DUALITYBIO-B (09606) has announced that updated efficacy and safety results from the Phase 1/2 DB-1311-O-1001 study (NCT05914116) for its investigational B7H3 antibody-drug conjugate (ADC), DB-1311/BNT324, will be presented at the 2026 American Society of Clinical Oncology (ASCO) Genitourinary (GU) Cancers Symposium, taking place from February 26 to February 28, 2026, in San Francisco, USA. The study evaluates the drug in heavily pre-treated patients with metastatic castration-resistant prostate cancer (mCRPC), including an analysis based on prior treatment with Lutetium-177 (177Lu)-PSMA-617. An abstract for the presentation was released on the official symposium website on February 23, 2026, local time.
In the dose optimization cohort of this Phase 1/2 study, patients with pre-treated mCRPC received DB-1311/BNT324 at doses of 6 mg/kg or 9 mg/kg every three weeks (Q3W). In the dose expansion cohorts (mCRPC post-Lu 177 treatment and mCRPC taxane-naïve), patients received 6 mg/kg Q3W. Treatment continued until disease progression or unacceptable toxicity.
As of the data cutoff date of September 5, 2025, 104 mCRPC patients had been treated with DB-1311/BNT324 (6 mg/kg, n=68; 9 mg/kg, n=34). After a median follow-up of 9.2 months (range 0.1-19.4), 52 patients (50%) remained on treatment. The median patient age was 70 years (range 45-90). The majority of patients were White (53%), followed by Asian (31%) and Black (13%). Patients had received a median of 4 prior lines of therapy (range 1-14).
Among 58 patients evaluable for tumor response (with measurable disease at baseline per RECIST 1.1), the unconfirmed objective response rate (ORR) was 41.4% (95% CI 28.6-55.1), and the confirmed ORR (cORR) was 34.5%. The disease control rate (DCR) was 87.9% (95% CI 76.7-95.0). The median duration of response (DOR) was 10.2 months (95% CI 7.2, Not Evaluable). Among 82 patients evaluable for radiographic progression-free survival (rPFS), the median rPFS was 11.3 months (95% CI 7.2, NE), with 6-month and 9-month rPFS rates of 72.0% and 63.0%, respectively. Overall survival (OS) data were not yet mature at the data cutoff; the 6-month and 9-month OS rates were 91.7% and 88.2%, respectively. The PSA50 response rate was 35.4%, with a median PSA DOR of 8.4 months (95% CI 4.4, NE).
The safety profile was consistent with previous reports. The most common adverse events were nausea and hematological events, which were primarily Grade 1-2.
A subgroup of 34 patients (33%) had received prior Lu 177 treatment. In this subgroup, the median age was 69 years (range 55-84); the racial composition was 65% White, 15% Asian, and 15% Black; the median number of prior therapies was 5 (range 2-14); and 24 patients (71%) remained on treatment. Outcomes were generally similar between patients with and without prior Lu 177 treatment, except for a shorter median PSA DOR observed in the Lu 177 pre-treated subgroup.
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