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‘Unique situation’: Mayne Pharma tests the limits with latest Cosette lawsuit

The Mayne Pharma vs Cosette takeover saga and ensuing legal battles have already reshaped Australian M&A. The latest, precedent-testing lawsuit could do so again.

Mayne Pharma is suing Cosette Pharmacuticals to seek damages on behalf of its shareholders. Shutterstock.

Mayne Pharma’s latest legal fight against its former US suitor Cosette Pharmaceuticals and its private equity backer Avista Healthcare could yet again reshape the Australian mergers and acquisitions landscape, according to top dealmakers.

The ASX-listed generics producer filed a fresh lawsuit against Cosette and Avista on Wednesday on behalf of its shareholders, arguing the American companies breached the terms of their failed $600 million takeover.

It’s the latest twist in a long saga that saw Cosette strike a deal to acquire Mayne for $600 million, then attempt to walk away through novel legal tactics after it downgraded its earnings in April. The Treasurer eventually killed the deal after Cosette suggested to the Foreign Investment Review Board (FIRB) it could shutter Mayne’s flagship manufacturing facility.

“Whether or not the case is successful, the work of lawyers and other advisers in seeking to avoid Mayne-Cosette situations in the future will continue apace,” King & Wood Mallesons M&A partner Daniel Natale told Capital Brief.