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A $2.26B all-cash acquisition that netted Pfizer zero surviving clinical assets. Both CD47/SIRP-alpha candidates—maplirpacept and TTI-621—were discontinued by 2026, with the lead program's trials terminated for poor recruitment, part of the industry's broader retreat from the CD47 pathway.
Pfizer acquired Trillium Therapeutics for $2.3B for immuno-oncology portfolio.
Pfizer to acquire Trillium Therapeutics Inc for $18.50 per share in cash representing implied equity value of $2.26 billion for CD47-SIRPa immuno-oncology…
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Pfizer acquired Trillium Therapeutics for approximately $2.26 billion ($18.50 per share) in an all-cash merger (closed November 17, 2021), gaining maplirpacept (TTI-622 / PF-07901801) and TTI-621 (PF-07901800), next-generation SIRPalpha-CD47 checkpoint inhibitors for hematological malignancies. Post-close the franchise underperformed: by May 2026 Pfizer had terminated its remaining maplirpacept clinical trials (NCT03530683 ended August 2024 and NCT05896163 ended May 2026, both cited as business decisions to pursue other oncology programs; a Phase 2 DLBCL study was terminated July 2025 for inability to recruit), and TTI-621 was discontinued. No active maplirpacept studies remain in the registry, leaving the $2.26B acquisition without a surviving clinical program — part of an industry-wide retreat from the CD47 pathway.
186K US cases/yr
CD47 is a 'don't eat me' signal overexpressed on cancer cells that prevents macrophage-mediated phagocytosis. Blocking the CD47-SIRPa interaction unleashes innate immune attack on tumor cells. This represents a second major immune checkpoint axis beyond PD-1/PD-L1, particularly relevant in hematologic malignancies including NHL, AML, and MDS where CD47 expression is elevated.
Trillium's lead molecules TTI-622 and TTI-621 are SIRPa-Fc fusion proteins that block CD47. Pfizer invested $25M in Trillium in 2020 before the $2.26B acquisition in 2021. The CD47 pathway is considered an emerging backbone immunotherapy for hematologic cancers, complementing checkpoint inhibitors.
185K US cases/yr · $25.0B Global Heme-Onc Market (2024)
CD47 is a "dont eat me" signal exploited by cancer cells to evade immune destruction. Multiple pharma companies invested billions in anti-CD47 approaches, but the class has broadly struggled with anemia side effects, competitive enrollment challenges, and insufficient efficacy signals.
Pfizer terminated both TTI-622 and TTI-621 from the Trillium acquisition. Gilead discontinued magrolimab. The CD47/SIRPalpha mechanism has not delivered clinical proof-of-concept sufficient for regulatory advancement across the industry.
Pfizer completed $2.3B acquisition of Trillium Therapeutics, gaining TTI-622 and TTI-621 SIRPalpha-Fc proteins for hematologic malignancies.
Trillium-derived CD47 pathway programs showed limited efficacy, mirroring industry-wide challenges including Gilead's magrolimab failure.
Pfizer terminated NCT05896163, the last maplirpacept (TTI-622/PF-07901801) trial, as a business decision to pursue other oncology programs; no active maplirpacept studies remain and TTI-621 was already discontinued. The $2.26B Trillium acquisition produced no surviving clinical program.
CD47/SIRPalpha programs failed to deliver compelling data. $2.3B increasingly unlikely to generate returns as CD47 approach faces industry-wide skepticism.
| Deal | Year | Value | Outcome |
|---|---|---|---|
| Pfizer Inc. / Trillium Therapeutics Inc. (this deal) | 2021 | $2.3B | 21 |
| Pfizer Inc. / BioNTech SE | 2020 | $748M | 100 |
| Pfizer Inc. / FoldRx Pharmaceuticals | 2010 | — | 99 |
| Pfizer Inc. / Medivation Inc. | 2016 | $14.0B | 86 |
| Pfizer Inc. / Wyeth | 2009 | $68.0B | 86 |
| Pfizer Inc. / Warner-Lambert Company | 2000 | $90.0B | 83 |
| Pfizer Inc. / Arvinas, Inc. | 2021 | $2.4B | 77 |
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