Those who have experience of the patent process in the chemical field will know the importance of supporting the application with experimental data.  This will help facilitate a smooth route to grant, and maximise the chances of arriving at a patent that will withstand challenges from third parties.  However, as is often the case, this has to be balanced with other competing factors.  For example, especially in a crowded and competitive field, waiting too long to obtain experimental data to support an initial filing increases the risk of a public disclosure or a competing filing that could jeopardise patent validity.  This can leave applicants with a difficult decision: commit to a patent filing now, without the ideal amount of experimental data, or delay the filing until such data becomes available, and increase the risk of these competing factors becoming an issue.

With this in mind, what can applicants do when matters beyond their control force them to commit to filing a patent before experimental data is fully available?

Identify the theory behind the invention

Ideally, to help establish inventive step, a patent application would include experimental data to evidence the beneficial effects of the invention – both in terms of what these effects are, and what achieves them.  However, if forced to file before the entirety of this data is available, then it is particularly important to consider the chemical principles behind the beneficial effects – in other words, the theory underlying the invention.  Not only will this help identify the key features of the invention (a critical part of any patent filing), but including discussion of this theory in the application can help justify the breadth of the patent claim, and increases the chances of successfully relying on post-filed data later on during European examination.

Consider what scope to cover, as well as what scope to avoid

As with any patent filing, it is worth considering what features or conditions are less likely to provide good results.  Understandably, the patent claim should be framed to avoid covering these areas, to minimise the risk of facing objections that the advantages of the invention are not achievable across its full scope.  However, identifying these areas of weakness can be challenging without confirmation from experimental data.  Therefore in these situations, as well as exploring what scope to avoid, it is well worth exploring what scope critically needs to be covered – i.e.  the ever-important question of what the “must have” patent scope is.  What, of your own products (or indeed your competitors’ products), do you need to cover to render the patent application to be of commercial value? This can identify the most valuable fall-back positions to include in the patent application, homing in around the most commercially preferred areas and (to the inventors’ best judgement) excluding scenarios that are less likely to provide good experimental results.

Note that the bar for experimental data is not equal for all claims

In Europe, the level of experimental data needed to support an application varies depending on the exact claim wording.  Therefore where data is not fully available in time for the initial filing, it is particularly important to choose the claim language to best guard against the absence of data becoming a fatal issue.  It is, in theory, possible to bolster an application’s inventive step position by relying on post-filed data.  However the same cannot be said for a lack of sufficiency (i.e.  the inability to reproduce the invention).  Therefore a level of caution should be exercised when (for example) stating a particular effect in the claim, or including a particular parameter.  Depending on how easy it is to achieve such effects or parameters in the field, including these in the claim could increase the risk of sufficiency issues, which cannot be cured with post-filed data.

Revisit the strategy after the initial filing

Once the initial application has been filed, it is worth using the priority year to generate additional data.  If this data simply confirms the predictions in the initial filing, then this data can either be included in a priority-claiming application, or relied on during European examination.  However, it is also possible that this additional data might reveal nuances behind the workings of the invention that were not previously apparent.  Should this arise, then a “follow-up” priority application can be filed – either in addition to the initial filing, or even as a replacement application.  Doing so likely has implications for the date by which prior art against the application is assessed – so for this reason, it is particularly prudent in these situations not to publish details of the invention at least until the final priority-claiming application has been filed.


Needless to say that in an ideal world, the filing of any patent application would be delayed until experimental data is fully available – usually, this is likely to be the best strategy.  However, when having to commit to a filing before this is possible: lock down the theory underlying the invention, consider your “must have” patent scope, be wary of claim language that might exacerbate the issue, and revisit the filing strategy once additional data becomes available.

If your company is involved in the chemical sector and considering patent protection, please get in touch with one of the authors of this article here or here, alternatively, you can contact us via