The implementation of the Inflation Reduction Act (IRA) Medicare Drug Price Negotiation Program has introduced a brand-new dynamic to pharmaceutical lifecycle management. One of the first ten selected drugs, Merck’s blockbuster dipeptidyl peptidase-4 (DPP-4) inhibitor Januvia (sitagliptin), represents the first real-world test case of how the launch of generic competition intersects with an established Medicare negotiated price.
Under the terms of Merck's patent litigation settlements, generic versions of Januvia and its combination product Janumet entered the U.S. market in May 2026. This market entry sets off a regulatory cascade under the IRA, as CMS evaluates the generics against its "bona fide marketing" standard to determine when to terminate Januvia's Maximum Fair Price (MFP) status.
Short Answer
In May 2026, generic versions of Januvia (sitagliptin) and Janumet (sitagliptin/metformin) launched in the United States, followed by Janumet XR in July 2026, pursuant to Merck's patent litigation settlements. These launches occurred ahead of the expiration of the primary Januvia salt-form patent (U.S. Patent No. 7,326,708 on November 24, 2026) and its pediatric exclusivity (7326708*PED on May 24, 2027). Under the IRA, the launch of a generic competitor triggers loss of a drug's status as a "qualifying single-source drug." Once CMS determines that "bona fide marketing" of a generic exists—meaning there is more than token or de minimis market availability—the negotiated Maximum Fair Price ($113/month for Januvia, a 79% discount from the brand's $527/month WAC) ceases to apply as of the first price-applicability year that begins at least nine months after that determination. Because Januvia's generics launch in May 2026, that nine-month buffer realistically points the MFP's end to the 2028 price-applicability year, not 2027.
Who This Is For
This policy analysis is designed for market access executives, reimbursement directors, and pharmaceutical regulatory counsel who track lifecycle planning, Medicare Part D formulary design, and the commercial impact of the IRA.
The Sitagliptin Patent and Generic Approval Profile
The FDA Orange Book lists multiple approved ANDAs for sitagliptin, which have been positioned for launch under Merck's patent settlements:
| Brand Name | Active Ingredient(s) | NDA Number | Primary Patent Expiration | Pediatric Exclusivity | Approved ANDA Sponsors | Agreed Generic Launch |
|---|---|---|---|---|---|---|
| Januvia | Sitagliptin phosphate | 021995 | November 24, 2026 (7,326,708) | May 24, 2027 (7326708*PED) | Watson (ANDA 202327), Sandoz (ANDA 202387), Apotex (ANDA 202425) | May 2026 |
| Janumet | Sitagliptin; Metformin HCl | 022044 | November 24, 2026 (7,326,708) | May 24, 2027 (7326708*PED) | Sandoz (ANDA 202388), Apotex (ANDA 202426) | May 2026 |
Critical Policy & Commercial Insights
1. The Patent Deflection and Litigation Settlement
Merck successfully defended its core sitagliptin salt-form patent (U.S. Patent No. 7,326,708) in litigation, preventing early generic entry that could have occurred upon the expiration of the basic compound patent. The settlement agreements established a compromise: generic manufacturers were permitted to launch their products in May 2026 (for Januvia and Janumet) and July 2026 (for Janumet XR), capturing the final months of Merck's patent monopoly while avoiding a trial.
This timing is crucial because the first cycle of Medicare negotiated prices (MFPs) took effect on January 1, 2026. Consequently, branded Januvia was subject to the $113/month negotiated price for only a few months before the generic floodgates opened.
2. The CMS "Bona Fide Marketing" Standard
Under Section 1192(c) of the Social Security Act, as added by the IRA, a drug is only eligible for negotiation and selection if it is a "qualifying single-source drug." A drug ceases to be qualifying when the FDA approves a generic or biosimilar product and CMS determines that the generic is being "actively and bona fide marketed."
To prevent manufacturers from using "token" or "authorized" generic launches to evade the negotiation program, CMS established a multi-layered test:
- Bona Fide Marketing: CMS reviews physical market data, including national sales volume, wholesaler distribution records, and prescription counts, to confirm the generic is widely available.
- Authorized Generics Exclusion: Under CMS guidelines, an authorized generic (a generic marketed under the brand sponsor's NDA) does not count as generic competition for the purpose of terminating the MFP, as it does not represent independent market competition.
- Proposed Codification: On June 12, 2026, CMS issued its first proposed rule for the Negotiation Program (published in the Federal Register June 16, 2026), which would codify the "bona fide marketing" standard and the process CMS uses to determine when independent generic competition has met the threshold to remove a drug from selection.
3. The MFP Discontinuation Timeline
Generic entry does not immediately terminate the negotiated price. The IRA establishes a specific timeline for when the MFP ceases to apply:
- Selection Year Status: If generic entry occurs during a year in which the drug is on the selected list (e.g., 2026), the MFP remains in effect for the remainder of that calendar year.
- CMS Determination Window: CMS monitors market data on an ongoing basis — Prescription Drug Event (PDE) claims, Average Manufacturer Price (AMP), and wholesaler distribution — to verify that the generic launch represents bona fide marketing rather than a token launch.
- Removal Date: Once CMS determines that a generic is being actively and bona fide marketed, the drug is removed from the selected list as of the first price-applicability year (calendar year) that begins at least nine months after the determination date. In other words, the nine-month buffer separates the determination from the year in which the MFP actually lapses.
For Januvia, because generic entry occurred in May 2026, CMS will monitor Watson, Sandoz, and Apotex sales through the second half of 2026. If the generic market presence is validated as bona fide, the earliest price-applicability year that can begin nine months after that determination is 2028 — so Merck remains obligated to provide the $113/month MFP through the 2027 cycle while the bona fide marketing determination and nine-month buffer run their course.
4. Payer and Manufacturer Implications
- Medicare Part D Formulary Design: For the remainder of 2026, Part D plans will have access to branded Januvia at the $113/month MFP. PBMs must balance this low brand price against the newly launched generics, which may carry steep discounts but lack the same administrative simplicity in the first few quarters.
- The Price Erosion Curve: Once the MFP is terminated (for Januvia, realistically the 2028 price-applicability year), the sitagliptin class will undergo standard generic price erosion. Payers will shift their preferences entirely to generic sitagliptin as multiple ANDA filers compete on price, eventually dropping the net cost well below the $113 brand MFP.
What to Monitor Next
- CMS Final Decision on Januvia: Watch for the official CMS announcement confirming whether sitagliptin generics have met the "bona fide marketing" standard, which will set the clock for Januvia's removal from the selected list (expected to take effect in the 2028 price-applicability year).
- Future Negotiated Drugs: This process establishes the precedent for other drugs on the first negotiation list (such as Eliquis and Jardiance) that face generic entry in the late 2020s.
Sources
- FDA, Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book), current edition. Januvia (NDA 021995) and Janumet (NDA 022044) patent lists and approved ANDAs (202327, 202387, 202425, 202388, 202426). https://www.accessdata.fda.gov/scripts/cder/ob/
- Centers for Medicare & Medicaid Services (CMS), Medicare Drug Price Negotiation Program: Revised Guidance, Section 40 & 90 (Bona Fide Marketing Standard). https://www.cms.gov/files/document/medicare-drug-price-negotiation-program-revised-guidance.pdf
- Centers for Medicare & Medicaid Services (CMS), Fact Sheet: Negotiated Prices for the Initial Price Applicability Year 2026 (Januvia negotiated price $113, 79% discount from $527 2023 WAC). https://www.cms.gov/files/document/fact-sheet-negotiated-prices-initial-price-applicability-year-2026.pdf
- Merck & Co., "U.S. Court of Appeals for the Federal Circuit Rules in Favor of Merck in Sitagliptin Dihydrogen Phosphate Patent Lawsuit" (settlement terms permitting May 2026 generic launch of Januvia/Janumet and July 2026 for Janumet XR; Patent 7,326,708 expiring Nov 24, 2026 with pediatric exclusivity to May 24, 2027). https://www.merck.com/news/u-s-court-of-appeals-for-the-federal-circuit-rules-in-favor-of-merck-in-sitagliptin-dihydrogen-phosphate-patent-lawsuit
- Federal Register, CMS Proposed Rule: Medicare Drug Price Negotiation Program and Medicare Prescription Drug Benefit Program (June 16, 2026), proposed § 429.130 (Bona Fide Marketing codification). https://www.federalregister.gov/documents/2026/06/16/2026-12059/medicare-drug-price-negotiation-program-and-medicare-prescription-drug-benefit-program
Disclaimer: This article provides independent regulatory and market access analysis for biopharma professionals and does not constitute clinical, legal, or investment advice.
