The Halozyme case pending before the Court of Justice of the European Union (CJEU) is expected to provide important guidance in the interpretation of the EU Regulation 469/2009 concerning Supplementary Protection Certificates for medicinal products in Europe (“the Regulation”).
The opinion of the Advocate General in case C-456/24 (Halozyme) was issued on 23 April 2026. In this article SIB partner Paolo Di Giovine and SIB LEX partner Mario Pozzi examine the reasoning of the Advocate General and attempt to envision which direction the final decision of the CJEU might take.
Facts in the case
The dispute originates from national proceedings in the Czech Republic, where Halozyme, Inc. (“Halozyme”), a pharmaceutical company established in the United States, is seeking a Supplementary Protection Certificate (SPC) for a combination medicinal product consisting of the therapeutic monoclonal antibody trastuzumab co-administered with recombinant human hyaluronidase (rHuPH20).
The case concerns the interpretation of Article 1(b) of the Regulation, which defines a “product” as “the active ingredient or combination of active ingredients of a medicinal product”.
Halozyme argues that the product contains two active ingredients: (i) the therapeutic monoclonal antibody, which exerts the primary disease-targeting effect, and (ii) recombinant human hyaluronidase, which enzymatically degrades hyaluronic acid in the extracellular matrix, thereby increasing tissue permeability and enabling efficient subcutaneous delivery and absorption of the co-administered drug.
According to Halozyme, both substances qualify as active ingredients because each performs a specific and essential pharmacological function contributing to the overall therapeutic effect of the medicinal product. In particular, hyaluronidase is not merely ancillary but plays an indispensable and active role by facilitating the mechanism through which the therapeutic agent achieves its intended efficacy.
On this basis, Halozyme argues that recombinant human hyaluronidase should not be classified as an excipient, notwithstanding its designation in the marketing authorisation.
The opinion of the Advocate General
The Advocate General has proposed a rather strict and formal interpretation: whether a substance qualifies as an “active ingredient” for SPC purposes must be determined by reference to the classification contained in the marketing authorization (“MA”) relied upon in support of the SPC application. In practical terms, if a substance is expressly classified as an excipient in the MA, it should not be reviewed as an active ingredient in subsequent SPC proceedings.
This interpretation gives central importance to the regulatory classification made during the MA process. It also limits the possibility for applicants to argue, before national patent offices, using complex scientific argumentations on whether an ancillary or facilitating substance may have a therapeutic contribution of its own. The Advocate General’s reasoning appears to favor legal certainty, administrative efficiency and consistency between the pharmaceutical regulatory framework and the SPC system.
Although the point is important, the outcome suggested by the Advocate General is not entirely surprising. In fact, the CJEU held in its previous decision in case C-443/17 (Abraxis Bioscience LLC v Comptroller General of Patents) – concerning a medicinal product consisting of paclitaxel, a known anti-cancer active ingredient, and albumin, which acted as a carrier in a nanoparticle formulation – that a carrier with no therapeutic effect of its own could not be regarded as an active ingredient within the meaning of Article 1(b), even if it allowed the active ingredient to exercise its therapeutic effect more effectively.
The CJEU therefore concluded that a new formulation of an old active ingredient, consisting of that active ingredient and a carrier with no therapeutic effect of its own, could not be treated as a product distinct from the active ingredient alone.
The Halozyme referral adds a further layer. The referring court asks, among other things, whether a substance expressly designated as an excipient in the MA can nonetheless be treated as an active ingredient for SPC purposes, particularly where it contributes to the overall therapeutic effect of the medicinal product.
Will the CJEU follow the Advocate General’s opinion?
In view of the authors, it is highly likely that the CJEU will follow the Advocate General’s Opinion.
The reason is not merely formalistic. The classification of a substance as an active substance or as an excipient in an MA is not arbitrary: it is the result of a technical and scientific regulatory assessment in view of the definition of medicinal product provided in the Directive 2001/83/EC. Allowing that classification to be reviewed in SPC proceedings would risk creating parallel and potentially inconsistent evaluations by patent offices and courts, which are not necessarily the appropriate forum for reassessing the regulatory status of medicinal product components.
In any event, the practical implications of this decision will be significant. Companies developing medicinal products involving complex formulations, delivery-enhancing technologies or biologically active excipients should pay close attention to the way each component is characterized in the regulatory file and, ultimately, in the MA. The SPC strategy cannot be separated from the regulatory strategy. If a component is expected to play a role in supporting future SPC protection, its regulatory classification may become decisive.
At the same time, the Advocate General’s approach may reduce uncertainty in borderline cases. It suggests that SPC eligibility should not depend on an ex post scientific debate about the ancillary effects of a substance, but rather on the regulatory identity of the product as defined in the MA.
This would make SPC prosecution more predictable, although potentially less flexible for innovative formulations where the boundary between “active ingredient” and “excipient” is scientifically complex.
The CJEU’s forthcoming judgment will therefore be closely watched; if it follows the Advocate General, the decision will reinforce a narrow and MA-centered interpretation of “active ingredient” under the SPC Regulation.
Author: Paolo Di Giovine, Mario Pozzi
