For patients living with chronic Hepatitis B, a specific question now has both a new answer and a new urgency: do you also have Hepatitis Delta?
On May 22, 2026, the FDA approved bulevirtide-gmod injection (Hepcludex; Gilead Sciences) as the first-ever treatment for chronic Hepatitis Delta Virus (HDV) infection in the United States. The approval is for adults without cirrhosis or with compensated cirrhosis, under the FDA's Accelerated Approval pathway.
Until May 22, 2026, there was no FDA-approved treatment for HDV in the United States. Clinicians relied on off-label interferon-based regimens with limited efficacy. Many physicians simply did not test for HDV because there was nothing to do with a positive result.
That reasoning no longer holds.
Why This Matters
Hepatitis Delta Virus is the most severe form of chronic viral hepatitis. It can only infect people who already have Hepatitis B Virus — because HDV requires the Hepatitis B surface antigen to replicate and form new viral particles. In virology, it is called a "satellite virus": dependent on HBV for its existence, but capable of causing devastation on its own.
According to the Hepatitis B Foundation, an estimated 4 percent of people in the United States living with chronic Hepatitis B also have HDV — approximately 80,000 people. Globally, there are an estimated 48 to 60 million HDV infections.
The clinical consequence of co-infection is severe: HDV dramatically accelerates liver disease compared to Hepatitis B alone. People with HDV co-infection progress to cirrhosis approximately three times faster than people with Hepatitis B alone, and their risk of developing hepatocellular carcinoma (liver cancer) is significantly multiplied.
As Wendy Carter, DO, acting director of the FDA's Office of Infectious Diseases, said in the approval announcement: "Today's approval fills a critical gap in care for patients with chronic HDV infection, who until now have had no FDA-approved therapies available."
What Bulevirtide Does
Bulevirtide is a first-in-class entry inhibitor. It works by blocking the receptor through which HDV (and Hepatitis B) enter liver cells — preventing the virus from infecting new hepatocytes rather than attacking the virus inside already-infected cells. This mechanism is distinct from existing Hepatitis B antivirals (nucleoside/nucleotide analogues), which suppress viral replication but do not prevent cell entry.
According to the Phase 3 MYR301 trial data reviewed by the FDA, administered as a daily 8.5 mg subcutaneous injection:
- At week 48: 20 percent of patients achieved undetectable HDV RNA
- At week 96: 36 percent achieved undetectable HDV RNA
- At week 144: 50 percent achieved undetectable HDV RNA in the immediate-treatment arm
- 90 percent of patients who achieved undetectable HDV RNA at 96 weeks remained undetectable for nearly 2 years post-treatment, in final data presented at the European Association for the Study of the Liver Congress 2025
The drug is approved as an 8.5 mg daily subcutaneous injection. A boxed warning is included: discontinuation of bulevirtide may result in severe acute exacerbations of both HDV and HBV infection, given the obligate co-infection biology. Patients who stop treatment must be monitored closely.
Who Should Be Tested for HDV Right Now
The clinical implication of this approval is direct: every chronic Hepatitis B patient who has never been tested for HDV should be tested now, because a positive result now leads to a treatment option.
Infectious disease and hepatology specialists recommend HDV antibody testing particularly for chronic Hepatitis B patients who:
- Were born in or have immigrated from high-HDV-prevalence regions: Mongolia, Central Asia (Kazakhstan, Tajikistan, Uzbekistan), Eastern Europe, Romania, West Africa, the Amazon basin of South America, and parts of the Middle East
- Have a history of injection drug use
- Have unexplained rapid progression of liver disease or elevated liver enzymes despite Hepatitis B treatment
- Have a sexual partner with confirmed HDV
- Have ever been tested for HDV prior to 2026 and had a positive antibody result (positive HDV antibody requires confirmatory HDV RNA testing)
Testing for HDV begins with an anti-HDV antibody test. A positive antibody test is followed by quantitative HDV RNA testing to confirm active infection.
The Case for Universal HDV Testing in Hepatitis B Patients
Before bulevirtide, many hepatologists argued against universal HDV testing in all Hepatitis B patients — the logic being: why identify something you cannot treat? That logic was always contested by patient advocates and researchers who argued that knowing about HDV was important even without a treatment, because it changes how aggressively liver disease is monitored and how other life decisions are framed.
Now, the logic against testing has been removed. Universal HDV antibody testing for all chronic Hepatitis B patients is the emerging standard.
As the Hepatitis B Foundation's president Chari A. Cohen stated: "All of us at the Hepatitis B Foundation are optimistic that the FDA's approval of Hepcludex will be a game changer, leading to improved HDV screening, diagnosis, care and treatment across the U.S."
What You Can Do Now
- If you have chronic Hepatitis B and have never been tested for Hepatitis Delta Virus, ask your hepatologist, gastroenterologist, or infectious disease specialist about an anti-HDV antibody test at your next appointment — or call to schedule one now.
- If you tested positive for HDV antibodies in the past, follow up with your physician about whether HDV RNA testing is warranted to assess for active infection.
- If you are diagnosed with chronic HDV and are interested in bulevirtide (Hepcludex), talk to your liver specialist about whether you meet the indication criteria (without cirrhosis or with compensated cirrhosis, and no active HBV co-infection requiring concurrent antiviral therapy that might interact).
- Bulevirtide is available by prescription from Gilead Sciences as of May 22, 2026. Contact your physician to begin the prior authorization and prescribing process.
Cost and Access: What Patients Should Know
HDV antibody testing is covered by most insurance plans when ordered by a physician for a patient with confirmed chronic Hepatitis B. Confirmatory HDV RNA testing is also typically covered. Bulevirtide (Hepcludex) is a specialty medication. Gilead Sciences offers a patient support program for insured and uninsured patients — contact them directly or through your physician's office for information on the Hepcludex patient assistance program.
What Happens Next
As an accelerated approval, bulevirtide's approval requires a post-marketing confirmatory study. Gilead is conducting additional research on longer-term outcomes and combination regimens. The approval in the U.S. follows earlier approvals in the European Union and United Kingdom where the 2 mg dose was approved, making it available to more patients globally. MedicalDaily will report on post-marketing study data and any guideline updates from hepatology societies.
The Bottom Line
Hepatitis Delta is the most severe form of viral hepatitis, and approximately 80,000 Americans have it as an undetected co-infection with Hepatitis B. Until May 22, 2026, there was nothing to offer those patients. Now there is. If you have chronic Hepatitis B and have never been tested for HDV, the most important medical conversation you can have with your doctor right now is a simple one: ask for the test.
