Merck's $6.7 billion acquisition of Terns Pharmaceuticals, announced this week, is not a pipeline deal. It is a defensive strike. The company is paying a 31 percent premium over the 60-day average share price, and 42 percent over 90 days, for a drug still in Phase I — an unusual sum for an asset that has not yet demonstrated pivotal data. That premium is the tell.
The drug is TERN-701, an allosteric BCR::ABL1 tyrosine kinase inhibitor for chronic myeloid leukemia. It is not, as one competitor publication initially reported, a CDK9 inhibitor. That error has been flagged and corrected. TERN-701 targets the myristoyl pocket of the BCR::ABL1 fusion protein — a different binding site entirely from the ATP-competitive inhibitors that have defined CML treatment for two decades. That distinction matters enormously for the patients this drug is designed to reach.
The patients are not an abstraction. CML is a blood cancer defined by the Philadelphia chromosome — a genetic rearrangement that creates the BCR::ABL1 fusion protein, which drives uncontrolled white blood cell production. The standard of care for two decades has been ATP-competitive tyrosine kinase inhibitors: imatinib, dasatinib, nilotinib, bosutinib, and ponatinib. These drugs transformed CML from a death sentence into a manageable chronic condition for most patients. But not all patients. Those who develop resistance mutations — particularly the feared T315I gatekeeper mutation, which resists most existing TKIs — run out of options. Some cycle through three, four, five prior therapies. Sixty percent of patients in the Terns trial had received three or more prior TKIs. More than a third had already failed asciminib, the Novartis drug approved in 2021 as a next-generation option.
This is the population TERN-701 was built for. The CARDINAL Phase I trial, which enrolled 63 patients with heavily pretreated disease, showed a 64 percent major molecular response rate across all evaluable patients at 24 weeks. At doses above 320 milligrams once daily — the dose range being advanced into pivotal development — the MMR rate climbed to 75 percent. No dose-limiting toxicities were observed. The maximum tolerated dose was not reached. In a disease where existing drugs often fail due to resistance or intolerance, that tolerability profile is not incidental.
The allosteric mechanism is the reason this works where others don't. Most TKIs bind the ATP pocket of BCR::ABL1 — the same pocket that mutations can reshape, allowing the protein to escape inhibition. TERN-701 binds the myristoyl pocket instead, a regulatory site that is structurally distinct from the ATP site. It does not compete with ATP. It works through a different physical constraint. That is why it remains active against mutant proteins that defeat every ATP-competitive inhibitor on the market. It is also why Novartis, which sells the ATP-competitive TKI asciminib under the brand name Scemblix, should be paying close attention.
Scemblix generated $1.29 billion in 2025 sales — up from $689 million in 2024, nearly doubling year-over-year. The Q4 2025 quarter alone brought in $391 million. That trajectory suggests the market for CML patients who've exhausted first- and second-line therapy is not small. It is growing fast, and it is currently underoccupied by a single competitor. If TERN-701 reaches its pivotal endpoints — a Phase II dose-selection decision is expected mid-2026, with a pivotal trial in second-line-plus patients targeted to begin late 2026 or early 2027 — it enters that space as the most differentiated entrant in years.
Merck needs this. Keytruda, the anti-PD-1 checkpoint inhibitor that has defined the company's oncology portfolio for a decade, generated more than $30 billion in 2025 revenue, accounting for nearly half of Merck's total sales. The drug loses U.S. market exclusivity in late 2028. There is no single successor that fills that gap, and the pipeline reads from multiple programs will take years to mature. Acquiring a hematology asset with a novel mechanism, an unmet-need patient population, a potential best-in-class profile, and a clear regulatory path is one way to reduce that dependency. The $5.8 billion accounting charge Merck expects to record when the deal closes — roughly $2.35 per share — suggests this acquisition is being treated as a significant strategic imperative, not a tuck-in.
The deal structure is a tender offer by a Merck subsidiary, subject to Hart-Scott-Rodino antitrust review. It is expected to close in Q2 2026. The FDA granted TERN-701 Orphan Drug Designation in March 2024 — a designation that provides market exclusivity incentives for rare disease treatments, in this case covering a blood cancer that is diagnosed in approximately 8,950 patients annually in the United States.
For Terns, the acquisition represents a return to the private market for a company that IPO'd in 2021 and spent the intervening years building a hematology franchise that attracted a premium buyer. CEO Amgen Burroughs called it a reflection of the team's commitment to oncology innovation. Dean Li, president of Merck Research Laboratories, was more specific: based on early clinical evidence, TERN-701 may have the potential to provide a meaningfully differentiated option for certain CML patients. That is carefully worded — "certain patients," "early evidence," "potential" — because the pivotal data does not yet exist. But the fact that Merck is writing a $6.7 billion check before that data arrives tells you something about how differentiated the company believes this candidate is.
The deeper signal is for the rest of the oncology sector. When a company with Merck's resources and competitive exposure pays a 42 percent premium over 90 days for a Phase I asset in a rare disease, it is making a statement about what it believes the competitive landscape will look like in five years. TERN-701 is not a hedge. It is a bet that the CML treatment paradigm is about to shift — that the patients who've exhausted existing options are not a niche, and that the next best-in-class therapy in hematology will be worth significantly more than the acquisition price in short order.
The Phase I data supports that thesis. Whether the pivotal trial confirms it is the question that will define this story for the next two years.
https://www.merck.com/news/merck-to-acquire-terns-pharmaceuticals-inc-expanding-its-hematology-pipeline-with-tern-701-a-novel-candidate-for-chronic-myeloid-leukemia-cml/
https://ir.ternspharma.com/news-releases/news-release-details/terns-highlights-additional-positive-phase-1-clinical-data
https://ir.ternspharma.com/news-releases/news-release-details/terns-pharmaceuticals-highlight-2026-priorities-and-program
https://www.reuters.com/business/healthcare-pharmaceuticals/merck-boosts-cancer-portfolio-with-67-billion-buyout-terns-pharma-2026-03-25/
https://www.precisionmedicineonline.com/precision-oncology/novartis-precision-oncology-trio-contribute-positively-2025-growth
https://www.syneticx.com/blog/merck.html
