Roughly half a year after the close of its deal to acquire Bayer spinout AiCurus, Asahi Kasei’s $920 million bet has paid off with an FDA green light.
Late Friday, the FDA signed off on Asahi Kasei’s pritelivir tablets, to be marketed as Hovilpri as a new treatment for mucocutaneous lesions caused by herpes simplex virus (HSV) infection. Specifically, the helicase inhibitor—representing the first novel mechanism for an HSV treatment in nearly three decades—has been approved in immunocompromised adults whose infection is refractory, with or without documented resistance, with acyclovir, valacyclovir or famciclovir.
The nod brings forward a new option to treat HSV-caused sores affecting the skin and mucous membranes and further bolsters the armamentarium for those herpes patients whose disease hasn’t responded to standard-of-care nucleoside analogue drugs.
The drug was developed by AiCuris Anti-infective Cures, which Asahi Kasei bought for 780 million euros (then worth some $920 million) earlier this year.
AiCuris, which spun out of German conglomerate Bayer back in 2006, has picked up other approvals in its history, too, including for the transplant infection preventative Prevymis, which was approved by the FDA in late 2017 and is currently marketed by Merck & Co. under an earlier licensing agreement. That medicine continues to function as a royalty stream for AiCuris.
As for Hovilpri, Asahi Kasei said in an Oct. 9 release that it expects to make the drug available in the U.S. before the end of 2026. The company did not comment on its current pricing or access strategy around Hovilpri.
The drug, taken at 100 mg daily by mouth after an initial 400-mg loading dose on day 1 of treatment, was cleared on data from the PRIOH-1 Part C phase 3 study, an open-label, comparator-controlled superiority trial that pitted Hovilpri against an investigator’s choice of treatment.
Investigators were able to select between IV foscarnet, IV or topical cidofovir or 5% topical imiquimod for the control regimen.
The study was able to knock out its primary endpoint after Hovilpri demonstrated superiority over the investigator’s choice control following 28 days of treatment, Asahi Kasei said Friday. By that 28-day mark, Hovilpri was also tied to a significantly higher rate of complete lesion healing at 63%, versus the 34% reported among the trial’s control arm.
This lines up with an adjusted treatment difference of 28.4% between the study drug and investigator’s choice treatment cohort, according to Asahi Kasei. Up to day 42, Hovilpri charted response rates of 82%, compared to 42% in the comparator wing of the study.
On the safety front, Asahi Kasei pointed out that in Part C of its phase 3 program, adverse reactions were reported less frequently in patients on Hovilpri at 22%, versus 54% among those who received an investigator’s choice of treatment. Discontinuations due to drug reactions also favored Hovilpri at a slim 2%, compared to 20% for the control.
“Refractory HSV can be a serious clinical challenge for immunocompromised adults, a population with limited treatment options,” Carl Kraus, Asahi Kasei’s chief medical officer, said in a statement. “The approval of Hovilpri reflects years of clinical research in refractory HSV and reinforces our commitment to advancing scientifically differentiated medicines for patients whose conditions remain difficult to treat.”
HSV represents a major global public health burden, with an estimated 3.8 billion people under the age of 50 infected with HSV-1—which typically results in sores around the mouth—in 2020, while around 520 million people between 15 and 49 years were living with the genital herpes variant HSV-2 that same year, per Asahi Kasei.
For patients whose immune systems function as intended, HSV infection can often present without symptoms. But in immunocompromised adults, including hematopoietic stem cell and solid organ transplant recipients, people living with HIV and patients with cancers or autoimmune and inflammatory conditions, herpes infection can occur more frequently and be more severe, Asahi Kasei said.
As an oral treatment, Asahi Kasei further believes Hovilpri could have an edge over the frequently intravenous treatments that are used as alternatives for immunocompromised patients who don’t respond to nucleoside analogue therapies like acyclovir.
When it announced the close of its AiCuris deal earlier this year, Asahi Kasei said it expected Hovilpri could address some 15,000 immunocompromised patients in the U.S., with peak revenue for the drug “expected to exceed $400 million” in the mid- to late-2030s.
Further ahead, AiCuris has wrapped up phase 1 testing on another asset coded AIC468 for BK virus infection in kidney transplant and hematopoietic stem cell transplant recipients, where Asahi Kasei said it has spied a potential market opportunity in excess of $1 billion.
At the top of October, Asahi Kasei announced plans to wrap the AiCuris brand, plus those from prior buyouts of Veloxis Pharmaceuticals and Calliditas, under the singular Asahi Kasei Therapeutics banner.