Merck buys Silence and its siRNA pipeline for $1.3bn
Merck KGaA has reached a deal to acquire UK-based Silence Therapeutics in an all-cash, $1.3 billion deal that will boost its presence in RNA-focused drugs and give it a late-stage drug candidate for rare disease polycythemia vera (PV).
The German group is offering $20 per American Depository Share (ADS) for London-based Silence, which is an 82% premium on Silence's average trading price in the previous 30 days.
In return, it will get rights to divesiran, a short interfering RNA (siRNA) being prepared for pivotal trials in PV, a chronic blood cancer in which the bone marrow produces too many red blood cells, and a potential rival to Takeda and Protagonist's recently approved Mimrylo (rusfertide).
The excess levels of red blood cells in PV put patients at risk of blood clots that can cause serious cardiovascular problems, such as stroke and heart attack, and have traditionally been controlled by routine blood draws (phlebotomy) to reduce them to normal ranges.
While Mimrylo works as a mimetic of hepcidin, which helps to control the production of red blood cells in the body, divesiran acts in a different way, switching off a gene called TMPRSS6 that regulates endogenous hepcidin levels.
In the phase 2 SANRECO trial reported in August, Silence's drug achieved an 88% response rate – defined as no need for phlebotomy and keeping the percentage of blood cells in total blood volume (haematocrit) at 45% or less – compared to 19% in the placebo group.
Divesiran was given by subcutaneous dosing every six or 12 weeks in the study, while Mimrylo's approved dosing is by subcutaneous injection once per week.
PV affects around 90,000 people in the US, with a similar number in Europe. At the moment, drug treatments approved by the FDA for PV also include hydroxyurea or interferons, which are not particularly effective at controlling blood counts and can be poorly tolerated, as well as Novartis' JAK 1/2 inhibitor Jakafi/Jakavi (ruxolitinib) as a second-line option for refractory patients.
Merck's healthcare chief executive, Danny Bar-Zohar, said that buying Silence will give the company "an entry point into haematology through a biologically validated mechanism of action" and will help its efforts to build "a differentiated, sustainable pipeline."
Along with divesiran, Silence's roster of drug candidates includes an Lp(a)-targeting siRNA, zerlasiran, which is in a phase 2 trial evaluating whether it can reduce the risk of cardiovascular complications in people with atherosclerosis, along with several preclinical candidates.
Merck is recognised as needing to beef up its R&D pipeline after some major setbacks in late-stage projects, such as multiple sclerosis therapy evobrutinib and cancer candidates xevinapant, and bintrafusp alfa. It is also facing headwinds for key products, including blockbuster MS therapy Mavenclad (cladribine), which lost patent protection in the US earlier this year.
If the deal goes through, Silence would be the third major acquisition for Merck in the last couple of years, coming after it bought SpringWorks for $3.9 billion in 2025, adding two FDA-approved products for rare tumours – and Bio-Techne for $11.3 billion earlier this year to increase the scale of its life sciences tools business.
