Small interfering RNA (siRNA) technology is integral to a process called gene silencing, which prevents cells from producing troublesome elements – such as proteins responsible for diseases.

Using gene silencing, the idea is doctors can arrest or reverse conditions targeting their root causes. The approach has been researched to treat patients with cancer, infectious diseases and neurodegenerative disorders.

The scientific community sees it as a promising area, but still at a very early stage of development (even though the first work in the area started a decade ago). There are many barriers to overcome, especially in terms of delivering the drug to the right part of the body and its toxicity.

The players

In 2018, Onpattro was the first siRNA-based drug to be approved. It was developed by US firm Alnylam Pharmaceuticals, Inc. (NASDAQ:ALNY), and is used to treat a neurodegenerative disease called hATTR amyloidosis.

Onpattro encases the siRNA into a fat particle to deliver the drug directly into the liver, in an infusion treatment, to alter or halt the production of disease-causing proteins.

In 2019 it generated US$166mln in sales. But Onpattro is just the “tip of the iceberg”, analysts say.

Silence Therapeutics’ breakthrough

Silence Therapeutics PLC (LON:SLN) made the headlines recently after clinching a deal with pharma giant AstraZeneca PLC (LON:AZN).

The FTSE 100-listed major will use Silence’s technology to develop treatments for liver, heart and lung diseases.

AstraZeneca will make a US$60mln cash payment and is subscribing for US$20mln of Silence shares initially. The Anglo-Swedish giant will then fork out US$10mln for each selected target, followed by US$140mln of development ‘milestones’ and up to US$250mln in commercialisation payments.

Tiered royalties on any sales would range from “high single-digit to low double-digit”, Silence said in a statement. Conservatively, based on just three drug development areas, the deal is worth a notional US$1.3bn.

“Financials are quite impressive,” commented Emma Ulker, analyst at Proactive.

“It does show that there is something there, the technology offers some promise.”