✦ Sac-TMT: Seventeen Phase 3 TrialsNarrow moat

Merck & Co. (MRK) — the future bets

Merck is running 17 Phase 3 trials of sac-TMT, and Blackstone is paying $700 million toward them.

Merck's largest single development bet is sacituzumab tirumotecan, or sac-TMT, an investigational anti-TROP2 antibody-drug conjugate being developed in collaboration with Kelun-Biotech1. The programme includes 17 ongoing global Phase 3 trials across multiple tumour types2, and the first Phase 3 results, from the TroFuse-005 trial in certain patients with advanced or recurrent endometrial cancer, met the primary endpoints of overall survival and progression-free survival3.

Antibody-drug conjugate commitments ($M)4,000Daiichi Sankyo upfront, 20231,500Daiichi continuation payments700Blackstone funding for sac-TMTMerck Form 10-K FY2023 and Form 10-Q Q2 2026; continuation payments 2 x 750
Two bets on one class.

The scale of the programme is itself the bet. Seventeen late-stage trials is the kind of investment a company makes when it hopes a drug can do in the next decade some of what Keytruda did in the last.

Merck is sharing the cost. In October 2025 it agreed a funding arrangement under which Blackstone Life Sciences will pay Merck $700 million in the fourth quarter of 2026 to fund part of the drug's development costs4, and $200 million was recorded as a reduction of research expense in the second quarter5.

Antibody-drug conjugates are also the area of Merck's 2023 Daiichi Sankyo collaboration, which cost an aggregate $5.5 billion charge6. Merck is therefore betting on the same class twice.

The Blackstone money has already shown up in the accounts: $200 million of it was recorded as a reduction of research expense in the second quarter of 20267, ahead of the $700 million payment due in the fourth quarter8.

Sac-TMT is the widest bet in the pipeline. The number of ongoing Phase 3 trials, 17 in August 20269, is a crude but useful gauge; a shrinking count as trials read out without new ones starting would say the drug is working in fewer cancers than hoped.

Moat trajectory: Widening

First Phase 3 positive; 17 Phase 3 trials ongoing.

The number that tests this moat
Reported
Ongoing global Phase 3 trials of sac-TMT
17 (August 2026)

The breadth of the bet; a falling count without new starts would mean it works in fewer cancers.

Source: Merck Q2 2026 results release ↗
References
  1. ReportedMerck's largest single development bet is sacituzumab tirumotecan, or sac-TMT, an investigational anti-TROP2 antibody-drug conjugate being developed in collaboration with Kelun-Biotech.
    Merck second-quarter 2026 results release, Form 8-K exhibit 99.1 - sales by product and pipeline highlights. — Q2 2026 · publ. 4 August 2026 · source ↗
  2. ReportedThe programme includes 17 ongoing global Phase 3 trials across multiple tumour types, and the first Phase 3 results, from the TroFuse-005 trial in certain patients with advanced or recurrent endometrial cancer, met the primary endpoints of overall survival and progression-free survival.
    Merck second-quarter 2026 results release, Form 8-K exhibit 99.1 - sales by product and pipeline highlights. — Q2 2026 · publ. 4 August 2026 · source ↗
  3. ReportedThe programme includes 17 ongoing global Phase 3 trials across multiple tumour types, and the first Phase 3 results, from the TroFuse-005 trial in certain patients with advanced or recurrent endometrial cancer, met the primary endpoints of overall survival and progression-free survival.
    Merck second-quarter 2026 results release, Form 8-K exhibit 99.1 - sales by product and pipeline highlights. — Q2 2026 · publ. 4 August 2026 · source ↗
  4. ReportedIn October 2025 it agreed a funding arrangement under which Blackstone Life Sciences will pay Merck $700 million in the fourth quarter of 2026 to fund part of the drug's development costs, and $200 million was recorded as a reduction of research expense in the second quarter.
    Merck & Co. Form 10-Q for the quarter ended 30 June 2026 - segment profits on the recast basis, the Cidara and Terns acquisitions, the Halozyme litigation, China shipments, loss of exclusivity events and the balance sheet. — Q2 2026 · publ. 7 August 2026 · source ↗
  5. ReportedIn October 2025 it agreed a funding arrangement under which Blackstone Life Sciences will pay Merck $700 million in the fourth quarter of 2026 to fund part of the drug's development costs, and $200 million was recorded as a reduction of research expense in the second quarter.
    Merck & Co. Form 10-Q for the quarter ended 30 June 2026 - segment profits on the recast basis, the Cidara and Terns acquisitions, the Halozyme litigation, China shipments, loss of exclusivity events and the balance sheet. — Q2 2026 · publ. 7 August 2026 · source ↗
  6. ReportedAntibody-drug conjugates are also the area of Merck's 2023 Daiichi Sankyo collaboration, which cost an aggregate $5.5 billion charge.
    Merck & Co. Form 10-K for fiscal 2023 - product sales for 2021-2023, the Prometheus, Daiichi Sankyo and Imago charges, impairments, receivables concentration and the Zhifei distribution arrangement in China. — FY2023 · publ. February 2024 · source ↗
  7. ReportedThe Blackstone money has already shown up in the accounts: $200 million of it was recorded as a reduction of research expense in the second quarter of 2026, ahead of the $700 million payment due in the fourth quarter.
    Merck & Co. Form 10-Q for the quarter ended 30 June 2026 - segment profits on the recast basis, the Cidara and Terns acquisitions, the Halozyme litigation, China shipments, loss of exclusivity events and the balance sheet. — Q2 2026 · publ. 7 August 2026 · source ↗
  8. ReportedThe Blackstone money has already shown up in the accounts: $200 million of it was recorded as a reduction of research expense in the second quarter of 2026, ahead of the $700 million payment due in the fourth quarter.
    Merck & Co. Form 10-Q for the quarter ended 30 June 2026 - segment profits on the recast basis, the Cidara and Terns acquisitions, the Halozyme litigation, China shipments, loss of exclusivity events and the balance sheet. — Q2 2026 · publ. 7 August 2026 · source ↗
  9. ReportedThe number of ongoing Phase 3 trials, 17 in August 2026, is a crude but useful gauge; a shrinking count as trials read out without new ones starting would say the drug is working in fewer cancers than hoped.
    Merck second-quarter 2026 results release, Form 8-K exhibit 99.1 - sales by product and pipeline highlights. — Q2 2026 · publ. 4 August 2026 · source ↗
Sources
Generated September 25, 2026