Cidara leaps, then drops, after antifungal drug aces phase 2

Cidara discontinued development of the topical version of rezafungin in 2016 after it failed a midstage trial in vulvovaginal candidiasis. (Nadine Doerlé)

Cidara Therapeutics' lead antifungal candidate hit its primary objectives in a phase 2 trial. The topline data puts Cidara on track to start phase 3 trials midyear, testing the drug, rezafungin, as both a preventive and therapeutic measure for serious, invasive fungal infections. 

The news is a boon for the San Diego-based biotech, which, after being named to the 2014 Fierce 15, had to dump the topical version of rezafungin, previously called CD101, after a phase 2 flop in vulvovaginal candidiasis. At the time, the company said discontinuing the topical treatment would free up resources to advance "other promising candidates," including the intravenous version of rezafungin, developed for candidemia.

Cidara's stocks were up 14% in premarket trading Monday on the news, but dropped back down 22% after the market opened.

The STRIVE trial reported efficacy data from 92 treated patients, as well as safety and tolerability data from 104 patients. The treated patients were split into three groups: The first received a 400-mg, once-weekly IV dose of rezafungin for two to four weeks, while the second was given 400 mg in the first week and 200 mg for up to four weeks total. The third group was treated with caspofungin, an antifungal from Merck. 

Both dosing regimens were generally well tolerated in patients with candidemia and/or invasive candidiasis, with the 400/200-mg regimen coming out tops. 

“This is the first time that any antifungal has shown the potential to be a safe and effective once-weekly treatment option for patients with difficult-to-treat and deadly invasive Candida infections, which may enable patients to leave the hospital earlier, saving money and improving care,” said Cidara CEO Jeffrey Stein, Ph.D., in the statement.

“It is especially encouraging to note the consistent trends in relative outcomes improvement among patients on the rezafungin 400/200 regimen as compared to those on the comparator caspofungin. With these data in hand, we can confidently select the dosing regimens for our two upcoming Phase 3 pivotal trials of rezafungin in treatment and prophylaxis.” 

The first pivotal trial will gauge the efficacy of rezafungin in about 150 patients with candidemia and/or invasive candidiasis in a similar trial design to STRIVE, but with a different primary outcome: 30-day all-cause mortality. The second trial will test the ability of a 90-day rezafungin regimen to stave off fungal infections in patients undergoing allogenic bone marrow transplant. The primary endpoint will be fungal-free survival. Both trials are expected to produce topline data in 2020.

Editor's note: This story was updated to include Cidara's stocks after the market opened Monday.