Pharma BD Deal Intelligence

Merck & Co. Inc. / Acceleron Pharma Inc.

2021 · Acquisition/Merger · $11.5B · Complete

Merck paid $11.5B for Acceleron to acquire sotatercept, a first-in-class activin signaling inhibitor for pulmonary arterial hypertension. Marketed as Winrevair (approved 2024; label expanded Oct 2025 on the ZENITH trial to include reduced risk of clinical worsening and death), it reached $525M in Q1 2026 sales (+88% YoY) on a >$2B annualized run-rate — a blockbuster in a disease with no prior disease-modifying therapy.

CALLED IT — OFF BY 12
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Top 25 largest deals of the 2020s

Ranks computed across 828 graded deals (Critic + Outcome Score both present).

The coverage arc

Sep 30, 2021 BioPharma Dive Neutral

Acceleron provides biggest biopharma deal this year, with $11.5B sale to Merck.

Oct 27, 2025 Merck Press Release - ZENITH Label Expansion Bullish

FDA approved updated WINREVAIR indication (Oct 27, 2025) adding reduced risk of clinical worsening (hospitalization for PAH, lung transplantation, death);…

Apr 30, 2026 Merck Press Release - Q1 2026 Results Bullish

WINREVAIR Q1 2026 sales $525M (88% growth; 87% ex-FX), driven by continued U.S. uptake and early launch in Japan and Europe.

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Merck acquired Acceleron Pharma for approximately $11.5 billion ($180 per share in cash), gaining sotatercept, an investigational first-in-class activin signaling inhibitor in Phase III for pulmonary arterial hypertension, and REBLOZYL (luspatercept) for anemia in rare blood disorders.

Key facts

Disease & market context

Pulmonary Arterial Hypertension (PAH)

50K US cases/yr · $7.5B Global PAH Market (2024)

Disease Overview

Pulmonary arterial hypertension is a progressive, life-threatening disease of the pulmonary vasculature. WINREVAIR (sotatercept) is the first disease-modifying therapy, acting on the TGF-beta superfamily to rebalance vascular cell proliferation. STELLAR showed unprecedented 84% reduction in death or clinical worsening.

Transformative Treatment

WINREVAIR approved March 2024 as first-in-class activin signaling inhibitor. Q2 2024 sales of $70M exceeded expectations. Analysts project $2B+ peak sales by 2028. Background therapies (ERA, PDE5i, prostacyclin) remain standard but WINREVAIR adds on top as disease-modifying agent.

Deal timeline

Related deals — scored

DealYearValueOutcome
Merck & Co. Inc. / Acceleron Pharma Inc. (this deal)2021$11.5B90
Merck & Co. Inc. / Peloton Therapeutics Inc.2019$2.2B88
Merck & Co. Inc. / AstraZeneca PLC2017$8.5B87
Merck & Co. Inc. / Moderna, Inc.2022$250M86
Merck & Co. Inc. / Moderna, Inc.2016$250M84
Merck & Co. Inc. / Eisai Co., Ltd.2018$5.8B83
Merck & Co. Inc. / Prometheus Biosciences Inc.2023$10.8B77

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