A new investigational drug, CBP-1018, is showing encouraging results in treating metastatic castration-resistant prostate cancer (mCRPC). According to updated findings from a phase I/II clinical trial, the bi-ligand–drug conjugate (Bi-XDC) demonstrates both manageable side effects and promising disease control, offering hope to patients who have exhausted standard treatment options.

As of August 31, 2024, a total of 120 patients had been enrolled in the trial, with researchers closely monitoring both the drug’s safety and its ability to slow cancer progression. Among these, 76 patients received CBP-1018 at what is considered a therapeutically active dose (0.14 mg/kg or higher). These patients were heavily pre-treated, with 67.1% having previously undergone taxane chemotherapy and at least one second-generation androgen receptor pathway inhibitor (ARPI), while 21.1% had also received PARP inhibitors, a class of drugs used in genetically targeted prostate cancer therapies.

The drug’s ability to shrink or control tumors was particularly promising. Among 25 patients with measurable target lesions, the objective response rate (ORR)—which measures significant tumor shrinkage—was 20%, while the disease control rate (DCR), which includes both tumor shrinkage and stabilization, was an impressive 88%. Additionally, 60% of patients showed a reduction in tumor size, suggesting that CBP-1018 is effectively targeting and suppressing cancer growth.

One of the most critical indicators of success in prostate cancer treatment is radiographic progression-free survival (rPFS)—the time during which a patient’s cancer does not worsen based on imaging scans. The median rPFS had not yet been reached at the data cutoff, signaling that many patients were still benefiting from the treatment. At seven months, an estimated 70% of patients remained progression-free, and at 12 months, around 60% were still responding positively.

For the subgroup of 48 patients who had prior taxane chemotherapy and ARPI treatments, the seven-month rPFS rate was 66%, demonstrating that CBP-1018 is effective even in heavily pre-treated cases where options are typically limited.

The trial also provided reassurance regarding safety and tolerability. Only 8.3% of patients (10 out of 120) required a dose reduction due to treatment-related adverse events (TRAEs), and just 4.2% (5 out of 120) had to discontinue treatment altogether. The most commonly reported side effects were temporary blood-related toxicities, which were expected and easily manageable. Unlike some other antibody-drug conjugates (ADCs), which often cause severe nerve damage or vision problems, CBP-1018’s neurological side effects were mild—only 11.7% of patients experienced peripheral neuropathy, all of which were classified as grade 1 (mild), and only one patient reported a reduction in visual acuity.

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