On 9 October 2026, Mayne Pharma Group Limited (ASX:MYX) announced that it had received a letter from the US Food and Drug Administration (FDA) confirming that it has fulfilled its post-marketing requirement (PMR) for IMVEXXY (estradiol vaginal inserts). The company said this leaves no remaining FDA post-marketing requirements for the product.

What the FDA confirmed

The PMR was an observational safety study with a primary endpoint of evaluating the risk of endometrial cancer in postmenopausal women prescribed very-low-dose vaginal estrogen (VLDVE) products, including IMVEXXY. The FDA reviewed the final study report and concluded that the requirement has been fulfilled.

IMVEXXY is FDA-approved for the treatment of moderate-to-severe dyspareunia, a symptom of vulvar and vaginal atrophy due to menopause.

Study design and results

The study was conducted by independent research organisation RTI Health Solutions using two large US health-insurance claims databases covering commercial and Medicare Advantage populations. Results were presented at the ISPE 2026 annual meeting in Milan and announced to the ASX on 20 August 2026.

The analysis included more than 9.5 million postmenopausal women, of whom approximately 86,700 used VLDVE products. In propensity score-matched analyses and in the pooled meta-analysis, there was no evidence of an association between VLDVE use as prescribed and endometrial cancer risk compared with non-use. The pooled hazard ratio was 1.00 (95% confidence interval 0.69 to 1.45). About 89% of treatment episodes involved no concomitant systemic estrogen.

Additional evidence cited

Mayne cited a 2026 observational analysis of approximately 1.9 million women with recurrent urinary tract infections published in the Journal Urology, which found lower observed rates of sepsis, hospital admission and mortality among women with a vaginal estrogen prescription. The company noted the study was retrospective and observational, shows association rather than causation, and was not specific to IMVEXXY.

The release also refers to a joint American Urological Association and American Urogynecologic Society guideline recommending local low-dose vaginal estrogen for appropriate patients with genitourinary syndrome of menopause. It states IMVEXXY delivered FY26 net sales of US$29.3 million, up 8%, with total prescription growth of 6%.

Sector backdrop

Post-marketing requirements are studies the FDA asks sponsors to conduct after approval to assess specific safety questions. Fulfilling one closes that item for the product’s regulatory file but does not by itself change the approved labelling.

Observational studies using claims databases can assess large populations but cannot establish causation, and their results depend on how exposure and outcomes are identified.

Risks shareholders should weigh

Completing the PMR does not change IMVEXXY’s labelling. The release refers to potential future removal of a boxed warning only as a possibility, and any such change would be a decision for the FDA.

The study is observational and based on Insurance Claims data, so residual confounding cannot be excluded. The confidence interval of 0.69 to 1.45 is wide enough to include both lower and higher risk estimates.

IMVEXXY’s sales depend on prescriber and patient uptake, reimbursement and competition in the US menopause market. FY26 net sales of US$29.3 million represent one product among the company’s portfolio, and the release does not provide forward guidance.

What’s next

Mayne said it has no remaining FDA post-marketing requirements for IMVEXXY. Shareholders may wish to watch for further labelling discussions with the FDA, prescription data and company updates on its Women’s Health portfolio.