USD 1.3B for a Once-Quarterly Shot: Merck KGaA Buys Silence as siRNA Moves from Platform Story to Single-Product Cash Flow

On 19 October Merck KGaA agreed to acquire Silence Therapeutics at USD 20 per ADS in cash — an enterprise value of USD 1.1B and equity value of about USD 1.3B, a 130% premium to the prior close. Lead asset divesiran is a TMPRSS6 siRNA dosed subcutaneously once every three months, with an 88% vs 19% Phase 2 response rate.

On 19 October, Germany's Merck KGaA announced a definitive agreement to acquire London-based Silence Therapeutics (NASDAQ: SLN) for USD 20 per ADS in cash. Each ADS represents three ordinary shares (equivalent to USD 6.6667 per share), implying an enterprise value of USD 1.1B and an equity value of roughly USD 1.3B. The consideration is a 130% premium to the 16 October close, the last trading day before announcement, and an 82% premium to the 30-day volume-weighted average price of USD 10.99. Silence's US shares more than doubled on the day. The deal will be implemented via a UK scheme of arrangement and is expected to close in Q1 2027.

What is being bought: a validated mechanism with an unusually low dosing frequency

The lead asset, divesiran, is a siRNA targeting TMPRSS6. The mechanism runs: silence TMPRSS6, raise hepcidin — the master regulator of iron metabolism — limit iron availability for red-cell production, control haematocrit and reduce the need for frequent therapeutic phlebotomy in polycythaemia vera (PV). It is dosed subcutaneously once every three months.

The Phase 2 SANRECO data underpin the valuation: an 88% response rate versus 19% for placebo (p<0.0001), and mean phlebotomies reduced to 0.2 per patient over weeks 0-36 versus 2.1 on placebo (p<0.00001), irrespective of background cytoreductive therapy. Tolerability was good, injection-site reactions were infrequent and self-limiting, and two Grade 1 anaemia cases were assessed by investigators as treatment-related. The company describes the asset as Phase 3-ready. The pipeline also includes zerlasiran for elevated lipoprotein(a) and earlier programmes in high cholesterol, obesity and immune disease, all on the mRNAi GOLD platform.

The competitor is Mimrylo from Takeda and Protagonist. William Blair analyst Myles Minter argues USD 1.3B looks relatively low: Takeda's implied peak sales estimate for Mimrylo in PV is USD 1B-2B, and Merck is buying not just that single asset but an entire siRNA platform with room to expand into further indications. Conversely, the deal removes the execution risk of commercialising independently in an increasingly crowded market.

Merck's M&A cadence: from platforms to specialty cash flow

This is Merck's third major acquisition in under two years: SpringWorks Therapeutics for USD 3.9B in 2025, a pending USD 11.3B takeover of life-sciences tools company Bio-Techne, and now Silence at USD 1.3B. Group CEO Kai Beckmann frames it as continuing to transform the pipeline toward highly specialised areas of unmet need. Danny Bar-Zohar, CEO Healthcare, adds two more specific terms — entry into hematology and a biologically validated mechanism of action.

That phrasing is worth noting. In the 2020-2023 wave of siRNA deals, buyers talked about platform value and technology positioning. In 2026 they price on validated mechanism, a well-defined patient population and very low dosing frequency. PV is a small population with an unambiguous diagnostic pathway and a single standard of care — phlebotomy — which makes the commercial model unusually clean. That is what earns a 130% premium.

Capital markets: RNAi is heating up in both private and public markets

This is not an isolated event. On 1 October, ADARx Pharmaceuticals raised more than USD 500M in a Nasdaq IPO. City Therapeutics completed an approximately USD 230M IPO, following a USD 135M Series A in 2024 and a USD 99.5M Series B in 2026, with pipeline assets including the Factor XI RNAi programme CITY-FXI and a potential first-in-class RBP4 therapy for Stargardt disease. On 13 October, Souffle Therapeutics closed a USD 135M Series B.

Together they point one way: progress in next-generation delivery, chemical stabilisation and extrahepatic targeting has reopened investor appetite for nucleic-acid medicines. And RNAi's relative advantage — two to four doses a year with predictable adherence in chronic disease — suddenly looks more acceptable to payers in a 2026 where GLP-1 has normalised self-injection.

Three levels of transmission to CXDMO

First, order structure. Commercial siRNA assets behave nothing like antibodies or small molecules: few molecules, highly predictable annual volume per product, and extreme purity and impurity-profile requirements. Once-quarterly dosing means kilogram-scale phosphoramidite monomer demand, duplex annealing, and tight control of n-1, n+1 and phosphodiester impurities. CDMOs are no longer taking on many products in small clinical batches but few products in long-cycle commercial supply — which inverts capacity planning: what matters is dedicated lines, locked monomer supply and long-term stability packages, not general reactor utilisation.

Second, capacity positioning. At CPHI Milan 2026, Agilent announced a USD 725M oligonucleotide expansion betting on enzymatic ligation, with the first phase starting up in March 2027. The timing shows large players are already building for the commercial phase of siRNA rather than waiting for confirmed orders.

Third, the Chinese divergence. Jiuzhou Pharmaceutical confirmed in its Q3 2026 investor call that oligonucleotide capabilities are under construction within a capex framework capped at RMB 1B a year. WuXi AppTec is moving solid-phase peptide capacity from 100,000 L toward 130,000 L. Asymchem's emerging businesses, including chemical macromolecules, reached RMB 1.923B in the first nine months, up 50.20%, but at a 30.95% gross margin. Meanwhile, the 16 October Announcement No. 48 from MOFCOM and MOST proposes adding siRNA process platforms to the prohibited export list — aimed at transfer of technology ownership, with pure outsourced manufacturing services outside scope. Domestic siRNA assets will therefore split into two paths: local closed-loop production for the China market, and service exports for overseas customers. The first determines capacity; the second determines valuation.

Editorial: the siRNA anchor is shifting from 'platform' to 'dosing frequency x patients'

In the platform era, valuation tracked pipeline count and target coverage. In the single-product cash-flow era, it tracks a very simple formula: once every three months, times rare-disease patient count, times net price. That is why an asset with only Phase 2 data can fetch USD 1.3B — PV's treatment pathway is simple enough that annual phlebotomy count can serve as the efficacy endpoint, minimising both regulatory friction and commercial modelling uncertainty.

The lesson for CXDMO is that certainty is worth more than scale in oligonucleotide orders. CDMOs that can offer three things together will hold pricing power through this cycle: guaranteed scheduling for Phase 3 and commercial batches, a complete stability and impurity-profile package, and dual-sourced phosphoramidite monomer supply. Conversely, capacity that can only claim 'we can synthesise oligonucleotides' will face price pressure once new large-scale lines from Agilent and others come online in 2027-2028.

Three risks to track: divesiran's Phase 3 has not yet started, so enrolment speed and endpoint choice in PV remain open; Mimrylo could reach the market first; and the Lp(a) space around zerlasiran is already crowded with siRNA and ASO programmes, which may compress the commercial window. The deal also requires the UK scheme of arrangement and customary conditions — whether it closes in Q1 2027 as planned will be the first signal of regulatory posture.