Saved by an obvious mistake – ToolGen’s patent amendments

In brief

In the latest chapter of the Australian arm of the worldwide CRISPR patent dispute, ToolGen has successfully amended the claims of its patent application by relying upon an “obvious mistake” in the original drafting of its claims. These amendments now overcome previous adverse findings by the Federal Court regarding the validity of the claims. The decision in ToolGen Incorporated v Fisher (No 3) [2024] FCA 539 serves as a useful reminder of the principles for, and utility of, correcting an obvious mistake, even where the effect is to broaden the claims.

Background

We previously reported on Justice Nicholas’ findings regarding the validity of the patent application (on appeal from a decision of a delegate of the Commissioner of Patents), in particular in relation to its priority claims. His Honour found that each of the claims of the patent application would, if granted, be invalid.

Following his Honour’s findings, ToolGen sought leave to amend the claims of the patent application pursuant to s 105(1A) of the Patents Act 1990 (Cth) (the Patents Act). The opponent did not oppose the amendment application. The Commissioner of Patents provided a brief analysis of the claim amendments but did not otherwise wish to be heard on the proposed amendments.

The Commissioner’s position

Claim 1 of the patent application as proposed to be amended was based on claim 10 before amendment. Proposed amended claim 1 specified that one of the two components of the claim is an in vitro transcribed single guide RNA. Claim 10 before amendment, on the other hand, specified that this component is a “nucleic acid encoding a guide RNA”. The Commissioner considered this to mean that claim 10 is limited to a method in which the guide RNA must be transcribed from nucleic acid encoding the guide RNA in the eukaryotic cell.

The Commissioner’s reasoning was based on Nicholas J’s finding that claim 19 (which is dependent on claim 10), which contemplates that the guide RNA will have been transcribed outside the cell, lacked clarity because claim 10 requires that the guide RNA be transcribed in the cell.

The Commissioner considered that ToolGen’s proposed amendments were not allowable because proposed amended claim 1 falls outside the scope of the claim 10; i.e. the amendments would result in a change in the scope of the claim from a nucleic acid encoding the guide RNA to the guide RNA itself.

Obvious mistake?

ToolGen sought solace in s 102(3)(a) of the Patents Act, arguing that claims 10 and 19 when read together contain an “obvious mistake”. Section 102(3)(a) provides that where an amendment is to correct a clerical error or an obvious mistake, the requirements in s 102 regarding allowability of amendments do not apply.

The claims of a patent serve to give the public notice of the limits of the monopoly. Because amendments are retrospective, amendments which broaden the claims are not allowed – they would turn earlier non-infringing activities into acts of infringement. The narrow exceptions to this rule are amendments for the purpose of correcting a clerical error or obvious mistake. The theory is that an obvious mistake cannot have misled a person skilled in the art.

ToolGen submitted that, in circumstances where the specification discloses the use of in vitro transcribed guide RNA as part of the invention, the skilled addressee would appreciate that by claim 19 the patent applicant intended to claim this, not guide RNA being transcribed from a nucleic acid in the eukaryotic cell. It follows that the skilled addressee would appreciate that the correction of that mistake would involve removal from independent claim 10 the inconsistent requirement that the guide RNA be transcribed from nucleic acid in the cell.

Justice Nicholas considered the principles relevant to what constitutes an obvious mistake, which we summarise below:

• Both the error itself and the necessary correction must be obvious to the person skilled in the art.
• “Mistake” is a failure to express the real intention of the writer of the specification.
• The correction required does not cease to be “obvious” because there is more than one way of expressing it.
• It is not an obvious mistake if extraneous evidence, beyond what is required to put the court in the position of a person skilled in the art, is needed to show the mistake.

Findings

Justice Nicholas considered that the skilled person would understand there to be a mistake in the “composite claim” (i.e. claim 10 when read with claim 19) because claim 10 describes a guide RNA produced in vivo and claim 19 describes a guide RNA produced in vitro. The skilled person reading the specification would find the mistake plainly apparent on the face of the specification.

His Honour also regarded the relevant correction of the mistake as one which would be obvious to the person skilled in the art. His Honour considered that the skilled person would clearly understand from reading of the specification that the various embodiments of the system described include embodiments in which the guide RNA is created in vitro before introduction into the cell, as well as embodiments in which nucleic acid encoding the guide RNA is introduced into the cell where the guide RNA is subsequently transcribed. His Honour further considered that the skilled person would understand that claim 10 is directed at embodiments in which the guide RNA is produced in vivo and that claim 19 is directed at embodiments in which the guide RNA is an in vitro transcribed RNA.

The relevant correction would, therefore, involve re-writing the composite claim to eliminate the inconsistency in language between claims 10 and 19 so that, rather than referring to nucleic acid encoding a guide RNA, the composite claim instead refers to an in vitro transcribed guide RNA. The result is that claim 10 would continue to include use of a guide RNA produced in vivo and the composite claim would include use of a guide RNA produced in vitro.

His Honour therefore held that proposed amended claim 1 corrects an obvious mistake in the composite claim in a manner that would be obvious to a person skilled in the art.

Key lesson

Amendments to correct obvious mistakes are an exception to the rule in s 102 of the Patents Act that amendments must not broaden the scope of the claims. Although amendments to correct mistakes can be allowed, even in a manner which broadens the claims, both the mistake and its correction must be obvious.