HN0037

HN0037 is an investigational oral tablet from Phaeno Therapeutics, developed in China to treat outbreaks of genital herpes and cold sores. It is a helicase-primase inhibitor, meaning it blocks a piece of machinery HSV needs to copy itself, which is a different target from the acyclovir family.

It has completed a healthy-volunteer Phase 1 study and a placebo-controlled Phase IIa study in recurrent genital herpes. A second Phase IIa study, in recurrent cold sores, is registered as still recruiting. The developer said in August 2026 that both Phase II trials were complete, so the two records disagree and this page does not resolve them.

No Phase II result has been published anywhere a reader can check it. The only figures that exist are the developer's own summary statements, without denominators, confidence intervals or primary-endpoint statistics, so this page reports them as claims rather than as findings.

The developer announced a Chinese breakthrough-therapy designation for the genital-herpes indication in August 2026. That is an expedited review pathway, not approval, and HN0037 is not available to patients anywhere.

HN0037 is a small-molecule tablet, written in Chinese records as HN0037片 and occasionally as HN-0037. Its trials used 10 mg and 50 mg tablets.

A helicase-primase inhibitor blocks the enzyme complex that unwinds and primes viral DNA so it can be copied. Acyclovir, valacyclovir and famciclovir work at a different step: they are nucleoside analogues, decoy building blocks the virus mistakes for the real thing. HN0037 is therefore a genuinely separate mechanism rather than a variation on the existing drugs, which is not by itself a clinical advantage.

The developer is 辉诺生物医药科技（杭州）有限公司, which uses the English name Phaeno Therapeutics. The name Huino Biopharmaceutical Technology, which appears in some listings, is a different romanization of the same company and not a separate organization.

Two patent reviews, from 2022 and 2024, state that the compound is covered by Medshine Discovery patent applications and was in-licensed by Phaeno Therapeutics. The developer's own January 2026 release calls HN0037 independently developed. This page keeps both statements attributed rather than choosing between them.

The program is therapeutic rather than preventive: it treats people who already have HSV rather than trying to stop infection.

Both Phase IIa trials studied episodic treatment, meaning a single dose that the participant takes themselves within 48 hours of the first warning signs or the first lesion. Neither studied suppressive therapy, which is continuous daily dosing to reduce how often outbreaks happen.

Both trials used the same primary endpoint: the proportion of participants whose lesions were aborted, measured at days 3, 5 and 7. An aborted lesion is an outbreak that never progresses to a blister.

The developer frames the long half-life measured in Phase 1 as supporting one dose per episode. That is a pharmacokinetic rationale for the dosing design, not evidence that a single dose works.

The Phase 1 study, CTR20210378, enrolled 88 healthy adults aged 18 to 45 at one hospital in Zibo. It gave single doses from 10 to 400 mg and 14 days of once-daily dosing, and ran from March 2021 to January 2022. Its primary endpoint was safety and its secondary endpoint was pharmacokinetics, meaning how the body absorbs, distributes and clears the drug.

The genital-herpes Phase IIa, CTR20252614, enrolled 90 adults with recurrent genital herpes across 13 Chinese sites led by Huashan Hospital. Participants had to have normal immune function and to test positive for HSV-1, HSV-2 or both, so the trial admitted people whose genital herpes came from either type. Enrollment began in August 2025 and the registry records completion on March 31, 2026.

The cold-sore Phase IIa, CTR20253323, is the same design in recurrent herpes labialis across 10 sites, with a target of 90 participants. Enrollment began in October 2025.

When that record was read in full on September 8, 2026 it showed 60 of the 90 participants enrolled, no completion date and no results summary. A status re-check on September 9, 2026 still listed the trial as ongoing and recruiting.

The developer stated on August 3, 2026 that both Phase II trials were complete. Those two records disagree, and this page does not resolve the disagreement.

Registry fields can lag actual events, and the developer may be describing the end of dosing rather than the closure of the registry record. Neither explanation is established by any checked source, so HN0037 is not described here as having completed its cold-sore trial. The disagreement also matters for how the cold-sore figures below should be read, because the developer reported them for a trial its own registry entry still shows as recruiting.

The published Phase 1 report describes exposure rising proportionally from 10 to 120 mg and less than proportionally from 200 to 400 mg. It reports significant accumulation at steady state, a half-life of 50.4 to 61.0 hours, and a marginal food effect at 200 mg.

Its authors report that adverse-event rates did not differ between HN0037 and placebo, and conclude the drug was safe and well tolerated. That is the authors' conclusion from a small healthy-volunteer study, eight of whose eleven authors work for the developer, and only the abstract was accessible.

A Phase 1 study in healthy volunteers measures how a drug behaves in the body and whether it causes obvious harm. It cannot show whether the drug helps anyone with herpes, because nobody in it had an outbreak to treat.

No result from either Phase IIa trial has been posted to the registry, published in a journal, or made available in a readable conference abstract through September 8, 2026.

The developer reports that in the genital-herpes trial both dose groups shortened median episode duration by about 50 percent against placebo, with a lesion-abortion rate nearly three times placebo. It reports that in the cold-sore trial a single dose shortened median episode duration by about 38 percent, with a lesion-abortion rate nearly twice placebo.

Those figures carry no denominators, no absolute rates, no confidence intervals, no p values and no primary-endpoint analysis. Nothing about them can be independently checked, and their size cannot be described here.

The developer also reports that the genital-herpes abstract was presented at the 2026 International Herpesvirus Workshop and won an award, and that the cold-sore abstract was accepted for IDWeek 2026. Neither abstract was accessible in the checked routes, so neither adds anything a reader can inspect.

The most defensible evidence-maturity label is early human evidence. Placebo-controlled Phase IIa work has been done, which would ordinarily support a stronger label. But the results exist only as developer summaries, and a label describing controlled efficacy evidence would tell readers that checkable controlled results exist when they do not.

What the checked record establishes is narrow. A new-mechanism oral HSV drug has completed a healthy-volunteer study and a placebo-controlled outbreak-treatment study in China, and its developer describes the outcome as positive.

What it does not establish is that HN0037 works. A sponsor summary can establish what the sponsor said and that a trial reached a milestone. It cannot establish an effect size, and these summaries do not report the analysis their claims would rest on.

The trials measured lesions and episode duration after a single dose taken during an outbreak. They do not establish reduced viral shedding, reduced transmission to a partner, fewer future recurrences, or any effect on the latent virus that causes recurrences. China's breakthrough-therapy designation is a mechanism for faster regulatory review rather than a statement about proven benefit, and it is not approval.

The developer also claims that HN0037 leads all same-target inhibitors, is significantly superior to acyclovir in preclinical work, and is the first new-mechanism HSV drug in nearly 40 years. No primary source checked through September 8, 2026 supports any of the three. A laboratory potency advantage would not in any case predict a clinical one.

HSVHQ records HN0037 as active at Phase 2. One Phase IIa is complete on the registry, a second is registered and enrolling, and the developer was making public statements about the program in August 2026. Development is China-only in the checked record: no ClinicalTrials.gov record, WHO portal record, FDA product or readable European regulatory record was identified through September 8, 2026, and all three registered trials are Chinese domestic studies.

HN0037 is not approved, marketed or available anywhere on the checked evidence. Nothing in the checked record indicates the program has stopped, and program activity and trial status are separate facts that point the same way here.

The result that would most change this record is a published Phase II report, a posted registry results summary, or a readable conference abstract carrying denominators and an effect estimate with its uncertainty.

A registered Phase III trial would confirm the developer's stated plan, as would the appearance of HN0037 in the Chinese regulator's own public breakthrough-therapy listing. A completion status and a results summary on the cold-sore trial's record would resolve the disagreement described above.

Any registration outside China would be the first sign that development extends beyond the Chinese market.