Interim data from a Phase 2 clinical trial of Sirnaomics Ltd’s STP705 shows a dose response with complete response, as well as improved or stable cosmetic result with no significant cutaneous skin reactions among patients with cutaneous basal cell carcinoma (BCC).

The new data also suggests a favorable safety profile as there are no drug related adverse events or serious adverse events.

STP705 is a  siRNA (small interfering RNA) therapeutic that acts as a dual TGF-β1/COX-2 inhibitor. TGF-β1 and COX-2 are known as gatekeeper targets for oncology and fibrosis disease drug development.  TGF-β1 regulates a broad range of cellular processes, including cell proliferation, differentiation, apoptosis, extracellular matrix production, angiogenesis, inflammation and immune response, while COX-2 is a proinflammatory and proliferative mediator. Sirnaomics is developing STP705 for non-melanoma skin cancer, including squamous cell carcinoma in situ, skin BCC, dermal fibrosis, and solid liver tumor

The Phase 2 open label, dose escalation study is designed to evaluate the safety, tolerability and efficacy of various doses of STP705 administered as localized injection in patients with BCC. The primary endpoint is to determine the proportion of participants with a complete response of treated BCC at the end of treatment, which is defined as the absence of detectable evidence of BCC tumor cell nests. The secondary endpoints are to determine the safe and effective recommended dose of STP705, and an analysis of biomarkers common to BCC formation pathway, including TGF-β1 and COX-2.

The interim analysis is comprised of three dose escalation cohorts ranging from 30μg to 90μg with five patients in each group, for a total of 15 patients enrolled in the trial so far. Participants received injections of STP705 once a week for up to six weeks. In cohorts B and C, which received doses of STP705 at 60µg and 90µg respectively, three out of five patients achieved a complete response. Cohort A, which received a 30µg dose, saw a complete response in one out of five participants.

"This interim data indicates that STP705 achieved therapeutic responses from patients with BCC, in addition to the positive readouts from patients with SCC, which further demonstrates our leadership in developing RNAi-based treatments for skin cancers," says Patrick Lu, Ph.D., the founder, Chairman of the Board, Executive Director, President and CEO of Sirnaomics, in a news release. "We look forward to seeing the results of our next data readout in this Phase II study with the rest of participant cohorts, which will give us more insights into the efficacy of STP705 as we seek to move this important therapeutic candidate forward."

"These encouraging interim results from the Phase II clinical trial of STP705 suggest that we are on a path to potentially offer a treatment for patients with BCC that would be an alternative to surgical excision of these lesions," adds Michael Molyneaux, M.D., Executive Director and Chief Medical Officer at Sirnaomics. "There is an unmet need for non-surgical treatments for various types of nonmelanoma skin cancers that reduce scarring and achieve high rates of complete response, which we have begun to see in this arm of the study."

The remaining part of the Phase II study will include two additional cohorts of five subjects with dosing of 120μg and 180ug, for a total of 25 participants in the clinical trial.