Shares of Day One Biopharmaceuticals Inc. (NASDAQ: DAWN) skyrocketed more than 65% on March 6, 2026, after the company announced a definitive agreement to be acquired by French pharmaceutical group Servier for $21.50 per share in cash, valuing the deal at approximately $2.5 billion in total equity value.

Day One Biopharmaceuticals (DAWN) Stock Surges 66% on Servier's $2.5
Day One Biopharmaceuticals (DAWN) Stock Surges 66% on Servier's $2.5 Billion Acquisition Deal

The transaction sent DAWN stock soaring from a previous close of $12.78 to $21.20 at the close of trading, with volume exceeding 78 million shares—far above its average. After-hours trading held steady around $21.20–$21.23, reflecting strong investor enthusiasm for the buyout premium, which represents a substantial uplift from recent trading levels.

Servier, an independent international pharmaceutical company governed by a foundation, described the acquisition as a strategic move to bolster its rare oncology portfolio. The deal centers on Day One's flagship product, OJEMDA (tovorafenib), the only U.S. Food and Drug Administration-approved monotherapy for pediatric low-grade glioma (pLGG) in patients with specific BRAF alterations.

OJEMDA, an oral, brain-penetrant, selective type II RAF kinase inhibitor, targets relapsed or refractory pLGG in patients six months and older harboring BRAF fusions, rearrangements, or V600 mutations. Approved by the FDA in April 2024 under accelerated approval, the drug has shown rapid commercial traction.

Day One reported preliminary 2025 net product revenue of $155.4 million for OJEMDA, marking 172% year-over-year growth. In its fourth-quarter and full-year 2025 financial results released Feb. 24, 2026, the company posted Q4 net product revenue of $52.8 million and reaffirmed 2026 U.S. net product revenue guidance of $225 million to $250 million.

The acquisition expands Servier's oncology ambitions, particularly in pediatric and rare cancers with high unmet needs. Servier gains access to OJEMDA and Day One's broader pipeline, including programs in early to late-stage development targeting adult and pediatric solid tumors.

"Servier's successful track record in rare cancers and its commitment to advancing targeted therapies makes it the ideal home for our portfolio," Day One CEO Jeremy Bender said in the announcement. "Joining Servier represents a unique opportunity to extend the reach of our science and our lead program in pediatric low-grade glioma."

The deal follows Day One's January 2026 acquisition of Mersana Therapeutics, which added Emiltatug ledadotin (Emi-Le), a B7-H4-targeted antibody-drug conjugate (ADC) in Phase 1 for adenoid cystic carcinoma and other solid tumors. Updated Phase 1 data for Emi-Le is expected mid-2026.

Day One's pipeline also includes DAY301, a PTK7-targeted ADC in Phase 1 dose escalation for locally advanced or metastatic solid tumors, with initial data anticipated in the second half of 2026.

The FIREFLY-1 pivotal Phase 2 trial supported OJEMDA's approval, while the FIREFLY-2 Phase 3 study in frontline pLGG completed enrollment in early 2026, with results expected to support potential label expansion.

Regulatory momentum continues internationally. In late February 2026, the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) issued a positive opinion for conditional marketing authorization of OJEMDA in relapsed or refractory BRAF-altered pLGG, under Day One's ex-U.S. licensing agreement with Ipsen Pharma SAS.

The Servier acquisition is subject to customary closing conditions, including regulatory approvals and tender offer completion, with an expected close in the second quarter of 2026. Servier plans a tender offer for all outstanding shares.

Analysts had previously viewed Day One favorably, with consensus price targets around $23–$26 before the deal, implying significant upside. The buyout premium aligns with those expectations while providing certainty amid biotech sector volatility.

Some investor alerts emerged post-announcement, with firms like Kahn Swick & Foti and Halper Sadeh investigating the adequacy of the price and process for shareholders. Such reviews are common in public company acquisitions but do not necessarily indicate issues.

Day One, founded with a focus on disrupting traditional drug development for pediatric and young adult cancers, has built a commercial-stage profile rapidly since OJEMDA's launch. The company's emphasis on targeted therapies for life-threatening diseases, particularly in underserved populations, attracted Servier's interest.

For investors, the deal caps a strong run for DAWN, which has delivered triple-digit year-to-date returns in 2026 amid pipeline progress and revenue growth. The stock's 52-week range spanned $5.64 to $21.23, with the acquisition pushing it to new highs.

As the transaction advances, attention turns to integration, potential synergies in Servier's oncology efforts, and continued momentum for OJEMDA's global rollout. The buyout underscores ongoing consolidation in rare oncology, where targeted therapies command premiums for their precision and impact on small patient populations.

Day One's journey from clinical development to commercial success—and now acquisition—highlights the value of focused innovation in pediatric oncology. Shareholders await confirmation of the deal's close, while the broader biotech market watches for ripple effects on similar rare-disease players.