Johnson & Johnson Inc.’s blockbuster patent for a low estrogen birth control pill has drawn plenty of challenges. But J&J’s lawyers at Covington & Burling must be doing something right, because Lupin Pharmaceuticals Inc. has now became the eighth generic drug company to abandon a bid to invalidate it.

According to a brief order issued Monday in Newark, N.J., federal court, Lupin and J&J have reached a settlement that blocks Lupin from selling a generic version of Ortho Tri-Cyclen Lo until December 31, 2015. U.S. District Judge Stanley Chesler rejected Lupin’s invalidity arguments back in September 2012. As pat of the settlement, Lupin has dropped its appeal of Chesler’s ruling to the U.S. Court of Appeals for the Federal Circuit.

The deal could be worth more than $1 billion in sales to J&J, since Ortho Tri Cyclen Lo is a $400 million a year drug.

The settlement also helps Lupin limit its potential losses. If the Federal Circuit had affirmed Chesler, Lupin would have been blocked from selling Ortho Tri-Cyclen Lo until 2019, when J&J’s patent on the drug expires. Since other generic drug makers already have the right to begin selling generic Ortho Tri-Cyclen a few years from now, it wasn’t much skin off of J&J’s back to make a similar arrangement with Lupin.

In basic terms, J&J’s claimed invention is using a birth control formula containing 25 microgram dose of estrogen–a slight reduction from the amount used other contraceptive pills. It’s common sense that the less hormones pumped into the body the better, so one could argue that J&J’s purported invention was plainly obvious.

Barr Labotories Inc. (now owned by Teva Pharmaceutical Industries Ltd.) made that very argument back in 2008, when it launched a generic version of Ortho Tri Cyclen Lo "at risk"–i.e., before resolving invalidity claims against J&J in court. Chesler took the unusual step of issuing a preliminary injunction blocking Barr from selling its generics. After looking over the prior art, he ruled that J&J’s lower dose of estrogen was indeed an advancement, and that many scientists has once thought such a low dose couldn’t work.

Several months worth of Barr’s products were already in the hands of distributors at the time of Chesler’s order, and Barr was forced to pay a royalty to J&J on those sales. In the wake of Chesler’s ruling, five other generic drug makers, including Watson Pharmaceuticals Inc. and Sun Pharmaceutical Industries Ltd., reached settlements with J&J.

Lupin decided to try its luck at a bench trial last summer. It hired the IP boutique Leydig Voit & Mayer to rehash the argument that J&J’s patent is invalid. Chesler rejected Lupin’s arguments in a September 2012 opinion, ruling that "defendants’ principal obviousness argument could serve as a textbook example of an argument founded on hindsight."

Covington partner George Pappas, who represented J&J against Barr and Lupin, declined to comment. We couldn’t immediately reach Robert Green of Leydig Voit, who represented Lupin.