180-day exclusivity for first generic filers

On Aug. 25, 2026, the US Court of Appeals for the D.C. Circuit ruled on a fight over who may sell generic rifaximin 550 mg tablets, and when. The three-judge panel affirmed the lower court in part and reversed it in part⁸, then sent one question back to FDA with orders to apply a stricter test. The prize in dispute was a single 180-day period.

That period is the reward federal law gives the first generic company willing to attack a brand drug's patents. It dates to the Drug Price Competition and Patent Term Restoration Act of 1984¹, better known as Hatch-Waxman. A company that files a generic application with a Paragraph IV certification, a statement that a listed patent is invalid, unenforceable or will not be infringed, is generally eligible for 180 days³ in which FDA will not make later Paragraph IV generics of the same drug effective.

Six months with few or no generic rivals can be worth a great deal to a manufacturer, and the timing of that window decides when everyone else can launch. That is why the rules are litigated so often.

Who counts as a first applicant

Congress rewrote the rules in the Medicare Prescription Drug, Improvement, and Modernization Act of 2003² (MMA). Since then the statute has defined a first applicant as one that, on the first day any substantially complete abbreviated new drug application (ANDA) with a Paragraph IV certification is submitted for a drug, submits such an application and lawfully maintains the certification.

Two things follow from that wording. Several companies can share first-applicant status if they all file on the same first day, which FDA's January 2017 draft guidance on 180-day exclusivity⁴ confirms. And the application has to be substantially complete when it arrives, a judgment FDA makes on receipt, so a thin filing does not hold a place in line.

Filing is only the opening move. The generic company must notify the brand sponsor and patent owner, and if they sue for infringement within 45 days, FDA approval is generally postponed for 30 months, FDA explains³, unless the patent expires or a court finds it invalid or not infringed first.

FDA publishes the results of all this. Its Paragraph IV certifications list³ shows, drug by drug, the date of the first substantially complete Paragraph IV submission (recorded since March 2, 2004) and how many potential first-applicant ANDAs arrived that day. Drugs whose first challenge came before the MMA are marked "pre-MMA" and fall under the older rules, which required a patent-by-patent analysis.

What starts the 180-day clock

Under the 2003 amendments, the 180 days begin with the first commercial marketing of the drug by any first applicant, including marketing of the brand product itself by a first applicant. The original 1984 text¹ also let a court decision on the patent start the period, whichever came first. The MMA removed the court-decision trigger, so the period now runs only from launch.

Once it starts, a later applicant's ANDA can be approved 180 days after that first marketing. FDA's draft guidance adds a wrinkle that surprises people: a first applicant that forfeits its own exclusivity remains a first applicant⁴, does not have to wait out anyone else's 180 days, and can even trigger the clock for a co-first applicant that kept its eligibility. The approval-date rules themselves sit in FDA's regulation at 21 CFR 314.107⁵.

The exclusivity binds only later generic applicants that also filed Paragraph IV certifications. It does not stop the brand company from selling its own product, and it does not stop the brand from selling an authorized generic, the same drug under a generic label. That matters commercially. A Federal Trade Commission study found that first filers facing an authorized generic during the 180 days earned 40 to 52 percent less revenue⁷ in that window.

Six ways to forfeit

Before 2003, a first filer that never launched could in some cases hold up every other generic indefinitely. The MMA's Title XI² answered with six forfeiture events. If any one applies, that first applicant loses eligibility.

Forfeited exclusivity is not handed to the next company in line. It is simply gone for that applicant, and if every first applicant forfeits, nobody holds it. FDA's list labels that outcome "extinguished."

How a first filer can park the exclusivity

Lawyers call it parking: a first applicant holds the exclusivity without launching, and because the 180 days have not started, later filers wait behind it. It can happen when a first filer settles its patent case with the brand and agrees to enter on some future date.

The FTC flagged the pattern in a study it released on July 30, 2002. Of 20 settlements of patent litigation over generic entry before patent expiration, signed from 1992 to 2000, 14 "had the potential to delay the start of the generic applicant's 180-day marketing exclusivity,"⁶ the agency said, and it recommended changes to the law. Congress added the forfeiture provisions in the MMA the following year.

Failure to market was the main answer, and it has a gap. The second date in that test depends on each challenged patent being resolved, often by a later applicant winning a final judgment in court. Where no such ruling exists for a patent, that forfeiture may never be triggered.

What the D.C. Circuit decided in August

Two of the six provisions were at issue in the rifaximin case. On failure to market, the court sided with FDA: a first applicant holds one exclusivity period, forfeited entirely or not at all. Every Paragraph IV certification in its ANDA counts, so forfeiture under that provision needs a triggering event for each of those patents.

On the 30-month deadline for tentative approval, the panel went the other way. The exception for delays caused by a change in approval requirements, it held, requires but-for causation, a stricter test than the one FDA had applied. The court remanded to the district court with instructions to send the question back to FDA⁸ so the agency could apply that standard.

If the holding stands, FDA may find forfeiture more often when a first applicant took longer than 30 months to reach tentative approval and blamed the delay on shifting FDA requirements. How far it reaches will depend on any further appeal and on how FDA writes its decision on remand.

Checking a drug's exclusivity status

FDA's Paragraph IV list carries a 180-day decision status for many drugs, shown as eligible, deferred, non-forfeiture or extinguished, along with the dates of first approval and first marketing by a first applicant. The agency says it decides some forfeiture questions, including failure to market and failure to obtain tentative approval, only when a later ANDA is otherwise ready for approval³, because patent expirations and other events can change the answer until then.

For launches already made, FDA keeps a running list of first generic drug approvals⁹, which GxRadar has looked at year by year. GxRadar's approvals tracker counts all original ANDA approvals by year from FDA's Drugs@FDA data¹⁰: 648 in 2025, and 575 from January through Oct. 27, 2026. The Orange Book lists the patents that make a Paragraph IV challenge possible in the first place.

A separate 180-day exclusivity exists for competitive generic therapies, drugs with little or no generic competition. It has its own eligibility rules¹¹ and runs independently of the patent-challenge exclusivity. For the patent-challenge version, FDA's Paragraph IV page still points readers to the January 2017 guidance, which remains a draft.