Mayne Pharma to sue Cosette Pharmaceuticals and Avista Healthcare for breach of takeover terms
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The news: Mayne Pharma will commence proceedings in the NSW Supreme Court against Cosette Pharmaceuticals, its private equity backer Avista Healthcare Partners and Avista CEO David Burgstahler for breaching the terms of a failed $600 million takeover.
The numbers: In February, Cosette initially agreed to acquire Mayne for $7.40 per share. At last close, Mayne’s share price was $2.65.
The context: Mayne Pharma told the exchange it is seeking “substantial damages on behalf of Mayne shareholders against Cosette for breach of the [scheme implementation deed] SID and against the other defendants for inducing Cosette’s breach of the SID”.
The ASX-listed pharmaceutical company is also seeking “substantial damages” on its own behalf against the defendants.
Mayne previously rejected an effort to formally terminate the deal by Cosette in December, after it was blocked by Treasurer Jim Chalmers, on the grounds that Cosette has "materially breached" the SID before issuing its own termination notice.
Cosette is also appealing a NSW Supreme Court ruling that its previous attempts to terminate the deal had no grounds.
Chalmers killed Cosette’s proposed acquisition of Mayne in December 2025 amid concerns Cosette would shut Mayne’s flagship manufacturing facility in Salisbury, South Australia that emerged over a months long battle by the reluctant suitor to terminate the deal.
The source: ASX
