Merck & Co. Inc. Stock (US58933Y1055): HSR Waiting Period Expires for Terns Pharmaceuticals Acquisition

Merck & Co. Inc. advances its acquisition of Terns Pharmaceuticals after the Hart-Scott-Rodino waiting period expired on April 23, 2026. The move clears a key U.S. regulatory hurdle for the $53 per share tender offer, impacting MRK shares on NYSE.

Merck & Co. Inc. took a significant step forward in its planned acquisition of Terns Pharmaceuticals, Inc. with the expiration of the Hart-Scott-Rodino Act waiting period on April 23, 2026, at 11:59 p.m. ET. This U.S. antitrust clearance satisfies one of the conditions for completing the cash tender offer announced on April 7, 2026, according to the company release dated April 24, 2026.

The tender offer proposes $53.00 net in cash per share of Terns common stock, subject to more than 50% of shares being tendered. Merck, listed on NYSE under MRK, continues to pursue this deal amid its focus on expanding in oncology and other therapeutic areas, with consummation pending other customary conditions outlined in the SEC Schedule TO filing from April 7, 2026.

As of 29.04.2026

By the AD HOC NEWS editorial team – specialist desk for Healthcare stocks.

At a glance

• Name: Merck & Co. Inc.
• ISIN: US58933Y1055
• Sector/industry: Healthcare / Pharmaceuticals
• Headquarters/country: Rahway, N.J., USA
• Key markets: United States, Europe, Asia
• Main revenue drivers: Oncology drugs like Keytruda, vaccines, hospital products
• Primary listing/trading venue: NYSE (MRK)
• Trading currency: USD

How Merck & Co. Inc. makes money

Merck & Co. Inc. generates revenue primarily through its pharmaceutical portfolio, with a heavy emphasis on blockbuster drugs in oncology, vaccines, and cardiometabolic diseases. The company's business model relies on research and development investments to bring innovative therapies to market, followed by global commercialization through its own sales force and partnerships. Keytruda, its leading PD-1 inhibitor, has been a major contributor, holding a leadership position in immuno-oncology.

In addition to human health pharmaceuticals, Merck operates in animal health, providing vaccines and parasiticides for livestock and companion animals. This segment offers diversified revenue streams, reducing reliance on any single product category. The company also pursues strategic acquisitions, such as the ongoing Terns deal, to bolster its pipeline in areas like liver disease and oncology.

Manufacturing and supply chain efficiencies support profitability, with facilities across the U.S. and internationally ensuring steady product delivery. Merck's model emphasizes patent-protected exclusivity periods to maximize returns before generic competition enters.

The key revenue and product drivers for Merck & Co. Inc.

Oncology remains the cornerstone, driven by Keytruda, which accounted for a substantial portion of sales due to its use in non-small cell lung cancer and other indications. The drug benefits from first-mover advantages in combination therapies. Vaccines, including those for HPV and shingles, provide steady demand, particularly in the U.S. market.

Hospital and acute care products, along with cardiometabolic treatments, add to the mix. The recent FDA clearance for Idvynso, a two-drug HIV combination featuring Pifeltro and islatravir, opens new revenue potential in virology, approved as replacement therapy for suppressed patients. This approval came after addressing prior safety concerns in development.

The Terns acquisition, if completed, would enhance Merck's pipeline with Terns' assets in metabolic dysfunction-associated steatohepatitis (MASH) and oncology, aligning with growth areas. U.S. revenue exposure is significant, given domestic headquarters and NYSE listing.

Industry trends and competitive position

The pharmaceutical industry faces trends like accelerated AI integration for drug discovery and manufacturing, as seen in Merck's partnerships. Competition in immuno-oncology intensifies with players testing combinations against standards like Keytruda. Regulatory scrutiny on pricing and antitrust, as in the HSR process, shapes dealmaking.

In HIV and virology, new combinations like Idvynso compete with established regimens from peers. The MASH space, targeted by Terns, sees rising interest amid growing prevalence. Merck maintains a strong position through its scale, R&D spend, and U.S.-centric operations.

Patent cliffs loom, notably for Keytruda post-2028, prompting pipeline diversification via acquisitions and internal development. U.S. FDA approvals drive much of the innovation cycle.

Why Merck & Co. Inc. matters for U.S. investors

Merck & Co. Inc., headquartered in Rahway, N.J., reports in USD and trades on the NYSE, providing direct access for U.S. retail investors. Its heavy U.S. revenue from drugs like Keytruda and vaccines ties performance to domestic healthcare spending and FDA decisions, such as the recent Idvynso approval.

Regulatory events like the HSR expiration for the Terns deal highlight SEC and antitrust exposure relevant to American markets. With peers like Roche and Gilead active in overlapping areas, Merck's moves influence U.S.-listed pharma sector dynamics. Currency alignment eliminates forex risk for USD-based portfolios.

U.S. manufacturing sites and clinical trials further embed Merck in the domestic economy, making its pipeline progress a key watchpoint for investors tracking biotech M&A.

Which investor profile fits Merck & Co. Inc. stock — and which may not

Investors focused on large-cap healthcare with established blockbusters and acquisition-driven growth may find alignment with Merck's profile. Those monitoring oncology leadership and virology expansions track its quarterly updates closely. Dividend-oriented portfolios value its consistent payouts.

Profiles seeking high-growth biotech volatility or early-stage ventures may look elsewhere, given Merck's mature pharma scale. Short-term traders reacting to deal news like Terns fit event-driven strategies.

Risks and open questions for Merck & Co. Inc.

Key patent expirations, particularly Keytruda in 2028, pose revenue concentration risks as generics enter. Acquisition integrations, like Terns, carry execution uncertainties if tender conditions fail. Regulatory delays in pipeline assets, as seen in Idvynso's development path, can impact timelines.

Competition in immuno-oncology from combination trials and broader AI-driven efficiencies pressure margins. Antitrust reviews for future deals add scrutiny in the U.S. market.

What investors can watch next

Completion of the Terns tender offer hinges on share tender thresholds post-HSR clearance. Upcoming FDA decisions on Idvynso for treatment-naive patients could expand its label. Merck's AI partnership with Google Cloud may yield R&D updates.

Next items to watch

• Q2 2026: Terns acquisition outcome
• Ongoing: Idvynso label expansion

Bottom line

The expiration of the HSR waiting period on April 23, 2026, marks progress in Merck & Co. Inc.'s $53 per share acquisition of Terns Pharmaceuticals. This U.S. regulatory milestone, detailed in the April 24 company release, positions the tender offer closer to completion pending share tenders. Investors monitor this alongside pipeline advancements like Idvynso for broader implications in pharma M&A.

Disclaimer: This is not investment advice. Stocks are volatile financial instruments.