Spanish RNAi Drug Could Work Better Than Antihistamines for Eye Allergies

Sylentis has shown its RNA interference drug can significantly reduce eye allergy symptoms with fewer doses than standard antihistamine treatments.

Sylentis, based in Madrid, has preclinical data showing its RNA interference (RNAi) allergy drug SYL116011 could be a more effective treatment option for eye allergies than conventional antihistamines. A study in mice showed that the treatment reduced eye allergy symptoms such as swelling and tearing by 50 – 80%.

According to Sylentis, SYL116011 only needs to be given once a day, while antihistamines are usually given three to four times a day. Moreover, Sylentis reports SYL116011 caused fewer side effects like itchy eyes and drowsiness than antihistamines.


Sylentis’ RNAi treatment targets the causes of allergies with small interfering RNA (siRNA). These double-stranded RNA molecules bind to specific mRNA strands that encode allergy-causing proteins. When siRNA binds to the mRNA, it prevents the allergy-causing protein from being expressed.

RNAi could provide an alternative to allergy immunotherapies, which are not performing as well as expected in clinical trials. For example, Circassia stopped investing in its allergy pipeline last year after a placebo outperformed the treatment in two clinical trials. Last year, DBV Technologies’ peanut allergy treatment did not fare as well compared to a placebo as the company expected. It will be interesting to see whether Sylentis’ RNAi approach will yield better results when it enters clinical trials.

So far, however, RNAi is in the very early stages of commercial development. Sanofi and Alnylam may become the first to launch an RNAi drug with their treatment for the rare disease hereditary amyloidosis. Even though Sylentis is still in preclinical testing, its focus on allergies may turn out to be a fruitful niche in the RNAi treatment market.

RNAi treatments can be highly potent for long periods of time and can target any protein or gene in the body. Nonetheless, keeping RNAi molecules stable, delivering them effectively, and controlling unwanted toxic side effects are some of the challenges this technology still faces before becoming a widely used treatment option.

Images by Yurchanka Siarhei, Sementsova Lesia/Shutterstock

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