Merck KGaA has entered into an agreement to acquire British biotech Silence Therapeutics for $1.3 billion in a fully cash-based transaction, securing the German pharmaceutical company’s access to a compelling short interfering RNA (siRNA) drug development platform and a late-stage candidate targeting a rare blood cancer.
The deal values Silence at $20 per American depositary share (ADS), with each ADS representing three ordinary shares. The offer reflects an 82% premium to Silence Therapeutics’ average share price over the preceding month, underlining the strategic weight Merck places on the acquisition.
The Asset at the Heart of the Deal
The most prized asset within Silence Therapeutics’ pipeline is divesiran, a siRNA-based therapy under development for polycythemia vera (PV) — a chronic myeloproliferative neoplasm characterised by the excessive production of red blood cells, a condition linked to elevated risks of cardiovascular and thrombotic events.
Divesiran is engineered to selectively silence TMPRSS6, a gene that plays a role in regulating iron metabolism, thereby limiting the availability of iron required for red blood cell production. In August, Silence Therapeutics published positive Phase II clinical data from trial NCT05499013, in which 88% of patients on divesiran met clinical response criteria, compared to just 19% on placebo.
Competitive Landscape in Polycythemia Vera
The polycythemia vera treatment market is currently led by Mimrylo (rusfertide), developed by Takeda and Protagonist. Mimrylo received approval in the United States in August and operates through a different mechanism — mimicking hepcidin, a hormone that reduces iron levels — rather than the gene-silencing approach employed by divesiran.
Takeda has projected peak annual sales of $1 to $2 billion for Mimrylo. Analysts at William Blair, in a research note published following the Merck–Silence announcement, described divesiran as “best-in-field” and noted that — measured against Takeda’s forecasts — the deal valuation “does appear inexpensive considering Merck KGaA also gets the broader mRNAi GOLD siRNA platform as well.”
Silence’s Broader Pipeline
Divesiran is one of several drug candidates built on Silence Therapeutics’ proprietary siRNA platform, which enables these therapies to silence specific genes and prevent the production of targeted proteins. The next most advanced programme in the portfolio is zerlasiran, currently in a Phase II study (NCT05537571) focused on reducing elevated levels of lipoprotein(a).
Merck’s Strategic Rationale
Commenting on the planned acquisition, Kai Beckmann, Chief Executive Officer of Merck, stated: “The planned acquisition of Silence Therapeutics will strengthen our capabilities to serve patients with targeted speciality and rare diseases.”
The acquisition of Silence Therapeutics represents the third major deal Merck KGaA has completed in under two years. In July 2025, Merck acquired rare disease specialist SpringWorks Therapeutics for $3.9 billion. Earlier in June of the same year, the company agreed to pay $11.3 billion for life sciences company Bio-Techne — the largest single transaction for the pharma giant since 2015.
