November 24, 2025, Shanghai, China & Chicago, USA – Duality Biologics (Stock Code: 9606.HK) orally presented Phase 1 randomized controlled study (NCT06625671, Phase 1/2a study) data for DB-2304, a first-in-class BDCA2-targeted immune-modulating Antibody-Drug Conjugate (ADC), on Nov 22^nd at the 53rd Annual Autumn Immunology Conference (AIC 2025). Results demonstrated that DB-2304 was generally safe and well-tolerated in healthy participants, showed approximately linear pharmacokinetics (PK), and effectively reached and engaged the intended target, validating its pharmacological mechanism.

DB-2304 is the first globally patented BDCA2 ADC for autoimmune diseases, fully internally discovered and developed based on DualityBio's proprietary DIMAC platform. It will being investigated in clinical trials across the United States, Australia, Mainland China, and Taiwan, China. In Phase 2a of this Phase 1/2a study, the first patient with systemic lupus erythematosus (SLE) was successfully dosed in the United States.

The presented Phase 1 single-ascending-dose study assigned 50 healthy Australian participants with balanced baseline characteristics across five DB-2304 dose groups (1-20 mg/kg) and parallel prednisone and placebo control groups to evaluate the safety, pharmacokinetics (PK) ,and pharmacodynamics (PD) of DB-2304.

The exposures of the ADC, total antibody, and payload P2025 increased in an approximately dose-proportional manner across the 3-20 mg/kg dose range, demonstrating typical linear ADC pharmacokinetics. At the lower 1-3 mg/kg dose levels, the exposure of P2025 was minimal, indicating favorable linker stability. The observed half-life of the DB-2304 ADC was approximately 10 days, supporting a dosing frequency of every four weeks. Preliminary population PK/receptor occupancy (PopPK/RO) modeling predicted that a dose of 1 mg/kg Q4W can sustain high BDCA2 receptor occupancy of greater than 95%.

Regarding safety, DB-2304 was generally safe and well-tolerated in healthy participants. Only four treatment-related adverse events (TRAEs) were reported, all of which were Grade 1 in severity. No drug-related serious adverse events (SAEs) were reported.

Notably, DB-2304 treatment resulted in only a transient reduction of circulating plasmacytoid dendritic cells (pDCs), confirming its primary mechanism is functional inhibition rather than cell depletion – a favorable safety differentiator from depletion strategies. Furthermore, DB-2304 demonstrated dose-dependent Hypothalamic-Pituitary-Adrenal (HPA) axis suppression, with the change from baseline in serum cortisol AUC0-12hr being quantitatively lower than the effect of 10 mg prednisone. It also showed a favorable bone safety profile, as suppression of the bone formation marker serum P1NP was substantially less than that observed with 10 mg prednisone, with the exception of the highest dose (20 mg/kg). Even at this dose, the effect was transient, with recovery by the end of week 2.

"DB-2304 is a potential first-in-class BDCA2-targeted immune-modulating ADC and first to enter clinical development stage. The Phase 1 healthy volunteer data validate our biology-driven drug design rationale," said Dr.Yang Qiu, Chief Scientific Officer and GM of U.S. at DualityBio.. "We are advancing the clinical development of this innovative agent in patients with SLE and CLE and look forward to bringing a potential new ADC breakthrough to the treatment of autoimmune diseases."

About DualityBio

Duality Biotherapeutics (HKEX:09606) is a clinical-stage biotech company dedicated to the discovery and development of next-generation ADCs to treat cancer and autoimmune diseases. DualityBio has successfully built several cutting-edge ADC technology platforms with global intellectual property rights. Leveraging a robust pipeline, DualityBio is conducting multiple global clinical trials across 20 countries and has enrolled over 2,700 patients for multiple clinical-stage ADC candidates.

Additionally, DualityBio has established strategic collaborations with global MNCs and leading biotech innovators. As a global ADC powerhouse, DualityBio is developing novel ADCs, including bispecific ADC candidates, novel-payload ADC candidates, and autoimmune ADC candidates.

For more information, please visit: www.dualitybiologics.com.

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Investor Contact: IR@dualitybiologics.com