Can Biomarin stop Ascendis from importing its competing TransCon CNP against Voxzogo?
Zachary Silbersher
Biomarin Pharmaceutical sells Voxzogo, which is indicated for treatment of a genetic condition known as achondroplasia, which is the leading cause of short-limbed dwarfism. Ascendis Pharma has applied to the FDA for license to sell a competing drug, TransCon CNP. Hoping to stifle Ascendis’ path to the market, Biomarin has launched an ITC case seeking to block Ascendis from importing its drug into the US. For now, Ascendis is relying upon a safe harbor defense. Can Biomarin use its Orange Book patents to preemptively block a competing drug from Ascendis?
Voxzogo appears to be the first treatment for this condition. Biomarin has protected the drug by several patents in the Orange Book, including U.S. Reissue Patent No. 48,267 (RE267). On March 31, 2025, Ascendis filed an NDA with the FDA for approval to sell a competing drug for achondroplasia. Ascendis’ drug is currently known as TransCon CNP.
TransCon CNP has yet to be approved by the FDA, and it has not yet entered the market. Biomarin, however, moved to preemptively block Ascendis’ drug entry. On April 1, 2025, the day after Ascendis filed with the FDA for TransCon CNP, Biomarin commenced an action at the International Trade Commission (ITC) to block Ascendis from importing “certain drug products containing C-type natriuretic peptide (‘CNP’)” that infringe Biomarin’s RE267 patent. Ascendis purchases TransCon CNP from its supplier, Wacker, which is located in Europe. Accordingly, Biomarin was essentially using the ITC case to stifle Ascendis’ development of its competing drug for achondroplasia.
Ascendis has not yet received FDA approval for its achondroplasia drug, and it has yet to sell any product. Yet, importing a drug that infringes a competitor’s patent can also subject the importer to liability under the Patent Statute. Ascendis has been importing TransCon CNP into the US to develop the drug, and Biomarin is targeting that importing activity to try to shut down Ascendis’ development.
The Patent Statute, however, provides for what is called a “safe harbor” provision. Under this provision, importing or using an infringing drug is permissible under the Patent Statute as long as it is used for developing a drug and submitting an application to the FDA related to the drug. In other words, if you’re not yet commercializing a drug, but only conducting research for the purpose of seeking FDA approval, then, under the right circumstances, you can use and import a drug that infringes a competitor’s patent without facing liability. That’s the “safe harbor.” See 35 U.S.C. § 271(e)(1).
If Ascendis’ drug is not yet on the market, and the safe harbor provision permits importation of an infringing drug for research purposes, then what is the basis of Biomarin’s ITC complaint? Biomarin alleges that Ascendis is importing much more drug than is necessary for research purposes. In other words, Biomarin’s ITC complaint implies that Ascendis is stockpiling more drug than it needs right now so that it can sell it at a later time after it receives FDA approval. .
Ascendis disputes that it is stockpiling any drug. It claims that Biomarin has misread the import records and is overestimating by a large margin the amount of TransCon CNP imported by Ascendis. It also claims that, even if were importing excess drug, it could not be stockpiling it for future use because the product has a shelf-life, and much of the drug Ascendis is accused of stockpiling will expire before the FDA approves TransCon CNP for commercial sale.
Ascendis, for its part, tried to shut down the ITC case before it got started. It argued that it was clearly permitted to import TransCon CNP under the safe harbor provision, and that Biomarin’s complaint should be dismissed. The ITC denied that request. It found that ruling on Ascendis’ safe harbor defense was too fact-intensive and complex to warrant dismissing Biomarin’s ITC case at the early stage. This does not mean that the ITC categorically ruled against Ascendis on its safe harbor defense. Rather, the ITC only held that more discovery is needed before the court can make that determination.
Unhappy with that result, Ascendis took its case to district court. It filed a declaratory judgment action against Biomarin in California. In that complaint, Ascendis argued that its importation of TransCon CNP is clearly permissible under the safe harbor provision, and therefore, the district court should immediately rule that it cannot be infringing Biomarin’s patent. In short, Ascendis went to the district court to get the immediate relief it couldn’t get at the ITC.
Ascendis’ recourse to the district court smacked a bit of a stretch. Biomarin brought an ITC case alleging that Ascendis is infringing its patent. Ascendis tried to short-circuit that case by arguing the safe harbor provision clearly applies. The ITC did not disagree one way or the other, but ruled that more discovery is needed. Ascendis did not want to wait the full time that it will take the ITC case to resolve. The case is likely a burden on its development efforts as well as likely putting pressure on its stock and making investors edgy.
Yet, it’s questionable whether the district court would take up Ascendis’ ask. Even if the district court ruled in favor of Ascendis immediately, that ruling will not necessarily be binding on the ITC. Biomarin will necessarily seek an appeal, which could take another year at least, and Biomarin will have to lose that appeal before the district court’s ruling is binding. By that time, the ITC case may be over. All of this raises the risk of inconsistent rulings between the ITC and the district court. Further, if the ITC suggested that Ascendis’ safe harbor defense is fact-intensive enough to warrant further discovery, the district court might be wary of disagreeing with that finding.
Perhaps mindful of these risks, Ascendis voluntarily dismissed its declaratory judgment suit against Biomarin on July 7. By doing so, Ascendis stated that it “has decided to accede to Biomarin’s preference to litigate the safe-harbor defense in the ITC.” Ascendis Pharma A/S v. Biomarin Pharmaceutical Inc., Case No. 4:25-cv-03302 (N.D. Cal. Jul. 7, 2025) (ECF 45). By walking away from the suit in this manner, it’s not entirely clear what Asendis’ strategy was in the first instance with the district court gambit. By rushing to the district court, then pulling the plug almost just as quickly, it doesn’t project confidence that Ascendis is fully equipped to stave off Biomarin’s patent challenge.
The bigger problem for Ascendis—and its investors—is that at some point, it will have to reckon with Biomarin’s patent. Right now, Ascendis has a “safe harbor” defense to Biomarin’s patent, but that is only because Ascendis has yet to commercially launch its drug. Once it does commercially launch TransCon CNP, that safe harbor defense will no longer be available.
At that time, Ascendis will have to prove that Biomarin’s patent is either not infringed or invalid. If Ascendis cannot do that, then it may face liability. And because Biomarin is theoretically practicing the patent, then there is a very reasonable chance Biomarin can obtain an injunction against Ascendis’ TransCon CNP, i.e., shutting down the drug altogether until the patent expires in 2030. An injunction is not guaranteed even if Biomarin does prove infringement, especially for health-related products, but it’s undoubtedly a cloud that Ascendis investors may not want to shelter beneath.
This is not a Hatch-Waxman generic case. This is a garden-variety competitor-vs-competitor patent case. There are only presumably two players in the market for treatment for achondroplasia treatments. It is hard to imagine that Ascendis was not aware of Biomarin’s patent before developing its own drug. And it is equally difficult to imagine that Ascendis did not nail down a design around to avoid infringement or at least investigate the validity of the RE267 patent to meet the challenge when Biomarin eventually asserted it.
Unfortunately, even if Ascendis does succeed on its safe harbor defense at the ITC, investors may have to wait longer to find out if Ascendis can in fact get around Biomarin’s patent.