A clinical trial cohort of the investigational agent STP705 has successfully treated patients with cutaneous basal cell carcinomas, providing an alternative to surgery or other skin cancer treatment.
A small interfering RNA (siRNA) therapeutic agent used to treat patients with cutaneous basal cell carcinoma (BCC) led to complete response (CR) in all patients in the cohort at the highest dose in a clinical trial , according to a press release from Sirnaomics.1
In a phase 2 dose-escalation trial (NCT04669808), all 5 patients with cutaneous BCC who received the 180 μg dose of STP705 had CR. Additionally, they reported no adverse events (AEs) and no significant skin reactions.
“Achieving 100% CR is a clear indication that our treatment has the potential to be an alternative to treatments currently available to patients, which involve surgical excision of lesions,” said Michael Molyneaux, MD. , executive director and chief medical officer of Sirnaomics, said in a statement. “Reducing the healing rate and achieving a superior cosmetic outcome compared to surgery could be a potential benefit for patients with BCC and other non-melanoma skin cancers.”
STP705 is composed of 2 siRNA nucleotides that target TGF-β1 and Cox-2 mRNA expression, respectively. The drug is intended to downregulate the expression of these genes to inhibit tumor growth, providing an alternative to surgical excision or other invasive treatment for BCC.
The Phase 2 open label dose escalation study is designed to evaluate the efficacy, safety and tolerability of 5 different dose levels of STP705. Patients with a histologically confirmed BCC lesion with a minimum diameter of 0.5 cm and a maximum diameter of 2.0 cm were included. They could not have received prior treatment such as immunomodulators, certain topical agents, liquid nitrogen treatment, surgical excision (excluding diagnostic incisional biopsy), or curettage 4 weeks before the screening visit .
Patients received injections once a week for 6 weeks. The primary endpoint was the proportion of patients with histological clearance of the treated lesion within 6 weeks, and a secondary endpoint was the change in clinical diameter within this timeframe. The investigators also aimed to determine the safe and effective dose of STP705.
A previous interim analysis of cohorts that received lower doses of STP705 was reported in February 2022.2 Three dose escalation cohorts received doses of 30 µg, 60 µg, and 90 µg. One out of 5 patients in the 30 µg cohort had a CR, whereas there were 3 out of 5 CRs in the 60 µg and 90 µg cohorts. The 120 µg cohort had no data reported at this time or previously.
“The latest results from the Phase 2 clinical study of STP705 for the treatment of BCC, showing incredible efficacy with no drug-related or serious AEs, further validated the broad potential of this drug candidate for the treatment of prostate cancers. non-melanoma skin and beyond,” Patrick Lu, PhD, Founder, Chairman, Executive Director, President and CEO of Sirnaomics, said in a statement.1
STP705 is being studied in several clinical trials, including a phase 1/2 trial [NCT04293679] for cutaneous squamous cell carcinoma in situ [isSCC]where it demonstrated strong efficacy with 19 out of 25 patients achieving complete histological clearance.3 Another trial (NCT05421013) is investigating STP705 for isSCC of the face. It is also being studied outside of skin cancer in a trial (NCT04676633) of patients with cholangiocarcinoma and other types of disease.1
“Based on the successes of clinical studies in BCC and isSCC, Sirnaomics is spearheading the development of novel polypeptide-based siRNA treatments for various types of cancers,” Lu concluded.
1. Sirnaomics Achieves 100% Complete Response in Phase II Clinical Trial of STP705 for Treatment of Basal Cell Carcinoma of the Skin. Sirnaomics. August 29, 2022. Accessed August 30, 2022. https://bit.ly/3TwUKUK
2. Sirnaomics announces interim data from the Phase II clinical trial of STP705 for the treatment of cutaneous basal cell carcinoma. Sirnaomics. February 23, 2022. Accessed August 30, 2022. https://bit.ly/3PZCsYX
3. Nestor M, Berman B, Lu P, Molyneaux M. Safety and efficacy of TGF-β1/COX-2 neutralization therapy in adults with cutaneous squamous cell carcinoma in situ. J Drugs Dermatol. 2022;21(5):472-477. doi:10.36849/JDD.6384