Sirnaomics Announces Positive Interim Data from Phase IIb Clinical Trial of STP705 in Adults with Cutaneous Squamous Cell Carcinoma In Situ

Dose escalation cohort study is evaluating the safety, tolerability and efficacy of various doses of STP705 administered as intralesional injection in subjects with isSCC

GERMANTOWN, Md. and SUZHOU BIOBAY, China, Dec. 14, 2022 /PRNewswire/ -- Sirnaomics Ltd. (the "Company" or "Sirnaomics", stock code: 2257.HK), a leading biopharmaceutical company in discovery and development of RNAi therapeutics, announced today the interim results of part-one of an ongoing Phase IIb clinical trial of STP705 for the treatment of Cutaneous Squamous Cell Carcinoma In Situ (isSCC). The interim results showed that the majority (78%) of 32 patients with STP705 treatment achieved histological clearance. One of the three treatment cohorts achieved 89% histological clearance. STP705 is an siRNA (small interfering RNA) therapeutic that takes advantage of a dual-targeted inhibitory property and polypeptide nanoparticle (PNP)-enhanced delivery to directly knock down bothTGF-β1 and COX-2 gene expression.

The two-part, double-blind, randomized, placebo-controlled Phase IIb study is designed to evaluate the safety and efficacy of various doses of STP705, administered as an intralesional injection in subjects with isSCC. In the part-one of the study, we have treated 32 patients with 30 μg/ml, 60 μg/ml and 90 μg/ml of STP705, respectively, and 12 patients with 0 μg/ml placebo weekly. After six-week repeated dosing, we collected tissue samples from the treatment sites followed by histological analysis.

This interim report is specifically for part-one of the study results with a total of 44 patients. Based on our Phase IIb study plan, part-two of this study will include 60 additional subjects who will receive selected doses or placebo for a total of more than 100 subjects. Enrolled subjects will be randomly allocated to receive STP705 or placebo injection once a week for a total of six weeks. In the seventh week, the lesion will be excised.

"The positive clinical readouts of the part-one study of this Phase IIb trial provide a further validation of our STP705 for treatment of non-melanoma skin cancers." said Dr. Patrick Lu, Founder, Chairman of the Board, Executive Director, President and CEO of Sirnaomics. "With more clinical results from this study and the cutaneous Basal Cell Carcinoma (BCC) study (Sirnaomics News Release at PR Newswire, August 29, 2022), we feel more enthusiastic about this novel RNAi cancer therapeutics for treatment of Squamous Cell Carcinoma (SCC), addressing a broader unmet patient need."

"In our study thus far, patients who received various doses of STP705 over six weeks achieved better histological clearance of isSCC excised lesions than the patients who received a placebo," said Dr. Michael Molyneaux, M.D., Executive Director and Chief Medical Officer of Sirnaomics. "As we move into the latter phase of the clinical trial, we will use this information to determine which doses we deem most effective for treating SCC, which is a type of nonmelanoma skin cancer that affects millions of people in the U.S. Currently, there are only a small number of approved non-surgical treatments that exist for SCC."

This interim report of unblinded results of part-one of the Phase IIb study showed that 25 of 32 subjects with STP705 treatment resulted in a high ratio (78%) of histological clearance. Among three treatment cohorts, the 30 μg treatment group (N = 9) achieved the highest histological clearance (89%), while the 60 μg treatment group (N = 12) achieved 75%, and the 90 μg group (N = 11) achieved 73%, which are clearly higher than the placebo group (N = 12) which achieved 58%. There were no treatment-related AE's or SAE's and Local Skin Response Scores were stable or improved across all treatment groups.

About Non-melanoma Skin Cancer

Non-melanoma skin cancers (NMSC) are the most common forms of human neoplasia. NMSC constitute a large group of skin cancers that are not melanoma, including squamous cell carcinoma (SCC), basal cell carcinoma (BCC), Extramammary Paget's Disease (EMPD), Merkel cell carcinoma (MCC), and skin adnexal carcinomas. Among these, BCC and SCC account for the majority of NMSC with more than 5 million newly diagnosed cases estimated to occur in the U.S. every year. Along with BCC, SCC is one of two major subtypes of NMSC. NMSC treatment market in the U.S. is expected to increase from US$6.5 billion in 2020 to US$22 billion in 2030. In China, the market size of NMSC treatment was US$38 million in 2020 is also expected to grow faster in the coming years, reaching US$149 million in 2030.

A World Health Organization authorized report from "International Agency for Research on Cancer" (2019) has demonstrated that the number of deaths in 2018 globally for both men and women from NMSC is 65,155, where the mortality of Asia NMSC subjects represents 41.9% of the global total, which is significantly more than other individual areas.

Surgery is currently the most common treatment option for the treatment of NMSC. The various forms of surgical modalities carry significant cutaneous adverse events, risk of scar, infection and bleeding. As a result, there is a high unmet need for an FDA approved local injection therapy that is safe and effective.

About STP705

Sirnaomics' leading product candidate, STP705, is a siRNA (small interfering RNA) therapeutic that takes advantage of a dual-targeted inhibitory property and polypeptide nanoparticle (PNP)-enhanced delivery to directly knock down both TGF-β1 and COX-2 gene expression. The product candidate has received multiple IND approvals from both the U.S. Food and Drug Administration (FDA) and the Chinese National Medical Products Administration (NMPA), including treatments of cholangiocarcinoma, non-melanoma skin cancer and hypertrophic scar. STP705 has also received Orphan Drug Designation for treatment of cholangiocarcinoma (CCA) and primary sclerosing cholangitis (PSC). STP705 is currently in seven clinical trials for different indications: a Phase IIb for squamous cell carcinoma in situ (isSCC), a Phase II for basal cell carcinoma (BCC), a Phase I/II for keloid scarring, a Phase I/II for hypertrophic scar (HTS), a Phase I/II for facial isSCC, a Phase I for liver cancer (basket), and a Phase I for medical aesthetics treatment.

About Sirnaomics 

Sirnaomics is an RNA therapeutics biopharmaceutical company with product candidates in preclinical and clinical stages that focuses on the discovery and development of innovative drugs for indications with medical needs and large market opportunities. Sirnaomics is the first clinical-stage RNA therapeutics company to have a strong presence in both China and the United States, and also the first company to achieve positive Phase IIa clinical outcomes in oncology for an RNAi therapeutic for its core product, STP705. Learn more at www.sirnaomics.com.

SOURCE Sirnaomics Ltd.