Rezzayo antifungal okayed as Candida auris rings alarm bells

With infections caused by the fungal pathogen Candida auris spreading at an “alarming rate” in the US, according to the Centers for Disease Control and Prevention (CDC), Melinta has just picked up a timely FDA approval for its antifungal drug Rezzayo.

Melinta – which has US rights to Rezzayo (rezafungin) under license from Cidara – said the drug has become the first new antifungal in the echinocandin class to be approved in the US in more than a decade.

It has picked up a green light as a therapy for candidemia and invasive candidiasis in adults, with limited or no alternative treatment options, shortly after the CDC warned that infections with C auris nearly doubled in 2021, from 756 in the previous year to 1,471. It has continued to see an increase in case counts for 2022.

While the numbers are not massively high, it is a big concern because most of the cases tested were resistant to standard candidiasis therapies, making the pathogen “an urgent antimicrobial resistance threat,” according to the agency.

The infection isn’t usually serious in healthy individuals, but can be much more serious in immunocompromised people and those who are “very sick, have invasive medical devices, or have long or frequent stays in healthcare facilities,” it said.

A review in the journal Nature last year noted that AMR programmes have often excluded antifungals because fungi have been "widely neglected as a threat to public health."

That presents an opportunity for Melinta and Cidara, which secured FDA approval for their new drug largely on the strength of the ReSTORE phase 3 trial, which revealed the once-weekly drug was at least as effective as caspofungin, the current standard echinocandin therapy for serious candida-based infections.

“The FDA approval […] is tremendous news for those of us who have been hoping for a new option to treat our patients with these deadly fungal infections,” said lead investigator, George Thompson of the University of California, Davis, School of Medicine.

“Based on the totality of clinical data generated, Rezzayo has the potential to simplify the management of invasive candidiasis and enhance the continuity of echinocandin care.”

Melinta has said it intends to launch the new product in the summer. While it can be hard to make big sales off an antimicrobial drug reserved for later-line use, analysts at HC Wainwright have suggested it could make around $219 million at peak in the US, according to Reuters.

Rezafungin is also under regulatory review in Europe, and is being tested for other indications, including the prevention of invasive fungal diseases in adults undergoing allogeneic blood and marrow transplantation.

Cidara was also developing a topical formulation of the echinocandin, but abandoned the project a few years ago after it failed to show efficacy in a mid-stage vulvovaginal candidiasis study.

Shares in the company fell after news of the approval, which may be explained by profit-taking after a fairly steady increase in the stock since the start of the year.

Melinta licensed rights to rezafungin last year in a deal valued at up to $490 million, including $30 million upfront and $60 million in regulatory milestones. Cidara retains the rights to rezafungin in Japan and is seeking a partner, while Mundipharma has rights to the drug outside the US and Japan.