Merck KGaA to Acquire Silence Therapeutics for $1.3B

Merck KGaA has agreed to buy British biotech Silence Therapeutics for about $1.3 billion in equity value, with an enterprise value of roughly $1.1 billion. The purchase price of $20 per American Depositary Share translates to a 82 percent premium over the 30‑day volume‑weighted average share price. Merck will finance the deal with new debt issued under a UK scheme of arrangement, and the transaction is expected to close in the first quarter of 2027 once shareholder and regulatory approvals are obtained. The agreement gives Merck a Phase‑3‑ready siRNA candidate, divesiran, for the rare blood disorder polycythemia vera.

Drug Mechanism and Disease Context

Divesiran works by silencing the TMPRSS6 gene in liver cells, which normally inhibits the hormone hepcidin. By reducing TMPRSS6, hepcidin levels rise, locking iron in storage sites and limiting iron available for red‑blood‑cell production. This mechanism reduces the need for therapeutic phlebotomy, the routine removal of blood that patients with polycythemia vera require to keep their hematocrit below dangerous levels. Polycythemia vera is a chronic myeloproliferative neoplasm that raises the risk of thrombosis and can progress to more aggressive leukemias.

In the Phase‑2 SANRECO study, 48 phlebotomy‑dependent patients received divesiran and 88 percent met the primary endpoint of no phlebotomy between weeks 18 and 36 with a hematocrit under 45 percent, versus 19 percent in the placebo arm. The trial also recorded a dramatic drop in average phlebotomies, 0.2 per patient compared with 2.1 in the control group. Patients were treated every six or twelve weeks, and both dosing schedules produced similar response rates. The drug was well tolerated; only two cases of mild anemia were possibly related to treatment. Statistical analysis showed a highly significant difference with a p‑value below 0.0001.

Future Development and Market Impact

Silence plans to launch a Phase‑3 trial beginning in the first half of 2027, dosing every twelve weeks, and Merck’s resources will support this development and eventual commercialization. Beyond divesiran, Silence is advancing other siRNA programs such as zerlasiran for high lipoprotein(a) levels, and several earlier‑stage candidates targeting complement factor CFB and cholesterol pathways. The company’s mRNAi‑GOLD platform, coupled with GalNAc delivery technology, allows targeted siRNA molecules to degrade specific messenger RNAs in liver cells. Merck’s acquisition also brings a Berlin research site that has been central to the development of Silence’s platform since its 2005 acquisition of Atugen.

The deal underscores the growing importance of RNA interference as a therapeutic class, with several siRNA medicines already on the market for inherited metabolic disorders and cholesterol lowering. Merck’s investment signals that large pharmaceutical firms are willing to pay premium sums for clinically advanced siRNA assets, potentially reshaping partnership dynamics in the industry. The acquisition follows Merck’s earlier purchase of SpringWorks and its global rights to other rare‑disease drugs, reinforcing its strategy to build a differentiated portfolio. The transaction may also encourage smaller developers to demonstrate the clinical value of their platform technologies to secure future collaborations or acquisitions.