MHB088C is as a novel B7-H3-targeted antibody-drug conjugate (ADC). It incorporates the potent SuperTopoi payload, which is noted as being 5 to 10 times more potent than Dxd. Early data from the ongoing phase 1/2 study had previously shown MHB088C was generally well tolerated with initial signs of clinical activity. Here are the preliminary findings from a subset of patients with metastatic castration-resistant prostate cancer (mCRPC) from the dose expansion part of this study.

As of January 3, 2024, 36 mCRPC patients had been enrolled and received at least one dose of MHB088C. These patients were characterized as heavily pretreated, with 100% having received novel androgen axis drugs (NAAD) and 80% having received docetaxel.

Preliminary efficacy data in patients with measurable disease (n=21) showed an objective response rate (ORR) of 14.3% and a disease control rate (DCR) of 95.2%. The six-month radiographic progression-free survival (rPFS) was 87%. Preliminary data also indicated improvements in prostate-specific antigen (PSA) levels. Overall, MHB088C demonstrated promising anti-tumor activity in this heavily pretreated mCRPC population.

Regarding safety, MHB088C demonstrated a manageable safety profile, with safety data consistent with previous reports. The most common Grade ≥3 treatment-related adverse events were neutropenia (24.2%), platelet count decreased (11.1%), and anemia (15.2%).

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