Merck KGaA to Acquire Silence Therapeutics for $1.3 Billion

Rare Daily Staff

Germany’s Merck KGaA has agreed to acquire U.K. biotechnology company Silence Therapeutics in a deal valued at approximately $1.3 billion, a move that could strengthen Merck’s growing rare disease portfolio and advance an experimental treatment for polycythemia vera, a rare blood cancer.

The acquisition follows Merck’s purchase of SpringWorks Therapeutics last year and would expand its presence in areas of high unmet medical need. The company views rare diseases as a key growth area and said adding divesiran would help build a more differentiated pipeline. For Silence Therapeutics, the transaction offers access to the resources needed to conduct a global phase 3 program and potentially bring the therapy to market if future studies are successful.

The acquisition centers on divesiran, an experimental RNA-based medicine preparing to enter phase 3 clinical development for polycythemia vera. The treatment uses small interfering RNA, or siRNA, technology to silence a specific gene.

Polycythemia vera is a rare blood cancer in which the body produces too many red blood cells. The excess cells can thicken the blood and increase the risk of blood clots, stroke, heart attack, and other serious complications.

Many patients require regular phlebotomies—blood-removal procedures—to control their hematocrit, the proportion of blood made up of red blood cells. While effective, these procedures can be burdensome and may need to be repeated multiple times each year.

Divesiran takes a different approach. Rather than removing blood, it is designed to regulate the body’s iron metabolism by silencing the TMPRSS6 gene. This increases production of hepcidin, a hormone that helps control iron levels and limits the body’s ability to produce excess red blood cells.

In the phase 2 SANRECO study, 88 percent of patients treated with divesiran met the trial’s primary endpoint, compared with 19 percent of those receiving placebo. Patients receiving the therapy also required fewer phlebotomies during the study period, averaging 0.2 procedures compared with 2.1 in the placebo group.

The treatment appeared generally well tolerated. Reported injection-site reactions were infrequent, and investigators observed no new safety concerns during the study.

Divesiran is administered as a subcutaneous injection once every three months, a dosing schedule that could offer patients additional convenience.

The acquisition has been approved by both companies’ boards and is expected to close in the first quarter of 2027, pending shareholder and regulatory approvals. If completed, the transaction would add divesiran to Merck’s rare disease pipeline as it prepares for late-stage development.