Merck’s $6.7bn Terns Pharmaceuticals buy puts CML drug TERN-701 in play as Keytruda patent cliff nears

Merck (NYSE: MRK) has agreed to acquire Terns Pharmaceuticals, Inc. (Nasdaq: TERN) for $53.00 per share in an all-cash transaction valuing the clinical-stage oncology company at approximately $6.7 billion in equity, or $5.7 billion net of acquired cash. The deal, announced on March 25, 2026, is Merck’s third multibillion-dollar acquisition in roughly twelve months, and its clearest statement yet that the company intends to rebuild its oncology revenue base well before Keytruda faces biosimilar competition in 2028. The centrepiece of the transaction is TERN-701, an investigational oral allosteric BCR::ABL1 tyrosine kinase inhibitor in Phase 1/2 development for patients with chronic myeloid leukemia who have failed prior therapy. MRK shares traded around $119.59 on the day of the announcement, recovering from a four-week slide that had pushed the stock to near $113, while TERN surged toward the $53.00 offer price, erasing nearly a dollar of arb spread, on volume roughly thirty times its daily average.

Why is Merck acquiring Terns Pharmaceuticals before TERN-701 completes dose-expansion trials?

The timing of the acquisition is deliberate and signals a high conviction call. Merck is purchasing TERN-701 while it remains in Phase 1/2 development and before data from the full dose-expansion cohorts has been reported. That is an unusual posture for a company of Merck’s scale, which typically waits for clearer efficacy signals before committing capital of this magnitude. The explanation lies squarely in the competitive clock. Keytruda currently generates more than $30 billion in annual sales and represents close to half of Merck’s total revenue. When biosimilars enter the market, likely from 2028 onward, that revenue base faces structural erosion at a pace that will be difficult to offset through organic growth alone.

Merck has responded with a rapid capital deployment strategy. The Cidara Therapeutics acquisition for $9.2 billion and the Verona Pharma deal for $10 billion, both completed last year, broadened its respiratory and infectious disease exposure. The Terns transaction now extends that logic into a specific and well-defined oncology niche where the company believes it can secure a position before rivals do the same. Acquiring now, before full clinical read-outs, means paying a relatively modest absolute premium, but it also means assuming meaningful development risk.

What is TERN-701 and how does it differ from existing chronic myeloid leukemia therapies already on the market?

Chronic myeloid leukemia is caused by a chromosomal translocation between chromosomes 9 and 22, producing the Philadelphia chromosome and the resulting BCR::ABL1 fusion protein that drives uncontrolled white blood cell proliferation. The first generation of BCR::ABL1 tyrosine kinase inhibitors transformed CML from a near-fatal diagnosis into a manageable chronic condition roughly 25 years ago. Subsequent generations have improved on that foundation, but a meaningful patient population continues to experience treatment failure, resistance mutations, or intolerance to existing therapies.

TERN-701 attacks the BCR::ABL1 protein through a different binding mechanism, targeting the ABL myristoyl pocket rather than the ATP-binding site targeted by most approved inhibitors. This allosteric approach is shared with Novartis’ Scemblix, the current commercial reference point in this space, which analysts expect to generate more than $4 billion in peak annual sales. Early data from the CARDINAL trial, presented at the American Society of Hematology meeting in late 2025, suggested TERN-701 is achieving encouraging rates of major molecular response and deep molecular response at the 24-week mark, including in patients carrying high disease burden who had previously received multiple lines of therapy. No dose-limiting toxicities were observed during the dose escalation phase, blood pressure changes were clinically insignificant, and rates of lipase elevation were low, all of which are markers that matter to prescribers who have seen tolerability challenges in earlier-generation agents.

A separate CARDINAL cohort added in January 2026 is specifically evaluating TERN-701 at 500mg once daily in approximately 20 patients with BCR::ABL1 resistance mutations including T315I, M244V, and F359I/C/V. Coverage of the T315I mutation, historically called the gatekeeper mutation, has been one of the defining commercial differentiators in the CML field. If TERN-701 demonstrates efficacy across this resistance profile, its addressable patient population expands materially beyond the initial approved indication. The FDA’s Orphan Drug Designation, granted in March 2024, provides seven years of market exclusivity in the United States upon approval and underscores the agency’s recognition of unmet medical need in this area.

How does the $53 per share offer price compare to analyst valuations and what is the risk of a competing bid?

The deal premium, measured against Terns’ Tuesday closing price of $50.00, amounts to approximately 6%, one of the lowest spot premiums recorded in a publicly traded biopharma acquisition in recent years. Merck has structured its case around longer-dated volume-weighted averages: the $53.00 offer represents a 31% premium to the 60-day VWAP and 42% to the 90-day VWAP, reflecting the fact that TERN stock had already surged roughly six-fold over the preceding six months as clinical momentum built and takeover speculation intensified. TERN had a 52-week low of just $1.87 as recently as twelve months ago, against a high of $50.89, making the stock price trajectory itself a material complicating factor in reading the premium.

The market reaction has not been uniformly celebratory on behalf of Merck’s capital discipline. William Blair analysts concluded that the offer does not fully capture the potential of TERN-701 and raised the possibility that another bidder could emerge with a more attractive proposal. RBC Capital Markets acknowledged that the price leaves the door open for competing offers, specifically identifying AbbVie and Bristol Myers Squibb as strategically logical alternatives. Leerink Partners has maintained a price target of $58 per share on Terns and projected TERN-701 could reach blockbuster status by 2032, with peak annual sales around $6.2 billion by 2040. If that projection proves even broadly accurate, the $6.7 billion equity price represents a modest multiple of potential future revenues rather than the stretched valuation typical in late-stage oncology deals. The acquisition still requires a majority of Terns shareholders to tender their shares, and the presence of vocal analyst pushback on the premium leaves a non-trivial window for a counterbid before the tender offer formally commences.

What does the $5.8 billion accounting charge mean for Merck’s 2026 financial results and balance sheet capacity?

The transaction will be accounted for as an asset acquisition rather than a business combination, a classification that has significant earnings implications. Merck expects to record a charge of approximately $5.8 billion, equivalent to roughly $2.35 per share, in both its second quarter and full year 2026 GAAP and non-GAAP results. The non-GAAP inclusion is worth noting: most large-cap pharmaceutical companies exclude in-process research and development charges from their adjusted earnings when a deal is structured as a business combination, but an asset acquisition treatment requires the purchased R&D costs to flow through adjusted earnings as well. This will suppress Merck’s reported profitability metrics across 2026 in a way that will require careful communication to investors, particularly in the context of already elevated M&A spending over the past twelve months.

Merck’s balance sheet capacity, while tested, remains substantial. With a market capitalisation of approximately $295 billion and a credit profile that supports debt-financed acquisitions at investment-grade rates, the $5.7 billion net outlay is manageable. The company’s next earnings report is scheduled for April 30, 2026, and management will face investor questions about how much further capital deployment is planned and whether the current deal pipeline, which Davis has described as targeting oncology, immunology, cardiometabolic health, vaccines, and ophthalmology, can be funded without compromising the dividend, which currently yields approximately 2.8%.

How does TERN-701’s competitive profile stack up against Novartis Scemblix in the chronic myeloid leukemia market?

The competitive terrain for TERN-701, if it reaches approval, is dominated by Novartis’ Scemblix, which also uses an allosteric mechanism targeting the ABL myristoyl pocket and which has established a commercial franchise that is growing rapidly toward its projected multibillion-dollar peak. Scemblix earned its position by demonstrating superior molecular response rates relative to older agents in head-to-head comparisons, and it has secured a frontline indication in the United States that significantly expands its commercial opportunity. TERN-701 would be entering a market where the allosteric mechanism is no longer novel but where clinical differentiation on efficacy depth, onset speed, tolerability, and resistance mutation coverage could still carve out a substantial position, particularly among patients who have already received Scemblix or who carry resistance mutations that limit their options.

The William Blair assessment that TERN-701 has demonstrated unequivocal improvement in both efficacy and safety, with potential for more convenient dosing, reflects an optimistic read of early-phase data that has not yet been stress-tested in a large randomised controlled trial against an active comparator. Merck will need to design and execute that pivotal programme under its own auspices, a process that will consume three to five years and significant resources. The CARDINAL trial’s expansion cohorts, now enrolling at doses of 320mg and 500mg once daily across multiple arms including the resistance mutation cohort, will shape the regulatory strategy and the commercial differentiation narrative. Until those data mature, the $6.7 billion valuation rests on early signals and competitive logic rather than confirmatory Phase 3 evidence.

How does the Terns deal fit into Merck’s broader hematology strategy and its pipeline beyond Keytruda?

Merck has assembled a hematology pipeline of meaningful breadth alongside the Terns asset. Bomedemstat, an investigational oral LSD1 inhibitor, is in Phase 3 development; nemtabrutinib, a non-covalent BTK inhibitor, is similarly at the late-stage evaluation point; zilovertamab vedotin, an antibody-drug conjugate targeting ROR1, is in Phase 3; and MK-1045, a CD19xCD3 T-cell engager, is in Phase 1b/2. TERN-701 would complement this pipeline in a CML indication where none of Merck’s existing candidates are primarily positioned, extending the company’s hematology footprint into blood cancers driven by distinct mechanisms.

The strategic narrative Merck is constructing is one of portfolio depth across multiple haematologic malignancies, designed to give the company a durable oncology revenue stream that does not depend on any single mechanism or indication. Whether that narrative translates into commercial success will depend on execution across a complex multi-asset development programme while simultaneously managing the Keytruda franchise through its patent expiry transition. The $6.7 billion Terns bet is the latest and most prominent piece of that construction project, but it is emphatically not the last one planned.

What are MRK and TERN stock performance signals telling investors about market confidence in this deal?

Merck shares closed at approximately $116.37 on March 24, 2026, the day before the announcement, and traded between $116.35 and $120.12 on the announcement day itself, settling around $119.59 as of mid-session. The stock’s 52-week range spans $73.31 to $125.14, placing the current price in the upper half of that band but still roughly 4.4% below the 52-week high reached earlier in 2026. The one-month trajectory had been adverse before the announcement, with MRK losing approximately 7% over the prior four weeks amid broader pharmaceutical sector pressure. The modest intraday recovery on announcement day, rather than a sharp selloff, suggests the market is treating the transaction as strategically coherent even while absorbing the EPS charge.

Terns shares effectively locked to the $53.00 offer price on announcement day, trading at $52.78 with a volume of approximately 65 million shares against a daily average of roughly 2.2 million. The narrow spread between the share price and the offer price reflects efficient market mechanics given the all-cash structure and the Q2 2026 close timeline, but it also reflects the possibility of a competing bid, which would theoretically push the stock above $53.00 if credible. TD Cowen promptly downgraded TERN to Hold at the offer price, noting that the deal caps near-term upside. The broader calculus for TERN shareholders will come down to whether they tender into the Merck offer or hold for a potential competing bid that William Blair, RBC, and Mizuho have each floated as a plausible outcome.

Key takeaways: What does Merck’s acquisition of Terns Pharmaceuticals mean for the company, the CML market, and the broader oncology sector?

• Merck has agreed to acquire Terns Pharmaceuticals for $6.7 billion in cash, adding TERN-701, an investigational allosteric BCR::ABL1 inhibitor, to its oncology pipeline as the primary strategic response to Keytruda’s approaching patent expiry in 2028.
• The 6% spot premium against Terns’ closing price is among the lowest recorded in recent biopharma acquisitions of comparable scale, and multiple analyst teams including William Blair, RBC, and Mizuho have flagged the deal structure as potentially attracting a competing bid from AbbVie, Bristol Myers Squibb, or another strategic buyer.
• TERN-701’s allosteric mechanism, early clinical tolerability profile, and resistance mutation coverage position it as a potential challenger to Novartis’ Scemblix, which analysts project at $4 billion-plus in peak annual sales; Leerink projects TERN-701 could reach peak sales of approximately $6.2 billion by 2040.
• Merck is purchasing TERN-701 mid-Phase 1/2, before full dose-expansion data, a sign of high conviction but also of meaningful clinical and regulatory risk that the company will now absorb entirely under its own development programme.
• The $5.8 billion in-process R&D charge, flowing through both GAAP and non-GAAP results in Q2 and full year 2026, will suppress Merck’s reported earnings metrics and will require careful investor communication at the April 30, 2026 earnings release.
• This is Merck’s third multibillion-dollar acquisition in approximately twelve months, following the Cidara Therapeutics and Verona Pharma deals, confirming a sustained capital deployment strategy across oncology, respiratory, and infectious disease to rebuild its post-Keytruda revenue base.
• Merck’s existing hematology pipeline, which includes Phase 3 assets across LSD1 inhibition, BTK inhibition, and ROR1-targeting ADC modalities, now gains a CML-specific asset that extends the company’s presence across a broader range of haematologic malignancies.
• The transaction requires a majority tender from Terns shareholders, Hart-Scott-Rodino antitrust clearance, and other customary conditions; Merck targets a Q2 2026 close, but the tight spot premium and vocal analyst scepticism about value create a window for shareholder dissent or a competing process.
• For the broader CML competitive landscape, the deal intensifies pressure on Novartis’ Scemblix franchise and signals that allosteric BCR::ABL1 inhibition is being validated by a major buyer as a durable commercial opportunity rather than a niche one.
• Merck’s CEO has publicly identified additional M&A targets across oncology, immunology, cardiometabolic disease, vaccines, and ophthalmology, suggesting the dealmaking cycle is not yet complete and that further capital deployment against Merck’s $295 billion market capitalisation base remains a live investor consideration.