Australia kills Cosette’s Mayne Pharma (ASX: MYX) buyout—citing drug supply risk and sovereignty

Cosette Pharmaceuticals’ planned acquisition of Mayne Pharma Group Limited (ASX: MYX) has been blocked by Australia’s Treasurer, Dr Jim Chalmers, on the advice of the Foreign Investment Review Board. In a rare intervention, the AUD 660 million transaction, equivalent to roughly USD 430 million, was rejected on national interest grounds, following months of cross-departmental consultations and risk evaluations. The proposed scheme of arrangement, first announced in February 2025, would have seen U.S.-based Cosette Pharmaceuticals acquire 100 percent of Mayne Pharma’s issued shares at AUD 7.40 per share.

The Treasurer’s ruling came just days after the Takeovers Panel delivered its final, independent decision on November 19. Although the Panel did not weigh in on national security concerns, its conclusions marked a procedural milestone. Cosette Pharmaceuticals confirmed shortly after market open on November 21 that FIRB had issued formal advice opposing the deal. The Treasurer, relying on inputs from Treasury, the Therapeutic Goods Administration, and the South Australian Government, concluded that no conditions or undertakings could adequately mitigate the risks associated with the proposed foreign ownership of a key domestic pharmaceutical manufacturer.

What risks to pharmaceutical supply chain sovereignty were identified by Australian regulators?

At the heart of the objection was Mayne Pharma’s Salisbury manufacturing facility in South Australia, a U.S. Food and Drug Administration-approved site that plays a critical role in domestic drug production. The site is one of Australia’s few advanced pharmaceutical manufacturing assets with international regulatory recognition. Treasury’s assessment, supported by the Department of Health and Aged Care, flagged that Cosette Pharmaceuticals’ full ownership could jeopardize Australia’s access to essential medicines during emergencies or international supply shocks.

The government stated that the transaction posed “unique risks to the supply of critical medicines” that could not be managed through typical post-acquisition conditions or operational safeguards. Analysts covering Australia’s pharmaceutical landscape interpreted the decision as an attempt to maintain domestic control over key production infrastructure, especially in a global environment where geopolitical instability and post-pandemic volatility have amplified calls for healthcare sovereignty.

How does this decision fit into Australia’s broader foreign investment and national interest framework?

Australia’s foreign investment regime operates on a case-by-case basis, with a strong stated preference for openness and non-discrimination. However, in recent years, successive federal governments have taken a more cautious stance when it comes to acquisitions in sectors involving critical infrastructure, energy, and now healthcare. The Treasurer described the process leading up to the rejection as “careful and methodical,” noting that while Australia welcomes international capital, this transaction simply did not pass the national interest test.

This intervention falls within the government’s powers under the Foreign Acquisitions and Takeovers Act 1975, and serves as a warning that even seemingly commercial deals can be derailed if they intersect with strategic national assets or sovereign capabilities.

What were Cosette Pharmaceuticals’ strategic goals in acquiring Mayne Pharma?

Cosette Pharmaceuticals had positioned the acquisition as a game-changing move to expand its U.S. leadership in women’s health and dermatology. The merger would have added a suite of patent-protected products to its portfolio, including well-known brands such as Nextstellis, Annovera, Bijuva, and Imvexxy, as well as multiple late-stage development programs. Cosette aimed to leverage Mayne Pharma’s commercial infrastructure in both Australia and the United States, along with its contract development and manufacturing services business.

The deal would have also given Cosette Pharmaceuticals dual-country manufacturing reach, adding Mayne Pharma’s Salisbury facility to its own site in Lincolnton, North Carolina. The combined organization would have employed over 800 people, uniting complementary sales teams and R&D pipelines.

Cosette President and Chief Executive Officer Apurva Saraf described the acquisition at the time as “transformational,” citing opportunities to deepen commercial penetration, expand innovation investment, and enhance patient access in the United States and abroad.

How did Mayne Pharma respond following the FIRB decision and court hearing cancellation?

Mayne Pharma confirmed via an ASX filing on November 21 that it had received formal notice from Cosette Pharmaceuticals regarding FIRB’s objection. As a result, the Second Court Hearing, originally scheduled for November 23, was vacated, and the scheme is now unlikely to proceed. Cosette Pharmaceuticals also triggered the consultative clause under the Scheme Implementation Deed, requesting both parties enter good faith discussions to explore viable alternatives.

Mayne Pharma’s board acknowledged shareholder disappointment and stated it was reviewing its strategic options. While it has not ruled out future partnerships or transactions, any revised proposal would likely need to preserve Australian ownership or guarantee localized supply chain commitments to stand a chance under current regulatory conditions.

How did the FIRB decision affect Mayne Pharma’s share price, investor sentiment, and market positioning on the ASX?

Investor optimism, which had surged in February 2025 following the announcement of the AUD 7.40 per share offer, has cooled substantially. Mayne Pharma shares had traded at a significant premium over their pre-deal price in anticipation of a successful close. The FIRB rejection and regulatory optics have now introduced uncertainty over future strategic pathways. Market watchers expect short-term volatility as investors recalibrate based on the potential loss of the takeover premium.

However, some institutional investors have expressed confidence that Mayne Pharma’s manufacturing assets and U.S. commercial strength remain valuable on a standalone basis. The blocked transaction may even open the door for domestic pharmaceutical players or sovereign-backed capital pools to explore alternate tie-ups that align better with Australia’s national interest framework.

What does this ruling signal for future pharma M&A involving Australian manufacturing assets?

Analysts believe the Treasurer’s firm stance sets a precedent for future transactions in the healthcare sector. Deals involving domestic pharmaceutical production facilities, especially those with FDA or European Medicines Agency approvals, will now likely face heightened regulatory scrutiny. The focus has clearly shifted from merely evaluating financial fit and shareholder value to assessing long-term strategic resilience.

While Cosette Pharmaceuticals may explore non-controlling investments or licensing partnerships, the path to full ownership of Australian pharma infrastructure has narrowed. Industry observers expect FIRB to take an equally rigorous approach to any proposed acquisitions in digital health, biotech manufacturing, or clinical data infrastructure, where national resilience and medical sovereignty are now front and center.

What options remain for Cosette Pharmaceuticals after Australia’s rejection of the takeover?

Cosette Pharmaceuticals has not issued a public response beyond the formal notice submitted under the Scheme Implementation Deed. Whether it chooses to pursue a revised offer with modified ownership terms or seeks acquisition targets elsewhere in the Asia-Pacific remains to be seen. U.S. expansion in women’s health and dermatology remains a key objective for the firm, and Mayne Pharma had appeared to be the ideal strategic fit.

One possible path forward is a licensing or commercialization partnership that retains Australian manufacturing control. However, given the strong national interest language used by the Treasurer, many analysts believe the door to any material stake acquisition is effectively closed for now.

Key takeaways: What the Cosette–Mayne Pharma FIRB rejection reveals about Australia’s pharma M&A climate

• Australia’s Treasurer formally blocked Cosette Pharmaceuticals’ USD 430 million acquisition of Mayne Pharma Group Limited, citing national interest concerns following FIRB advice.

• The key issue was risk to the domestic supply of critical medicines, particularly due to Mayne Pharma’s FDA-approved manufacturing facility in South Australia.

• No set of conditions could adequately mitigate these national security and supply chain risks, according to advice from Treasury and other agencies.

• Mayne Pharma confirmed that the scheme of arrangement will no longer proceed, and the scheduled court hearing was vacated.

• Cosette had aimed to consolidate leadership in women’s health and dermatology through the acquisition, integrating a suite of patented brands and global operations.

• Investors had anticipated the deal’s closure, with Mayne Pharma’s share price trading near the AUD 7.40 offer. Sentiment has since cooled following the Treasurer’s ruling.

• The decision sets a strong precedent for tighter regulatory scrutiny over pharma assets with strategic manufacturing capabilities in Australia.

• Analysts suggest that future cross-border M&A in Australian healthcare will require domestic production safeguards to gain regulatory clearance.

• Mayne Pharma’s board is now exploring next steps, which could include new partnership structures or remaining independent.

• The case underscores Australia’s shift toward safeguarding pharmaceutical sovereignty, particularly in light of recent global supply chain disruptions.