Merck KGaA agrees $1.3bn cash buyout of London RNAi developer Silence Therapeutics

Merck KGaA said on 19 October that it will buy London-based Silence Therapeutics for $1.3 billion in cash, paying $20 for each US-listed American Depositary Share. The German group is buying its way into short-interfering RNA (siRNA) medicines and gaining divesiran, a drug for the rare blood cancer polycythemia vera (PV) that is being readied for registration trials¹².

The terms

BioPharma Dive puts the premium at 130%, the second highest this year among the larger deals it tracks¹. Measured against Silence's average trading price over the previous 30 days, the premium is 82%². Shareholders holding 14% of Silence's voting power have already backed the offer, and Merck KGaA expects to complete the deal in the first quarter of 2027¹.

The price compares with a small balance sheet. Silence had $72 million in cash and equivalents at 30 June, far short of what a Phase 3 programme would need¹. William Blair analyst Myles Minter said the sale “takes the execution risk off the table in an increasingly competitive space” and appeared to follow “a competitive bid process”¹.

The asset

In the Phase 2 SANRECO trial reported in August, 88% of patients on divesiran responded, against 19% on placebo. A response meant no need for blood draws and a haematocrit kept at 45% or less². The drug was injected under the skin every six or 12 weeks².

Divesiran raises levels of the iron-regulating hormone hepcidin by silencing the TMPRSS6 gene¹². Its nearest competitor is Mimrylo (rusfertide) from Takeda and Protagonist Therapeutics, a recently approved hepcidin mimetic dosed once a week². Analysts reviewing the Phase 2 data called divesiran potentially “best in class” and said it could match Mimrylo's forecast blockbuster sales¹. Cantor Fitzgerald analysts suggested it might not need a trial as large as the nearly 300 patients enrolled in Mimrylo's Phase 3¹. Agios Pharmaceuticals is developing a similar drug against the same gene¹.

PV affects around 90,000 people in the US and a similar number in Europe². Silence also brings zerlasiran, an siRNA targeting Lp(a) in a Phase 2 cardiovascular study, and several preclinical candidates².

What it means for the market

The deal is a bet on late-stage RNA medicine by a mid-sized pharma company under pipeline pressure. Merck KGaA has had late-stage failures with evobrutinib in multiple sclerosis and with the cancer candidates xevinapant and bintrafusp alfa, and its MS drug Mavenclad lost US patent protection this year². Silence would be its third large acquisition in about two years, after SpringWorks for $3.9 billion in 2025 and Bio-Techne for $11.3 billion this year².

Unlike SpringWorks, which came with approved drugs, Silence brings no product revenue¹. Merck's healthcare chief executive Danny Bar-Zohar called it “an entry point into haematology through a biologically validated mechanism of action”². For investors in UK and European RNAi companies, the 130% premium is a reference point for what a pharma buyer will pay for clean Phase 2 data in a rare disease with an approved competitor¹.

Caveats

Divesiran's efficacy rests on Phase 2 results, and the comparison with Mimrylo comes from analysts rather than a head-to-head trial¹². The deal still needs to close, which Merck KGaA expects in the first quarter of 2027¹.