Sirnaomics Gets FDA Guidance to Push Forward Development of RNA Therapeutic STP705 for Squamous Cell Carcinoma

Sirnaomics has shared phase 2a/2b clinical data regarding STP705, an RNA therapeutic being evaluated for the treatment of squamous cell carcinoma in situ (isSCC), with the FDA in an End of Phase-2 meeting and is now making moves towards a phase 3 clinical trial based on the agency’s guidance.¹

The company stated that this year it plans to initiate a single dosage study that will serve as a subgroup of a larger phase 3 clinical trial. STP705 consists of small interfering RNA oligonucleotides with a dual-targeted inhibitory property. It uses polypeptide nanoparticle-enhanced delivery and is intended to reduce expression of the TGF-β1 and COX-2 genes. In addition to the isSCC indication, STP705 is also being evaluated for the treatment of basal cell carcinoma (BCC), cholangiocarcinoma, non-melanoma skin cancer, and hypertrophic scars. STP705 was granted orphan drug designation by the FDA for the treatment of cholangiocarcinoma and primary sclerosing cholangitis. The company is prioritizing the late-stage clinical development for the isSCC indication, the ongoing phase 2 trial for BCC, and a phase 1 trial for fat remodeling. Across isSCC and BCC studies, STP705 has been evaluated in more than 100 patients; in these patients, no grade 3 or higher adverse events (AEs) have been observed.

“Moving STP705 for the treatment of isSCC into late-stage clinical development is a major milestone for our clinical program and for a dermatology/oncology application,” Patrick Lu, founder, chairman of the board, executive director, president, and CEO of Sirnaomics said in a statement.¹ “According to a 2020 research report from JAMA Dermatology, among patients with isSCC, the cumulative risk of developing an invasive SCC was 11.7% in men and 6.9% in women. Given the widespread prevalence of SCC lesions and a tremendous unmet need, Sirnaomics is dedicated to taking on the challenge for development of a novel therapeutic product with RNAi-based technology.”

Sirnaomics previously reported interim data from the first part of the phase 2b clinical trial in December 2022.² Among 32 patients who were treated with STP705, 78% showed histological clearance. Sirnaomics additionally noted that in the lowest dose cohort, in which 9 patients were treated at a dose of 30 µg/ml, 89%showed histological clearance. In the 60 µg/ml dose cohort, which included 12 patients, 75% showed histological clearance. In the 90 µg/ml dose cohort, which included 11 patients, 73% showed histological clearance. This portion of the study also included a cohort of 12 patients who were treated with a placebo; in this group, 58% showed histological clearance. In terms of safety, there were no treatment-related AEs or serious AEs reported. Sirnaomics also stated that across all treatment groups, Local Skin Response Scores remained stable or were improved.

“Based on the guidance from the type B meeting with the FDA, we currently have a clear path moving forward for late-stage development for STP705 as an innovative drug for treatment of isSCC,” Michael Molyneaux, MD, executive director and chief medical officer of Sirnaomics, added to the statement.¹ “Our data has demonstrated excellent safety and efficacy for the treatment of isSCC, and we look forward to advancing this program to late-stage development.”

REFERENCES
1. Sirnaomics advances STP705 for squamous cell carcinoma in situ into late-stage clinical development. News release.Sirnaomics Ltd. June 19, 2023. Accessed June 21, 2023. https://sirnaomics.com/en/news-room/press-release/20230619sirnaomics-advances-stp705-for-squamous-cell-carcinoma-in-situ-into-late-stage-clinical-development/
2. Sirnaomics announces positive interim data from phase IIb clinical trial of STP705 in adults with cutaneous squamous cell carcinoma in situ. News release. Sirnaomics Ltd. December 14, 2022. Accessed June 21, 2023. https://sirnaomics.com/en/news-room/press-release/20221214sirnaomics-announces-positive-interim-data-from-phase-iib-clinical-trial-of-stp705-in-adults-with-cutaneous-squamous-cell-carcinoma-in-situ/