Inventive-step assessment of selection inventions under Vietnam’s patent examination guidelines

Selection inventions are particularly relevant in the pharmaceutical field, where a claimed invention may involve the selection of a specific compound, sub-range, or embodiment from a broader disclosure in the prior art. Vietnam’s patent examination guidelines provide specific guidance on when such a selection may be considered to involve an inventive step.

General Principle

Under the relevant examination guidance, a selection invention is considered to involve an inventive step only if all three of the following conditions are satisfied:

1. the selection is associated with a particular technical effect compared with the known state of the art;
2. the technical effect is either a known effect demonstrated at a superior or unexpected level beyond what a person skilled in the art would anticipate, or a different technical effect that could not have been predicted by a person skilled in the art; and
3. the selection could not be readily achieved by a person skilled in the art.

These requirements indicate that novelty alone is not sufficient. Even where a selected compound or sub-range has not been specifically disclosed in the prior art, the selection must provide an unexpected technical contribution and must not have been an obvious choice for the skilled person.

Example 1: Selection of a specific compound from a broad chemical formula

The claim concerns a specific thieno[2,3-b][1,5]benzodiazepine compound. The closest prior art discloses a broad Markush formula encompassing the claimed compound but does not specifically describe it. Although the claimed compound satisfies the novelty requirement, its general therapeutic activity could reasonably be expected based on the known activity of the compounds covered by the prior-art formula.

Pharmacological testing demonstrates that the selected compound produces unexpected technical effects compared with known compounds falling within the same prior-art disclosure. In particular, it demonstrates therapeutic effects at a lower-than-expected dose and does not exhibit significant adverse effects observed with the known compounds.

Although the structural difference is relatively small, it results in an unexpected improvement in both pharmacological activity and side-effect profile. The selected compound therefore could not have been readily achieved by a person skilled in the art.

Accordingly, the claimed selection satisfies the inventive-step requirement.

Example 2: Application of a known technique to a known antibody

The claim concerns a formulation containing nivolumab for subcutaneous injection, with recombinant human hyaluronidase (rHuPH20) as an excipient.

Although nivolumab was known for intravenous administration, and the use of rHuPH20 to facilitate subcutaneous administration of monoclonal antibodies was already widely described and applied, the claim does not provide evidence of an unexpected technical effect resulting from the specific combination.

The conversion from intravenous to subcutaneous administration may provide practical benefits such as greater convenience and reduced treatment time. However, there is no experimental evidence demonstrating a superior therapeutic effect, reduced toxicity, or significantly improved clinical outcome compared with the known intravenous administration.

Since the use of rHuPH20 for facilitating subcutaneous delivery of biologics was already a known technique and had been applied to similar monoclonal antibodies, a skilled person could readily apply the known technique to nivolumab.

Therefore, the claimed subject matter does not satisfy the inventive-step requirement.

Key takeaway

The assessment of a selection invention under Vietnam’s patent examination guidelines requires more than showing that the selected subject matter is not specifically disclosed in the prior art. The selection must be associated with a particular technical effect, that effect must be superior, unexpected, or otherwise unpredictable, and the selection must not have been readily achievable by a person skilled in the art.