Claim interpretation can determine whether the invention is sufficiently disclosed
In T 1186/24, Technical Board of Appeal 3.3.08, 18 June 2026, the European Patent Office (EPO) considered how the wording of a claim affects the assessment of sufficiency of disclosure. The Board held that an expressly claimed alternative could not be read out of the claim merely because the patent did not teach how to perform it. As that alternative was not enabled, the patent was revoked.
The patent concerned a method for enzymatically synthesizing (-)-Ambrox, a specific form of a molecule used in perfumes. Claim 1 referred to two alternatives, wherein a mixture of isomers was enzymatically converted to (-)-Ambrox (first alternative), or to a mixture comprising (-)-Ambrox” (second alternative).
The Opposition Division had maintained the patent in amended form. Both the proprietor and the opponent appealed. A central issue before the Board was whether the first alternative in claim 1 required (-)-Ambrox to be the sole reaction product, or whether it should be interpreted as a reaction producing predominantly (-)-Ambrox but allowing the formation of other products.
The claim wording defined two distinct outcomes
The proprietor argued that the skilled person would interpret “(-)-Ambrox” in the context of the patent as a product enriched for (-)-Ambrox. This interpretation would allow other compounds to be produced by the enzymatic conversion as well. The Board rejected that interpretation.
According to the Board, claim construction must be guided by the claim wording, and not by considerations of sufficiency of disclosure. The description may assist where wording is ambiguous, but cannot override clear language or deprive an expressly claimed alternative of its independent technical meaning. The principle in T 190/99 of construing claims in a technically sensible manner did not justify a different approach (Reasons 3).
In the present case the use of “or” between the two alternatives in claim 1 was decisive. The alternatives “(-)-Ambrox” and “a mixture comprising (-)-Ambrox” had to represent different outcomes of the enzymatic conversion. Otherwise, the second alternative would be redundant. The Board therefore construed the first alternative as requiring an enzymatic reaction producing (-)-Ambrox without additional reaction products. It expressly distinguished this from the chemical purity of the products obtained using the claimed method (Reasons 4–5).
Consequence for sufficiency
That construction exposed a sufficiency problem. The examples of the patent showed consistently that enzymatic conversion produced other compounds in addition to (-)-Ambrox. The patent provided no teaching enabling the skilled person to prevent formation of those additional products while retaining production of (-)-Ambrox, nor was this part of the common general knowledge in the field. Achieving the first alternative would therefore have required a research programme and imposed an undue burden (Reasons 10–12).
The auxiliary requests did not remove or limit the problematic alternative. The same insufficiency issue consequently applied to all requests, and the Board revoked the patent (Reasons 15–16).
Analysis and implications
T 1186/24 illustrates the close connection between claim construction and sufficiency. Where a claim expressly presents technically distinct alternatives, the disclosure must enable each alternative across the relevant claimed scope. A description showing that only one claimed alternative works cannot justify interpreting another, clearly worded alternative as having no independent meaning.
The decision also underlines a drafting point: apparently similar alternatives connected by “or” may be treated as deliberately different. Then, their individual technical meaning needs to be considered when deciding whether each alternative is sufficiently disclosed.
