For the first time, a drug aimed squarely at the dengue virus has shown a hint that it can help people who are already sick. In a Phase 2 trial run across 12 hospitals in India, a single infusion of a lab-made antibody cleared the virus from patients’ blood faster and cooled their fever sooner than a placebo, with no serious side effects blamed on the drug. It is an early and fragile result, but for a disease that today has no specific treatment at all, even a preliminary signal is notable.
The antibody, called Dengue-mAb, is made by Serum Institute of India, the world’s largest vaccine manufacturer by volume. The company’s researchers, writing in JAMA Network Open, put it carefully: this is, in their words, the first evidence of a preliminary therapeutic effect in patients with dengue. The emphasis belongs on “preliminary.” The trial was small, and a quirk in who enrolled left the efficacy analysis leaning on a handful of patients.
What a single infusion did
- A one-time, two-hour intravenous infusion of Dengue-mAb cut the amount of virus in the blood faster than a placebo, and the effect got stronger at higher doses.
- Among the small group of patients who still had detectable virus at the start, 100% cleared it by 8 hours at the 5, 7, and 9 mg/kg doses, compared with 50% on placebo.
- Fever cleared within 24 hours in 100% of patients on the 5 and 7 mg/kg doses versus 58.3% on placebo.
- No serious adverse events were judged to be caused by the antibody, the trial’s co-primary safety goal.
| Finding | Plain-English meaning |
|---|---|
| A single infusion produced a larger drop in blood virus at 24 hours than placebo, at every dose (P = 0.04 to 0.001). | One dose measurably lowered how much virus was circulating, and the gap over the dummy drip was unlikely to be chance. |
| 100% of patients on 5 to 9 mg/kg cleared detectable virus by 8 hours, vs 50% on placebo. | At the higher doses, everyone with measurable virus was clear of it within a work-shift, twice the share seen with no drug, though only a few patients per group. |
| Fever gone within 24 hours in 100% of the 5 and 7 mg/kg groups, vs 58.3% on placebo. | Most treated patients had broken their fever within a day, compared with roughly six in ten given placebo. |
| No drug-related serious adverse events across 199 treated patients. | The antibody looked safe at the doses tested, which is the main thing a Phase 2 study is built to check. |
| Only 12.9% of the 250 enrolled had detectable virus in the blood at the start, versus the 50% the trial was designed around. | Far fewer eligible patients than planned, so the efficacy numbers rest on small subgroups and cannot yet be called proof. |
Trial parameters and outcome metrics
| Parameter | Trial details |
|---|---|
| Sponsor and funder | Serum Institute of India |
| Investigational agent | Dengue-mAb (formerly VIS513), single IV infusion |
| Design | Phase 2, single-blind, randomised, placebo-controlled, dose-ranging |
| Enrollment | 250 randomised (249 analysed), 226 completed |
| Doses tested | 3, 5, 7, and 9 mg/kg versus placebo |
| Locations | 12 tertiary care hospitals in India |
| Dates | September 2021 to May 2023 |
| Registry | CTRI/2021/07/035290 |
Why a dengue drug matters so much
Dengue is one of the fastest-spreading mosquito-borne diseases in the world, and medicine has almost nothing to offer against the virus itself. The World Health Organization estimates 100 to 400 million infections a year, with about half the global population now living where the disease can reach them. Most infections are mild or cause no symptoms, but a share of cases turn severe, with plasma leakage, bleeding, and shock that can kill.
For all of that, treatment today is entirely supportive. Doctors manage fluids, watch the blood counts, and give paracetamol for pain and fever, while avoiding ibuprofen and aspirin because they can worsen bleeding. There is no antiviral to shorten the illness or stop a mild case from tipping into a dangerous one. A drug that lowers the amount of virus in the body early, if it truly works, is aimed straight at that missing piece.
That is the promise the trial is chasing. An antibody is a protein the immune system normally makes to latch onto a specific target; a monoclonal antibody is a mass-produced copy of one. Dengue-mAb is built to bind the virus and blunt its ability to multiply, delivered as a single drip to someone already infected. It is a treatment, not a vaccine, and the two answer different questions.
The number that changes how you read the results
The headline percentages look striking until you see the denominators. The trial was designed on the assumption that half the enrolled patients would have virus measurable by its main culture-based test at the start. In reality, only 12.9% did. That single fact quietly reshapes everything downstream.
It means the marquee comparison, the share clearing virus by 8 hours, came down to groups of roughly four to eight patients each. When 100% of five people clear the virus and 50% of eight do on placebo, the direction is encouraging but the ground under it is thin. The stronger, more reassuring part of the study is the co-primary measure it was actually powered for: the drop in circulating virus at 24 hours, which beat placebo at every dose with results unlikely to be chance, and the clean safety record across all 199 treated patients.
So the honest reading is split. Safety: solid for a Phase 2. Efficacy: a real signal pointing the right way, on numbers too small to lean on. The researchers frame it exactly this way, and it is why they call the effect preliminary rather than proven.
What the study could not settle
Several limits sit on top of the small subgroups, and the authors list them plainly.
- The design was single-blind. Site staff knew who got the drug, though the analysing laboratories were masked and the main efficacy readouts were objective lab values rather than judgment calls.
- Many patients arrived late. A good number presented more than 48 hours after fever began, past the point where virus levels usually peak, and the timing relied on patients’ own memory of when symptoms started.
- The tests disagreed with each other. There was discordance between the rapid antigen test, the ELISA, and the PCR assay, and the older PCR method may miss newer circulating strains, so some cases may have been misclassified.
- No effect on hard outcomes was shown. No one in the trial progressed to severe dengue, which is good news, but with so few severe cases the study cannot say whether the antibody prevents the outcomes that actually threaten lives.
None of this sinks the drug. It defines the job of the next trial: enrol patients earlier, confirm infection with tighter tests, and power the study to measure clinical benefit, not just virus in the blood. The company says a Phase 3 program will use a more sensitive cell line to detect live virus.
What you should take from this if you live where dengue spreads
Nothing about your care changes today. There is still no approved antiviral for dengue, and this antibody is investigational, tested only in a research setting in India. If you get dengue, the advice is unchanged: rest, keep fluids up, use paracetamol rather than ibuprofen or aspirin, and seek urgent care for warning signs such as severe abdominal pain, persistent vomiting, bleeding gums, or sudden weakness.
What this result offers is a direction. After years in which dengue treatment meant only managing symptoms, a drug has shown, in a first careful test, that it can drive the virus down and appears safe doing so. Whether that translates into fewer severe cases and shorter illness is the question a larger trial now has to answer. It is a beginning worth watching, not a treatment you can ask for.
Related Coverage
Sources:
- Safety and Preliminary Efficacy of Dengue Monoclonal Antibody in Adult Patients: A Randomized Clinical Trial (Kulkarni et al, 2026), JAMA Network Open
- Monoclonal antibody shows promise against dengue viremia, fever in phase 2 trial, CIDRAP
- Dengue and severe dengue fact sheet, World Health Organization
Disclaimer: This article is for general information only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about any medical condition or before making health decisions.