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Pfizer’s Seagen deal holds on the ADCs it bought, not the pipeline it inherited
The Seagen pipeline’s first Phase 3 readout missed, and Pfizer’s $43 billion deal still holds up, because most of what Pfizer paid for was already on the market. Of the 13 Seagen-origin antibody-drug conjugates (ADCs) Sleuth scored after sigvotatug vedotin’s June 2026 survival miss in lung cancer, the four approved when the deal closed on December 14, 2023 are all delivering, and the nine-ADC pipeline has produced no new approvals.
The lesson for ADC buyers is to price the maturity of what they buy, not the size of the check.
All four ADCs approved at acquisition are delivering
Padcev (enfortumab vedotin, Nectin-4) keeps expanding in bladder cancer, Adcetris (brentuximab vedotin, CD30) added a diffuse large B-cell lymphoma approval, Tivdak (tisotumab vedotin, tissue factor) holds its cervical cancer indication, and disitamab vedotin (HER2), which Seagen licensed from RemeGen for markets outside Asia, is approved in China. Sleuth rates all four as delivering, meaning approved and expanding, as of June 2026.
These four products carry the deal, and all four were already approved on deal day.
The nine-ADC inherited pipeline has no new approvals
The pipeline Pfizer paid a premium for had one Phase 3 miss, four discontinued programs and four unproven programs as of June 2026. Sigvotatug vedotin (integrin beta-6) missed overall survival against docetaxel in previously treated non-squamous non-small cell lung cancer (NSCLC) in the SigVie-002 trial. The discontinued four are felmetatug vedotin (B7-H4), SGN-CD228A (CD228), and SGN-35C and SGN-35T (both CD30). Pfizer took a $1 billion impairment on felmetatug vedotin, disclosed in February 2025.
The unproven four are PDL1V (PF-08046054, PD-L1), whose Phase 3 has yet to read out; MesoC2 (mesothelin) and a CEACAM5-directed ADC, both in Phase 1; and PF-08046876 (B6C), an early integrin beta-6 program.
The premium Pfizer paid for pipeline has yet to return an approval.
Deal size has not predicted which ADC bets pay off
In Sleuth’s wider review of ADC deals since 2019, deal size did not predict the winners. AstraZeneca’s cheaper partnerships with Daiichi Sankyo on Enhertu and datopotamab deruxtecan are, in Sleuth’s view, the cleanest ADC wins of the era.
The sigvotatug miss is not a sign that ADCs are failing. Sleuth counts it as one of five misses among 34 ADC Phase 3 readouts since 2024, and it fits a pattern specific to second-line NSCLC, where no ADC has beaten docetaxel on overall survival in an unselected population.
For buyers, an asset’s stage and proof are a better guide to value than the size of the deal. Sleuth’s ADC Intelligence Report, Q3 2026 covers how the ADC deal market now prices preclinical platforms.
Portfolio status is as of June 2026, when Pfizer reported the SigVie-002 topline. The outcome classes (delivering, Phase 3 miss, discontinued, unproven) are Sleuth’s judgment from public readouts, approvals and disclosed discontinuations.
Frequently asked questions about Pfizer’s Seagen ADCs
How many ADCs did Pfizer acquire with Seagen?
Sleuth counts 13 antibody-drug conjugates in Seagen’s portfolio at the December 2023 close: four already approved (Padcev, Adcetris, Tivdak and disitamab vedotin) and nine in the pipeline. The count excludes tucatinib, a small-molecule TKI, and PF-08046037, an immune-stimulating antibody conjugate.
Has any Seagen pipeline ADC been approved since the acquisition?
No. As of June 2026, none of the nine pipeline ADCs Pfizer inherited had been approved: one had missed in Phase 3, four had been discontinued and four remained unproven.
What happened to sigvotatug vedotin?
In June 2026, Pfizer reported that sigvotatug vedotin did not significantly improve overall survival over docetaxel in 703 patients with previously treated non-squamous NSCLC in the Phase 3 SigVie-002 trial. Pfizer is continuing to test it with pembrolizumab in first-line NSCLC.
Which Seagen ADCs has Pfizer discontinued?
As of June 2026, felmetatug vedotin (B7-H4), SGN-CD228A (CD228), SGN-35C and SGN-35T (both CD30). Pfizer took a $1 billion impairment when it dropped felmetatug vedotin, disclosed in February 2025.
