Chemical patents in Europe
Chemical patents in Europe: what the EPO expects from non-European applicants
The European Patent Office asks the same basic questions as the USPTO: is your invention new, and is it more than an obvious step? For chemistry, the way it answers them often catches applicants from outside Europe off guard. I am Loek Steffanie, a European Patent Attorney with a background in chemistry, and this page covers the points where a chemical application from the US or elsewhere most often needs work for Europe.
Almost all of it comes down to the text you file first. In Europe, what is missing from that text cannot be added later.
What a chemical patent can protect in Europe
Chemical patent law in Europe is set by the European Patent Convention (EPC), and the EPO's Guidelines for Examination describe how examiners apply it. A chemical patent in Europe can claim a compound, a composition, a process or a use. You will know these categories from patent practice at home. What differs is how far each one reaches and what the EPO wants to see before it grants it.
- Compound claims cover the substance itself, whatever route is used to make it and whatever it is used for.
- Composition claims cover a mixture, usually defined by its components and their ranges. A formulation patent can be granted even when every component is known, provided the combination is new and inventive.
- Process claims cover the route. Under Article 64(2) EPC, a European patent for a process also extends to the products directly obtained by that process, so a chemical process patent can reach the product as well.
- Use claims cover a new use of a substance. Medical uses have their own claim format in Europe, which I come back to below.
Which category carries the most weight depends on where your product earns its money, and that is where I start. The fields of chemistry I work in are listed on my about page.
Markush claims at the EPO: one claim for a family of compounds
The EPO accepts Markush claims, and in chemistry they are routine. A Markush claim defines a core structure with variable positions and, for each position, a list of groups that may sit there.
The EPO tests such a claim on three points. The first is unity: the alternatives must have a common property or activity, and either share a significant structural element or belong to a recognized class of compounds (Guidelines F-V, 3.2.5). If the EPO finds that the grouping lacks unity, it searches only the invention first mentioned in the claims, and searching the others costs a further search fee for each one (Rule 64 EPC).
The second is novelty: one known compound that falls within your formula is enough to sink the claim in that form. The third is credibility: the effect you rely on has to be credible for substantially all compounds the claim covers, including those far from the ones you made.
In practice, that means spreading your examples and measurements across the formula, including the outer ends of each list, and writing narrower formulas into the description as fallback positions. Once the application is filed, that door is closed.
Selection inventions: when a sub-range or a single compound is still new
Chemistry often builds on a broad earlier disclosure: a range of 1 to 30 wt%, or a generic formula with long lists of substituents. In Europe, your narrower selection from such a disclosure can still be new. The EPO Guidelines (G-VI, 7) set out the tests.
- A sub-range is new if it is narrow compared to the known range, sufficiently far removed from any specific examples in the prior art, and cannot be directly and unambiguously derived from that prior art. Any specific value disclosed inside your range, whether as an example or as the endpoint of a range, destroys its novelty.
- A selection from two or more lists confers novelty. A specific compound that can only be reached by picking one substituent from one list and another from a second list is new over the generic formula, unless the prior art points to that combination.
- A choice from a single list does not. Picking one element from one list of specifically disclosed elements is not new.
Novelty is the first hurdle. For inventive step, the selection needs a technical effect that holds across the entire claimed range (Guidelines G-VII, 12). If the effect shows up in only part of the range, the EPO treats the problem solved as merely providing an alternative product or process. So measure inside and outside your range before you file, and show where the effect begins and ends.
Parameter and product-by-process claims in a chemical patent application
Two claim forms that come up often in chemistry, and that the EPO examines closely.
A parameter needs its measurement method
A polymer defined by its melt flow index or a powder by its particle size distribution: such parameters are allowed if they can be determined clearly and reliably by procedures that are standard in the field. The EPO expects the measurement method, or a reference to it, in the claim itself, unless it is common general knowledge or every known method gives the same result (Guidelines F-IV, 4.11). Put the method and its conditions in your first filing, because you cannot add them later.
Unusual parameters put the burden of proof on you
Define your product by a parameter nobody in the field uses, and the EPO may suspect it hides a lack of novelty. Proving that the parameter really sets your product apart from the prior art is up to you, and the EPO does not give you the benefit of the doubt (Guidelines F-IV, 4.11.1). Measuring the closest known products with your own method is the most convincing answer.
Product-by-process claims are judged on the product
A claim to "product X obtainable by process Y" is read as a claim to the product itself. It is allowed only if the product is new and inventive and cannot be defined in any other way, and a new process alone does not make a known product new (Guidelines F-IV, 4.12). If what is new is the route, claim the process.
Experimental data: what must be in the application on the filing date
A technical effect only helps your inventive step if the data shows it, and at the EPO the timing of that data matters as much as the result.
The effect has to be described in precise terms: a statement such as "unexpectedly good properties" does not support inventive step (Guidelines G-VII, 10.2). And the technical problem only counts as solved if it is credible that substantially all embodiments covered by the claim show the effect (Guidelines G-VII, 5.2).
You can file further test results during examination, and the EPO will not disregard them just because they were generated after filing. However, it relies on them only for an effect that the skilled person, reading the application as filed, would see as part of its technical teaching and of the same invention (Guidelines G-VII, 11). Later data can confirm an effect. It cannot introduce one.
In practice: decide before filing which effect carries your invention, state it precisely, and include comparative examples against the product or process a competitor or examiner is most likely to cite. If the comparison is still running, we decide together whether to wait, or to file now and add the results to the European application within the priority year.
Amendments and priority: why every fallback belongs in your first text
Under Article 123(2) EPC, a European application may not be amended so that it contains subject matter extending beyond the application as filed. The test is whether the amended text is directly and unambiguously derivable from the original (Guidelines H-IV, 2.1). The same test decides whether a claim is entitled to the priority date of your first filing (Guidelines F-VI, 2.2).
Chemical applications run into this rule in predictable places:
- Combinations from separate lists. If your text lists five solvents in one paragraph and four catalysts in another, a claim to one specific solvent with one specific catalyst singles out a combination. Unless the original text points to it, the EPO will treat that as added matter (Guidelines H-V, 3.3).
- Features lifted from an example. Taking one feature from a worked example into a claim, without the features it was disclosed with, is an intermediate generalization. It is allowed only if those features are not structurally or functionally linked (Guidelines H-V, 3.2.1).
- Ranges. If you disclose a general and a preferred range, you can usually combine the preferred limit with one end of the general range (Guidelines H-V, 3.5). So write ranges in tiers: broad, preferred and most preferred.
A provisional application may describe only a single embodiment. For Europe, I want the fallback positions, preferred ranges and meaningful combinations written out in the priority text itself, because whatever is missing there will not carry your US priority date.
Medical uses in Europe: the substance for use in treating a disease
In the US, a method of treating a disease with a compound is patent-eligible subject matter. Europe excludes methods for treatment of the human or animal body by surgery or therapy, and diagnostic methods practiced on the body (Article 53(c) EPC). The exclusion does not cover the substances and compositions used in those methods.
A European claim therefore takes the form "substance X for use in treating disease Y". Article 54(4) EPC allows this for the first medical use of a known substance, and Article 54(5) EPC for a second or further medical use, provided that use is new and inventive. A claim worded as "use of X for treating Y" is refused (Guidelines G-VI, 6.1).
If your US application claims methods of treatment, the European version needs rewriting. The application as filed must also make the therapeutic effect credible, with data or scientific reasoning, and later evidence cannot repair that (Guidelines F-III, 10). For authorized medicinal and plant protection products, a supplementary protection certificate can extend protection by up to five years after the patent expires, with strict deadlines of its own.
Getting your chemical patent application ready for the EPO
Most of what this page describes is settled before the European filing, and much of it before your priority application goes out. That is why I prefer to see the text early: a provisional or a draft, together with the data you have and the competing products you expect to face in Europe.
I read it the way a European examiner will. Do the Markush lists and ranges have examples near their edges? Does each parameter come with its measurement method? Are the fallback positions written out? Is there a comparison with the closest prior art?
Where something is missing, you can still fix it in the priority filing itself or, failing that, in the European application filed within the 12-month priority year. The filing routes and deadlines are on European patent protection, and the choice of countries and the Unitary Patent on European patent strategy.
Checked against the Guidelines
Your text read against the EPO Guidelines that the examiner works with, before anything is filed.
Gaps in the data
Where your examples leave part of a claim unsupported, I tell you which tests would close the gap.
The right comparison
I tell you which competing product or prior-art document your comparative examples should be measured against, so the effect holds up in examination.
Chemical patents in Europe: questions from companies outside Europe
Yes. A new compound can be claimed as such, and the patent then covers the compound however it is made and whatever it is used for. It has to be new, inventive and industrially applicable, and a compound selected from a known generic formula can still be new. I usually build the claim in layers, from a broad formula down to the compounds you actually made and measured.
Yes. A Markush claim covers a family of compounds: a core structure with lists of groups allowed at certain positions. The EPO accepts it when the compounds share a common property or activity and a significant structural element, or belong to a recognized class of compounds. At Patents4Business I spread the examples across the formula, so the claim can also be defended at its edges.
Yes, both. A formulation can be patented even when every ingredient is known, if the combination is new and inventive, for example because of an unexpected effect. A European process patent also extends to the products directly obtained by the process. When I weigh which of the two to pursue, one question carries a lot of weight: could you later prove what a competitor actually did?
Rarely without changes. Method-of-treatment claims have to be rewritten as claims to the substance for use, and parameter claims need their measurement method. For me those changes are routine, as long as the description already contains what the new wording relies on.
As evidence, yes, but it does not become part of the application. The EPO takes later data into account for an effect that the application as filed already makes recognizable as part of the same invention. That is why I check, before anything goes out, that the effect you will rely on is stated precisely in your first filing.
About the author
Loek Steffanie, european Patent Attorney
Loek Steffanie is a Dutch patent attorney and European Patent Attorney. He has a background in chemistry and more than 25 years of experience, a large part of it at an international chemical company. He connects technology, law and business to help companies protect their inventions and get more business value from them.
Last updated on July 29, 2026
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