When developing “patent‑expired” pesticides, it is equally important to conduct thorough patent research.

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2020-04-28

Recently, an online media outlet reported: Among the 42 patented pesticides whose patents have expired—totaling $8.4 billion in global sales—which ones deserve your attention? The article provides an incomplete tally of patent‑expired pesticides from 2015 to 2023, covering 42 active ingredients. These include 15 herbicides, 19 fungicides, 7 insecticides, and 1 herbicide safener. Of these 42 products, 22 recorded annual sales exceeding $100 million in 2018, with combined global sales of approximately $8.373 billion. …

The article provides patent numbers and expiration dates for both compound patents and individual isomer patents. Upon seeing this news, colleagues in the agrochemical industry were immediately intrigued, already beginning to consider project initiation even before the COVID‑19 pandemic has fully subsided. Given that agrochemical projects—particularly active‑ingredient development—typically require substantial investment, as a patent attorney I feel it both necessary and my duty to write an article offering a clear overview of the potential patent issues that may arise after a compound’s patent expires, in the hope that this will prove helpful to all.

First, following a compound patent, isomers may also be subject to separate patents. The aforementioned article mentions isomer patents for two active ingredients: spirotetramat and oxaziclomefone. Those in the know are aware that the isomer patents for both compounds have been declared invalid by the China National Intellectual Property Administration; however, the examination decisions have not yet attained final legal effect and remain under judicial review. According to information available to the author, these two cases were formally filed with the Beijing Intellectual Property Court one after another, but no court hearings have been held as of yet. Given the emergence of these cases, I believe most readers are already familiar with this type of patent issue, so further elaboration is unnecessary here. Nevertheless, it is worth reminding stakeholders that, during the project‑initiation phase, they should remain vigilant about the potential existence of such isomer‑related patents. Of course, if the parent molecule does not exhibit isomerism, there is no need to worry about these kinds of isomer patents.

Secondly, following a compound patent, a polymorph patent may also be filed. A particularly illustrative example is the fungicide pyraclostrobin. The aforementioned article only lists its compound patent, CN1068313B, which expired on June 20, 2015. In fact, eleven years after filing the compound patent, BASF submitted another patent application on June 19, 2006, covering the polymorphic forms of azoxystrobin. After examination by the China National Intellectual Property Administration, this patent was granted in September 2012 under grant number CN101203136B. In the United States, both polymorphs II and IV were granted; in China and Europe, however, only polymorph IV was granted. According to the text of the Chinese patent grant, claim 1 protects polymorph IV, with the specific content as follows:

In other words, if this polymorph cannot be avoided, the patent term for this product will effectively expire no earlier than 2026.

According to information available to the author, in addition to pyraclostrobin, at least the following agrochemicals also have polymorphic‑form patents: prothioconazole, benzobicyclon, and others. The situation with prothioconazole is essentially similar to that of pyraclostrobin. Following the filing of its compound patent, Bayer filed a polymorph patent in China, which was granted on May 26, 2010, under publication number CN1681390B; this patent will expire on July 9, 2023. In addition to Bayer, Syngenta also obtained a patent for the crystalline form of prothioconazole, granted on February 4, 2015, under publication number CN102083802B; this patent will expire on June 16, 2029. The invention covers both the DMSO solvate of prothioconazole and amorphous prothioconazole.

It should be noted that, compared with compound patents or isomer patents, polymorph patents offer somewhat weaker protection. The author believes there are at least two reasons for this: First, polymorphism applies only to solid substances; if the active ingredient remains dissolved in a solvent throughout the entire process, no polymorphic forms can arise, which may, in turn, constrain the choice of dosage forms. Second, many compounds exhibit multiple polymorphic forms as well as amorphous states, and the differences in efficacy among these distinct polymorphs may not be substantial from the perspective of a pesticide product. Consequently, gaps in the scope of polymorph‑related patent protection may exist.

Third, following a compound patent, there may also be patents on synthetic processes and corresponding intermediate compounds, as well as various formulation‑related patents. Given that these types of patents are relatively common and well‑known, we will not elaborate further here; however, we would like to emphasize that, when initiating a project, it is essential to conduct appropriate patent searches in these areas.

In summary, for agrochemical products, compound patents are undoubtedly the core patents, but they are not necessarily the only ones. If isomerism is involved, isomer‑specific patents can also pose significant obstacles. In some cases, polymorph patents warrant close attention as well. Patents covering synthetic processes and intermediates should likewise not be overlooked. In short, even when developing so‑called “patent‑expired” pesticides, thorough patent‑search efforts are essential; otherwise, all efforts may prove futile.

Source: AgroPages (World Agrochemical Network)

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