An Open Label, Dose Escalation Study to Evaluate the Safety and Efficacy of Intralesional Injection of STP705 in Adult Patients With Cutaneous Squamous Cell Carcinoma in Situ (isSCC)

This open label, dose escalation study is designed to evaluate the safety and efficacy of various doses of STP705 administered as an intralesional injection in subjects with cutaneous in situ squamous cell carcinoma (isSCC).

The primary objective of this study is to evaluate the safety, tolerability, and efficacy of various doses of STP705 administered as an Intralesional injection in subjects with cutaneous squamous cell carcinoma in situ skin cancer (isSCC). This study seeks to establish a safe and effective recommended dose of STP705 for the treatment of isSCC. Expression of biomarkers common to the isSCC formation pathway, including TGF-β1 and COX-2, will be evaluated.

The primary endpoint will be the proportion of participants with histological clearance of treated isSCC lesion at the End of Treatment (EOT). Histological clearance (HC) will be defined as the absence of detectable evidence of isSCC tumor cell nests as determined by central pathology review.

Secondary endpoints will include i) time to histological clearance of treated isSCC lesion over the 6 week treatment period, ii) proportion of participants with complete clinical clearance of treated isSCC lesion based on investigator assessment at the End of Treatment (EOT), iii) time to complete clinical clearance of treated isSCC lesion based on investigator assessment over the 6 week treatment period, and iv) the change in size of the treated isSCC lesion over the 6 week treatment period.

Safety and tolerability will be assessed by the number of incidence of adverse events (AEs) and serious adverse events (SAEs); the incidence of AEs and SAEs leading to discontinuation of trial medication; the incidence and severity of Local Skin Response (LSR); hypopigmentation and hyperpigmentation following treatment; and the tolerability of repeated Intralesional administration of STP705 as assessed by investigator-evaluation of injection site reactions for all patients and within each cohort.

In addition, safety measures will include clinically relevant changes or new abnormal findings in laboratory values, vital signs, electrocardiograms (ECGs), and physical examination variables.

25 adult patients are planned to be enrolled in the study. They will be divided equally among 5 cohorts (10, 20, 30, 60 and 120 μg dose levels) of 5 subjects each. Enrollment of the first two subjects in each dosing cohort will be staggered by at least 48 hours. Participants in the first cohort will attend the study center once weekly for an injection of STP705 into the isSCC lesion. The participants will receive injections of STP705 once a week for up to 6 weeks. The clinician will evaluate the tumor for clinical changes and reduction in size at each treatment visit for up to 6 weeks. If during the 6 weeks of treatment there is complete clinical clearance of the tumor, the treatments will end. At the End of Treatment visit, the residual tumor, or former tumor location will be excised for analysis. In the absence of dose limiting toxicities (DLT), the subsequent cohorts will receive increasing doses of STP705, following the same schedule of administration as the first cohort.

If any of the SAEs or dose limiting toxicities outlined above has occurred, the Data Safety Monitoring Board (DSMB) will conduct independent review of the data and will make a final decision for dose escalation to the next cohort.