On 25 June 2021, the China National Intellectual Property Administration (CNIPA) rendered a decision in favour of the patentee in a patent invalidity proceeding.(1) This decision upheld the validity of the compound patent concerning the second-generation antihistamine medication desloratadine citrate disodium. The petitioner did not institute an administrative proceeding and the decision has come into effect.


The patent at issue,(2) which is entitled "alkali-metal or alkali-earth metal complex salt of delotadine polyprotic acid and the medical composition thereof", protects the marketed drug desloratadine citrate disodium ("the complex salt"), which holds a significant share of the Chinese market in second-generation antihistamine medication.

The feud originated from a partnership that went sour. The petitioner's parent company and another subsidiary corporation thereof brought China's first active pharmaceutical ingredient anti-monopoly lawsuit against the patentee. The patentee then found that the petitioner, its parent company, and the said subsidiary were collectively engaged in manufacturing, selling and using the desloratadine citrate disodium product without securing a licence from the patentee.

The patentee therefore initiated a patent infringement proceeding against these entities before the court, seeking damages of over 90 million yuan ($14 million). As a countermeasure, the petitioner filed an invalidity action against the patent before the CNIPA in October 2020.

The petitioner submitted a substantial amount of evidence in the invalidity procedure, including notarised experimental records, to prove that the patent at issue was not sufficiently disclosed and was devoid of inventiveness.


Petitioner's arguments
The petitioner contended as follows:

  • The description of the patent at issue failed to incorporate the spectrogram data that could be leveraged by the person skilled in the art to ascertain the chemical structure of the complex salt prepared in the embodiment.
  • The experimental evidence showed that the complex salt could not be prepared through the documented method, and the data on the effect of the compatible stability of the complex salt and excipients mentioned in the description was devoid of authenticity. Therefore, the patent at issue did not sufficiently disclose the preparation method and the technical effects of the complex salt.

In addition, even if the effects documented in the description were to be considered, given that the patent at issue did not specifically confirm the crystal or other forms of the complex salt, it could not be deduced that the technical effects were achieved by the complex salt per se rather than the crystal form thereof.

Therefore, the disclosure of the description was insufficient and the inauthentic data surrounding the compatible stability should not be admitted in supporting the inventiveness of the patent.

Patentee's arguments
The patentee conducted a point-by-point rebuttal of the allegation as follows:

  • Although the petitioner had cited notarised experimental evidence, to which the petitioner had attempted to lend credence by the notarisation process, the evidence was fundamentally flawed with respect to experimenters, key raw materials, preparations and tests, which crippled its authenticity.
  • The description documented the preparation method for the complex salt and determined the melting point. It further characterised its water solubility and the compatible stability with excipients. Therefore, the patent at issue sufficiently disclosed the claimed complex salt, which had already met the examination criteria on sufficient disclosure.


The CNIPA made a detailed analysis of the petitioner's evidence and arguments, and its decision shed some light on several key issues in the granting and affirmation of patent rights. This included the questions of parameters in assessing the authenticity of experimental evidence and the sufficient disclosure of compound inventions.

Regarding the authenticity of the experimental evidence, the CNIPA found the patentee's argument tenable, affirming that the experimental evidence had major defects. CNIPA noted that:

  • the experimenters were stakeholders of the petitioner;
  • the process of sending samples to test had not been notarised; and
  • the key reaction materials had not been confirmed.

The CNIPA concluded that the notarised experimental evidence was inadmissible and that the patent at issue met the requirements of sufficient disclosure.

The CNIPA also considered the examination criteria for the sufficient disclosure of compound inventions. According to the CNIPA, compound inventions protect substances with specific chemical structures, and structural confirmation data such as spectrograms are not essential in patent drafting, as long as a skilled person can affirm that the compound could be obtained through the preparation method documented in the description. In addition, the compound invention did not involve the crystal or other solid forms, so these forms were therefore irrelevant to the matter of sufficient disclosure.


This decision could serve as a point of reference when it comes to drafting compound patents, the examination criteria for sufficient disclosure and the formality examination over the authenticity of experimental evidence in invalidity procedures.

For further information on this topic please contact Guan Yue at Wanhuida Intellectual Property by telephone (+86 10 6892 1000) or email ([email protected]). The Wanhuida Intellectual Property website can be accessed at www.wanhuida.com.

This article was first published by Managing IP.


(1) No. 50420.

(2) ZL02128998.0.