Bluejay's BJT-778 Monoclonal Antibody Achieves 100% Virologic Response and Up to 78% Combined Response in CHD Monotherapy

Bluejay Therapeutics, a clinical-stage biopharmaceutical company based in San Mateo, California, has revealed new data from its Phase 2 study on BJT-778, a fully human monoclonal antibody targeting hepatitis B virus surface antigen. The study investigates BJT-778 as a potential monotherapy for adults with chronic hepatitis D (CHD), the most aggressive form of viral hepatitis. Detailed results will be shared in an oral presentation at The Liver Meeting® 2024 of the American Association for the Study of Liver Diseases (AASLD).

CHD affects over 12 million people globally and has limited treatment options. Presenting author Dr. Kosh Agarwal, a Consultant Hepatologist and Transplant Physician at King’s College Hospital in London, emphasized the need for better treatment alternatives. The BJT-778 Phase 2 study data suggests that this monotherapy regimen could be a significant advancement in CHD treatment.

In the Phase 2 study, participants with measurable hepatitis D virus (HDV) RNA and hepatitis B virus (HBV) suppressed on nucleos(t)ides were assigned to one of three BJT-778 doses: 300 mg weekly (QW), 600 mg every week for 12 weeks then every two weeks (Q2W), and 900 mg every four weeks after a loading dose at week two (Q4W). The study included patients with compensated cirrhosis and well-controlled HIV.

Key study endpoints include safety and tolerability, virologic response (defined as ≥2 log10 HDV RNA IU/mL reduction from baseline or HDV RNA target not detected [TND]), ALT normalization in participants with abnormal baseline ALT, and the combined response of virologic response plus ALT normalization. According to FDA guidance, this combined endpoint is a reliable predictor of clinical benefit and supports the approval of new CHD treatments.

BJT-778 achieved a 100% virologic response across all dose groups, with up to 78% of participants reaching the combined endpoint of virologic response and ALT normalization. These effects were consistent across all doses, indicating a beneficial impact on liver inflammation due to reduced viral load.

By the last available timepoint for each dose, results were as follows:
- 300 mg QW: 100% virologic response by Week 44, including 60% with HDV RNA below the Lower Limit of Quantification (- 600 mg Q2W: 100% virologic response by Week 36, including 50% - 900 mg Q4W: 100% virologic response by Week 24, including 75%
BJT-778 showed a favorable safety profile at all doses, with no ≥ grade 3 adverse events (AEs), no severe AEs, and no treatment discontinuations due to AEs.

Dr. Nancy Shulman, Chief Medical Officer of Bluejay Therapeutics, highlighted the potential of BJT-778 to transform clinical practice and patient lives. The monotherapy demonstrated high virologic response rates, significant ALT normalization, strong safety, and convenient dosing regimens, supporting its advancement into larger, randomized controlled studies planned for commencement soon. Longer-term data from all dose arms is expected in the second half of 2025.

Additionally, Bluejay Therapeutics is advancing its chronic hepatitis B (CHB) functional cure development program. Data from a preclinical study showed that BJT-778 significantly increased hepatitis B surface antigen (HBsAg) uptake, enhancing HBV-specific CD4 T cell activation. This supports a dual mechanism of action through HBsAg removal and HBV-specific T cell immunity stimulation.

The company also presented data on cavrotolimod (CAVRO), a spherical TLR9 agonist. Preclinical characterization showed that CAVRO selectively activates TLR9, induces cytokine production, and stimulates cellular immune responses, indicating potential sustained control of hepatitis B infection. A Phase 1b study has begun to evaluate CAVRO in CHB participants.

Bluejay Therapeutics continues to focus on developing transformative therapies for viral hepatitis and liver diseases, with ongoing investigations into BJT-778 for CHD and CHB, and innovative programs targeting a functional cure for CHB.