging [MRI] or computed tomography [CT] scan) during the screening period and off systemic steroids (for at least 2 weeks prior to first dose).
* Another primary malignancy that has not been treated with curative intent, except for non-metastatic cutaneous basal cell or squamous cell carcinoma, or non-muscle invasive bladder cancer.
* Serious illness considered by the Investigator as incompatible with participating in this clinical study.
* Any condition that, in the opinion of the Investigator, would interfere with evaluation of the investigational product or interpretation of the patient’s safety or study results.
* Prior IL-12 therapy.
* Receipt of any vaccine within 30 days prior to the first dose of study treatment.
* Use of another anticancer therapy within 3 weeks prior to Cycle 1 Day 1 or 5 half-lives, whichever is shorter.
* Previously enrolled in this study.
* Actively enrolled in another clinical study unless it is an observational (noninterventional) clinical study or the follow-up component of an interventional study.
* Known severe hypersensitivity (Grade ≥ 3) to study treatment or any of the excipients of the products.
* Known psychiatric or substance use disorder that would interfere with the participant’s ability to cooperate with the requirements of the study.
* Currently pregnant (confirmed with positive pregnancy test), breast-feeding or planning to become pregnant within 60 days following treatment. For women of childbearing potential (WOCBP), a negative serum beta-human chorionic gonadotropin (β-HCG) result must be available within a 72 hour window before the first treatment dose.
* Women of childbearing potential not willing to use a highly effective method of contraception.
* Unwilling or unable to follow protocol requirements.