Merck KGaA has agreed to buy short interfering RNA (siRNA) drug developer Silence Therapeutics for $1.3bn, giving the German pharma company access to a promising therapy for a rare type of blood cancer.
The fully cash-based deal will see Merck pay $20 per American depositary share (ADS), with each of those representing three ordinary shares of British biotech Silence. The purchase price means Merck is paying an 82% premium to Silence’s average share price over the past month.
The jewel in Silence’s crown is divesiran, a siRNA therapy in development to treat polycythemia vera (PV), a rare blood cancer. Silence revealed positive Phase II clinical data (NCT05499013) for the drug candidate in August, with 88% of patients on divesiran meeting the clinical response criteria, compared to 19% on placebo.
PV, a chronic myeloproliferative neoplasm, is characterised by excessive production of red blood cells, which can be associated with a higher rate of death from cardiovascular and thrombotic events. Divesiran is designed to selectively silence TMPRSS6, a gene that helps regulate iron metabolism, to help limit the amount of the metal available for red blood cell production.
The PV market is currently dominated by Takeda and Protagonist’s Mimrylo (rusfertide). Approved in the US in August, Takeda has forecast peak annual sales of $1-2bn for the peptide. Unlike divesiran’s genetic focus, Mimrylo works by mimicking hepcidin, a hormone that lowers iron levels.
In a research note following the deal, William Blair analysts said they believe divesiran to be “best-in-field”, adding that – in the context of Takeda’s forecast – the deal valuation “does appear inexpensive considering Merck KGaA also gets the broader mRNAi GOLD siRNA platform as well.”
Divesiran is just one of Silence’s drugs built using the biotech’s siRNA platform. These therapies work by silencing specific genes to stop them from making proteins. The other most advanced asset in Silence’s portfolio is zerlasiran, which is in a Phase II study (NCT05537571) to lower high levels of lipoprotein(a).
“The planned acquisition of Silence Therapeutics will strengthen our capabilities to serve patients with targeted speciality and rare diseases,” said Kai Beckmann, Merck’s CEO.
The planned takeover of Silence is the third major acquisition for Merck in less than two years. In July 2025, the company bought rare disease specialist SpringWorks Therapeutics for $3.9bn. In June this year, Merck agreed to pay $11.3bn for life sciences company Bio-Techne, marking the largest outlay for the pharma company since 2015.
For Silence Therapeutics, which was founded in London in 1994, its exit reflects a successful year for British biotechs. In January, Amgen acquired Dark Blue Therapeutics for up to $840m, with Eli Lilly then purchasing sleep drug biotech Centessa Pharmaceuticals for $6.3bn in June.
