Pharma BD Deal Intelligence

GlaxoSmithKline plc / Tesaro Inc.

2018 · Acquisition/Merger · $5.1B · Complete

The coverage arc

Source summaries from our enrichment pipeline; follow links for originals.

All 7 sources with sentiment breakdown →

GSK acquired Tesaro for approximately $5.1 billion in cash ($75.00 per share) via tender offer and merger (announced 3 Dec 2018, completed 22 Jan 2019), gaining Zejula (niraparib), an oral PARP inhibitor for ovarian cancer, plus the then-early-stage anti-PD-1 antibody dostarlimab (TSR-042) and additional immuno-oncology pipeline assets. The deal was widely criticized at signing as a rich multiple (~22.9x trailing revenue) for a Zejula franchise that has since plateaued and declined (FY2025 Zejula sales GBP 419M, down 7% on US volume/price pressure, IRA Part D redesign, and a 2022 FDA label restriction). The deal's value has instead come from the pipeline: dostarlimab, marketed as Jemperli, reached ~GBP 600M in FY2025 (+89% YoY) on endometrial-cancer expansion and carries a >$2.5B 2030 sales ambition. In December 2024 Jemperli received FDA Breakthrough Therapy Designation in locally advanced dMMR/MSI-H rectal cancer after a trial reported a 100% clinical complete response in all 42 patients who completed treatment, with a pivotal readout expected in 2H 2026 and a potential filing in 2027 — a pipeline optionality that materially offsets the original 'overpaid for a niche PARP asset' critique.

Key facts

• Announced Dec 03, 2018
• Closed Jan 22, 2019
• Deal value $5.1B
• Deal type Acquisition/Merger
• Therapeutic area Oncology
• Indications Ovarian Cancer, Breast Cancer, Prostate Cancer, Lung Cancer
• Key assets niraparib (Zejula), dostarlimab (TSR-042), anti-TIM-3 antibody, anti-LAG-3 antibody
• Mechanism PARP inhibitor, Anti-PD-1 checkpoint inhibitor

Related deals — scored

Compare all 7 side-by-side →

← Browse all deals  ·  How we score deals

More: 2018 deals  ·  GlaxoSmithKline plc deals  ·  Oncology deals