The German science and technology group Merck KGaA has agreed to acquire the UK biotech Silence Therapeutics in a deal valued at approximately $1.3bn, expanding its pipeline of RNA-based medicines and strengthening its position in rare diseases.
The transaction, unanimously approved by Silence Therapeutics’ board, is expected to close in the first quarter of 2027, subject to customary closing conditions.
It will be funded through proceeds from new debt and implemented through a UK scheme of arrangement.
siRNA therapy targets rare blood cancer
The acquisition will add divesiran, a potentially best-in-class investigational siRNA therapy, to Merck’s pharmaceutical development pipeline.
The treatment is designed for phlebotomy-dependent polycythaemia vera (PV), a rare blood cancer characterised by excessive red blood cell production.
Divesiran selectively silences the TMPRSS6 gene, which regulates hepcidin, a key hormone involved in iron metabolism.
By increasing hepcidin levels, the therapy aims to restrict iron availability for red blood cell production, helping control haematocrit levels and reduce the need for therapeutic phlebotomy.
The candidate is administered subcutaneously once every three months and is considered ready to progress into Phase III development.
In the Phase II SANRECO study, divesiran achieved an 88% responder rate, compared with 19% for placebo.
During weeks 0-36, patients receiving the treatment underwent a mean of 0.2 phlebotomies, versus 2.1 in the placebo group.
Merck said the therapy was generally well tolerated, with no new safety findings observed in the trial. Further clinical development will be needed to establish its safety and efficacy.
Merck expands precision medicine pipeline
The deal supports Merck’s strategy to build a specialised medicines portfolio focused on areas of high unmet medical need.
It follows the group’s 2025 acquisition of SpringWorks Therapeutics, which expanded its capabilities in rare tumours and other specialised diseases.
Silence Therapeutics’ broader pipeline includes zerlasiran, an investigational siRNA treatment targeting elevated lipoprotein(a), a cardiovascular risk factor, as well as earlier-stage programmes for cholesterol, obesity and immune-related diseases.
The company’s RNA interference platform uses siRNA molecules to silence specific messenger RNA sequences before they can direct the production of disease-associated proteins.
This approach offers a route to selectively targeting biological pathways that may be difficult to address with conventional medicines.
Merck said the acquisition would provide an entry point into haematology while adding technology and development programmes that could support its longer-term growth in precision medicines.
