Soterios Pharma Announces Positive Phase 2 Results for STS-01 in Alopecia Areata, Demonstrating 100% Hair Regrowth in Over a Quarter of Patients

On May 30, Soterios Pharma announced positive results from its Phase II clinical study of STS-01, a non-steroidal topical therapy for the treatment of patients with mild-to-moderate alopecia areata.

Analysis showed that the trial met its primary endpoint and multiple secondary endpoints, with more than a quarter of patients achieving complete hair regrowth after treatment. According to the company’s press release, STS-01 has the potential to become the first approved therapy and standard of care for mild-to-moderate alopecia areata.

Soterios Pharma is a UK-headquartered, clinical-stage life sciences company focused on developing and commercializing therapies for dermatological conditions with significant unmet medical needs. The company’s approach leverages deep scientific expertise in medical dermatology to identify “de-risked” opportunities that improve patients’ lives.

The data released pertain to a randomized, placebo-controlled, multiple-dose Phase 2 trial designed to evaluate the efficacy and safety of STS-01 in patients with mild-to-moderate alopecia areata over a 24-week treatment period. A total of 158 subjects were enrolled and randomly assigned to receive one of four doses of STS-01 (0.25%, 0.5%, 1%, or 2%) or placebo. Efficacy was assessed based on the Severity of Alopecia Tool (SALT) score. Patients with mild-to-moderate alopecia areata had a SALT score of <50, indicating more than 50% scalp hair coverage.

Analysis showed that at 24 weeks, 75.9% of patients treated with once-daily topical 1% STS-01 achieved the primary efficacy endpoint (improvement in SALT score >30%), compared with only 36.7% of patients receiving placebo (p<0.0096).

Furthermore, complete hair regrowth (SALT 0) was achieved in 19% and 27% of patients treated with 1% and 2% STS-01, respectively, compared to only 3% of patients receiving placebo. In terms of safety, STS-01 was well tolerated, with no serious adverse events reported. STS-01 is based on a mechanism with a well-established safety profile, modulating inflammatory responses and T-cell proliferation by disrupting signal transduction pathways.

Research data indicate that alopecia areata is the second most prevalent form of hair loss worldwide, affecting approximately 147 million people globally, including about 4 million in China. A six-province survey in China reported a prevalence rate of 0.27%, with nearly 18.1% of patients diagnosed before the age of 18.

In the United States, mild-to-moderate alopecia areata (hair loss <50%/SALT score <50) accounts for more than half of the 800,000 patients with alopecia areata. The impact on quality of life in patients with mild-to-moderate alopecia areata is comparable to that in patients with severe alopecia areata; however, there are currently no approved therapies for these patients.

Alopecia areata is an autoimmune disorder in which the immune system attacks hair follicles. The scalp is the most commonly affected site, but hair loss can also occur in the eyebrows, eyelashes, facial hair, or other areas of the body.

The pathogenesis of alopecia areata remains unclear; it is currently believed to result from an autoimmune attack on hair follicles mediated by immune cells and inflammatory cytokines. Furthermore, emotional distress and stress are recognized as triggering factors for alopecia areata. Following the onset of the condition, patients may develop psychiatric disorders such as recurrent depressive disorder, depression, and anxiety disorders. Anxiety and depression, in turn, can exacerbate alopecia areata, creating a vicious cycle. Due to the incompletely understood pathogenic mechanisms, current treatments yield unsatisfactory outcomes and are associated with high recurrence rates.

As people pay increasing attention to hair-related issues, the "hair loss economy" has emerged, reflected in the pharmaceutical industry by the research and development of related innovative drugs. According to Frost & Sullivan, the market size for hair loss treatment in China is projected to reach RMB 41.2 billion in 2026, with a compound annual growth rate of nearly 12%.

Although treatment options for alopecia areata remain limited, numerous pharmaceutical companies have entered the field. In 2019, Aclaris’s JAK inhibitor failed in Phase II clinical trials for alopecia areata. It was not until June 14 that Olumiant, approved by the FDA, broke the lack of targeted therapies in this area.

In June 2022, the U.S. FDA announced approval of baricitinib (brand name Olumiant), an oral JAK inhibitor jointly developed by Eli Lilly and Incyte, for the treatment of adult patients with severe alopecia areata. The press release noted that this marks the first systemic therapy approved by the FDA for the treatment of alopecia areata.

In 2023, the FDA approved Litfulo (ritlecitinib), a dual kinase inhibitor developed by Pfizer, for the treatment of severe alopecia areata in patients aged 12 years and older. According to the press release, this marks the first time the U.S. FDA has approved a therapeutic agent for adolescents (aged 12 and above) with severe alopecia areata.

The FDA also accepted Sun Pharmaceutical’s New Drug Application (NDA) in October 2023 for deuruxolitinib, a potential “best-in-class” oral JAK inhibitor, for the treatment of patients with moderate-to-severe alopecia areata. Currently, rezpegaldesleukin, Nektar Therapeutics’ potential “first-in-class” regulatory T cell (Treg)-modulating therapy, is being evaluated in Phase 2 trials for its efficacy in treating atopic dermatitis and alopecia areata.

In China, JAK inhibitors from Pfizer and Eli Lilly have already received regulatory approval. Domestic pharmaceutical companies such as Hengrui Medicine, Zeltis Pharma, and Kelun Pharmaceutical also have related products in development, with some having entered Phase III clinical trials, making their future progress highly anticipated.