There’s big difference between the regulations of European Patent Office (EPO) and Intellectual Property Authority of Vietnam.
1/ EPO generally accepts second medical use claims in the format ‘Compound X for use in the treatment of disease Y’.
Other similar wordings are also accepted and summarized in EPO Guidelines for Examination (G-VI 7.1.2).
The above-cited wording is based on Article 54(5) of the European Patent Convention (EPC), which provides the statutory basis for second (or further) medical use claims at EPO.
According to Article 54(5), a substance or composition – but not a device – of the prior art “for any specific use” in a method referred to in Article 53(c) of EPC is novel if the specific use is not disclosed in the prior art.
Article 53(c) excludes from patentability methods for treatment of the human or animal body by surgery or therapy and diagnostic methods practiced on the human or animal body.
Thus, a compound for any specific use in a method of treatment is novel if this use is not part of the prior art. In this way, EPO explicitly provides purpose-limited product protection for inventions that can be protected by neither a product claim, due to lack of novelty, nor a method claim, due to exclusion from patentability.
The answer from Vietnam is No.
Method of treatment claims have never been acceptable in Vietnam. In the past, such claim was often converted into a substance claim. At present, such converted claim is not accepted.