Pharmaceutical patents: preliminary injunctions still available, despite complexities in undertaking as to damages calculations

For the first time in several years, two contested applications for preliminary injunctions (PIs) have been granted by the Federal Court in Australian pharmaceutical patent cases. The two decisions follow a string of cases in which Judges had cast doubt about whether the balance of convenience favours the granting of an injunction, once the Court weighs the difficulty of assessing damages for infringement (in a non-restraint scenario) against the difficulty of assessing damages on an undertaking as to damages (in a restraint scenario).

These two recent decisions reaffirm the long-standing principle that to resist a PI application where the patentee has a strong prima facie case on infringement, the alleged infringer will likely need to have a compelling invalidity attack – and an alleged lack of inventive step based on disputed technical evidence is unlikely to meet that description (Janssen Pharmaceutica NV v Juno Pharmaceuticals Pty Ltd [2025] FCA 1538; AstraZeneca AB v Pharmacor Pty Ltd [2026] FCA 88).

The patent and the products in Janssen v Juno

Janssen owns Australian Patent No. AU2008340101, “Dosing regimen associated with long acting injectable paliperidone esters”, which, in summary, claims dosing regimens for administering paliperidone palmitate long-acting injectable (PPLAI).

Janssen’s Australian licensee markets three versions of PPLAIs under the brand names INVEGA SUSTENNA, INVEGA TRINZA and INVEGA HAFYERA (for one-, three- and six-monthly administration respectively). Janssen currently enjoys market exclusivity.

Juno threatened to launch generic versions of the one-monthly INVEGA SUSTENNA product, under the brand names PALJUNA MONTHLY and VALINO MONTHLY. Juno's two products differed in their approved product information:

• The approved product information for VALINO MONTHLY mirrored that of the originator INVEGA SUSTENNA, and included instructions for a dosing regimen that mirrored the relevant patent claim integers;

• The approved product information for PALJUNA MONTHLY included instructions for prescribers to use "INVEGA SUSTENNA (available from another supplier)" for part of the relevant dosing regimen, the PALJUNA MONTHLY product being described as suitable for the monthly maintenance dosing only.

Janssen commenced proceedings alleging threatened patent infringement and applied for a PI .

Juno denied infringement and opposed the application for a PI, including on the basis of a foreshadowed revocation cross-claim that would be based upon alleged lack of inventive step and false suggestion to the Commissioner of Patents.

A strong prima facie case of infringement

Having regard to the form of the patent claims, Janssen's case on infringement primarily focused on alleged infringement by supply under section 117 of the Patents Act 1990 (Cth), authorising infringement, and/or joint tortfeasorship.

Justice Burley found that Janssen’s infringement case was particularly strong in respect of VALINO MONTHLY, in view of the dosing instructions in the product information being substantially identical with those in Janssen's product information for INVEGA SUSTENNA. Juno did not dispute whether those dosing instructions amounted to authorisation of use in accordance with the claimed methods, or joint tortfeasorship, or infringement under section 117 of the Act.

The infringement analysis for PALJUNA MONTHLY was more complex, although Justice Burley was ultimately satisfied that there remained a strong prima facie case for infringement.

Juno unsuccessfully argued that:

• The instructions directed prescribers to use Janssen's own INVEGA SUSTENNA for the initiation phase of the dosing regimen, and that because the use of INVEGA SUSTENNA was authorised by Janssen, there could be no primary infringement;

• In the absence of any primary infringement, there could be no finding of secondary infringement under section 117 and/or authorising of infringement and/or joint tortfeasorship; and

• By the same reasoning, the absence of any primary infringement meant that there could be no liability in damages for any such secondary infringement.

Justice Burley was not persuaded that this argument undermined the strength of Janssen's prima facie case on infringement. His Honour found Juno’s PI effectively sanctioned and facilitated the use of PALJUNA MONTHLY as part of a treatment regimen that included infringing initiation and maintenance doses.

Non-infringing uses

Juno also argued – in relation to both of its products – that some uses would not fall within the scope of the patent claims: eg., prescriptions for patients with mild renal impairment, missed doses, or deviations from the PI by psychiatrists.

While Justice Burley accepted that non-infringing uses likely represented a “small but non-trivial cohort,” his Honour concluded that the “vast majority” of uses would still fall within the scope of the patent claims, supporting a strong prima facie case for infringement.

Validity attack not strong enough to undermine case on infringement

Juno asserted that the patent was invalid, based on lack of inventive step and false suggestion. The lack of inventive step case relied upon the common general knowledge combined with one prior art document, which itself referred to three clinical trials. Each party relied on evidence from multiple subject-matter experts.

Significantly, both grounds of alleged invalidity turned on complex, disputed technical facts, not well suited to determination in an application for a PI, where time is limited and cross-examination of witnesses almost never occurs. As Justice Burley observed:

"Considering a challenge based on lack of inventive step, especially in the discourse of patents concerning pharmaceutical products, involves a complex process of fact finding and legal analysis. … The difficulties in resolving these questions prior to a final hearing have recently been recognised … The ground of invalidity is ill suited to the objective that Juno seeks to attain, which is to demonstrate weakness in the prima facie case of infringement asserted against it." [emphasis added ]

On the facts of this case, Justice Burley considered the invalidity arguments to be arguable, but declined to assess their ultimate strength given conflicting expert evidence and the need to construe the specification as a whole at trial. Therefore, the invalidity challenges did not materially weaken Janssen’s infringement case.

Balance of convenience favoured restraint, despite damages complexity

Having considered infringement and validity, Justice Burley turned to consider the overall balance of convenience.

Among the factors considered, the Court weighed up the comparative difficulty in assessing:

• Damages for infringement (in a non-restraint scenario), assuming an injunction is not granted, Juno launches its products during the patent term, and Janssen's patent is ultimately found to have been valid and infringed;

• Damages on the usual undertaking as to damages (in a restraint scenario), assuming an injunction is granted, but Janssen's patent is ultimately held to have been invalid and/or not infringed, leading Juno to claim on the undertaking.

Informing this weighing exercise, the Court received expert evidence from forensic accountants called on behalf of both parties, as well as extensive lay evidence and modelling about the market conditions in various counterfactual scenarios.

Importantly, Justice Burley accepted Juno's argument that damages on the undertaking as to damages would likely be more complex than assessing damages for infringement. This reasoning follows similar observations made by various judges since Justice Jagot's comments in 2018 in Sigma v Wyeth about the surprising complexity involved in assessing damages on an undertaking as to damages.

Despite favouring Juno's argument on the complexity, when weighing all of the factors – including the relative strength of each party's prima facie case – Justice Burley still felt the balance weighted in favour of an injunction.

AstraZeneca v Pharmacor: the pendulum swings back in favour of PIs

Endorsing Justice Burley’s reasoning in Janssen, Justice Downes granted AstraZeneca a PI on 16 February to restrain Pharmacor Pty Ltd from launching generic versions of AstraZeneca's dapagliflozin tablets, marketed under the brand name FORXIGA and used to treat diabetes, chronic kidney disease and heart failure (AstraZeneca AB v Pharmacor Pty Ltd [2026] FCA 88).

In that case, it was not in issue that the Pharmacor products would fall within the scope of AstraZeneca's Australian Patent No. 2003237886. Rather, the issue before Justice Downes was whether Pharmacor's invalidity position was sufficiently strong to displace the conclusion that AstraZeneca had a strong prima facie case of infringement.

Justice Downes held that it was not and that the balance of convenience favoured the grant of a PI.

Her Honour emphasised that the status quo was AstraZeneca’s statutory exclusivity until October 2027, and that allowing launch would disrupt that position despite admitted infringement. While recognising that it may be in the public interest for FORXIGA to be sold at a lower price – an argument weighing against the injunction – Justice Downes stressed the broader purpose of the patent system. As her Honour noted, a patent confers a statutory monopoly to encourage and reward invention for the benefit of all, and failing to restrain infringement in these circumstances risked undermining the Australian patent system, with potentially adverse consequences for future research, development, and the licensing of pharmaceutical products.

The speed of the Court’s handling is also notable. AstraZeneca filed its PI application in mid-December 2025; the matter was heard within seven weeks, and judgment with full reasons was delivered just ten days later. The substantive proceedings have been listed for trial on an expedited timetable, commencing in August 2026 – fewer than nine months after the proceeding began. These compressed timelines illustrate the Court’s willingness to fast-track PI applications where commercial circumstances demand urgent resolution.